Speaker
Description
- Introduction
Agroforestry systems (AFS) especially alley cropping systems with short rotation coppices (SRC), have emerged as promising solutions for mitigating climate change by offering carbon sequestration and greenhouse gas (GHG) emission reduction benefits compared to conventional agriculture practices. While AFS has shown promise in mitigating climate change, it is worth noting that agroforestry is not a one-fits-all solution, considering the multitude of possible systems that can be designed for various site-specific pedo-climatic conditions. The efficiency of agroforestry in climate change mitigation relies on a detailed understanding of local conditions and respective management strategies, including crop rotations and tree species selection. In this context, there is a knowledge gap on SRC's specific role and effectiveness and the quantification of SRC contributions within the agroforestry framework for mitigating climate change. This study aims to address this gap by evaluating the contribution of SRC agroforestry systems to climate change mitigation building on long-term data of an experimental agroforestry-system in Germany. - Materials and Methods
The study site in Wendhausen, Northern Germany, covers an area of 30 hectares with an elevation of 85m A.S.L. The climate in the region is temperate, with average annual temperature of 9.8°C and average annual precipitation of 616 mm (Swieter et al., 2019). The soil properties are heterogeneous, with the soil in the agroforestry control system (ACS) characterized by a silty clay texture, while a clayey loam texture characterizes the reference cropland field.
The experiments include an AFS with a control field of about 3 hectares located next to it. The AFS consist of nine poplar strips with a distance of 10 m wide (from tree to tree);10,000 plants/ha with planting association 0.5 m x 2 m. Tree strip widths are 96 m (wide agroforestry area), 48 m (narrow agroforestry area) plus a 1.5 m seam width on each side. Trees are 3 polar clones: Max (P. nigra x P. maximowiczii), Hybrid 275 (Populus maximowiczii x P. trichocarpa), Koreana (P. koreana x P. trichocarpa). In both, the AFS and the control, crop rotation includes winter oilseed rape and winter wheat.
Primary data from various AFS management processes and secondary data collected from various sources including databases such as the Ecoinvent are used to establish the life cycle inventory for the different AFS-treatments and cropland control treatment. A detailed model of the system showing various operations are shown in Figure 1. The impact assessment focuses solely on the impact category climate change (GHG). It follows the life cycle GHG emissions (from cradle to farm gate), in accordance with DIN EN ISO 14040 (DIN, 2021) within the study's system boundaries (Figure 1). To derive the life cycle GHG emissions, two functional units (FU): (1) total GHG emissions per hectare (GHGL; kg CO2e ha– 1) and (2) carbon footprint per unit product (CFP; kg CO2e kg−1) are calculated as follows:
Total GHGL (kg CO2e ha−1) = Upstream emissions (kg CO2e ha−1) + On-field emissions (kg CO2e ha−1) + Downstream emissions (kg CO2e ha−1)………………………….(1)
Total CFP (kg CO2e ha−1 ) = (Total GHGL)/(Wood / Yield) (〖kg CO2e ha〗^(-1)/(MT 〖ha〗^(-1) ))……………………....(2)
Results and Discussion
The study assesses greenhouse gas (GHG) emissions in an agroforestry system (AFS), emphasizing the significant contributions of fertilizer inputs and N2O emissions in the crop component. Emissions in the tree component stem from CO2, CH4, and N2O from soil management and agricultural activities. Soil organic carbon (SOC) changes positively impact AFS versus cropland farming. Higher diesel consumption in AFS cropping is attributed to machinery maneuvering around trees. AFS shows potential for climate change mitigation through carbon capture and substitution of fossil fuels with short rotation coppice (SRC) wood. However, the comparison of AFS with cropland may provide an incomplete picture and the comparison of AFS with cropland, pure SRC might be a fairer, and policy relevant option that should be considered.The study highlights the importance of site-specific factors in determining the effectiveness of agroforestry systems in mitigating climate change.
References
DIN, E. (2009). 14040: Umweltmanagement–Ökobilanz–Grundsätze und Rahmenbedingungen. DIN: Berlin, Germany.
Swieter, A., Langhof, M., Lamerre, J., & Greef, J. M. (2019). Long-term yields of oilseed rape and winter wheat in a short rotation alley cropping agroforestry system. Agroforestry Systems, 93, 1853-1864.
| Keywords | agroforestry; climate change; green house gas; life cycle assessment; trade off |
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