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Competition for above- and below-ground resources depends on their availability and results in varied growth partitioning. This becomes clear as the supply and limitation of the main resources influence the slope of the size-growth relationship in stands. Nevertheless, growth partitioning among trees, especially among black locust (R. pseudoacacia) trees is not understood in sufficient detail. To scrutinize and estimate the mode of competition of R. pseudoacacia, this research analyzed 1333 trees in Germany in 10 study sites, consisting in total 27 sample plots, with similar climate but varying soil conditions. The stand age ranged from 2 to 32 years, with a diameter at breast height ranging from 0.6 to 29.1 cm. The main focus of the study was to evaluate the impact of nitrogen, phosphorus, and water supply on the competition mode of R. pseudoacacia by varying growth partitioning. We applied the size–growth relationship in a mixed-effects model with a random intercept and slope. Fixed effects were the basal area, phosphorus, water, the sunlight competition index, and the interactions between below- and above-ground resources. Site specific effects of the analyzed stands were quantified with the aid of the random effects. Depending on the supply and limitation of phosphorus and water, this study determined how the competition mode as well as the growth partitioning among R. pseudoacacia trees were influenced. Hence, if phosphorus and water availability increased, then the competition for above-ground resources (primarily sunlight) and the slope of the size–growth relationship increased. Large trees grew disproportionately more than smaller trees. If the available phosphorus and water decreased, then the competition for the below-ground resources increased and the slope of the size–growth relationship decreased – to be more flattened. Moreover, it was found that available nitrogen as a below-ground resource had no influence on the mode of competition. In summary, phosphorus was the most important nutrient and, together with water, was the main driver of growth partitioning among R. pseudoacacia trees.
Native grasslands are endangered by non-native plant invasion worldwide, including foothills fescue grasslands in North America. Large populations of non-native plant species have established in these disturbed fescue grasslands, forming dense monocultures and spreading into undisturbed areas. Soil disturbance and plant invasion can alter the arbuscular mycorrhizal fungi (AMF) community, an important symbiotic partner of most land plants, which could negatively affect native plant reestablishment. The objective of this study was to assess whether AMF communities on a fescue grassland shifted in response to disturbances by landfill storage and gravel quarrying and with invasion of non-native plant species relative to undisturbed grassland. Soil and root-AMF samples were procured from disturbed and undisturbed areas at three sites. Plant canopy cover and species richness were assessed. Soils were analyzed for pH; electrical conductivity; total nitrogen, carbon and phosphorus; and available nutrients. For relative AMF taxa abundance assessment, NS31 and AMF specific primer AML2 were used to amplify a central fragment of the V3 and V4 region of the 18S rRNA gene. AMF were characterized using 454 pyrosequencing and multiplexed barcoded samples amplified from genomic
DNA isolated from roots. There were 92 AMF, including 15 potentially novel taxa detected. AMF communities in disturbed and undisturbed sampling locations were distinct except for one site, and indicator AMF virtual taxa (VT) for undisturbed grassland and disturbed sites were identified. AMF richness was higher in undisturbed (72 VT) than disturbed (64 VT) sites and AMF richness was positively correlated with plant species richness, diversity and native plant cover, and negatively correlated with non-native plant cover. There were 43 AMF VT on undisturbed and disturbed sites, 62% with higher relative abundance on disturbed sites. Site disturbance shifted AMF communities relative to undisturbed native fescue grassland; thus restoration success with native plants might be highly dependent on reintroducing native AMF.
Marginal land (MagL) use for biomass production has received a lot of attention in the past decades. This alternative land use is free from conflicts with food crops, however it presents multiple challenges. The major issue to be resolved is the definition of marginal lands, which varies between disciplines and is often determined based on management goals. Moreover, concerns over the impacts of MagL use on environment, ecosystem services and sustainability have to be addressed.
In response to these issues, the SEEMLA approach proposes an algorithm and tools to support MagLs identification and mapping, as well as the assessment of their potential for biomass production. The SEEMLA algorithm assesses land marginality using the Muencheberg Soil Quality Rating (M-SQR) developed by Mueller et al. (2007). The algorithm also incorporates criteria to eliminate MagLs that may not be exploitable for bioenergy due to ecological and environmental issues or regulatory and legal restrictions and constraints posed by national or EU policies applied. Finally, MagL suitable for bioenergy production is categorized based on climatic zone and crop suitability. Alternative exploitation scenarios are developed for each class of MagL. Life Cycle Assessment (LCA) will determine the sustainability of each scenario, considering also the results of the pilot sites that have been established in Germany, Greece and Ukraine.
Transitioning towards agroforestry demands systematic productivity assessments of such systems under different climatic and edaphic conditions. In this regard, the Land Equivalent Ratio (LER) serves as a valuable productivity indicator of agroforestry since it evaluates yields from growing trees and crops together in comparison to yields from monocultures over the same period. Consequently, our objective was to evaluate the overall productivity of two agroforestry systems in Forst (Brandenburg) and Wendhausen (Lower Saxony) by means of LER. Our approach followed two assumptions: (i) the yields of trees and crops had equal economic importance and (ii) the economic importance was given solely by the annual crop, the yield of trees representing a supplementary profit. The resulted values for LER were consistently above their specific threshold, corroborating the greater efficiency of agroforestry systems rather than monoculture. Additionally, this study highlighted the importance of choosing the appropriate assumptions when calculating the LER.
Linear woody-features, such as hedgerows, windbreaks, and riparian buffer strips, composed of trees and/or shrubs are anthropogenic features, established in the past for different purposes, such as provision of field boundaries, protection from wind and supply of fuelwood. Today, they are primarily valued for their ecological benefit, while their production function has received rather little attention. This study assessed the biomass potential of existing linear woodyfeatures in a study area in southern Brandenburg, Germany. The merchantable tree volume of the measured woody-features ranged between 240 m3 ha-1 and 710 m3 ha-1, depending on the relative proportion of trees and shrubs. The results suggest that the biomass potential of linear woody-features with predominant tree proportion per hectare can be higher than this of forests.
A strategy for utilising the production function of these woody-features should take into account the provision of benefits such as wind protection, habitat provision and landscape aesthetics.
In Brandenburg, north-eastern Germany, climate change is associated with increasing annual temperatures and decreasing summer precipitation. Appraising short rotation coppices (SRCs), given their long-time planning horizon demands for systematic assessments of woody biomass production under a considerable spectrum of climate change prospects. This paper investigates the prospective growth sensitivity of poplar and black locust SRCs, established in Brandenburg to a variety of weather conditions and long-term climate change, from 2015 to 2054, by a combined experimental and simulation study. The analysis employed (i) a biophysical, process-based model to simulate the daily tree growth and (ii) 100 realisations of the statistical regional climate model STAR 2K. In the last growing period, the simulations showed that the assumed climate change could lead to a decrease in the woody biomass of about 5 Mg ha -1 (18%) for poplar and a decrease of about 1.7 Mg ha -1 (11%) for black locust trees with respect to the median observed in the reference period. The findings corroborate the potential tree growth vulnerability to prospective climatic changes, particularly to changes in water availability and underline the importance of coping management strategies in SRCs for forthcoming risk assessments and adaptation scenarios.
Agroforestry is receiving increasing attention in Germany because of its capacity to address some of the negative consequences of intensive agriculture. However the actual uptake and maintenance of agroforestry by farmers remains low. The aim of this study was to identify the opportunities and obstacles to agroforestry in Germany and to identify potential measures which could address the obstacles and increase agroforestry adoption. Qualitative interviews with 32 farmers indicated that the legal framework and administrative burden associated with agroforestry in Germany was a major obstacle. The farmers recognised that agroforestry provided environmental benefits, but these do not always increase farm profitability. Agroforestry was identified as a viable alternative to conventional farming systems, especially in less productive areas, not profitable when managed in a conventional way. To enhance the implementation of agroforestry the simplification of the legal framework is crucial. Modern agroforestry should be better recognized by existing policy measures providing payments for environmentally friendly farming. Ultimately, an integrated approach for environmental benefits and production objectives is required, which is based on rewarding farmers for providing ecosystem services (ESs) and a stronger public involvement in sustainable land use practices. Rewarding farmers for ESs could increase the interest in agroforestry in highly productive areas, enhancing sustainable land use in the long term.
The cultivation of bioenergy plants at fertile, arable lands increasingly results in new land use conflicts with food production and cannot be considered as sustainable, therefore. Marginal lands have been frequently considered as potential alternative for producing bioenergy from biomass. However, clear definitions and assessment methods for selecting marginal lands and for calculating potentials are still widely missing. The project “SEEMLA” aims at triggering the exploitation of currently underused marginal lands for biomass production for energy purposes. Study sites have been selected in different European countries: Germany, Greece and Ukraine. The selected sites represent a wide variety of different types of marginal lands. Based on a soil assessment set given by the Muencheberg Soil Quality Rating (SQR) system potentially “marginal” sites have been investigated. The SQR system allows for clearly distinguishing between soils of higher and lower quality. Soils with SQR scores below 40 are regarded as “marginal”. They can be classified into different groups with regard to the importance of soil hazard indicators as valuated by the SQR approach. The calculated SQR scores correlate significantly with biomass yields of bioenergy plants. Further, the SQR method was adapted for use in a GIS study on marginal land potentials in Europe. 46 % of the investigated European area could be classified as “marginal” with SQR scores below 40. From that area 22.6 % can be considered as potentially suitable for producing renewable resources after eliminating protected sites or other places not suitable for any kind of land use. Taking the ecological demands of selected bioenergy plants into account it is possible to give first preliminary recommendations for regional crop cultivation. It can be concluded, that Europe offers a large potential for renewable resources from marginal sites. However, the implementation into practice is often impeded by missing or varying policies and regulation. A proper implementation needs clear regulations and also incentives for farmers at European level.
Climate change is expected in Brandenburg, eastern Germany, in terms of increasing annual temperature and changes in climate variability, as well as the number of extreme weather events. Since agroforestry systems have a planning horizon of several decades, long-term yield assessments are required in order to evaluate the economic profitability and environmental sustainability of such systems. Accordingly, our aim was to simulate the tree growth of poplar trees (Populus nigra x P. maximowiczii) in an agroforestry system in Brandenburg for the next forty years. For this purpose, we used the process-oriented Yield-SAFE model, a parameter-sparse, biophysical model developed for the simulation of plant growth in agroforestry systems. For the investigated period from 2011 to 2014, the validation simulations showed clear correlations with the observed values for woody tree biomass. For the unfolding period from 2015 to 2055, a variety of possible climate changes (including higher evaporation requirements and reduced water availability) and their uncertainties were incorporated into our assessment. The tree yield sensitivity to future climatic conditions was evaluated using 100 realizations of a scenario of the statistical regional climate model Statistical Analogue Resampling Scheme (STAR), which assumes an increase in annual temperature of 2K, as well as decreasing annual precipitation by 30–40 mm. The Yield-SAFE model responded sensitively to changes in the meteorological input data, showing that (1) shifts in temperature and/or precipitation would have a directly proportional influence on tree growth and (2) the impact of potential climate changes on tree growth must be assessed in terms of the complex interaction of various influencing factors. This was evidenced, for example, by the fact that higher average annual temperatures could either increase the tree growth due to a prolonged vegetation period or, on the contrary, decrease the tree growth due to higher potential evapotranspiration. The model results are important for the sustainable planning and management of agroforestry systems, upcoming risk assessments, and example analysis of adaptation scenarios in the near and distant future.
Das Hühnerwasser-Einzugsgebiet ist ein 6 ha großes, künstlich geschaffenes Wassereinzugsgebiet im Tagebau Welzow-Süd in Südost-Brandenburg. Das Zweischichtsystem mit einer Ton- und einer darüber liegenden Sandschicht wurde im Jahr 2005 fertiggestellt und ohne weitere Rekultivierungsmaßnahmen für Forschungszwecke bereitgestellt. Es lässt exemplarisch die Untersuchung der initialen Landschaftsgenese zu. Insbesondere die Entwicklung von einem zunächst noch abiotisch kontrollierten hin zu einem biotisch gesteuerten System lässt sich hier beobachten. In diesem Beitrag werden beispielhaft einige in diesem Kontext aufgetretene Interaktionen zwischen abiotischen und biotischen Strukturelementen vorgestellt. Dies sind zum einen Erosions- und Sedimentationsprozesse und ihre Wechselwirkungen mit der Vegetation. Zum anderen wird der Einfluss der Vegetation auf die Grundwasserentwicklung dargestellt.
