Plant biochemistry and microbial community composition interactions determine litter decomposition dynamics

Plant biochemistry (nutrient content and carbon chemistry) controls litter decomposition through limiting microbial community composition and activity. We investigated the impacts of litter biochemistry on microbial community composition and enzyme production in the laboratory. We selected six Hawaiian forest species from three phylogenetic groups - angiosperms, basal ferns, and polypod (more recently derived) ferns. The six species exhibited an unusually wide range of nutrient content (N, P, cations) and carbon compounds (lignin, phenolics, cell wall sugars). Freshly senesced litter was sterilized and decomposed for one year on a low-nutrient substrate of sand, vermiculite, and soil inoculum; nutrients were added to some microcosms. Nutrient dynamics were analyzed over time. Additionally, we investigated microbial community activity and composition (using enzyme assays and qPCR) and litter carbon chemistry (using py-GCMS). The six species decomposed at very different rates, with decomposition constants ranging from 1.75 (an angiosperm) to 0.14 (a basal fern). Plant species varied in the type and amount of fungal communities, and resultant polyphenol oxidase and lignin peroxidase production, supported on their litter. We show that some biochemical differences with significant consequences for decomposition are conserved across closely related species.