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BTU
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.
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.
Conventional agricultural practices have often been associated with negative externalities, such as land degradation, pollution of soil and water resources, loss of biodiversity, and decreased provision of ecosystem services (ES). In response to these negative effects, the number of indicator-based attempts to assess ES provided by land use systems has increased. However, decisions regarding the importance of the different ES are usually made subjectively. Following an objective approach through the use of a partial order ranking method, this study aimed to assess several non-provisioning ES supplied by alley cropping system (ACS) in comparison with conventional agriculture (CA). The main objective of the study was to verify the applicability of partial order ranking to an ecologically-based assessment, focusing on soil, water, and biodiversity indicators. Results from 40 hypothetical scenarios representing various site conditions of agricultural fields in Germany were calculated using the Ecosystem Services Assessment Tool for Agroforestry (ESAT-A), a toolbox designed to assess selected ES of ACS following an empirical approach. The results were ranked using partial order and were visualized by a Hasse diagram. The findings depict partial order ranking as a promising technique to support decision making in order to find priority scenarios and indicators where the provision of ES can be enhanced by establishing ACS. The minimal scenarios under CA identified with simultaneously low values of all indicators were perceived as target scenarios for establishing ACS. The values of the indicators for the current land use system need to be taken into account in order to avoid scenarios where high tradeoff was suggested. Additionally, this approach can be extended and utilized at the field level to aid farmer decisions on which land use strategy is the most suitable alternative to increase the provision of ES.
In Central Europe, short rotation coppice systems for the production of woody biomass come increasingly into focus as these wood plantations offer an opportunity to sustainably produce biomass for energy production and to sequester substantial amounts of CO2 within the plantations and the soils at the same time. In this study, a modeling analysis of the C cycle of a poplar (Populus suaveolens Fisch. x Populus trichocarpa Torr. et Gray cv Androscoggin) and a black locust (Robinia pseudoacacia L.) SRC is presented. The calculations were performed with the bookkeeping C-model shortcar. The calculated estimates of C accumulation within the biomass, the litter layer, and the soil were validated against field data and published results from a selection of scientific studies. For the SRC on reclaimed mine sites a high C sequestration potential was found which amounted in the reference scenario over a period of 36 years to an accumulated net biome production of about 65 Mg C ha-1 for R. pseudoacacia and about 9 Mg C ha-1 for poplar, while the latter clearly suffered from the harsh growth conditions at the reclamation sites. Summarizing, the results suggested a high potential of SRC for C sequestration and C emission mitigation, especially on marginal sites.