Czech forest drought: warming boosts evaporation and risk

Warming is increasing evaporation in Czech forests, which raises the risk of drought even when rainfall stays almost unchanged. That is the picture from long-term measurements in a number of forest catchments, presented at a scientific conference on forest hydrology.

Heat boosts evaporation

The data show that rising temperatures lead to more evaporation and less water runoff from forest catchments. Warm winters and a shrinking store of water in the snowpack remain a problem too. Forest drought and its effect on trees also differ from the usual meteorological and agricultural drought.

Different tree species manage water in different ways, and their strategy also depends on how much water is currently in the soil. In Czech conditions most data exist for spruce and beech, while the behavior of other species has not been studied enough. The forest water balance also matters for replenishing groundwater.

Scientists’ data should be pooled

The presentations showed that universities and research institutes hold a lot of data that should be processed and interpreted jointly. Participants also discussed the role of dead wood and the moss layer in the water cycle, and how chipping logging residues affects the water regime of forest soils, tree health and the survival of plantings.

Erosion and hands-on experience

Much attention went to the erosion of forest soils: gullies usually form after downpours where forestry machinery moves. Proposed remedies include carefully routing forest roads and technical measures, as well as filling in gullies that have already formed. Representatives of Šumava National Park, Vojenské lesy a statky (Military Forests and Estates), the National Forest Centre in Zvolen and the company Aqua Terra Inova described their work on restoring peatlands and keeping water in the landscape.

Practical experience was also discussed on a field trip to forest holdings of the Diocese of Ostrava-Opava (Vrbno forest administration), where the Forestry and Game Management Research Institute (VÚLHM) carries out hydrological monitoring together with the Czech Hydrometeorological Institute. The conference was held under a project of the National Agency for Agricultural Research on the effects of climate change on small forest catchments.

Around Prague, based on reporting by ekolist.cz