Distinct microbial communities alter litter decomposition rates in a fertilized coastal plain wetland

Abstract

Anthropogenic disturbances have led to increased deposition of nitrogen (N) and phosphorus (P) into soils. Nutrient enrichment of soils is known to increase plant biomass and also increase rates of microbial litter decomposition. Thus, examining plant-soil-microbial interactions and their influence on decomposition rates is essential for predicting microbial contributions to carbon (C) cycling as atmospheric deposition persists. This study explores how changes in organic C, nitrogen (N), and phosphorus (P) caused by long-term nutrient enrichment and known litter-type composition influence soil microbial community structure and function. It is hypothesized that long-term nutrient enrichment causes shifts in soil microbial community structure that lead to higher rates of litter decomposition. Further, plant litter with a lower C: N ratio (compared to high C:N ratio litter) is expected to decompose faster due to an available N source provided to nutrient-starved microbes. We leverage a long-term experimental fertilization and disturbance by mowing experiment to test how nutrient enrichment affects decomposition and soil bacterial community structure in a nutrient poor coastal plain wetland. In each of eight replicate mowed/fertilized and mowed/unfertilized plots, bags of two different litter types (high C:N ratio rooibos tea and low C:N ratio green tea) were buried for 111 days. We characterized litterassociated and bulk soil microbiomes using 16S rRNA bacterial sequencing and quantified litter mass losses. As predicted, the green tea litter decomposed faster than the rooibos tea litter.Results also revealed that distinct bacterial communities were involved in decomposing rooibos tea litter (higher C:N ratio) more quickly in fertilized compared to unfertilized especially under drier soil conditions, while decomposition rates of green tea litter (lower C:N ratio) were similar between fertilized and unfertilized plots. Bacterial community structure in part explained litter decomposition rates, and long-term fertilization and drier hydrologic status affected bacterial

Soil Nutrient and Vegetation Diversity Patterns of Alpine Wetlands on the Qinghai-Tibetan Plateau

“…Generally, a high organic content in the soil should have a positive effect on plant communities because of the resources from decomposing plants [67]. However, in the GTAP wetlands, soil has a higher C:N ratio and is expected to decompose slower owing to the lack of available N sources for nutrient-starved microbes, resulting in lower plant species diversity [68]. Soil pH was significantly negatively related to biomass and was not significantly related to species diversity in the GTAP wetlands.…”