Silica decouples fungal growth and litter decomposition without changing responses to climate warming and N enrichment.

Ongoing global changes, such as climate warming and increasing supply of reactive nitrogen (N), are expected to affect essential ecosystem processes such as the decomposition of plant litter. Determining the influence of environmental heterogeneity on the magnitude of these effects remains an important task, with silicon (Si) availability being a notable component of this heterogeneity, especially for grasses. We conducted an outdoor enclosure experiment to test if increased Si supply to a widespread foundation species (.Phragmites australis) alters the effect of climate warming and excess N supply on litter decomposition by curbing fungal decomposers. Consistent with expectations, Si supply during plant growth reduced fungal biomass in decomposing leaf blades by 50%, an effect that was doubled by excess external N supply. These strong impacts, however, did not directly translate to reduced litter decomposition or associated changes in nutrient dynamics. Instead, plant tissue-specific effects determined the influence of Si, N, and elevated temperature on litter mass loss. Specifically, Si accelerated the decomposition of leaf sheaths, warming enhanced leaf-sheath and leaf-blade decomposition, and N decreased the decomposition of culm litter, in line with expectations based on differences in litter chemistry. Thus, despite highly detrimental effects of Si and N on fungal decomposers, compensation by other members of the microbial community could dampen the realized impact of these global-change factors on the decomposition of plant litter in the future. [ABSTRACT FROM AUTHOR]