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BTU
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.
Alley-Cropping - Ein klima-adaptierbares Landnutzungssystem zur nachhaltigen Biomasseproduktion
(2008)
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.
Since the 1920s, more than 80.000 ha of land have been affected by lignite opencast mining activities in the Lusatia region (Eastern Germany), resulting in the evolution of large post-mining landscapes with substrates poor in humus and nutrients. As a consequence, the current conventional crop production on these post-mining areas is restricted. Against this background, the increasing demand for woody biomass for bioenergy, and thus the cultivation of fast growing trees for woody biomass production, could represent a promising option to enhance the productivity of land reclaimed from mining. Accordingly, considerable research has been carried out over the last two decades on reclamation technology, in addition to attempts to improve the soil quality through the use of different fast growing tree species in the Lusatia lignite region. Through such studies, it has been shown that it is possible to cultivate a sustainable supply of bioenergy wood through the use of black locust (Robinia pseudoacacia L.) trees, even under the unfavourable growth conditions of the marginal post mining areas. Since this knowledge is mainly based on studies of monocultural plantations (SRC), in 2007 a short rotation alley cropping system (SRACS) was established in the reclaimed lignite mining site “Welzow-Süd” with the purpose of obtaining fresh insight. The present paper evaluates the positive impacts of agroforestry land-use in terms of soil fertility, agricultural crop production, and soil protection against wind erosion based on the results of several years of examination made in this degraded area.
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.
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.
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 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.
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.
Als Pionierbaumart besiedelt die Robinie (Robinia pseudoacacia) schnell offene Flächen und gilt im Vergleich zu anderen mitteleuropäischen Baumarten als relativ gut angepasst an trockene Standorte mit lockeren Böden. Sie gehört zu den wenigen Baumarten Mitteleuropas, die zur biologischen Stickstoff-Fixierung (BNF) befähigt sind. In dieser Studie soll der jährliche Eintrag von Stickstoff (N) aus der biologischen N-Fixierung der Robinie in Kurzumtriebsplantagen und Agroforstsystemen abgeschätzt werden.
Agroforestry systems for the production of woody biomass in marginal regions in Northeast Germany
(2011)