Daniel Gliksman, Sabine Haenel, José M. Grünzweig
Decomposition of organic matter is a key factor determining the global carbon cycle, and thus affects the on-going changes in climate. The decay of above-ground plant material (litter) in drylands is not well understood, reducing the accuracy of predictions for the carbon cycle. Recently, water vapour and dew were identified as enabling substantial microbial decomposition of litter during rainless periods. We asked if the changes caused by microorganisms degrading litter during dry periods affect litter degradation in the wet season and the amount of nitrogen (N) in the litter. We placed litter samples in the field at the beginning and the end of the dry season and found, as we hypothesized, that microbial activity during the dry season affected litter mass and N loss during the wet season. Low microbial activity in the dry season led to inhibition of mass loss in the wet season, while high microbial activity led to facilitation of mass loss. Higher microbial activity during the dry season also caused strong inhibition of N loss from litter during the wet season, probably by enhancing the dry-season N loss. A second experiment manipulating the levels of microbial activity in the dry season supported our key results from the first experiment. Knowledge of biotic modifications of litter during dry periods, and their implication for the degradation of organic material during wet periods, enhances our understanding of litter decay in drylands. Furthermore, it can improve our capacity to predict and understand the global carbon cycle.