Resolving the Dryland Decomposition Conundrum: Some New Perspectives on Potential Drivers

Abstract

Decomposition of organic matter is a crucial component of biogeochemical cycles that strongly controls nutrient availability, productivity, and community composition. The factors controlling decomposition of litter in arid and semi-arid systems remain poorly understood, with an unresolved disconnect between meas- ured and modeled decay rates. In contrast, decay rates in mesic systems are gener- ally quite successfully predicted by models driven by climatic variables. Here, we explore the reasons for this disconnect by reviewing literature on the biotic and abiotic controls over dryland decomposition. Recent research on decomposition in drylands suggests that several key drivers of dryland decomposition have been historically overlooked and not included in models. In particular, UV photodegra- dation and soil transport processes, both a function of vegetation structure, may strongly influence dryland decomposition dynamics. We propose an expanded framework for studying dryland decay that explicitly addresses vegetation structure and its influence on decomposition. Spatial heterogeneity of vegetation in dryland systems necessitates considering how the spatial and temporal context of vegetation influences soil transport patterns and UV photodegradation, both of which may in turn affect abiotic and biotic decomposition processes.