Linking variability in soil solution dissolved organic carbon to climate, soil type, and vegetation type

Lateral transport of carbon plays an important role in linking the carbon cycles of terrestrial and aquatic ecosystems. There is, however, a lack of information on the factors controlling the concentration of dissolved organic carbon (DOC) in soil solution across large spatial scales and under different soil, vegetation and climate conditions. We compiled a database on DOC in soil solution and analyzed it with the aim, firstly, to quantify the differences in DOC concentrations among terrestrial ecosystems, climate zones, soil and vegetation types at global scale and, secondly, to identify potential determinants of the site-to-site variability of DOC concentration in soil solution across European broadleaved and coniferous forests. Overall, we found larger DOC concentrations in organic than in mineral soil and temperate sites showed larger DOC concentrations than boreal and tropical sites. For both forest types, nitrogen availability played a key role for the site-to-site variability of DOC, probably by regulating the microbial activity. Aluminum and iron are also important determinants of DOC variability, reflecting pH controls on DOC concentrations. Site productivity was more important for explaining DOC in broadleaved forests, whereas water balance was more important in coniferous stands. Overall, our results show that the magnitude and the controlling factors of DOC in soil solution differ between forest types