Water supply during the vegetation period (FOEN, WSL)
The trees often have less water available during the vegetation period. The water supply during the vegetation period is decisive for the growth and vitality of the forests. The availability of water can be calculated from the difference between precipitation and potential evaporation. This is the climatic water balance. If the soil reservoir is added, the site water balance is calculated. The site water balance is closely related to the occurrence of trees, their vitality and growth. The tree species have different demands on the water supply. While oaks are frugal, spruce need considerably more water during the vegetation period.
Climate change and its impacts on humans and the environment are among the central societal challenges of the 21th century. According to the current scenarios of the International Panel on Climate Change the climate over the next 100 years in Switzerland will become warmer, dryer and more extreme.
The program «Forests and Climate Change» was launched in 2009 as a joint effort of the Federal Office for the Environment (FOEN) and WSL. It has come to an end in September 2018. Within its scope solid fundamentals were developed to evaluate the effects of climate change on tree species composition and forest growth.
Further information: www.wsl.ch
Link to the map: map.geo.admin.ch