Elevated atmospheric CO2fuels leaching of old dissolved organic matter at the alpine treeline

摘要: [1] Dissolved organic matter (DOM), the mobile form of soil (SOM), plays an important role in C cycling and nutrient transport. We investigated effects 5 years CO2 enrichment (370 versus 570 μmol mol−1) on DOM dynamics at alpine treeline, including analysis fast-cycling components such as low molecular weight acids (LMWOAs), dissolved carbon (DOC) biodegradability, decomposition 14C-labeled oxalate. Concentrations DOC canopy throughfall were 20% higher elevated CO2, probably driven by carbohydrate concentrations leaves. In layer, increased water-extractable 17% solution cm depth 20%. The 13C tracing recently assimilated revealed that input recent plant-derived (<15% total DOC) was smaller than CO2-induced increase DOC. This strongly suggests enhanced mobilization native DOC, which is supported significant increases nitrogen (DON). mainly attribute these to a stimulated microbial activity indicated basal respiration rates (+27%). oxalate more rapidly mineralized from high soils. LMWOAs, but also those “hydrophilic” biodegradable (6% DOC), were, however, not affected suggesting production consumption “labile” balance. summary, our data suggest speeded up SOM late successional treeline ecosystem older through activity. Such “priming effect” implies can accelerate turnover SOM, thus, it may induce increasing losses old thick layers.