Alpine peatlands are highly vulnerable ecosystems worldwide and are endangered by global warming. Peat moss metabolism and growth are governed by rainfall and the level of the water table in the moor. In a protected alpine peatland three sites with different distances from the open water and the water table were chosen to evaluate higher plant diversity and to determine the photosynthetic performance of some plants and of the peat moss layer (mainly Sphagnum sp.) at these sites using fast fluorescence kinetics (OJIP-test). The photosynthetic activity of peat moss decreased with greater distance from the water level. In contrast, photosynthesis of Carex was impeded at higher water levels. In the context of global warming, if increasing temperature and stronger winds dry the peat moss cover, the differences in observed stress response by a changing water table, we expect that higher plants will overgrow the peatmoss site, a phenomenon already partially observed in recent decades.