Agroforestry, the integration of trees into farmland, is a promising approach to enhancing agroecosystem resilience and mitigate climate change. The potential of agroforestry systems (AFS) lies in the ability of trees to improve resource use by accessing both aboveground and belowground compartments and to contribute to soil rehabilitation through increased organic matter inputs. In recent years, the number of field studies and meta-analyses on AFS has increased considerably. However, these studies often focus on a limited set of soil parameters, despite the inherent complexity of soil health, which requires consideration of diverse metrics. A deeper understanding of the effects of AFS on soils and water cycles is essential to evaluate their contribution to resilient agroecosystems. This thesis aims to address this gap through: i) a second-order meta-analysis to synthesize existing knowledge, identify research gaps, and provide a comprehensive quantitative assessment of multiple soil health indicators; ii) a field study to evaluate the effects of AFS on soil health; iii) an investigation into (soil) water dynamics and crop stress. Using random effect and robust Bayesian meta-analysis, I will determine whether the soil-related impacts of AFS are exhaustively represented in the existing meta-analysis literature and evaluate the extent to which these findings can be scaled up. This work will offer a quantitative overview of AFS benefits across different climatic regions and inform decision-makers about the global potential of AFS implementation. In a network of 33 agroforestry farms in Switzerland, I will examine how AFS characteristics and management practices influence soil health, assessed through physical, chemical, and biological indicators. This research will support farmers in optimizing AFS design and management to improve soil health. Finally, I will explore the resilience of AFS to increasing weather variability by analysing seasonal water dynamics—specifically soil moisture and matrix potential—in a selected subset of systems. I will also assess crop yield variability and δ¹³C isotopic signatures in the field. These analyses will provide insights into the trade-offs and challenges of water provision in AFS under Swiss conditions. Taken together, this work will shed light on below-ground interactions in agroforestry systems and represent a step toward understanding their contribution to building more resilient agricultural systems.
