Comparing tree ring chronology and soil water model for a hydric hemiboreal forest

Air temperature and hence potential evapotranspiration trends are clearly positive worldwide, while precipitation trends are unclear largely due to large inherent variability. Apparently, because of climate change increasing evapotranspiration is likely to lead to depletion of soil water reserves in many ecosystems, but ecosystem feedbacks can have a nonlinear impact of the water regime. For example, in a hemi boreal forest at a hydric setting, higher evapotranspiration due to higher temperatures can lead to improved soil aeration, facilitating the rejuvenation of woody vegetation and further increase of transpiration. Process-based soil water models can be used to investigate such phenomena. However, the models need to be validated. Long time series of the forest soil water regime are sparce. Instead, the tree-ring width data (chronology) can be used as a proxy for growing conditions in the past, as the soil water regime has the firs order controlling factor. We are constructing a Hydrus-1D soil-water model for three hydric forest sample plots in Latvia using the e-obs data set for model forcing. The model results then are compared to the local tree-ring chronology, particularly examining pointer years as extreme cases for evaluating hydrological situation. The model will provide opportunity for scenario investigation of the interactions between climate and soil water regime in hemiboreal forest ecosystem. This work was supported by ERDF postdoctoral research project “Groundwater and soil water regime under climate change” (No. 1.1.1.2/VIAA/3/19/524).