Biotic and abiotic modifications of leaf litter during dry periods affect litter mass loss and nitrogen loss during wet periods

1. Decomposition of organic matter in semiarid ecosystems is a key component of the terrestrial carbon (C) cycle. The well-known inaccuracies in predicting litter decay in water-limited regions were lessened by considering solar radiation as an abiotic decay driver of photodegradation. Moreover, exposure to high solar irradiance in dry periods often led to massive facilitation of litter decay in subsequent wet periods (“photoacceleration”), though in many studies this effect was absent. 2. Recently, water vapor and dew were identified as modulators enabling substantial microbial degradation during rainless periods. Here we asked, (i) if the activity of microorganisms modifies litter traits, such as litter quality and microbial community in dry periods, consequently altering the loss of litter mass and nitrogen (N) in wet periods, and (ii) whether it can co-occur with photoacceleration. 3. By successively introducing litter to the field at the beginning and the end of the dry season, we...