Final Activity Report Summary - CLISO (Climate change impacts in a karst landscape of the Austrian Alps: effects on the soil resources) The impacts of climatic changes can significantly alter a soil's inherent quality. Soil organic matter deserves special attention in this context because of its key role in many important soil processes, its rapid response to environmental changes, and its feedbacks to the atmospheric climate system. The overall objective of this project was to enhance the understanding of climate change impacts on the soil resources of Alpine ecosystems, with particular emphasis on soil organic matter. Experimental studies were conducted in the Hochschwab massif of the Austrian Limestone Alps. Several methodological approaches were combined in YRs 1 and 2 of the project to investigate climate effects on soil processes: (1) the empirical study of soils along a climatic gradient (i.e. an altitudinal climosequence); (2) manipulation experiments (i.e. translocation of soil cores to climatically different areas); (3) in-situ decomposition experiments in different elevation zones. The climosequence study revealed significant altitudinal changes in soil organic matter quantity and quality as well as microbial community composition. The soil organic carbon stocks showed an increase with increasing altitude from 900 to 1500 m above sea level (asl) followed by a decrease from 1500 to 1900 m asl. At the high-elevation sites, decreased net primary production and/or increased soil erosion may have counteracted the accumulation of soil organic matter, thus leading to lower carbon stocks. The quality of soil organic matter (analysed with Fourier-transform infrared spectroscopy) also changed along the studied climosequence, e.g. the aliphatic band (2920 cm-1) showed a significant increase with elevation. The ergosterol contents indicated altitudinal shifts in microbial community composition, with decreasing contributions of fungi with increasing elevation. The bacterial/fungal biomass ratio calculated using marker phospholipid fatty acids (PLFA) further confirmed this trend. First results (over an observation period of one year) from the soil translocation and decomposition studies showed (1) that the translocation of soil cores from higher to lower elevation zones resulted in rapid changes of microbial community composition, and (2) that litter decomposition proceeds significantly more slowly at high-elevation sites compared to low-elevation sites. During YR 3 of the project, additional monitoring will be conducted to enable the characterization of longer-term trends. Also in YR 3, the experimental data will be used to calibrate existing nutrient cycling models for the studied Alpine environment. The models will then be used to assess the impacts of projected future climate change on the soil resources and associated environmental consequences. Mountain regions are known to be especially vulnerable to climatic changes; however, process-based information on the climate sensitivity of alpine ecosystems is still scarce to date. The present project has generated such information for the Austrian Limestone Alps. The employed multi-methodological approach will further aid in discerning temporal response patterns and bridge the gap between short-term (and possibly transitory) responses and longer-term ecosystem change.