Although biological soil crusts can be found in open landscapes worldwide, their species composition depends on soil properties such as texture and pH, on microclimate, and their respective developmental stage. In addition, local variations in water holding capacity and/or chemical properties of soils influence the formation of spatial patterns and different types of biocrusts on the landscape level. For the evaluation of biocrusts functions and their impact on soil carbon pools, the analysis of the interrelationship between photosynthetic activity and the variations of spatial distribution pattern and types of biocrust is indispensable. For this purpose, an image processing approach was applied that combined chlorophyll fluorescence analyses and multispectral BNDVI to comprehensively characterize the spatial patterns of photosynthetic hotspots in biological soil crusts. For image analysis, five biological soil crust samples with different ratios of substrate, mosses and lichens were collected on an inland dune system in Lieberose, dominated by the moss Polytrichum piliferum, and the lichens Cladonia fimbriata and C. coccifera. RGB-images of the biocrusts were taken with a standard consumer camera Nikon 5200, BNDVI images with a modified Canon S110 NIR camera and chlorophyll fluorescence images with a modular open FluorCAM FC 800-O/1010, respectively. BNDVI and Fv/Fm were nearly in the same range for all biocrust samples related to the total surface area. Although mosses showed higher BNDVI than lichens within the separate biocrust samples. F0 and Fm increased with species coverage and with advancing biocrust development. Overlapping of BNDVI with F0 and Fm images showed that not all crustal organisms contribute to BNDVI and chlorophyll fluorescence. The overlapping areas of BNDVI and F0 ranged between 13% and 29%, that of BNDVI and Fm between 17% and 47%. Matching of RGB, BNDVI and CFI allows visualizing spatial pattern with high or low photosynthesis in biocrusts.
Experimental catchments with well-known boundaries and characteristics may contribute valuable data to hydrological, critical zone and landscape evolution research. One of the most well-established and largest constructed catchments is the Chicken Creek catchment (6 ha area including a 0.4 ha pond, Brandenburg, Germany) representing an initial ecosystem undergoing a highly dynamic ecological development starting from clearly defined starting conditions. The water balance dynamics of the catchment was calculated using a simple mass balance approach to reveal the impact of ecological development during 12 years. Water storage in the catchment was calculated from a 3D-model of groundwater volumes, soil moisture measurements and water level recordings of the pond. The catchment water balance equation was resolved for evapotranspiration, the only part that was not measured directly. Due to the known boundary conditions and the inner structure of the catchment, we were able to quantify the different storage compartments and their role in hydrologic response. Our results indicate that for small catchments with a highly dynamic ecological development like the Chicken Creek, the knowledge about saturated and unsaturated storage volumes enables a good estimate and closure of the water balance using a rather simple approach, at least in annual resolution. We found a significant relationship between vegetation cover in the catchment and calculated ET. Time series of meteorological, hydrological, soil and vegetation data over 12 years enabled us to characterize the transient development of the catchment and to evaluate the effect of different feedback mechanisms on catchment hydrology. The dataset from the Chicken Creek catchment indicate at least three phases in ecosystem development, where initial abiotic feedbacks (e.g. erosion) were followed by more and
more biotic controls (e.g. biological soil crusts, vegetation succession and growth). Data from Chicken Creek in high spatial and temporal resolution provide a valuable database underlining the high importance of abiotic/biotic feedback effects that change the hydrologic functioning and response of the catchment more than the water balance itself revealed and thus have to be included in catchment models.
Im Rekultivierungsbereich des Braunkohletagebaus Welzow-Süd wurde der Einfluss der Schnitttechnik auf die Biomassequantität, die Stockausschlagfähigkeit und die Entwicklung von Robinien Wurzelbrut untersucht.
Für diesen Zweck wurden die Folgen der Holzernte mittels Forstmulcher und Motorsäge miteinander verglichen.
Soil pollutants such as hydrocarbons can induce toxic effects in plants and associated arbuscular mycorrhizal fungi (AMF). This study was conducted to evaluate if the legume Lotus corniculatus and the grass Elymus trachycaulus and arbuscular mycorrhizal fungi could growin two oil sands processing by-products after bitumen extraction fromthe oil sands in northern Alberta, Canada. Substrate treatmentswere coarse tailings sand (CTS), a mix of dry mature fine tailings (MFT) with CTS (1:1) and Pleistocene sandy soil (hydrocarbon free); microbial treatments were without AMF, with AMF and AMF plus soil bacteria isolated from oil sands reclamation sites. Plant biomass, root morphology, leaf water content, shoot tissue phosphorus content and mycorrhizal colonization were evaluated. Both plant species had reduced growth in CTS and tailings mix relative to sandy soil. AMF frequency and intensity in roots of E. trachycaulus was not influenced by soil hydrocarbons; however, it decreased significantly over time in roots of L. corniculatus without bacteria in CTS. Mycorrhizal inoculation alone did not significantly improve plant growth in CTS and tailings mix; however, inoculation with mycorrhizae plus bacteria led to a significantly positive response of both plant species in CTS. Thus, combined inoculationwith selected mycorrhizae and bacteria led to synergistic effects. Such combinations may be used in future to improve plant growth in reclamation of CTS and tailings mix.
Difficulties in quantitatively closing the water balance of catchments arise when upscaling point measurements and from insufficient knowledge of the physical boundaries, inner structure, and storage volumes of natural catchments. In addition, there is a strong need for generalizing the relationship between catchment characteristics and hydrological response. Therefore, experimental catchments with well-known boundaries and conditions could contribute valuable data to hydrological and critical zone research. One of the most well-established and largest constructed catchments is the Chicken Creek catchment (6 ha including a pond, Brandenburg, Germany) representing an initial ecosystem undergoing highly dynamic ecological development starting from clearly defined starting conditions. Directly after completion of the construction, extensive monitoring equipment was installed to track the ecosystem development and to capture the
spatiotemporal variability of meteorological, hydrological, ecological, and soil conditions and vegetation succession. In this study, we focused on the water balance dynamics of the Chicken Creek catchment for the period 2005 to 2015 as influenced by ecological development. Water storage in the catchment was calculated from a three-dimensional model of groundwater volumes, soil moisture measurements, and water level recordings of the pond. The catchment water balance equation was resolved for evapotranspiration, the only part that was not measured directly. Time series of meteorological, hydrological, and ecological data for 10 yr enabled us to characterize the transient development of the catchment and to evaluate the effect of different feedback mechanisms on catchment hydrology.
Global agricultural productivity depends on the use of finite phosphorus (P) resources of which not only the topsoil, but also subsoil, can hold immense reserves. To assess potential soil contribution to plant nutrition, we compared the P status of Stagnic Cambisol profiles in experimental plots that received different P fertilizer applications (control, triple superphosphate (TSP), compost, compost+TSP) for 16 years. Sequential fractionation was combined with P K-edge X-ray absorption near edge structure (XANES) spectroscopy to identify the chemical P speciation. Fertilized topsoils (21 to 69 kg P ha-1 a-1) showed P reserves larger by a factor of 1.2 to 1.4, and subsoil P reserves larger by a factor of 1.3 to 1.5 than those of the control. P-XANES revealed the predominance of inorganic P species such as moderately labile Fe- (46 to 92%), Al- (0 to 40%), and Ca- (0 to 15%) P compounds besides organic P (0 to 13%) in all treatments. The fertilizer application slightly altered P speciation throughout the profiles, but the type of fertilizer had no significant effect on it. Optimal plant growth requirements are restricted by the exchangeable P from the solid phase within the soil solution. Therefore, ongoing research focuses on the accessibility of P from P loaded amorphous Fe- and Al-hydroxides, previously identified as the predominant abiotic P forms. To assess their P desorption potential, P-33 rhizotron experiments combined with P-33 isotopic exchange kinetics (IEK) are underway. Preliminary results indicated that besides differences in P binding capacity of soil hydroxides, physical soil parameters, such as the matric potential, strongly control soil P availability, thus plant P acquisition rates can vary among different soil types. Our results gained new detailed information about P bioavailability under agricultural practice. The investigations towards P bioaccessibility may contribute to improved interpretation of soil P tests and reduced fertilizer recommendations.
Impact of crystallization of iron and aluminium hydroxides on the mechanisms of phosphate binding
(2017)
Für die pflanzenbauliche Bewertung von Agroforstsystemen spielen mögliche Effekte von Agroforst-Gehölzen auf die Erträge der Ackerkulturen eine entscheidende Rolle. Eine Beeinflussung der Ackerfruchterträge kann direkt (z.B. durch Beschattung) oder indirekt (z.B. durch zusätzliche Nährstoffeinträge oder eine Veränderung des Mikroklimas) erfolgen. Ziel dieser Studie war es, mögliche Einflüsse von Energieholzstreifen auf die Begleitvegetation einerseits und auf die Kohlenstoff- und Nährstoffgehalte des Bodens andererseits zu quantifizieren und ggf. mit räumlichen Ertragsdifferenzen in Beziehung zu setzen.
Derzeit lebt mehr als die Hälfte der Weltbevölkerung in Städten, Tendenz weiter steigend. Die Sicherstellung der Versorgung dieser Menschen mit Nahrungsmitteln wird künftig den Druck auf die Landwirtschaft in ländlichen Gebieten weiter erhöhen. Die Nahrungsmittelproduktion wird dabei stärker als zuvor durch das Umweltbewusstsein der Verbraucher einerseits und andererseits durch die Verminderung landwirtschaftlicher Produktionsfläche zugunsten der Stadtentwicklung beeinflusst werden (Vira et al. 2015). Die Folgen des Klimawandels (u.a. reduzierte Wasserverfügbarkeit, höheren Verdunstung, Zunahme von Witterungsextremen) werden zu Ertragsschwankungen führen (EEA 2017) und so die Landwirtschaft vor neue Herausforderungen stellen. Dies gilt vor allem für ertragsschwächere Standorte mit einem hohen Risiko für klimawandelbedingte Witterungseinflüsse. Vor diesem Hintergrund kann die agroforstliche Landnutzung, durch eine höhere Adaptionsfähigkeit gegenüber der Klimavariabilität (Kanzler et al. 2016) und der Möglichkeit zur ökologischen Aufwertung von Ackerflächen, aktiv zu einer stabilen, leistungsfähigen Landwirtschaft beitragen. Der folgende Beitrag widmet sich Untersuchungsergebnissen aus der Vegetationsperiode 2017 zum Mikroklima auf einem agroforstlich genutzten Ackerstandort in der Lausitz, Brandenburg.
Photosynthesis and respiration of biological soil crusts (BSCs) sampled along a mobile inland dune catena were determined to evaluate the applicability of Odum’s P/R ratio, determined under controlled conditions, for estimation of ecosystem maturity. The theory is that in the early stages of ecological succession, the total photosynthesis (P) exceeds the rate of community respiration (R), so that the P/R ratio is greater than 1, and that P/R approaches 1 as succession occurs. In the special case of organic pollution, the P/R ratio is typically less than 1. Samples were collected in the deflation zone of the dune near the crest (BSC1, thickness 2-3 mm), at the lee side of grass tussocks at the slope (BSC2, thickness 2-4 mm) and near the base (BSC3, thickness 4-6 mm). Non crusted sand was used as control (BSC0). Photosynthesis, respiration, crust biomass, as well as fossil and allochthonous pedogenic carbon entering the system with mineral substrate were determined. The respiration of the BSC1 was dominated by the degradation of allochthonous organic matter, leading to a diminished P/R ratio. The better developed BSC2 and BSC3 were less influenced by allochthonous organic matter, where BSC maturity increased downslope with biomass increase. No significant relation between the P/R ratio and soil water tension was found. Crust carbon pools increased and flows intensified, but mineralization constants decreased with system maturation. It was concluded that Odum’s P/R ratio and accumulation of recalcitrant to biodegradation organic matter are indicative for biocrust maturity.
Eine zunehmende Knappheit ackerbaulicher Standorte und der zugleich steigende Bedarf an nachwachsenden Rohstoffen für die energetische und stoffliche Nutzung lösen verstärkt Konflikte zwischen der Nahrungsmittelproduktion und der Biomasseproduktion aus. Marginale Standorte kommen entsprechend immer stärker in den Blickpunkt als mögliche Erweiterungsflächen für die Biomasseproduktion. In der wissenschaftlichen Auseinandersetzung fehlt allerdings eine eindeutige Definition für derartige marginale Standorte. Gerade im Hinblick auf eine mögliche Reduzierung von Nutzungskonflikten ist die Abgrenzung zu stillgelegten, aber agrarisch nutzbaren Standorten oder zu natürlichen Badlands, mit naturschutzfachlichen Potentialen oftmals schwierig. Das EU H2020-Projekt SEEMLA untersucht Potentiale und Verfügbarkeit von marginalen Standorten europaweit. In Deutschland, Griechenland und der Ukraine wurden Pilotstandorte eingerichtet, auf denen der Anbau von Bioenergiepflanzen exemplarisch durchgeführt wird. Für eine erste Bewertung der Standortspotentiale und auch der Ursachen der Marginalität der Standorte wurden Bodenuntersuchungen an allen Pilotstandorten nach den Vorgaben des Muencheberger Soil Quality Rating-Verfahrens (SQR) (1) durchgeführt und die Standorte klassifiziert. Das SQR-Verfahren bewertet ausgewählte Boden- und Standortseigenschaften und bezieht zusätzlich mögliche limitierende Faktoren (Hazard Indicators) wie Versauerung, Versalzung, Vernässung etc. mit ein, um eine Gesamtbewertungszahl zur Bodenfruchtbarkeit zu ermitteln. Dieser Beitrag stellt anhand der SEEMLA-Standorte exemplarisch Böden marginaler Standorte vor. Mit Hilfe der SQR Hazard Indicators werden charakteristische limitierende Faktoren vorgestellt. Es wird zudem versucht, die untersuchten Standorte in eine mögliche Klassifikation marginaler Standorte einzupassen und ihre Eignung für die Biomasseproduktion einzuschätzen.
