Uncertainty of water balance simulations related to soil parameterization in Alpine forests under climate change conditions

Stockholm

2024

3646

Bandaufführung

40005290

Climate-change-induced stress in forest ecosystems will have consequences for society worldwide. A decent understanding of future ecological conditions is required to identify suitable actions for dampening these stresses. A major impact of climate change is the gradual shift in water balance which can lead to drought stress in forest stands in many parts of the world. Soil-vegetationatmosphere transport (SVAT) models are useful tools for investigating the water balance under current and future climate conditions. However, using such models in Alpine environments with spatially heterogeneous edaphic conditions strongly depends on the parameterization of soil properties. The present study investigates the sensitivity of water balance simulations and their uncertainty towards soil characteristics under current and future climate conditions. A lumped, physically-based SVAT model (LWF-Brook90R) was used to reproduce the water balance at 1823 mapped forest sites in Tyrol (Austria). For the soil parameterization, detailed laboratory analyses based on samples taken at multiple depths were available for 102 locations. At all other locations soil texture classes and bulk density in each soil horizon had been assessed with field methods. Based on interpolated meteorological observations and bias-corrected climate projections, the water balance was derived under current (1991-2020) and future conditions (2036-2065, 2071-2100). Using generic parameterizations of forest stands of native tree species (European beech, Norway spruce, European black pine), the uncertainty of the modelling results and derived drought stress indicators towards soil input parameters was evaluated. To do so, the soil parameters (texture, bulk density, organic content) were systematically sampled at each site to represent the respective texture class mapped in the field and the variability indicated by the laboratory results. The results suggest that soil parameterization has a strong influence on the resulting water balance components (e.g., evaporation, transpiration). Depending on the considered representative concentration pathway scenario, the soil-related uncertainty can be in the same order as projected changes due to climate change. This highlights the importance of reliable soil parameterizations for assessing climate change impacts on the water balance in Alpine forests. This work was carried out within the WINALP21 project, funded by the INTERREG VI-A program (grant number BA0100020).