Project Details
Projekt
SP2: Water and nutrient fluxes
Subject Area
Soil Sciences
Ecology of Land Use
Ecology of Land Use
Term
since 2024
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 517723694
The overall objective of FORMULA is to evaluate the performance of silvo-arable agroforestry systems and to improve the mechanistic understanding of spatial patterns of Nature's Contribution to People (NCP). Sub-project SP2 focuses on the NCPs ‘regulation of freshwater quantity’, ‘regulation of freshwater quality’ as well as ‘soil formation and protection’. In particular, SP2 quantifies gradients in soil moisture, evaporation, transpiration, and soil nutrient content and turnover within agroforestry systems. The first objective of SP2 is to assess how the introduction of trees into arable fields affects the spatial dynamics of soil moisture, water fluxes and water flux partitioning (evaporation versus transpiration). The second objective is to assess the nutrient budget, nutrient use efficiency and spatial patterns of nutrient leaching (especially nitrogen) in successional agroforestry systems compared to treeless cropping systems. To achieve these objectives, SP2 tests two sub-project specific hypotheses. The first hypothesis states that soil moisture content increases with distance from the tree row due to higher transpiration by trees and grass strips. The second hypothesis suggests that tree and grass roots provide a "safety net" that reduces nutrient leaching losses near the tree line. Conversely, higher soil moisture and nutrient availability lead to increased leaching losses towards the centre of the crop alley. The expected net effect is lower nutrient leaching and higher nutrient use efficiency in agroforestry systems compared to treeless cropping systems, due to improved yield stability, nutrient capture and uplift by deep tree roots. The sub-project is divided into five work packages (WP). WP1 investigates soil moisture dynamics in space and time. It uses data from distributed soil moisture and temperature sensor networks to quantify spatial and temporal patterns. WP2 works on disentangling water fluxes between crops and trees. Stable isotopes of water will be measured to understand and unravel water fluxes between crops and trees within agroforestry systems. A low-cost soil nutrient mobility assessment method using resin bags in an innovative setup will be validated in WP3. The method will be applied in WP4 to quantify nutrient mobility gradients and to detect nutrient losses. Finally, WP5 will investigate nitrogen turnover processes and the nitrogen uptake of crops and trees through an in situ 15N labelling experiment. SP2 will lead the joint 15N experiment in collaboration with the coordination SP. Overall, in synergy with the other SPs of FORMULA, SP2 will provide a fundamental understanding of the effects of trees on the spatial and temporal dynamics of water and nutrient cycling in agroforestry systems, which will provide the basis for optimising these systems to maximise their benefits while minimising their limitations compared to treeless cropping systems.
DFG Programme
Research Units
Co-Investigators
Dr. Kathrin Grahmann; Professorin Dr. Suzanne Jacobs; Dr. Philipp Kraft