The term “marginal land” refers to generally unfavourable site conditions for traditional economic agriculture or forestry. The definitions of marginality differ widely and also the scientific perspective on this type of land is very heterogeneous. However, with regard to the fast growing competition for arable lands between agricultural food production and the increasing need for growing renewable resources, such marginal lands could offer a mitigation option. Whereas agriculture is concentrating rapidly on the most fertile soils, the production of biomass as the renewable basis for various products could be shifted to sites with lower soil fertility. This in general is the main objective of the H2020 funded EU project SEEMLA (acronym for “Sustainable exploitation of biomass for bioenergy from marginal lands”). This project aims at an establishment of suitable innovative land-use strategies for a sustainable production of plant-based energy on marginal lands, while improving general ecosystem services. This approach will be tested in selected casestudy regions in Europe on marginal lands with different reasons for their marginality. One of the central tasks of this project was the characterization and classification of the investigated marginal sites according to a common definition. For that reason the Muencheberg Soil Quality Rating (SQR) system1 was adapted and applied at sites
in Germany, Greece and Ukraine. This paper gives an overview of the importance and properties of different soil parameters and ecological site conditions for this classification. Even if the occurrence of the single site limitations epends on regional conditions, some generalizations are possible. Based on the respective dominating soil related restrictions, a classification of types of marginality and of marginal lands can be derived also with regard to their land use potentials for renewable resources. Further, cultivating biomass on marginal lands may offer remediation potentials with regard to the described ecological restraints of marginal sites.
Landscapes and ecosystems are complex systems with many feedback mechanisms acting between the various abiotic and biotic components. The knowledge about these interacting processes is mainly derived from mature ecosystems. The initial development of ecosystem complexity may involve state transitions following catastrophic shifts, disturbances or transgression of thresholds. The Chicken Creek catchment was constructed in 2005 to study ecosystem development
of an initial ecosystem at the landscape scale. The world´s largest constructed catchment has a hillslope-shaped 6 ha size with defined boundary conditions and well-documented inner structures1. For 12 years, we have been monitoring the development of different system compartments2,3. The fast formation of patterns and increasing heterogeneity were challenges for the monitoring program. Starting with a regular 20 × 20 m grid in the initially homogeneous system, monitoring installations were continuously complemented by more pattern and patch oriented measurements in order to catch up with both the spatial and temporal dynamics of the catchment. The monitoring program includes both
high-resolution temporal recordings (e.g., groundwater levels, discharge, meteorological data, soil moisture), spatial sampling campaigns (e.g., soil properties) and annual vegetation surveys. In addition, we use drone images to document the site development. The presentation describes the monitoring approach and adaptation with examples from vegetation, soil and hydrological data at different spatial and temporal scales. From the monitoring data we were able to derive different phases during initial development that are characterized by abiotic/biotic feedback mechanisms controlling catchment functioning. Detailed monitoring of the Chicken Creek catchment with known boundary conditions and structure information could help in disentangling general feedback mechanisms between hydrologic, pedogenic, biological and geomorphological processes as well as in gaining a more integrative view of succession and its drivers during the transition from initial, less complex systems to more mature ecosystems. Long-term time series of data are the key for a better understanding of these processes and the effects on ecosystem self-organization and resilience.
The formation of dunes in central Europe reflects ample sediment supply during the last deglacial hemicycle. A Quaternary inland dune complex in southern Brandenburg, Germany, was studied to frame the duration of pedogenesis in two outcrops containing buried paleosols. An integrative approach, which combined geomorphological, sedimentological, pedological and chronological methods was used to identify aeolian deposition events, ensuing pedogenesis and anthropogenic remobilization. At the outcrops, which were situated approximately 2 km apart from each other, a total of twelve samples of the aeolian sands were dated using optically stimulated luminescence (OSL) and a further six samples using 14C dating. Although the dunes have similar morphological features, these forms have a different history of aeolian sand deposition and pedogenesis. At the older dune (Gl 1) the surface soil is a well developed Podzol, whereas soil development of the younger dune (Gl 2) is clearly in an initial state. The studied sites of the dune complex also differ in grain size distribution and in the presence of buried soils, thereby indicating a climatic impact on aeolian remobilization.
Plant growth can be highly dependent on symbiotic partners, such as arbuscular mycorrhizal fungi (AMF) that improve the plant's nutrient uptake. However, less is known about whether AMF can beneficially influence spatial root distribution, especially in soils with patchy nutrient concentrations. This study was conducted to evaluate root distribution and plant response of Lotus corniculatus and Calamagrostis epigeios in a heterogeneous nutrient poor soil under different mycorrhizal conditions.
Heterogeneous soil conditions of a reclamation site in the Lusation mining district, consisting of a nutrient poor sandy soil with embedded large silt-clay fragments, were used for this rhizotron experiment. Treatments were non-mycorrhizal and mycorrhizal L. corniculatus and C. epigeios in sterile soil and in sterile soil with a fungal free soil solution and mycorrhizal plants in a non-sterile soil. Mycorrhizal fungi were exogenous (Funneliformis mosseae and Rhizophagus irregularis) in sterile soil and indigenous mycorrhizal fungi in non-sterile soil. Plants were grown in rhizotrons, with clay-silt fragments in a sandy soil matrix. Treatment response variables were root density, root and shoot biomass, shoot tissue nutrient concentrations, and percentage of roots in clay-silt fragments relative to total root biomass, mycorrhizal colonization and intraradical fungal alkaline phosphatase (ALP) activity.
Exogenous mycorrhizal L. corniculatus plants had higher root mass density in clay-silt fragments than indigenous mycorrhizal and non-mycorrhizal plants while C. epigeios had only higher root mass density in clay-silt fragments relative to sandy soil only in exogenous mycorrhizal plants in sterile soil with soil solution. Nonmycorrhizal C. epigeios shoot biomass in sterile soil did not significantly differ from that of exogenous mycorrhizal treatments. The greatest shoot biomass for both plant species, was with the highest percentage of roots in clay-silt fragments relative to the total root system. Exogenous mycorrhizal plants of both species had highest shoot phosphorus concentrations in sterile soil with soil solution. However, intraradical fungal ALP activity was highest in indigenous mycorrhizal plants. The results indicate that mycorrhizal conditions can have a strong influence on spatial root development. The consequences are that conditions, which promote root growth, lead to more roots in nutrient rich clay-silt fragments and thus enhance plant exploitation of heterogeneously distributed soil nutrients.
Various ecological functions of biocrusts are mostly determined by their bacterial and fungal abundance and community diversity, which has not yet been fully investigated. To provide more insights into this issue, we collected samples of moss biocrusts, fixed sand, and mobile sand from a watershed with semi-arid climate on the Loess Plateau of China. The relative abundances and community diversities of soil bacteria and fungi of the samples were determined using high-throughput DNA sequencing. Finally, we analyzed the characteristics of bacterial and fungal community of the moss biocrusts and their relationships to the content of soil nutrients. Our results showed that the moss biocrusts had 1048 bacterial OTUs (operational taxonomic units) and 58 fungal OTUs, and their Shannon diversity indexes were 5.56 and 1.65, respectively. The bacterial community of the moss biocrusts was dominated by Acidobacteria (24.3%), Proteobacteria (23.8%), Chloroflexi (15.8%), and Actinobacteria (14.5%), and their fungal community was dominated by Ascomycota (68.0%) and Basidiomycota (23.8%). The moss biocrusts had far more bacterial OTUs (≥56.9%) but similar number of fungal OTUs as compared with the uncrusted soil, and their Sorenson’s similarity coefficients of bacterial and fungal communities were less than 0.768 and 0.596, respectively. Moreover, the contents of soil nutrients (C, N, P) were significantly correlated with the OTU numbers of bacteria and the relative abundances of bacteria and fungi. Our results indicated that moss biocrusts harbor a large number and high diversity of bacteria and fungi, and these diversified bacteria and fungi play important roles in ecosystem functioning through improving soil fertility.
On many post mining sites in the Lusatian Mining District (East Germany) soil heterogeneity consists of sandy soil with embedded clay-silt fragments. Those clays silt fragments might act as nutrient hotspots. Arbuscular mycorrhizal fungi in an infertile ecosystem could enhance a plant’s ability to selectively forage for those nutrients and thus to improve plants nutrient supply. In our study we investigated whether silt-clay fragments within a sandy soil matrix induced preferential root growth of Lotus corniculatus and Calamagrostis epigeios, whether arbuscular mycorrhizae influenced root foraging patterns, and to what extent selective rooting in clay silt fragments influenced plant growth were addressed in this research. Soil types were sterile and non-sterile sandy soil and clay-silt fragments. Treatments were with and without arbuscular mycorrhizae, with and without soil solution, and soil solution and mycorrhizal inoculum combined. Root biomass, root density and intraradical fungal alkaline phosphatase activity and frequency were determined in fragments relative to sandy soil. Furthermore, temporal relationship of number of roots in fragments and plant height was assessed. Lotus corniculatus showed strong selective rooting into fragments especially with those plants treated with commercial cultivated arbuscular mycorrhizae; Calamagrostis epigeios did not. Without arbuscular mycorrhizae, L. corniculatus growth was significantly reduced and selective rooting did not occur. Selective rooting induced significant growth spurts of L. corniculatus. Roots in fragments had higher fungal alkaline phosphatase activity suggesting that mycorrhizal efficiency and related plants phosphorus supply is enhanced in roots in fragments. The application of cultivated arbuscular mycorrhizal fungi significantly and quickly influenced root foraging patterns, especially those of L. corniculatus, suggesting mycorrhizae may also enhance the ability of other plants to selectively forage for nutrients and could therefore play an important role in early plant establishment on infertile reclamation sites.
The profitability of reclaiming post-mining areas depends on the tree biomass productivity and the restoration of ecosystem functions, such as improving soil and water quality. Agroforestry systems, regarded as combined land-use systems of trees and crops, have the ability to facilitate soil development while reducing wind speed, soil erosion and evaporation. Achieving the maximum biomass productivity of the tree stands depends on the corresponding soil conditions and water availability, but is also influenced by stand structure and the competition between individual trees. For this purpose, black locust (Robinia pseudoacacia L.) trees were planted in a Nelder design in 2010, on a reclaimed post-mining site of the open-cast lignite mining in Welzow Süd (Brandenburg, Germany). Black locust is regarded as a drought-adapted tree species and commonly used for the reclamation of former lignite mining sites in Lower Lusatia, Germany. The Nelder design encompasses angles of arc of equal measure and with the same origin traversed by successive circumferences set at a predefined radial distance. Accordingly, a total of 1071 trees were planted in Welzow Süd at the intersection between 63 spokes and 17 circumferences and at densities ranging from 0.4 to 8.0 m2, with the aim of examining the influence of stand density on the tree growth in a timeframe of six years. In order to evaluate the biomass production of the trees and to determine an optimal planting density on a marginal land, various scenarios were assessed with the help of the Yield-SAFE model, a parameter-sparse process-based agroforestry model. The study revealed the consequences of choosing different tree densities on the tree biomass productivity and water use of trees in relation to the competition for light and water.
The Chicken Creek catchment was constructed in 2005 to study ecosystem development of an initial ecosystem at the landscape scale. The site has an area of 6 ha with defined boundary conditions and known inner structures. Since more than 10 years, we are monitoring the unrestricted development of different system compartments. The fast development, the formation of patterns and increasing heterogeneity were challenges for the monitoring program. Starting with a regular 20 x 20 m grid in the initially homogeneous system, monitoring installations were continuously complemented by more pattern and patch oriented measurements in order to catch up with both the spatial and temporal dynamics of the catchment. The monitoring program includes both high-resolution temporal recordings (e.g. groundwater levels, discharge, meteorological data, soil moisture), spatial sampling campaigns (e.g. soil properties) and annual vegetation
surveys. In addition, we use drone images to document the site development. The presentation describes the monitoring approach and adaptation with examples from vegetation, soil and hydrological data at different spatial and temporal scales.
Marginal lands are often considered as unfertile and not productive. They are widely excluded from modern land use by conventional agriculture. Assessment of soil fertility usually shows very low productivity potentials at least for growing traditional crops. However, it can be frequently observed that natural succession at different types of marginal lands leads to very diverse and nonetheless productive ecosystems. Examples can be found at abandoned former industrial or transportation sites which were set aside and not further maintained – and also in post-mining landscapes. In one of the lignite open cast mines of the State of Brandenburg in Eastern Germany a landscape observatory was
established in 2005 for observing this natural ecosystem development under marginal site conditions. The site of 6 ha is part of the post-mining landscapes of Lusatia which are often characterized by poor soil conditions and clearly reduced soil fertility. It is named “Hühnerwasser-Quellgebiet” (Chicken Creek Catchment) after a small stream that is restored again after destruction by the mining operations. It is planned to serve as the headwater of this stream and was left to an unrestricted primary succession. A comprehensive scientific monitoring program is carried out since the start of ecosystem development in 2005. The results offer exemplary insights into the establishment of interaction networks between the developing ecosystem compartments. After 10 years a large biodiversity, expressed by a high number of species, can be found at this site as the result of natural recovery processes. A large number of both tree species and individuals have settled here. Even if no economic use of the site and of the woody biomass produced by these trees is planned, an overall assessment of the biomass production was carried out. The results showed that the biomass production from natural succession without any application of fertilizers etc. is directly comparable with yields from adjacent post-mining sites where trees are grown in agroforestry systems for bioenergy production. This reflects the general potentials of marginal lands with regard to biomass production.
