Litter in aridlands usually exhibits a prolonged standing dead phase after senescence; however, our knowledge of aridland litter decomposition is almost exclusively derived from studies of litter on the soil surface. We know little about the ways in which abiotic and microbial processes affect standing litter decomposition, particularly in the context of global change. In this study, we conducted a 26-month in situdecomposition experiment in a typical steppe to investigate the potential mechanisms governing the decomposition of standing litter under ambient and drought conditions.
Results/Conclusions
We show that the decomposition rate (k) of standing litter is 92% faster than that of soil surface litter under ambient precipitation. The rapid decomposition of standing litter is the collective effect of (1) a high level of dissolved organic carbon (DOC) leaching associated with high DOC production caused by fluctuations in temperature and relative humidity and (2) high microbial decomposition due to the greater nighttime moisture content combined with the higher DOC concentration of standing litter. Drought treatment significantly decreased the litter decomposition rate and eliminated the difference in decomposition between standing and soil surface litter, which was primarily attributed to low DOC leaching loss and low microbial decomposition under drought conditions. Moreover, the standing phase conditions the litter, leading to more rapid decomposition after the litter falls to the soil surface and increasing the efficiency with which the litter forms soil organic carbon.