Autor:innen:
Dr. Daniel Schwindt | Georg-August Universität Göttingen - Geographisches Institut | Germany
Dr. Michael Dietze | Georg-August Universität Göttingen - Geographisches Institut | Germany
Dr. Simon Drollinger | Georg-August Universität Göttingen - Geographisches Institut | Germany
Dr. Jago Jonathan Birk | Georg-August Universität Göttingen - Geographisches Institut | Germany
Dr. Michael Klinge | Georg-August Universität Göttingen - Geographisches Institut | Germany
Prof. Dr. Daniela Sauer | Georg-August Universität Göttingen - Geographisches Institut | Germany
In the course of climate change, central Europe is currently facing increases in the intensity and duration of droughts and heat waves and, meanwhile, also in the frequency of heavy precipitation events. Related edaphic droughts have caused massive damage to forests. They are increasing due to shifts in precipitation patterns that also affect soil-hydrological functions. Surface runoff and preferential flow - both vertically and laterally - increase, leading to increasing heterogeneity in the soil-moisture distribution.
However, the analysis of soil-moisture dynamics is usually based on point measurements that do not fully capture this heterogeneity. Here, we combined established point measurements with geophysical methods to assess the spatio-temporal soil-moisture dynamics from the slope scale to the root-zone scale. Thereby, we explored, how vertical and lateral subsurface water flow, and soil-moisture distribution along a slope are affected by (i) subsurface architecture, including textural variations and preferential flow paths; (ii) hydrological extremes (droughts and precipitation events).
Our study area is located in a beech forest 10 km NE of Göttingen, near Ebergötzen (central Germany). The local soil pattern is dominated by Cambisols that developed in periglacial slope deposits with varying admixtures of loess, overlying Triassic sandstone. Meteorological data, throughfall, stemflow, soil moisture, matric potential, and sap flow are recorded at 15 min time intervals. Thus, soil-moisture dynamics are measured on a point-by-point basis with high temporal resolution, providing an ideal set-up to validate complementary approaches that are able to capture spatial heterogeneity. We used primarily high-resolution electrical resistivity tomography, combining long-term (fortnightly/monthly) and event-based measurements (e.g., during and immediately after thunderstorms).
Our data indicate that soil desiccation during prolonged dry periods proceeded relatively uniformly, with tree-root water uptake locally causing enhanced dynamics. In contrast, soil rewetting after precipitation events was spatially highly variable. Our results stress once more the importance of preferential flow for both vertical and lateral redistribution of water in soils, particularly in sloping terrain. They point to the urgent need for spatially highly resolved measurements to obtain a better understanding of soil-moisture dynamics under climate change.