Land degradation is recognized as the main environmental problem that adversely depletes soil organic carbon (SOC) and nitrogen (SON) stocks, which in turn directly affects the fertility and productivity of soils. Degraded soils and marginal lands are characterized by low fertility, poor physicochemical and biological properties and are almost free of soil organic matter (SOM), limiting their functional properties and, hence, their productivity. To enhance or restore the fertility of these soils, natural soil amendments such as biochar, lignite or humic acids can be added. A greenhouse experiment was carried out to investigate the effect of different application rates (5, 7.5, 11, 15, 28 t ha-1) of N-modified lignite (NL) incorporated in a nutrient-poor sandy soil from a recultivation site on plant growth, water use and nitrogen use efficiency of summer wheat. Additionally activated biochar (BC) was tested to see whether any differences exist between N-modified lignite and activated biochar at the same Capplication rates. All variants with soil amendments displayed a much higher grain and straw yield and water use efficiency compared to the control sample. The differences were significant for the 28 t ha-1variant followed by the variant with 5 t ha-1 NL. With the 7.5 t ha-1 NL higher biomasses, water and nitrogen use efficiency could be achieved compared to the variant treated with BC at the same C-content. This study shows that even small amounts of N-modified lignite can increase growth, water and nitrogen use efficiency of summer wheat on marginal lands.
One of the main issues that the forest sector is facing is to achieve a balance between the demand for biomass &wood production and the need to preserve the sustainability and biodiversity of forest ecosystems. The purposes of the new approaches are to ensure more efficient management of ecosystems and implement intensive forestry that will increase biomass production & timber yields. To achieve this, we need to determine the macroeconomic potential of the various options available, including the use of biotechnology and genetics. The success of the forests plantations capacity may be solved through forest certification, based on: a) Stabilization of the forests and soils structure. b) Hierarchy of biomass production in the forest’s management process. c) rganization and implementation of effective plantation on marginal lands. d) Maintenance or increase of forest productivity by introducing new items as and when they are required. It is important to evaluate of the influence of factors such as the quality of soils of plantation areas, the utilization of the genetic resources and the management of forest operations with the environmental economic criteria such as net present value of benefits (NPV) and the corresponding flow annuities (EACF).The existing evaluations studies showed that the quality of the plantation areas has the most influence and through validated quality seed production can generate an increase in the NPV up to 73%. The importance of seedlings quality in timber and bio-energy production on marginal lands based on the literature it is estimated according to the heredity of the characteristics of the wood structure (except shrinkage). This clearly indicate that seedlings with the appropriate morphological characteristics can significantly improve the growth performance and help to support the development of biomass plantations oriented in tailor-made timber and bio-energy production.
In 2016, D.A.M.T, the Hellenic Forest Service for northern Greece (Macedonia and Thrace Regions), with the support of BTU Cottbus-Senftenberg Reseach Center Landscape Development and Mining Landscapes experts and following common standard protocols of the SEEMLA project, established three plots, in the northeastern part of Greece, in Rodopi prefecture (main forest species for biomass production: Pinus Nigra, Pinus Brutia and Robinia Pseudacacia). Nearby productive ecosystems (including forests etc.) or successional sites will be used as references for estimating the potentials of MagL. Further existing plantations of energy crops on similar MagL, will be used to assess potential crop yields. These plots represent different types of marginal lands, they were specifically selected for SEEMLA purposes (reliable and sustainable exploitation of biomass) and are entirely different from other inventories, used for typical
forest operations in Greece. The main differences are:
- an intensively studied core area,
- Soil Quality Rating (SQR) method measurements,
- Soil Classification Maps - parameters estimation (land capability classes and landforms),
- tightly spaced plantations (1,5 m x 1,5 m),
- cropping systems,
- shorter rotations and
- the need for special forest management study.
The combination of these requirements with the soil conditions of the area has created significant issues on plots establishment and accurate recording of supply chain stages. Main expected SEEMLA impacts are:
• provide a substantial amount of EU energy needs from marginal/degraded land,
• avoidance of land use conflicts by strengthening the ability to use MagL for biomass production for energy,
• reduction of EU-wide greenhouse gas,
• mitigation of conflicts regarding sustainability and biodiversity for the utilization of MagL for biomass production,
• growth of plantations of bioenergy carriers from MagL at competitive costs,
• expansion of economic opportunities for farmers, foresters and rural regions in general through biomass production on MagL and related processing activities,
• investments in new technologies and the design of new policy measures.
Due to the unfavourable chemical and physical soil quality parameters and the potential presence of contaminants, former industrial sites can hardly be utilized as arable land and can thus be classified as marginal areas. Still, as far as possible, they can effectively be used for the production of alternative energy, including the cultivation of fast growing trees. Apart from being a source of bioenergy, trees might facilitate the stabilization, remedation, contaminant extraction and degradation and, not on the last place, to enhance soil quality improvement on former industrial areas. This process is known as phytoremediation and has successfully been applied on industrial sites of various organic and inorganic contamination. The former manufactured gas plant site (2500 m2) “ehemalige Leuchtgasanstalt” Cottbus, contaminated, among others, with iron cyanides undergoes phytoremediation with simultaneous biomass production since 2011. The project “Biomass-Remediation” is fully financed by the German Railways JSC. A dense (23700 stems/ha), mixed cover of willow (Salix caprea), poplar (Populus maximowicii Henry x Populus trichocarpa Torr. et Gray (Hybrid 275)) and black locust (Robinia pseudoaccacia) trees has been planted on the site. Throughout the five years of remediation, a successful long-term stabilization of the site has been achieved as a result of the nearly outright established tree stock and the dense planting. Annual monitoring of the cyanide levels in the leaf tissue of the trees on the site and results from greenhouse experiments indicate the ability of all tree species to extract and transport the cyanide from the soil. Additonally, the greenhouse experiments suggest that the willows might be able, although not to a full extent, to detoxify the contaminant by splitting the CN moiety. The contaminated biomass material might easily be dealt with through regular harvests and subsequent incineration. Phytoremediation with simultaneous biomass production for bioenergy offers an environmenatlly-friendly and a cost-effective solution of the problem with contaminated former industrial areas in the context of marginal land use options.
An ever growing demand for energy and the widely proposed switch from fossil fuels to more sustainable energy sources puts the cultivation and use of bioenergy plants into focus. However, bioenergy production on regular and fertile agricultural soils might conflict with the worldwide growing demand for food. To mitigate or omit this potential conflict, the use of low quality or marginal land for cultivation of bioenergy plants becomes favorable. Against this background the definition and assessment of land marginality and, respectively, the evaluation whether and to which extent specific areas are marginal and thus convenient for sustainable bioenergy production, becomes highly relevant. Within the framework of the EU funded Horizon 2020 project SEEMLA, we attempted to asses land marginality of designated test sites in the Ukraine, Greece and Germany by direct field survey. For that purpose, soil and site properties were investigated and evaluated by applying the Muencheberg Soil Quality Rating (SQR) method, developed at the Leibniz Centre for Agricultural Landscape Research (ZALF). The method deploys a comprehensive set of biogeophysical and chemical indicators to describe and finally evaluate the quality of the soil and site by a score ranging from 1 to 100 points. Field survey data were supported by additional laboratory tests on a representative set of soil samples. Practical field work and analysis of field and lab data from the investigated sites proved the applicability of the SQR method within the SEEMLA context. The SQR indices calculated from the field and lab data ranged from 2 to < 40 and clearly demonstrated the marginality of the investigated sites in the Ukraine, Greece and Germany, which differed considerably in respect to their characteristics. Correlating the site quality index to yield data reflecting yield estimations for common bioenergy plants such as willow (Salix sp.), black locust (Robinia pseudoacacia) and poplar (Populus sp.) cultivated at the respective test sites, revealed that SQR might additionally reflect the potential yield of the investigated sites.
Soils of marginal lands are characterized by a variety of different soil conditions depending on substrate properties, climate influences, the availability or even the excess of water. However, a number of soil properties can be found frequently at marginal sites which can be regarded as main restrictions of marginal lands and which clearly limit the potential of such sites with regard to land use potentials. The Muencheberg Soil Quality Rating Index (SQR) considers the most important soil related factors responsible for these restrictions. Examples are acidification processes, soil compaction and water saturation or salinization. These soil properties are assessed as “soil hazard indicators” and have crucial impact on the overall soil score provided by the SQR concept for soils of marginal sites. This paper gives an overview of the importance of different soil hazard indicators found at case study sites of the H2020 project SEEMLA. These sites are located in Greece, Ukraine and Germany and represent a large variety of different climatic and geological conditions within Europe. Even if the occurrence of the single site limitations depends on regional conditions some generalizations are possible. Based on the respective dominating soil related restrictions a classification of types of marginality and of marginal lands can be derived.
Extremes in soil water, temperature, pH and inorganic nutrient availability can highly influence mycorrhizal formation and nutrient acquisition. However, the influence of soil heterogeneity and seasonal soil changes on fungal alkaline phosphatase (ALP) activity in mycorrhizal roots is unknown. Whether the activity of intraradical fungal ALP is influenced by soil texture heterogeneity, soil depth, nutrient concentrations and root density during the growing season were addressed in this research. The root system of Lotus corniculatus grown on a reclamation site was analyzed for intraradical mycorrhizal ALP activity in 0–10, 10–20 and 20–30 cm depth increments of sandy soil and in clay–silt fragments (mostly localized in 10–20 cm) from May to September. Root length density and water soluble nutrient contents in sandy soil and clay–silt fragments were determined for each sample. Soil water content and soil temperature data of a nearby site were used for climate conditions on sampling dates. Fungal ALP activity in roots growing in clay–silt fragments was higher than in those growing in sandy soil, independent of sampling date. Fungal ALP activity in sandy soil increased with soil depth which is related to decreasing root densities and lower nutrient concentrations. However, nutrient dense clay–silt fragments significantly positively influenced local mycorrhizal ALP activity in L. corniculatus roots, suggesting that the ability of mycorrhizae to selectively take up phosphorus and other nutrients from those nutrient hot spots is enhanced and could play a significant role in successful establishment of pioneer plant species on infertile reclamation sites.
In a five-year old alley cropping system in Brandenburg, Germany, the extension of the root system of black locust (Robinia pseudoacacia L.) trees into the neighbouring agricultural field alleys was investigated. Along transects between the hedgerows and the middle of the neighbouring field alleys, samples were collected at distances of 1.30, 4.3 and 49.3 m to the hedgerow border and for the soil depths 0-15, 15-30, 30-45 and 45-60 cm by using an auger with a diameter of 8 cm. Roots were separated from the soil by means of washing and sieving. The root samples were then sorted and analysed for root length densities and dry masses. The results indicate a logarithmic decrease of root length densities and root masses of black locust with increasing distance to the trees, although, the number of positive samples was too small to conduct a substantiated statistical analysis. In result, the authors assume that the tree roots did not extend into the agricultural alley for the considered soil depths substantially, but, nevertheless, suggest a modified sampling method or/and the investigation of older tree stands for future studies.
Depth gradient of soil C, N and S contents in an alley cropping system for biomass production
(2017)
In a six-year-old alley cropping system with fast growing trees for biomass production (ACS), the depth distribution of soil contents of carbon (C), nitrogen (N) and sulphur (S) under the trees (poplar) and under the neighbouring agricultural field was investigated. The measured soil contents were usual for agricultural sites and showed a significant decrease with increasing soil depth under the trees. These results might indicate that the introduction of trees into agricultural areas leads to an alteration of the soil distribution pattern of C, N, S from a pattern typical for agricultural soils (more or less constant values at least within the ploughing horizon from 0-30 cm) to a pattern more typical for forest ecosystems (comparatively higher values in the topsoil, lower values in the deeper soil). However, for more reliable results measurements should be repeated and preferably older stands should be investigated.
Mit der Zunahme von extremen Witterungsereignissen ist die Auswahl von angepassten Baumarten und Klonen von großer Bedeutung für den Agrarholzanbau in der Lausitz. So zählte der Sommer 2015 zu den drittwärmsten Sommern in Deutschland mit langanhaltenden Trockenzeiten und Hitzeperioden auch in Brandenburg. Die ökophysiologischen Reaktionen von Robinien und Hybrid-Pappeln (Klon Max 1) auf Hitze- und Trockenstress wurden in einem Agroforstsystem bei Neu Sacro, Brandenburg untersucht. Die ökophysiologische Anpassungsfähigkeit wurde hinsichtlich der Photosyntheseleistung (Chlorophyllfluoreszenz), dem Wasserpotential, der 13C/12C Diskriminierung und dem Blatt-N-Gehalt untersucht. Gut wasserversorgte Bäume der beiden Arten zeigten keine wesentlichen Einschränkungen in Bezug auf die Photosyntheseleistung und dem Nährstoffhaushalt, da am Standort ein Grundwasseranschluss auch während der Trockenheit gewährleistet war. Bedingt durch kleinräumige Bodenheterogenitäten kann es allerdings auch örtlich zu Wassermangel kommen. An diesen Standorten zeigten die Pappeln deutliche morphologische und ökophysiologische Anzeichen von Trockenstress. Bei der sommerlichen Hitze zeigte die Photosynthese der beiden Baumarten eine hohe Plastizität.
