Mixing effects of litter decomposition at plant organ and species levels in a temperate grassland

Abstract

Non-additive effects during the decomposition of mixed litter at species level have important consequences on ecosystem nutrient cycling, whereas such effect at plant organ level remains unclear. We investigated mass loss and nutrient release of single and mixed litter from leaf and culm for a dominant grass and of shoots for two dominant grasses under both ambient and enriched N conditions in a temperate grassland. We found comparable mixing effects on litter mass loss and nutrient release at organ and species levels after 2-yr decomposition. Nitrogen enrichment stimulated litter mass loss of all litter types but did not alter the mixing effects on mass loss. Further, N enrichment enhanced the non-additive effects of mixing on N release at plant organ level but not at species level. This study extend the non-additive effects of litter decomposition from inter-specific level to intra-specific level by highlighting the synergistic interaction between leaf litter and culm litter during decomposition. Given the existence of non-additive mixing effects at plant organ level, it is more difficult to predict litter decomposition and nutrient cycling in herbaceous communities.