BEF-China

Nutrient resorption and litter decomposition recycle about 90% of nitrogen (N) for plant growth. Plants benefit from mycorrhizal symbiosis to enhance their nutrient access. When competition intensifies, whether mycorrhizal plants can adjust the trade-off between nutrient resorption and litter decomposition to optimize their N supply remains unresolved. We studied nutrient strategies of arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) trees in a subtropical forest diversity experiment, where the two mycorrhizal types were evenly planted in mixtures of 2, 4, 8 or 16 tree species. We found that net primary production (NPP) of EcM sub-communities declined but NPP of AM sub-communities increased with tree species richness. Tree species richness reduced nutrient resorption efficiency (NRE) of EcM trees, which increased leaf litter N concentration and thus its decomposition. However, by reducing the lignin concentration of leaf litter and increasing the richness of saprophytic fungi, tree species richness promoted NRE and litter decomposition for AM sub-communities. This demonstrates that AM trees are more effective in maintaining their N supply than EcM trees with increasing diversity, suggesting a new mechanism to explain the dominance of AM trees in high-diversity subtropical forests.<b></b>