Der folgende Beitrag widmet sich der Frage, inwieweit sich mikroklimatische Änderungen in einem Agroforstsystem (AFS) bedingt durch die Gehölzkomponente kleinräumig auf die gemessene Evaporation sowie auf die Produktivität von Winterweizen (Triticum aestivum) auswirken. Hierfür wurden im Zeitraum von März bis August 2016 Untersuchungen auf einem ca. 40 ha großen Agroforstschlag und einer angrenzenden, konventionell bewirtschafteten Freifläche bei Neu Sacro (Landkreis Spree-Neiße, Brandenburg) durchgeführt. Neben mikroklimatischen Kenngrößen wie der Lufttemperatur, der relativen Luftfeuchte, der Windgeschwindigkeit und der Globalstrahlung wurde auch die Evaporation nach Piche bestimmt. Ergänzend wurden Ertragsmessungen zum Kornertrag und Messungen zum Blattflächenindex (LAI) des angebauten Winterweizens durchgeführt. Neben Änderungen der Tagesminima der relativen Luftfeuchtigkeit im Nahbereich der Gehölzstreifen wurde eine Reduktion der durchschnittlichen Windgeschwindigkeit von bis zu 51 % gegenüber der Freifläche festgestellt. Die Minderung der Evaporation im Vergleich zur Freifläche betrug je nach Witterung bzw. Nähe zum Gehölzstreifen bis zu 58 % und wurde dabei maßgeblich durch die Windgeschwindigkeit beeinflusst. Räumliche Unterschiede ergaben sich auch bezüglich des Kornertrags sowie beim LAI. So fielen die Kornerträge im Agroforstsystem mit bis zu 9,2 t ha-1 gegenüber ca. 7,0 t ha-1 für die Referenzfläche überwiegend höher aus. Mit Ausnahme des Leebereichs in 3 m Entfernung zum Gehölzstreifen lagen auch die LAI-Werte des AFS über jenen der angrenzenden Freifläche. Diese ersten Ergebnisse deuten darauf hin, dass in AFS durch Gehölzstrukturen neben der Windgeschwindigkeit auch die Wasserverdunstung im Bereich der angrenzenden Ackerkulturen gemindert werden kann. Die mikroklimatischen Unterschiede wirkten sich dabei potentiell auch positiv auf das Wachstumsverhalten bzw. den Ertrag des Winterweizens aus. Vor dem Hintergrund einer Verringerung der potentiellen Evaporation und einer hieraus resultierenden höheren Wasserverfügbarkeit für die Ackerkulturen könnte die agroforstliche Landnutzung zukünftig auch für trockenheitsgefährdete Gebiete Mitteleuropas eine vorteilhafte Anpassungsstrategie des Ackerbaus an den Klimawandel darstellen.
Dieser Beitrag befasst sich mit dem Einfluss von Baumstreifen auf die Ackerfrucht Zuckerrübe (Beta vulgaris) innerhalb eines Agroforstsystems mit im Kurzumtrieb bewirtschafteten Gehölzstreifen (Alley-Cropping-System). Ziel der Untersuchungen war es, positiv und negativ wirkende Interaktionen zwischen Baumstreifen und Ackerfruchtflächen abzuwägen und so Erkenntnisse für die Optimierung künftiger, vergleichbarer Systeme zu erhalten. Betrachtet wurden vor allem Ertragsparameter der Zuckerrüben wie Rübengewicht, Blattmasse und Zuckergehalt. Außerdem wurde der Einfluss von Trockenstress auf die Faktoren Saccharosegehalt und Wüchsigkeit untersucht. Hierzu wurden festgelegte Ackerbereiche in verschiedenen Abständen zu den Gehölzstreifen sowie auf einer Referenzfläche beprobt und das Erntegut feldfrisch gewogen. Des Weiteren wurden zu Vermessungszwecken und zur Trockengewichtsbestimmung Teilproben aus den geernteten Zuckerrüben entnommen. Für die Bestimmung des Zuckergehalts wurden zusätzlich ganze Rüben beprobt. Die Ergebnisse zeigten deutliche Ertragseinbußen der Zuckerrüben in direkter Nähe zum Gehölzstreifen. Allerdings konnten Ertragssteigerungen im Lee-Bereich der Gehölzstreifen sowie bei mittleren Abständen zu den Gehölzstreifen nachgewiesen werden. Der Zuckergehalt der Rüben erwies sich unter Trockenstress von der Ertragsmenge bzw. vom Gewicht der einzelnen Rübe unbeeinflusst. Insgesamt zeigte die Agroforstfläche signifikant höhere Erträge als die Referenzfläche.
Damit Landwirte Agroforstsysteme verstärkt umsetzen, müssen Agroforstflächen mindestens genauso förderberechtigt sein wie konventionelle Ackerfruchtflächen. Bislang finden Agroforstsysteme im deutschen Agrarförderrecht jedoch keine Berücksichtigung. Da die Agroforstwirtschaft eine sehr komplexe Form der Landnutzung ist, muss eindeutig dargelegt werden, unter welchen Bedingungen es sich um Agroforstflächen handelt und wann nicht. Hierfür ist eine Definition von Agroforstschlägen erforderlich, die den Agrarbehörden eine Kontrollfähigkeit ermöglicht. Eine solche Definition, die Gehölzkulturen und Ackerkulturen auf einem Schlag vereint, ist bislang nicht mit dem deutschen Agrarförderrecht vereinbar. Dennoch erscheint es sinnvoll und notwendig, dass sich in den Agrarbehörden, vor dem Hintergrund einer verstärkt geforderten Multifunktionalität in der Landwirtschaft, mehr und mehr von sektoralen Denkmustern verabschiedet und neuen integrativen Landbausystemen zugewandt wird. Hierzu könnte die agrarförderrechtliche Implementierung von Agroforstsystemen einen wertvollen Beitrag liefern. Der folgende Aufsatz zeigt mit dem Vorschlag für eine Agroforstschlag-Definition einen konkreten Lösungsansatz für den behördlichen Umgang mit dieser Bewirtschaftungsform auf.
Der Lehrstuhl Bodenschutz und Rekultivierung der Brandenburgischen Technischen Universität Cottbus-Senftenberg (BTU CS) ist Projektpartner in dem von der Europäischen Union im Rahmen des Programms Horizon 2020 geförderten Forschungsprojekts SEEMLA → „Sustainable exploitation of biomass for bioenergy from marginal lands in Europe“ → „Nachhaltige Nutzung von Biomasse für Bioenergie von marginalen Standorten in Europa“. Übergeordnetes Ziel des Projektes ist die Ermittlung des Biomassepotenzials, das auf marginalen Standorten innerhalb von Europa nachhaltig produziert und energetisch verwertet werden kann. Die BTU CS hat in diesem Kontext Untersuchungen zur Bewertung der Marginalität von potenziellen Biomasse-Produktionsstandorten in Deutschland, Griechenland und der Ukraine durchgeführt. Zu diesem Zweck wurde das Müncheberger Soil-Quality-Rating System (SQR) (Müller et al. 2007) eingesetzt.
Der parallele Anbau von Ackerfrüchten und Agrarholz in Agroforstsystemen führt zu einer ökologischen Aufwertung der landwirtschaftlichen Nutzfläche und hat auch positive Auswirkungen auf das Mikroklima zwischen den Gehölzstreifen. Bei streifenförmigen Agroforstsystemen (Alley Cropping) in Brandenburg konnte eine deutliche Reduktion der Windgeschwindigkeit und von Temperaturextremen sowie ein Anstieg der relativen Luftfeuchtigkeit beobachtet werden (Böhm et al. 2014,
Kanzler et al. 2015). Eine Reduzierung der Windgeschwindigkeit führt zudem zu einer Minderung der potentiellen Evaporation. Dabei stellt sich die Frage, wie sich diese Veränderungen kleinräumig auf die gemessene Evaporation und auf die Produktivität der Ackerkulturen auswirken.
Multifunctional land use systems, such as agroforestry, are able to deliver several ecological services to agriculture in addition to the concurrent production of woody biomass and arable crops. For example, trees in agroforestry systems can provide shelter for wildlife and supply additional nutrients to adjacent arable fields through leaf litter inputs and fine root turnover. In addition, tree-strips have the ability to improve the groundwater quality underneath the tree-strip itself and possibly underneath adjacent fields. Unlike these commonly measured ecosystem services the microclimate conditions in temperate agroforestry systems are still a comparatively new study area (Kanzler et al. 2015, Böhm et al. 2014). This might be due to the complexity of the microclimate, which depends on various parameters such as the plant height, the planting density, and the orientation of the tree-strips. The objective of this study was to investigate the potential influence of tree-strips on microclimate using high resolution data loggers.
Agroforestry systems are receiving increasing attention in the temperate region due to their ability to counteract negative consequences of intensively managed agricultural fields. Examples of traditional agroforestry (AF) in central Europe are orchard meadows "Streuosbt", hedgerows "Knicks" and windbreaks. Traditional AF systems are considered to be areas of high natural and cultural value (HNCV), and as such have been recognized to support high biodiversity levels. Recently, modern AF systems which are well adapted to the current farming practices and are compatible with mechanized agriculture have emerged. Modern practices such as alley cropping system for woody biomass production (ACS), composed of strips of fast growing trees and agricultural crops grown in alleys between the tree rows, can supply market goods and environmental services at the same time (Gruenewald et al. 2007, Quinkenstein et al. 2009). However, farmers in Germany have been reluctant to implement the latter systems, because agricultural policies have limited the number of trees within agricultural systems, while the former have been in danger of abandonment throughout Europe. As a result many farmers have lost interest in AF, and those that inherited land with traditional AF systems may not recognize them as such, because they are not recognized as AF according to the EU policy. The aim of this work was to investigate familiarity with agroforestry in Germany.
Agroforestry for arable farmers is not a common practice in Germany. However, alley cropping for woody biomass production is of interest because of its high potential to concurrently provide a biomass feedstock and an arable crop. One of the systems that exists, although at an experimental level, is the integration of rows of fast growing trees, such as poplar or willow, with arable crops.
The experimental plots were initially established as part of the German joint research project “AgroForstEnergie - Economic and Ecological Evaluation of Agroforestry Systems in Farming Practice“, funded by the German Federal Ministry of Food and Agriculture (AgroForstEnergie 2015). The goal of this project was to study alley cropping systems, which concurrently produce a woody biomass feedstock and conventional agricultural crops. Currently the work is continued through the AGFORWARD Project.
The State of Brandenburg is known for its light sandy soils that are prone to wind erosion. The introduction of tree hedgerows within the agricultural landscape can reduce wind erosion (Böhm et al. 2014). In addition, microclimatic conditions such as soil moisture, wind speed reduction, relative humidity and air temperature have been more favourable for plant growth in crop alleys compared to reference crop areas (Böhm et al. 2014; Quinkenstein et al. 2009).
Sugar beets are a common crop for conventional agricultural systems in Western Europe. As part of agroforestry systems, sugar beets have rarely been studied. Even though sugar beets can root up to a depth of 2 meter, their yields can be significantly reduced due to a lack of water (Hoffmann 2010; Bloch et al. 2006). Agroforestry systems that consist of tree hedgerows and crop alleys, also known as Alley Cropping Systems, have the potential to increase plant moisture in comparison to conventional agricultural systems (Quinkenstein et al. 2009).
This study aims to assess tree hedgerow effects on sugar beets. The objectives of this study were to; 1) assess how tree hedgerows planted at three distances affected sugar beet yields; 2) to correlate soil moisture values of the top 15 cm with sugar beet yields at the same distance of the tree row; 3) to assess the effects of drought stress on sugar beet yield.
Agroforestry (the integration of trees with crop and/or livestock production) offers a pathway to diversify agricultural production. Agroforestry systems have the potential to improve on-farm use of water through enhanced soil water holding capacities, the provision of shade, and the creation of wind shelter. These three characteristics can also improve the resilience of agricultural production in response to changing weather patterns. The objectives of this study were: 1) to measure how alley cropping systems with varying alley widths affect crop microclimate, 2) to measure the effects of this microclimate on sugar beet (Beta vulgaris) yields, and 3) to assess how moisture availability affects sugar beet growth patterns. Measurements were made in a 70 ha alley cropping system comprising black locust (Robinia pseudoacacia L.) and hybrid poplar Max1 (Populus suaveolens subsp. maximowiczii x P. nigra). A sugar beet crop was grown during the relatively dry growing season of 2015. Sugar beet yields were reduced in close proximity to the hedgerow, but yields were higher at and beyond an intermediate distance when compared with those in a nearby conventional agricultural field. Moisture availability significantly affected growth patterns of sugar beet roots.
