Decomposition of plant litter is a fundamental biogeochemical process, integral to ecosystem nutrient cycles. While numerous studies have yielded rich amounts of data describing how litter chemical content relates to its decomposition, most focus only on initial chemistry as an indicator of how litter will behave throughout decomposition. This limits our understanding of later stages of decay, which are important for long-term ecosystem processes and biogeochemical cycling. If litter chemistry does not change in parallel to the initial differences, our ability to predict the later stages of decomposition will be limited. We analyzed changes in litter chemistry throughout decomposition from a variety of litter species from across multiple ecosystems using archived litter decomposition samples. We explored whether diverse plant litter types maintain initial chemical differences throughout decay, remaining chemically unique, or if decomposing litter follows different chemical trajectories over the course of decomposition. Further, we investigate how these trajectories relate to litter decay rate, and we attempt to identify the local environmental drivers, including climate and decomposer communities that may influence the patterns and temporal variability in litter chemistry during decomposition.
We have collected 43 datasets from completed litter decomposition studies, primarily from Long-Term Ecological Research (LTER) sites, in which some measure of litter chemistry was measured throughout decomposition (i.e., beyond initial chemistry). Of these datasets, the most frequently-measured chemical parameters are %C and %N (75 and 100% of studies, respectively). %P is measured less often (35% of studies), and other elements (e.g., Na, S, Fe, Mg, etc.) are measured infrequently (2-20% of studies). Almost half of the studies measure lignin (47%), and only one fifth of the studies measured some category of phenolic compounds. Of the 43 datasets we have selected, 37% of them measure some aspect of the decomposer community throughout decomposition. Most of these focus on the microbial community, such as enzyme analysis, phospholipid fatty acids (PLFA), or bacterial biomass, though some also measure nematodes, microarthropods, and insects. The data from these various datasets, in addition to new analyses on these existing samples, will clarify whether the suite of litter chemical characteristics known to influence decomposition follow consistent patterns throughout decay across systems (e.g., forest, desert, agriculture, etc.), or whether initial litter chemistry is the main determinant, which will aid our prediction of nutrient return and C dynamics in the litter layer.