Climate change in Central Europe results in the gradual replacement of spruce trees with beech. To model its potential impact, we used 22-year data of soil moisture under both tree species. The drier the summer season, the greater the difference between the two: the main reason was the higher transpiration of beech canopy compared to spruce. An accelerating transition of the Central European montane forest water balance from a fully energy-limited state towards water-limitation was documented.