Agroforstliche Landnutzung als Maßnahme zur Verbesserung des Gewässerschutzes in der Agrarlandschaft
(2016)
Degradation of soils and the destruction of vegetation as a result of anthropogenic disturbances affect ecosystem functions and properties worldwide. In Brandenburg (NE Germany) various ecosystems were degraded by different human activities like surface mining and military activities on sand dunes. These resulted in degraded open landscapes with an initial soil development. These new ecosystems are characterized by a high vulnerability to erosion, low water holding capacity, lack of nutrients, or low pH. For rehabilitation of degraded soils and vegetation, these post-mining and mobile sand dunes need specific restoration measures, but beside inappropriate soil characteristics, insufficient water availability can limit plant growth. Even located in the temperate zone of Europe, Brandenburg belongs to the driest regions in Germany and faces long drought periods. In this context, the determination of the influence of biocrusts on carbon accumulation during initial ecosystem succession, small-scale investigations on photosynthetic capacity and active phase regarding biocrust formation and developmental stage, which vary from initial green algae-crusts to biocrusts dominated by soil lichens or mosses, are necessary. Hence, succession of biocrusts result in a spatiotemporal heterogeneity and distribution pattern. We could show that varying species abundance, composition, and crust succession affect photosynthetic capacity, and hence, carbon fixation capability. Different spatial hotspots could be analyzed under field conditions and monitored during the season. Long-term measurements of climatic parameters, which include radiation, temperature, precipitation, and desiccation of biocrusts, will be linked to photosynthetic performances under lab conditions. This spatial model can help to understand the impact of biocrusts on carbon accumulation in initial soils. Due to the potential to colonize soil surface under harsh conditions without human support, advantages of biocrusts can be used systematically as a supporting rehabilitation measure for physical stabilization, gain of organic carbon, and hence, facilitates the growth of indigenous vegetation during primary succession.
Inorganic phosphorus (P) plays an important role as plant nutrient in fertilizers, but also as a major pollutant to aquatic ecosystems by leaching from arable land. The mobility and bioavailability of P depends on adsorption, desorption and precipitation processes at soil mineral surfaces. In the soil matrix, P can be found in the forms of iron, aluminum or calcium complexes, adsorbed on mineral surfaces. P reactions in soil, especially the fixation on iron and aluminum (hydr) oxides, have been thoroughly studied. But the much slower process of P release has to be attended as well regarding the prospective supply of fertilizers and the use of plant available P pools in arable soils. The P adsorption ability of pedogenic oxides depends on their crystallinity, while soils contain both crystalline minerals such as goethite or ferrihydrite, as well as amorphous iron and aluminum compounds. In this study, long-term adsorption and desorption experiments were carried out to investigate the P binding mechanism during the sorption processes at certain time steps. For adsorption experiments, various experimental conditions such as pH, P ionic strength, competitive ions such as SO4 2- and Ca2+ as well as time will be considered. For desorption experiments, a Flow-Through-Reactor-Technique will be applied to investigate desorption kinetics and processes under nearly natural conditions without disturbance of the mineral-solution interface. Additionally, the release of P from the iron and calcium phosphates vivianite and hydroxyapatite, a main supplier of inorganic P and model substance for bone char, will be investigated. By using Fourier-Transformation-Infrared-Spectroscopy, changes of P binding mechanisms during ad- and desorption processes and easily as well heavily purgeable P can be detected. Aim is to identify fundamental processes of P fixation and mobilization as well as to specify similarities and differences of P binding on crystalline and amorphous reactive surfaces of pedogenic oxides.
Mining activities can strongly affect ecosystem properties by destruction of naturally developed soils and removal of vegetation. The unstructured substrates show high bulk densities, compaction, low water infiltration rates, reduced water holding capacities and higher susceptibility to wind and water erosion. In the initial stage of the ecosystem development, the post-mining sites are open areas without or with a low cover of higher vegetation. It is well-known that biocrusts are able to colonize the soil surface under such extreme conditions without human support and affect soil hydrological processes such as water infiltration, run-off or re-distribution. Investigations were conducted on two former lignite open-cast mining sites, an artificial sand dune on the reclaimed watershedWelzow “Neuer Lugteich” and a reforestation area in Schlabendorf (Brandenburg, north-east Germany). The aim was to relate the hydrological characteristics of the topsoil to successional stages of biological soil crusts on reclaimed soils and their influence on repellency index and water holding capacity compared to pure mining substrate. Our study emphasized the influence of changing successional stages and species composition of biological soil crusts, forming a small-scale crust pattern, on water repellency and retention on sandy soils in temperate climate. Different successional stages of soil crusts were identified from initial scattered green algae crusts, dominated by Zygogonium spec. and Ulothrix spec., and more developed soil crusts containing mosses such as Ceratodon purpureus and Polytrichum piliferum. Lichens of the Genus Cladonia were more pronouncedly contributed to biocrusts at later and mature stages of development. The repellency index on the one hand increased due to the cross-linking of sand particles by the filamentous green algae Zygogonium spec. which resulted in clogging of pores, and on the other hand decreased with the occurrence of moss plants due to absorption caused by bryophytes. The determination of the water retention curves showed an increase of the water holding capacity, especially in conjunction with the growth of green algae layer. The absorption capacity of soil crust biota as well as a decreased pore diameter in the green algae layers positively affected the water retention of crusted soil compared to pure substrate. The occurrence of bryophytes with later succession weakened the repellent behavior of the biocrusts, increased infiltration, and might have affected the run-off at small-scale on biocrusts. Certainly, the biological soil crusts showed water repellent properties but no distinctive hydrophobic characteristics. On both locations, similar trends of water repellency and retention related to crustal formation were observed, in spite of different relief, reclamation time and inhomogeneous distribution of crustal organisms.
Biological soil crusts serve as a vanguard for improving the ecological environment in arid, semi-arid desertification areas.It is a good indicator of the level of improvement which the local ecological evironment is undertaking. In desert areas, water condition is a key factor of improving the ecological environment. As a first layer protection, biological crusts play an important role in local vegetation succession due to their abilities to conserve and maintain moisture. Using Maowusu desert in Yanchi of Ningxia province as an example, after three years of research, this paper chooses three kinds of biological crusts including lichen, moss and cyanobacterial which are under the cover of Artemisia ordosicaas research objects. The results of this study indicate that, the closer biological crusts are to Artemisia ordosica vegetation, the thicker they become. In the same position of Artemisia ordosica vegetation, the
thickness of moss crusts is the highest, followed by lichen crusts, and the thickness of cyanobacterial crusts is the lowest. Biological soil crusts coverage protects the natural water content of soil layers from 0 to 5cm. Also, it effects falling water to infiltrate deeper, and cannot prevent the surfacewater content from evaporating effectively. The effect of biological crusts blocking water infiltration decreases with the increase of rainfall. At the same rainfall level, moss crusts provide the strongest water infiltration blockage, followed by lichen crusts and cyanobacterial crusts. With the increase of rainfall, the depth of water infiltration increases.At the same rainfall level, the relationship of water infiltration depth is as follows: cyanobacterial crusts > lichen crusts > moss crusts. With the increase of biological crusts thickness, they blocking water infiltration capacity is stronger, and the depth of water infiltration is smaller. Analysis on the characteristic of simulated rainfall process on biological crusts shows that sandy land can be fixed by applying appropriate artificial biological crusts to build a sustainable forest protection system and to create a stable ecosystem in desertification area.
A leaf net photosynthesis model is presented driven by light and modulated by temperature and air humidity. From this the seasonal variation of CO2 uptake and release could be modelled to estimate the annual carbon fluxes of sun and shade leaves. In fully expanded leaves light is the major factor determining daily carbon balances, and highest observed daily carbon gains in sun leaves amounted to 748.9 mmol CO2 m-2 day-1 in poplar and to 536.3 mmol CO2 m-2 day-1 in black locust, while the annual carbon gains amounted to 46,824 mol CO2 m-2 in black locust and 66,803 mol CO2 m-2 in hybrid poplar. Results obtained via gas exchange measurements and from the leaf model clearly indicate a potentially better growth performance of the poplar compared to black locust on the investigated site. The presented photosynthesis model provides a good and realistic estimation for seasonal carbon balances on the leaf level for both species.
The use of sewage sludge as fertiliser is a common practice in Europe, where sewage sludge is usually applied on a plant-available N or total metal concentration basis; as a result, phosphorus (P) concentrations can be well above crop needs. The objective of the study was to evaluate the effect of three doses of sewage sludge (0, 200, and 400 kg total N ha⁻¹ year⁻¹) combined with lime (2.5 Mg CaCO3 ha⁻¹) or without lime on the P in soil and pasture, tree growth and pasture production in a silvopastoral system established with Populus canadensis Moench over seven consecutive years. The P availability varied with the soil pH (a result of lime and sewage sludge applications) throughout the study. In general, an increase of the soil acidity (pH 5.39) increased the amounts of Fe and Al in the soil solution, which form very strong bonds with P, thereby reducing the P availability (M3-P: 20.99 g kg⁻¹). The effect of lime on the P availability gradually declined in the years following its application. However, in the latter part of the study (2007–2008), due to the higher residual effect of the sewage sludge compared with lime, the doses of sewage sludge (200 and 400 kg N total ha⁻¹) increased the concentrations of P (200N: 37.31 g kg⁻¹ and 400N: 48.71 g kg⁻¹) and Fe (200N: 321.51 mg kg⁻¹ and 400N: 341.56 mg kg ⁻¹) in a Mehlich 3 solution, the concentration of P in the pasture (200N: 2.53 g kg⁻¹ and 400N: 2.81 g kg⁻¹) and the amount of P extracted by the pasture (200N: 8.78 kg ha⁻¹ and 400N: 10.34 kg ha⁻¹), resulting in possible reduction in environmental problems. Further, due to its agronomic benefits as a source of plant nutrients and organic matter, fertilisation with high quality sewage sludge could be recommended for silvopastoral systems under edaphoclimatic conditions similar to those in this study.
In the temperate zone short rotation coppice systems for the production of woody biomass (SRC) have gained great interest as they offer a pathway to both sustainable bioenergy production and the potential sequestration of CO₂ within the biomass and the soil. This study used the carbon model SHORTCAR to assess the carbon cycle of a poplar (Populus suaveolens Fisch. x Populus trichocarpa Torr. et Gray cv. Androscoggin) and a black locust (Robinia pseudoacacia L.) SRC. The model was calibrated using data from established SRC plantations on reclaimed mine sites in northeast Germany and validated through the determination of uncertainty ranges of selected model parameters and a sensitivity analysis. In addition to a ‘reference scenario’, representing the actual site conditions, 7 hypothetical scenarios, which varied in climate conditions, rotation intervals, runtimes, and initial soil organic carbon (SOC) stocks, were defined
for each species. Estimates of carbon accumulation within the biomass, the litter layer, and the soil were compared to field data and previously published results. The model was sensitive to annual stem growth and initial soil organic carbon stocks. In the reference scenario net biome production for SRC on reclaimed sites in Lusatia, Germany amounted to 64.5 Mg C ha⁻¹ for R. pseudoacacia and 8.9 Mg C ha⁻¹ for poplar, over a period of 36 years. These results suggest a considerable potential of SRC for carbon sequestration at least on marginal sites.
Peat mineral soil mix (PMM) and forest floor mineral soil mix (FMM) are cover soils commonly used for land reclamation, while coarse woody debris (CWD) can be added to create structural diversity and provide an additional source of organic matter. However, the effect of cover soil type and CWD on emission rates of greenhouse gases, such as carbon dioxide (CO₂) methane (CH₄) and nitrous oxide (N₂O) in reclaimed oil sands soils has not been studied. Soil respiration, CH₄ uptake and N₂O emission rates were studied in a factorial experiment consisting of 2 cover soils (FMM vs PMM) × 2 sampling distances from the CWD (near vs away from CWD). Greenhouse gas emission rates were measured in July, August, and September 2012 and 2013 using static chambers. Soil respiration rates were greater in FMM than in PMM regardless of the distance from CWD at each sampling time (p < 0.05). Rates ranged from 461 to 1148 and 293 to 677 mg CO2 m⁻²h⁻¹for FMM and PMM, respectively, in 2012, and from 355 to 1318 and 235 to 700 mg CO2 m⁻²h⁻¹, respectively, in 2013. The CWD increased soil respiration by 22–33% in FMM but not in PMM. Soil respiration rates were positively related to microbial biomass carbon (p = 0.004) and nitrogen (p < 0.001). Soil respiration rates decreased from July to September in 2012 and 2013, and were positively related to soil temperature (p < 0.01) but not with soil water content measured at 5 cm depth. Methane uptake rates were greater in FMM (0.026–0.037) than in PMM (0.015–0.028 mg CH₄⁻²h⁻¹. The CWD increased CH4 uptake rates only in July and August 2012 in FMM, and were negatively related to soil water content (p < 0.001) but not to soil temperature. Nitrous oxide emission rates (0.001–0.016 mg N₂O m⁻²h⁻¹) were not affected by either cover soil type or CWD. Global warming potential of CO₂, CH₄ and N₂O effluxes was greater in FMM than in PMM and near CWD than away from CWD, especially in FMM. Our study demonstrates that applying CWD for oil sands reclamation increases organic matter decomposition (increased CO₂ evolution), driven by the effect on microbial populations. Results from this study provide support to findings in earlier studies that CWD application benefits vegetation establishment through enhancing soil processes in reclaimed oil sands lands.
