Assessing the drought resilience of different land management scenarios using a tracer-aided ecohydrological model with variable root uptake distributions

Abstract. Land use strongly influences water partitioning, availability, and ecohydrological resilience in drought-sensitive regions. Forest management plays a critical role through its effects on water use, which depends on species composition, stand density, rooting depth, canopy structure, and age. However, the ecohydrological consequences of different forest management strategies – particularly in terms of blue and green water fluxes – remain poorly quantified for land use planning. This study conducted a series of modelling experiments using the tracer-aided conceptual ecohydrological model EcoPlot-iso as a decision-support tool. We investigated how variations in forest type (e.g., broadleaf vs. conifer), density, and root distribution influence water partitioning and ecohydrological resilience under different wetness conditions in the drought-sensitive lowland Demnitzer Millcreek catchment (DMC), northeastern Germany. Baseline simulations (2000–2024) across several land use types were used to develop a reference forest for comparison with alternative forest management scenarios. A key innovation in this version of EcoPlot-iso was the integration of a depth-dependent root water uptake function, allowing simulation of transpiration across forests with different rooting distribution, stand ages, and species compositions. The model was calibrated and validated using seven years of soil moisture and three years of soil water isotope (δ²H) data through a multi-criteria approach. Results showed that, on average, evapotranspiration was 8 % higher under conifers than broadleaf forests, and 12 % higher than agroforestry. Agroforestry, in contrast, provided the highest groundwater recharge – 11 % and 4 % more than conifers and broadleaf forests, respectively. Significant differences in water partitioning between dry and wet years were observed across management scenarios. Our findings highlight the potential of agroforestry, such as crop–tree mixtures, to mitigate drought impacts. The modelling framework provides a means to quantify and visualise the effects of land use change on water availability, supporting more informed decision-making for resilient land and water management.