A Cross-System Analysis of Litter Chemical Dynamics Throughout Decomposition

Decomposition of plant litter is a fundamental ecological process, integral to soil formation, soil organic matter chemistry, and biogeochemical cycling. However, much of our understanding of decay dynamics focuses on rates of litter mass loss and therefore carbon dynamics, with relatively less exploration of the chemical nature of litter decomposition during which the degradation of litter structural and metabolic compounds into fragments are either metabolized or ultimately incorporated into soil humus. Our understanding of the patterns of changes in litter chemistry throughout decomposition is incomplete, as few studies have measured chemical content beyond initial litter chemistry and throughout decay, and particularly not chemistry beyond carbon and nitrogen. The existing literature also reports idiosyncratic instances of litter chemical convergence and divergence. We used archived litter decomposition samples and data from across the U.S. Long-Term Ecological Research Network to investigate the trajectory of a comprehensive array of litter chemistry, including nutrient, structural, and metabolic parameters, across a wide variety of plant functional types and ecosystems, throughout the first 70% of mass loss. Our results do not yield a universally common pattern of litter chemical trajectories across all functional types and regions, and very limited evidence of convergence or divergence in chemistry over time, mostly within the nutrient elements. We provide details about the behavior of individual chemical parameters to functional type and region over decay. Changes in plant communities driven by global change may alter nutrient cycling and SOM formation through persistence or divergence on litter chemistry inputs.