The Science

Root litter represents a significant carbon input to soil organic matter; however, few studies have considered how soil environment affects root litter decay rates, or how decaying roots influence the decay of leaf litter and soil organic matter. Given that forest soil environments are in large part determined by the type of root fungus that associates with trees, researchers investigated how these tree-associated fungal groups affect litter decay.

The Impact

This research incorporated an extensive experimental design, which provides a framework for testing future hypotheses about litter-soil organic matter interactions and identifies novel mechanisms that necessitate further exploration in situ. This study lays the groundwork for further research to determine the generality of tree root fungus influence on litter decay.

Summary

Researchers used a factorial combination of fungal (i.e., mycorrhizal) soil type (including mixtures of mycorrhizal soils), litter treatments (roots, leaves, and combinations), litter mycorrhizal types, and replications, resulting in 144 different microcosms to measure the interactions of these factors on litter decay. Of the two primary root fungus types, arbuscular mycorrhiza (AM) and ectomycorrhiza (ECM), researchers found that AM root litters decompose faster. The study also demonstrated that decaying roots increased leaf litter mass loss, but only in microcosms containing soils of the same origin. Overall, these results suggest that features of root, leaf and soil organic matter decay are intertwined, and that measurements of these processes in isolation may lead to incorrect estimates of the magnitude and source of carbon losses from soils.

Principal Investigator

Joshua B. Fisher
UCLA, JPL
joshbfisher@gmail.com

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
daniel.stover@science.doe.gov

Funding

DOE BER Environmental System Science (formerly Terrestrial Ecosystem Science) program and the  NSF Ecosystem Science program.

References