In low precipitation periods – where and how is the limited available water distributed and what possibilities are there for improving retention in the soil and the landscape? Researchers discovered that vegetation has a major influence on this. Using the example of the drought-sensitive Demnitzer Muehlenfliess in Brandenburg, they quantified visible and invisible water flows during and shortly after the drought of 2018. In the Demnitzer Mühlenfliess, the team investigated two sites with land uses typical for the region: a mixed forest site with sandy soils and a deep rooting zone; and grassland site with loamier soils and a shallower rooting zone. The forest soil was much drier, which is due to the characteristics of soil and plants.
For example, during the drought, the uppermost metre of the sandy soil in the forest contained only 37 litres per square metre, and under grassland there were as much as 146 litres of water per square metre. The treetops/leaf canopy of the forest shielded part of the rain that evaporated directly from the leaves and never reached the ground. Moreover, the sandy forest soil caused faster water flow through the soil and decreased water storage. Rainfall penetrated deeper into the soil, but was reabsorbed by the trees during the growing season before reaching the groundwater. Under the grassland, the water continuously recharged the groundwater. The soil could store more water. As the plants only took water from the upper soil, this led to “older” soil water.
The researchers work together with the agricultural and forestry sectors to bring their research results into practice. “We see that after the further dry seasons in 2019 and so far in 2020, the groundwater levels will continue to fall. The vegetation has still not been able to recover due to the low rainfall in the winter months. Unfortunately we are far from “normal” conditions.”
Source: Science Daily
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