Effects of Historical and Likely Future Scenarios of Land Use on Above- and Belowground Vegetation Carbon Stocks of an Alpine Valley

Long-term trends including depopulation and shifts in agricultural policies and management have led to large-scale land-use changes throughout the European Alps which are likely to affect the size of carbon (C) stocks of the respective land-use types. This article analyzes landscape-scale changes of C-stocks present in the vegetation in relation to historical land use (1865), current land use (2003), and three contrasting scenarios of future land use (2020) in the Stubai Valley, Austria. Results show that more than 47% of the total valley area and more than 90% of the usable agricultural area have undergone a change in land use during the last approximately 140 years. Changes of land use were seen to peak between 1954 and 1973 and slow down there after. Phytomass and C-stocks in 1865 amounted to 63.1 Mg ha(-1) and 30.8 Mg C ha(-1), and increased until 2003 to 75.8 Mg ha(-1) and 37.2 Mg C ha(-1), respectively. Evaluations along an altitudinal gradient indicate the highest C gain to be in the sub-Alpine belt (more than doubling of the C-stock) due to the abandonment of pastures and hay meadows. All future scenarios project only a minor increase in phytomass (0.3-2.8 Mg ha(-1)) and C-stocks (0.2-1.4 Mg C ha(-1)) because major elements of the landscape (forests, rocks, screes) will be either largely unaffected or are unimportant in their spatial extent (built environment).