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Inneralpine valleys are experiencing repeated summer droughts, which have caused a die-back of pine forests since the 1990s. Drought limits the metabolic activity and hence C cycling in the plant and soil system. The net effects of drought on soil organic matter (SOM) storage is, however, ambiguous as drought affects both C inputs and outputs. Moreover, in the long-term, water limitation is also altering above-and belowground diversity due to species-dependent resistance and adaptation to drought. In our study, we explored how ten years of irrigation of a water-limited pine forest in the central European Alps altered above-and belowground diversity and C cycling in the plant and soil systems. The decadal long irrigation during summer time strongly increased ecosystem productivity with litter fall and fine root biomass being increased by+ 50 and+ 40%, respectively. At the same time, soil CO2 efflux was stimulated …