Litter chemistry changes more rapidly when decomposed at home but converges during decomposition–transformation

Abstract

Recent evidence suggests that soil organic matter (SOM) is largely composed of microbial products rather than plant compounds that resist decomposition. The chemical transformation of leaf litter components during decomposition is critical in controlling SOM formation. Plant leaf litter tends to decompose faster in its native environment than when it is placed under other vegetation types. This home-field advantage (HFA) suggests that decomposer communities are specialized to most efficiently degrade the litter found in their native environment, possibly through the production of specific enzymes that degrade unique compounds within that litter. Could this affect the degree to which leaf litter chemistry is altered during decomposition? We used pyrolysis-molecular beam mass spectrometry (py-MBMS) to analyze whether the chemistry of aspen and lodgepole pine litter was altered to a greater degree when decomposed in its home environment compared to an away environment. We had previously reported a 4% HFA for pine litter decomposition rates in this reciprocal experiment, and attributed that effect to differences in decomposer communities. Our high-resolution analysis revealed that litter chemistry also changed to a greater extent in its home environment. The changes in litter chemistry were more pronounced for the more recalcitrant pine litter, suggesting that decomposer community specialization is more important for recalcitrant litter. The accumulation of microbial products and microbially-transformed plant components resulted in an overall convergence in litter chemistry as decomposition proceeded, but the imprints of both initial litter chemistry and decomposer communities remained evident. The detection of new compounds in decomposed litter and the HFA effect on litter chemistry suggest that decomposer communities affect both the rate at which individual compounds within litter are decomposed, and the chemical nature of compounds that are incorporated into SOM.