Mining sites are harsh environments and establishment of root associated symbiotic fungi may be crucial for plant establishment and long term community development. Diamond mining in the Northwest Territories produces large amounts of processed kimberlite, and in some cases lake bed sediment and reclamation is needed for re-establishment of ecosystem function. This study investigated early fungal colonization with arbuscular mycorrhizae and dark septate endophytes on common reclamation substrates of different ages, relative to native tundra. Natural colonization of vegetation free sites with mycorrhizal spores on a trajectory associated with substrate age and type was very low. Fungal spore
quantity and diversity was significantly accelerated by establishment of vegetation. Dark septate endophytes dominated native site Cyperaceae whereas reclamation site grasses were dominated by arbuscular mycorrhizae. Topsoil amendment was most effective for fungal colonization on reclamation substrates suggesting that a single application of topsoil can have a long term effect on the soil fungal community.
Als mehrjährige Bioenergiepflanze kann Sida hermaphrodita eine wichtige Rolle für den Anbau auf marginalen Standorten in der nahen Zukunft spielen. In einem kontrollierten Topfexperiment wurde der Einfluss von verschiedenen Kompostgehalten (10, 20, 30, 50%) und mineralischem Stickstoffdünger (100 kg N ha–1) auf Biomasse, Wuchshöhe und Kohlenstoffallokation während der Etablierungsphase untersucht. Weiterhin wurden ökophysiologische Parameter (Gaswechsel, Chlorophyllfluoreszenz, Chlorophyllgehalte) mit nicht-destruktiven Methoden bestimmt. Die Ergebnisse des Experimentes zeigen, dass sowohl die Stickstoffdüngung als auch die Kompostgabe positive Effekte für das Wachstumsverhalten hat. Während der Etablierungsphase erreichten die gedüngten Pflanzen eine mittlere Pflanzenhöhe von bis zu 127 cm (maximale Wuchshöhe 168 cm). Die Photosynthese wurde nicht durch die unterschiedlichen Behandlungen beeinflusst. Die mittlere CO2-Austauschrate variiert zwischen 5,8 und 9,9 μmol m–2 s–1 und die Elektronentransportrate zwischen 34,5 und 53,9 μmol m–2 s–1. Die Verwendung von Kompost und Stickstoff ist für eine bessere Biomasseproduktion von Sida in marginalen Böden möglich, auch wenn das Wachstum im ersten Jahr limitiert ist und es negative Rückwirkungen auf die Bestandesetablierung gibt.
Soils and groundwater on sites of the former Manufactured Gas Plants (MGPs) are contaminated with various complex iron-cyanides (Fe-CN). Phytoremediation is a promising tool in stabilization and remediation of Fe-CN affected soils, however, it can be a challenging task due to extreme adverse and toxic conditions. Phytoremediation may be enhanced via rhizosphere microbial activity, which can cooperate on the degradation, transformation and uptake of the contaminants. Recently, increasing number of scientist reports improved plants performance in the removal of toxic compounds with the support of arbuscular mycorrhizae fungi (AMF). Series of batch experiments using potassium hexacyanoferrate (II) solutions, in varying concentrations, were used to study the effect of ryegrass roots (Lolium perenne L.) inoculation with Rhizophagus irregularis and a mixture of Rhizophagus irregularis, Funneliformis mosseae, Rhizophagus aggregatus, and Claroideoglomus etunicatum on Fe-CN sorption. Results indicated significantly higher colonization of R. irregularis than for the mixture of AMF species on ryegrass roots. Sorption experiments revealed significantly higher reduction of total CN and
free CN content in the mycorrhizal roots, indicating greater cyanide decrease in the treatment inoculated with R. irregularis. Our study indicates contribution of AM fungi in phytoremediation of Fe-CN contaminated soil.
Arbuscular mycorrhizal fungi (AMF) are integral functioning parts of plant root systems and are widely recognized for enhancing contaminants uptake and metabolism on severely disturbed sites. However, the patterns of their influence on the phytoremediation of iron–cyanide (Fe–CN) complexes are unknown. Fe–CN complexes are of great common interest, as iron is one of the most abundant element in soil and water. Effect of ryegrass (Lolium perenne L.) roots inoculation, using mycorrhizal fungi (Rhizophagus irregularis and a mixture of R. irregularis, Funneliformis mosseae, Rhizophagus aggregatus, and Claroideoglomus etunicatum), on iron–cyanide sorption was studied. Results indicated significantly higher colonization of R. irregularis than the mixture of AMF species on ryegrass roots. Series of batch experiments using potassium hexacyanoferrate (II) solutions, in varying concentrations revealed significantly higher reduction of total CN and free CN content in the mycorrhizal roots, indicating greater cyanide decrease in the treatment inoculated with R. irregularis. Our study is a first indication of the possible positive contribution of AM fungi on the phytoremediation of iron–cyanide complexes.
Alley cropping system is an agroforestry practice in which arable crops are cultivated between tree hedgerows. For more than 15 ye ars we have been doing research in agroforestry which has been carried out on different experimental sites in the field covering about 250 acres of alley cropping, more areas with short rotation coppice, and other tree-based field experiments located close to C ottbus / Germany. The presence of woody species in the alley cropping production system has been shown to contribute significantly to carbon sequestration, nutrient cycling, improved water availability for crops, stimulation of higher soil faunal activities, soil erosion control, soil fertility improvement and sustained levels of crop production.
Alley cropping systems have also come into focus for reclamation of post-mining areas where the initial content of soil organic matter (SOM) is generally close to zero and soil fertility is very low. The increase of SOM in reclamation areas depends on amount of biomass production and return to soil, and mechanisms of C protection. Production of Robinia pseudoacacia L. under alley cropping system has received considerable interest in these areas as an alternative to agricultural crops and an additional wood source, while acting as a potential C sink to counterbalance greenhouse gases emissions. The woody biomass accumulation of R. pseudoacacia reached 29.8 t drymass ha-1 after 6 years of establishment on reclaimed mine sites in northeastern Germany. Due to its high potential of litterfall production and N2 fixation, R. pseudoacacia contributed to improve soil physical, chemical and biological properties though increasing SOM, converting spoils into productive and sustainable soils. For this reason, in the temperate zone, agroforestry systems attract more and more public attention as they offer a promising and comprising way for adapting agricultural production to climate change and providing comprehensive ecosystem services. A comprehensive assessment of the ecosystem services in agroforestry systems in temperate regions should consider the potential to produce biomass and food, the evaluation of the carbon and nutrient budgets, the assessment of the potential impact of agroforestry on biodiversity at landscape scale and finally the exploration of the sustainability functions and socio-economic cross-cutting issues. These key parameters are relevant to policy by providing current and reliable information on the interactions between land management, ecosystem services and society.
The constructed Hühnerwasser (“Chicken Creek”) catchment is an ecohydrological system in an initial state of development. The catchment with an area of 6 ha was built up from quaternary sediments in the post-mining landscape of Lusatia in Eastern Germany and serves as a critical zone observatory for detecting ecosystem transition. The soil substrate is characterized as sands to loamy sands with low carbonate contents but significant amounts of gypsum in the sediments of the catchment. The catchment undergoes a strong transition from an abiotic system in the initial years to a system with growing influence of biota. Concerning the hydrology, a regime shift from surface runoff to groundwater flow dominated processes is significant. It is of interest, whether the catchment transition is also reflected by hydrogeochemical indicators. We assume gypsum dissolution as dominant process at the catchment scale. In order to investigate the hydrogeochemical evolution of the catchment we analysed electric conductivity, calcium and sulphate concentrations and pH-values of biweekly composite samples from 2007-2013 of the atmospheric deposition, of runoff and soil water. The two observation points in the flowing water represent surface runoff and groundwater discharge respectively. Soil
water has been analysed at four soil pits in three depths. The monitoring data were provided by the Research
Platform Chicken Creek. From the macroscopic data analysis we found an exponential decay of the electric conductivity, calcium and sulphate concentrations in the flowing waters and some of the soil pits. In the flowing water, the decrease slope of the electric conductivity and the calcium and sulphate concentrations is almost identical. The calcium / sulphate molar ratio as an indicator of gypsum dissolution is almost equal to one up to 2010, afterwards more calcium than sulphate is released. The pH-values in the flowing and soil water are generally higher than in the atmospheric deposition, they do show variabilites but no trend behaviour. The time series analyses showed that the interannual variability of the hydrogeochemical properties is less pronounced in the first years of ecosystem development than in the later years. This leads to the conclusion, that in the first years, gypsum dissolution is the major source for calcium and sulphate in the soil and the flowing waters. The increasing interannual variability and changes in the calcium / sulphate ratio in the later years might be interpreted as hydrogeochemical response to the development of vegetation and acidification due to the development of the rhizosphere.
Alley cropping systems (ACS) are agroforestry practices in which perennial trees or shrubs are grown in wide rows and arable crops are cultivated in the alleys between the tree rows. Recently, ACS which integrate stripes of short rotation coppices into conventional agricultural sites have gained interest in Germany. These systems can be used for simultaneous production of crops and woody biomass which enables farmers to diversify the provision of market goods. Adding trees into the agricultural landscape creates additional benefits for the farmer and society also known as ecosystem services. An ecosystem service provided by land use systems is carbon sequestration. The literature indicates that ACS are able to store more carbon compared to agriculture and their implementation may lead to greater benefits for the environment and society. Moreover, carbon sequestration in ACS could be included in carbon trading schemes and farmers rewarded additionally for the provision of this ecosystem service. However, methods are required which are easy to use and provide reliable information regarding change in carbon sequestration with change of the land use practice. In this context, our aim was to develop a methodology to assess carbon sequestration benefit provided by ACS in Germany. Therefore, the change of carbon in both soil and biomass had to be considered. To predict the change in soil carbon our methodology combined the 2006 IPCC Guidelines for National Greenhouse Gas Inventories and the soil organic carbon balance recommended by the Association of German Agricultural Investigation and Research Centers (VDLUFA). To reflect the change in biomass carbon average annual yields were adopted. The results showed that ACS established on agricultural sites can increase the carbon stored because in the new soil-plant system carbon content is higher compared to agriculture. ACS have been recommended as suitable land use systems for marginal sites, such as post-mining areas. In such areas soil carbon usually increases at a faster initial rate compared to agricultural land which means that these areas could provide high level of carbon sequestration service in the short term. The approach will be broadened to include assessment of other ecosystem services provided by ACS in Germany which would increase the possibility to adequately compensate farmers for the supply of environmental benefits.
Alley cropping systems which integrate strips of short rotation coppices into conventional agricultural sites (ACS) have recently gained increasing interest in Germany. These ACS can be used for the simultaneous production of crops and woody biomass which enables farmers to diversify the provision of market goods. Integrating trees into the agricultural landscape can create additional benefits for the farmer and society also known as ecosystem services (ES). The scientific literature suggests that ACS are able to provide additional benefits as compared to conventional agriculture. Among the important ES provided by ACS are carbon sequestration, soil fertility, water quality, groundwater recharge, and biodiversity. However, assessment methods are required which are easy to use and provide reliable information regarding change in ES with change of the land use practice. In this context, our aim was to develop a methodology to assess selected ES provided by ACS in Germany. For this purpose an indicator set was selected from the literature and linked with the relevant ES previously identified. Furthermore, a model was developed to facilitate the calculation of the indicators. The results showed that ACS established at agricultural sites have higher capacity to provide ES as compared to single-crop agriculture. The capacity of ACS with 50% trees is higher than the capacity of ACS with 30% trees which suggests that the capacity of the system to provide ES increases with increased proportion of trees. The methodology seems to be a promising tool to facilitate the assessment of ES provided by the land management practices considered. In the long term this measurement approach can be broadened to include monetary evaluation of ES. This will enable rewarding farmers for providing environmental benefits therefore, accurately compensating them for the outputs supplied.
The importance of short rotation forests and agroforestry systems for woody biomass production for bioenergy will increase in Central Europe within the next decades. In this context, black locust (Robinia pseudoacacia) has a high growth potential especially at marginal, drought-susceptible sites such as occur in Brandenburg State (Eastern Germany). As a pioneer tree species black locust grows under a wide range of site conditions. The native range of black locust in Northern America is classified by a humid to sub-humid climate with a mean annual precipitation of 1020 to 1830 mm. In Central and Eastern Europe, this species is cultivated in a more continental climate with an annual precipitation often below 600 mm. Therefore, black locust is known to be relatively drought tolerant compared to other temperate, deciduous tree species. Because of its N2-fixation ability black locust plays generally an important role for the improvement of soil fertility. This effect is of particular interest at marginal sites in the post-mining landscapes.
