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This study investigates changes in soil phosphorus (P) in different fertilization treatments applied since 1902 on Chernozem soil at a “Static Fertilization Experiment” in Germany. Total and plant-available soil P, and soil P balances were assessed at 0–30, 30–60, and 60–90 cm depth layers in unfertilized “Zero”, mineral “NK” and “NPK”, and combined mineral and organic “FYM + NK” (farmyard manure + NK) and “FYM + NPK” fertilization treatments. P-use efficiencies were determined for each crop in rotation (sugar beet, spring barley, potato, and winter wheat). The 110 yr of P fertilization at rates between 22 and 55 t ha−1 yr−1 resulted in a significant increase of available P contents. P stocks increased up to 60 cm depth. Total P accumulation comprised 1.4 t ha−1 for NPK, 1.3 t ha−1 for FYM + NK, and 3.1 t ha−1 for FYM + NPK. Crops cultivation without P fertilization in Zero and NK treatments resulted in negative P balances and reduction of available P below recommended levels. Reduction of mineral P application rates after 1981, along with crop variety-dependent yield increases, resulted in an improved P-use efficiency. An organic fertilization combined with mineral N and K fertilizers (FYM + NK) was found to be the most P-efficient treatment for Chernozem soils.
This study assessed the provision of additional ecosystem services by two alley cropping systems for production of woody biomass located in Germany (Farm A and Farm B) as compared to conventional agricultural management. Stripes of fast growing trees in both farms were planted at different distances from each other and occupied various proportion of the agroforestry area. The results of nine indicators of soil, water and biodiversity related to ecosystem services were thus compared under consideration of different farm conditions and management. The additional provision of benefits in Farm A was expected in terms of reducing erosion by wind and reducing the risk of nitrate leaching to groundwater. In Farm B the main effect was related with improving biodiversity. The design of the tree stripes within the system affected the reduction of wind erosion as well as the improvement in biodiversity and was an essential factor determining the provision of ecosystem services by alley cropping systems.
Purpose Soil erosion is a significant environmental impact of surface mining affecting the initial establishment of vegetation, especially on steep slopes, during reclamation. Consequently, we investigated the potentials of biological geotextiles constructed from two local plants, Pennisetum purpureum and Broussonetia papyrifera, in reducing erosion and sedimentation during reclamation at Newmont Ghana Gold Limited.
Materials and methods Six experimental plots were constructed on a 33% slope waste rock, covered with a 70-cm layer of stockpiled subsoil. Concrete gutters, lined with silt fence, were installed at the lower end of each plot to collect eroded sediment.
The two kinds of biological geotextiles, BYork^ mat and elephant grass mat, were used with bare ground as control in a randomized block design with two replicates each. Data on sediment yield was collected after each substantial rainfall. The performance of each geotextile in reducing soil loss was expressed as a percentage from the mean total sediment yield.
Results and discussion With total precipitation of 306 mm in the period April 18, to July 4, 2016, both elephant grass mat and York mat significantly (p < 0.05) reduced soil loss by 56.6% and 97.3%, respectively, compared to the control, indicating both mats were effective in erosion and sediment control. The relatively high performance of York mat was mainly attributed to its more fibers that provided less surface cover (70%) as well as flexibility of the fibers which enabled the mat to absorb more water during rainfall thus increasing its weight. This increase in weight promoted better drapability, with better erosion and sediment control. Gully formations at the site were primarily due to high concentrated runoff flows from the top of reclaiming benches, with time delays between completion of earthworks, geotextile placement, and seeding of plants as predisposing factors.
Conclusions The York mat (YM) and the elephant grass mat (EM) individually acted as cover and protected the highly erodible graded mine slope against the erosive forces of tropical rain and runoff until vegetation establishment. Even so, planning and coordinating the reclamation program such that all earthworks are completed at the end of the dry season to enable geotextile installation and plant seeding at the onset of rains, together with installation of temporary slope drains in preventing gully formations from concentrated runoff flows, are considered to contribute significantly to the general reclamation success at Newmont Ghana Gold Limited (NGGL) and similar mine sites.
The cultivation of bioenergy plants in fertile, arable lands increasingly results in new land use conflicts with food production and cannot be considered as sustainable. Marginal lands have been frequently considered as potential alternatives 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 evaluated 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. Thus, 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 regulations. A proper implementation needs clear regulations and also incentives for farmers at the European level.
Das Buch bietet eine umfassende aktuelle Zusammenfassung und Bewertung der bisherigen Forschungserfahrungen zum Thema Agrarholz und berücksichtigt sowohl Plantagenwirtschaft als auch agroforstliche Nutzungsformen. Es greift die verschiedenen Aspekte der Etablierung von Agrarholz in der Landwirtschaft aus Sicht der Pflanzenökologie und der Ökosystemforschung auf und diskutiert diese im Kontext mit der Produktivität und dem Agrarholz-Management. Zudem werden auch Aspekte der historischen Landnutzung, der Landschaftsplanung und des praktischen Flächenmanagements behandelt und wesentliche Grundlagen zur Biologie, Genetik, Landschafts-)Ökologie, und der Nutzung von Agrarholz vermittelt.
This study investigates the spatial and temporal impact of microclimate conditions caused by poplar hedgerows in a short rotation alley cropping system (SRACS), and their effect on the atmospheric evaporative demand (AED) and the grain crop yield of winter wheat (Triticum aestivum var. Patras) in direct comparison to a common agricultural crop system. Microclimate was measured at nine positions distributed at the SRACS and an adjacent open field in Brandenburg State (Germany) from March to August 2016. Our hypothesis was that microclimate and AED was improved at SRACS, with traceable effects on the crop yield. The analysis of air temperature and water vapour deficit (VPD) data revealed significantly (p B 0.05) lower daytime values from June to August at the crop alley of the SRACS, which were generally most frequent at the poplar hedgerow and 3 m west positions. By contrast, wind speed was reduced at almost all the positions of our crop alley and during the entire measurement period during both day and night. The AED measured on sampling days in July was significantly (p B 0.001) reduced at the whole crop alley, with values from 24 to 32% in comparison to the open field. We observed a strong linear relationship (R2 & 0.78–0.99) between AED on one side and wind speed and VPD on the other side. The average grain yield within the SRACS was 16% higher than on the OF. However, our microclimate data were insufficient to explain this yield surplus.
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. We propose a conceptual framework of feedback processes in early states of ecosystem development affected by spatiotemporal environmental drivers. To test this concept, we used 10-year time series of hydrological, biological, geomorphological, and soil data from the constructed catchment Chicken Creek.” The 6ha site was left to unrestricted development since 2005 and was intensively monitored. The data showed a very rapid development of the site with an increasing complexity and heterogeneity. In the first years, stochastic signals like the initial substrate conditions and external drivers like extreme weather events were the most important factors resulting in abiotic/abiotic feedback mechanisms shaping the morphology of the site and creating site diversity. Initial abiotic feedback mechanisms between water and substrate were soon followed by abiotic/biotic feedbacks between biological soil crusts, invading vegetation, geomorphology, and hydrology resulting in state transitions of catchment functioning.
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.
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.
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.
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.