A new conceptual model on the fate and controls of fresh and pyrolized plant litter decomposition

Abstract

In recent years, litter decomposition stud- ies have begun to move beyond the concept of mass loss to consider the fate of fresh and pyrolized decomposing plant material in the ecosystem. How- ever, these concepts have yet to be incorporated into conceptual models of litter decomposition. Under- standing how fresh and pyrolized plant litter chemical traits control the partitioning of mass loss to dissolved organic carbon (DOC) leaching and respiration to CO2 would help to inform models of litter-soil-atmosphere carbon (C) cycling. To test these controls, we incu- bated five fresh and one pyrolized leaf litters with differing chemistry and measured DOC and CO2 fluxes as well as changes in substrate and dissolved organic matter (DOM) chemistry over time using Fourier transformed infrared spectroscopy and wet chemistry. We found that the amount of hot water extractable C was a strong predictor of initial DOC leaching, while the lignocellulose index (Lignin/ (Lignin ? a-Cellulose)) was a strong inverse predic- tor of later stage DOC:CO2 partitioning. Changes in substrate and DOM chemistry indicated a progression of substrate availability for leaching: from soluble plant components, to partially decomposed cellulose and lignin, to microbial products. Based on these results we developed a new conceptual model that demonstrates how chemical traits of fresh and py- rolyzed plant litter can be used to predict the fate of aboveground organic matter decomposition and form a better linkage between aboveground decomposition and terrestrial ecosystem C cycling.