In order to estimate the N2-fixation potential of black locust at marginal sites leaf samples were taken from black locust trees in short rotation plantations planted between 1995 and 2007 in post-mining sites south of Cottbus (Brandenburg, NE Germany). The variation of the natural 15N abundance was measured to evaluate the biological nitrogen fixation. The nitrogen derived from the atmosphere can be calculated using a two-pool model from the quotient of the natural 15N abundances of the N2-fixing plant and the plant available soil N. Because representatively determining the plant available soil N is difficult, a non-N2-fixing reference plant growing at the same site with a similar root system and temporal N uptake pattern to the N2-fixing plant is often used. In our case we used red oak (Quercus rubra) as a reference.
The average nitrogen content in the leaves of black locust ranged from 3.1% (C/N 14.8) in 15 years old trees to 3.4% (C/N 14.4) in 3 year-old trees, respectively. A higher content of nitrogen was found in leaves of re-sprouted trees with 4.3% (C/N 11.5). The estimated percentage of nitrogen derived from the atmosphere (% NdfA) in black locust was 63% – 83% compared to 56% in seabuckthorn (Hippophaë rhamnoides) and 79% in common broom (Genista scuparia). The annual leaf biomass production of black locust varied between 1325 (2 years old trees) and 2576 kg/ha a (4 years old trees). The estimated leaf nitrogen fixed by Robinia was approx. 30.5 - 59.2 kg/ha a.
From the results, we can conclude that the biological nitrogen fixation by Robina is an important factor for the nitrogen balance of short-rotation plantations on nutrient poor-soils.
Following surface disturbance, quaternary sands are the basic substrate for soil development in the Lusatian reclamation area. These substrates mostly contain few organic matter and, hence, are nutrient poor. Accumulation of soil carbon is an important factor for ecosystem development, where biological soil crusts initially influence soil processes and promote ecosystem succession. The compositional structures of biological soil crusts at various developmental stages and their photosynthetic properties were investigated on two former open-cast lignite sites, currently under reclamation, an artificial sand dune in Welzow Süd, and a forest plantation in Schlabendorf Süd (Brandenburg, Germany). As development of biological soil crusts progressed, their contents of organic carbon and total chlorophyll increased. The ratio of these parameters, however, varied with the relative contribution of lichens and mosses in particular. Also maximum photochemical efficiency, net photosynthesis and respiration increased with crustal development. An additional evaluation of NDVI and chlorophyll fluorescence images showed that especially moss-dominated biocrusts had higher photosynthetic capacity compared to green algae-dominated biocrusts or soil lichens, so the photosynthetic capacity showed to be highly species-specific. The ratio of gross photosynthesis to respiration indicated a higher ecological efficiency of biocrusts dominated by green algae than of lichen-dominated biocrusts. The occurrence of soil lichens reduced net CO2 fixation and increased CO2 release due to the enhanced mycobiontic respiration. During crustal succession, the rise of photosynthesis-related parameters is not necessarily linear as a result of the highly heterogenic distribution of the different crustal organisms between biocrusts of similar developmental stages as well as between those growing at the two study sites. Therefore, the evaluation of relevant ecophysiological parameters highlighted that not all biocrust-forming organisms similarly contribute to the ecophysiological behavior of biological soil crusts. Nevertheless, the occurrence of the biological soil crusts promoted soil formation and accumulation of soil carbon in initial soils.
Investigations were done on two former open-cast lignite mining sites under reclamation, an artificial sand dune in Welzow Süd, and a forest plantation in Schlabendorf Süd (Brandenburg, Germany). The aim was to associate the topsoil hydrological characteristics of green algae dominated as well as moss and soil lichen dominated biological soil crusts during crustal succession with their water retention and the repellency index on sandy soils under temperate cli-mate and different reliefs.
The investigation of the repellency index showed on the one hand an increase due to the cross-linking of sand parti-cles by green algae which resulted in clogging of pores. On the other hand, the occurrence of moss plants led to a de-crease of the repellency index due to absorption caused by bryophytes. The determination of the water retention curves showed an increase of the water holding capacity, especially in conjunction with the growth of green algae layer. The pore-related van Genuchten parameter indicate a clay-like behaviour of the developed soil crusts. Because of the inho-mogeneous distribution of lichens and mosses as well as the varying thickness of green algae layers, the water retention differed between the study sites and between samples of similar developmental stages. However, similar tendencies of water retention and water repellency related to the soil crust formation were observed.
Biological soil crusts should be considered after disturbances in the context of reclamation measures, because the ini-tial development of green algae biocrusts lead to an increasing repellency index, while the occurrence of mosses and a gain in organic matter enhance the water holding capacity. Thus, the succession of biocrusts and their small-scale succes-sion promote the development of soil and ecosystem.
Salt tolerance of agricultural crops has been studied since the 1940, but knowledge regarding salt tolerance of woody crops is still in its initial phase. Salt tolerance of agricultural crops has been expressed as the yield decrease due to a certain salt concentration within the root zone as compared to a non-saline control. The most well-known plant response curve to salinity has been a piece-wise linear regression relating crop yield to root zone salinity. This method used the hypothesis that crops tolerate salt up to a threshold after which their yield decreases approximately linearly. Critique to this method included its lack of sensitivity to dynamic factors such as weather conditions. As a result, other classification indices have been developed, but none is as well accepted as the threshold-slope model. In addition to a mini-review of the key salt tolerance studies, our objective was to classify salt tolerance levels of poplars and willows. Initial classification showed that salt tolerance of these genera ranged from sensitive to moderately tolerant.
Forest floor mineral soil mix (FMM) and peat mineral soil mix (PMM) are cover soils commonly used for upland reclamation post open-pit oil sands mining in northern Alberta, Canada. Coarse woody debris (CWD) can be used to regulate soil temperature and water content, to increase organic matter content, and to create microsites for the establishment of microorganisms and vegetation in upland reclamation. We studied the effects of CWD on soil microbial community level physiological profile (CLPP) and soil enzyme activities in FMM and PMM in a reclaimed landscape in the oil sands. This experiment was conducted with a 2 (FMM vs PMM) × 2 (near CWD vs away from CWD) factorial design with 6 replications. The study plots were established with Populus tremuloides (trembling aspen) CWD placed on each plot between November 2007 and February 2008. Soil samples were collected within 5 cm from CWD and more than 100 cm away from CWD in July, August and September 2013 and 2014. Microbial biomass was greater (p<0.05) in FMM than in PMM, in July, and August 2013 and July 2014, and greater (p<0.05) near CWD than away from CWD in FMM in July and August samplings. Soil microbial CLPP differed between FMM
and PMM (p<0.01) according to a principal component analysis and CWD changed microbial CLPP in FMM (p<0.05) but not in PMM. Coarse woody debris increased microbial community functional diversity (average well color development in Biolog Ecoplates) in both cover soils (p<0.05) in August and September 2014. Carbon degrading soil enzyme activities were greater in FMM than in PMM (p<0.05) regardless of distance from CWD but were not affected by CWD. Greater microbial biomass and enzyme activities in FMM than in PMM will increase organic matter decomposition and nutrient cycling, improving plant growth. Enhanced microbial community functional diversity by CWD application in upland reclamation has implications for accelerating upland reclamation after oil sands mining.
Halophytes develop various morphological and physiological traits that enable them to grow successfully on saline substrates. Parasitic plants on halophytic hosts may also encounter salt stress. We investigated the mistletoe Plicosepalus acaciae (syn: Loranthus acacia; Loranthaceae), which occurs on 5 halophytic and at least 10 non-halophytic hosts in the Southern Arava Valley (Israel). Plicosepalus acaciae is a common parasite north of Eilat to the Dead Sea area and in the Jordan Valley. Morphological and physiological responses of P. acaciae to salinity were investigated by comparison of plants on halophytic with those on non-halophytic hosts. Ion patterns of different host–parasite associations were determined as was the development of leaf succulence at different growth stages. The leaf water content of P. acaciae increased and leaves developed succulence when growing on halophytic hosts, especially on Tamarix species, where leaf water content was three times higher than that on non-halophytic hosts and the leaf volume increased four to five times. The reason for increased succulence was a higher ion concentration of, and osmotic adjustment with, Na+ and Cl2. Plicosepalus acaciae showed a high morphological and ecophysiological plasticity, enabling it to cope with salt stress, and can be classified as a facultative eu-halophyte, which increases its halo-succulence according to the host. Host–parasite associations are a model systemfor the investigation of halophytes under different salt stress conditions.
The pioneer tree black locust (Robinia pseudoacacia L.) is a drought-resistant tree and, in symbiosis with Rhizobium, able to fix dinitrogen from the atmosphere. It is, therefore, an interesting species for marginal lands where soil amelioration is sought in addition to economic gain. However, the interaction between soil water availability, carbon allocation and nitrogen fixation is important for a successful establishment of trees on marginal lands and has not yet been investigated for black locust. Twoyear-old trees were grown under various soil water conditions and drought cycles. The stable isotopic composition of C (δ 13C) and N (δ 15N) of the leaves was used to identify i) the effective drought condition of the treatments and ii) the portion N accrued from the atmosphere by the biological nitrogen fixation. Drought-stressed plants significantly reduced their total aboveground biomass production, which was linearly linked to tree transpiration. The shoot:root ratio values changed from 2.2 for the drought-stressed to 4.3 for the well-watered plants. Our investigation shows that drought stress increases the nodule biomass of black locust in order to maintain biological nitrogen fixation and to counteract the lower soil nitrogen availability. The biological nitrogen fixation of drought-stressed trees could be maintained at relatively higher values compared to the well-watered trees. The average leaf nitrogen content varied between 2.8% and 3.0% and was not influenced by the drought stress. Carbon fixation, carbon allocation, and biological nitrogen fixation are to some extent balanced at low irrigation and allow Robinia to cope with long-term water constraints. The combination of black locust’s ecophysiological and morphological plasticity make it interesting as a biomass source for bioenergy and timber production, even in nutrient-limited and drought-affected areas of Europe.
Stimulated by the rising demand for bioenergy, forestry practices for energy production are of increasing importance worldwide. Black locust (Robinia
pseudoacacia L.) is a suitable tree species for biomass production in shortrotation plantations in East Germany, especially on marginal land where insufficient water and nutrients are a limiting factor for tree growth. Our study aims to clarify the spatial and temporal variability of the black locust growth through the analysis of the plant water status, and to evaluate the effect of adverse edaphic conditions on growth performances, amplified by periods of summer drought. The study was carried out at two sites presenting comparable climatic but different edaphic conditions: (i) fertile agricultural soil; and (ii) heterogeneous unstructured soil from a reclaimed post-mining area. During the vegetation period, the growth rate decreased in both sites following the plant water status in terms of pre-dawn leaf water potential. Particularly in the post-mining area, due to the adverse edaphic conditions, below the critical pre-dawn water potential value of -0.5 MPa, the stem growth was drastically reduced during a period of summer drought. However, the trees could cope with the extreme soil and weather conditions in the post-mining site without perishing.
Black locust (Robinia pseudoacacia L.) is a drought-tolerant fast growing tree, which could be an alternative to the more common tree species used in short-rotation coppice on marginal land. The plasticity of black locust in the form of ecophysiological and morphological adaptations to drought is an important precondition for its successful growth in such areas. However, adaptation to drought stress is detrimental to primary production. Furthermore, the soil water availability condition of the initial stage of development may have an impact on the tree resilience. We aimed to investigate the effect of drought stress applied during the resprouting on the drought tolerance of the plant, by examining the black locust growth patterns. We exposed young trees in lysimeters to different cycles of drought. The drought memory affected the plant growth performance and its drought tolerance: the plants resprouting under drought conditions were more drought tolerant than the well-watered ones. Black locust tolerates drastic soil water availability variations without altering its water use efficiency (2.57 g L−1), evaluated under drought stress. Due to its constant water use efficiency and the high phenotypic plasticity, black locust could become an important species to be cultivated on marginal land.
Soil water availability, nutrient supply and climatic conditions are key factors for plant production. For a sustainable integration of bioenergy plants into agricultural systems, detailed studies on their water uses and growth performances are needed. The new bioenergy plant Igniscum Candy is a cultivar of the Sakhalin Knotweed (Fallopia sachalinensis), which is characterized by a high annual biomass production. For the determination of transpiration-yield relations at the whole plant level we used wicked lysimeters at multiple irrigation levels associated with the soil water availability (25, 35, 70, 100%) and nitrogen fertilization (0, 50, 100, 150 kg N ha–1). Leaf transpiration and net photosynthesis were determined with a portable minicuvette system. The maximum mean transpiration rate was 10.6 mmol m–2 s–1 for well-watered plants, while the mean net photosynthesis was 9.1 μmol m–2 s–1. The cumulative transpiration of the plants during the growing seasons varied between 49 l (drought stressed) and 141 l (well-watered) per plant. The calculated transpiration coefficient for Fallopia over all of the treatments applied was 485.6 l kg–1. The transpiration-yield relation of Igniscum is comparable to rye and barley. Its growth performance making Fallopia a potentially good second generation bioenergy crop.