BEF-China

Mycorrhizae are symbiotic associations between terrestrial plants and fungi in which fungi obtain nutrients in exchange for plant photosynthates. However, it remains unclear how different types of mycorrhizae affect their host interactions and productivity. Utilizing a long-term experiment with a diversity gradient of arbuscular (AM) - and ectomycorrhizal (EcM) trees, here we show that the type of mycorrhizae critically controls the effect of diversity on productivity. With increasing diversity, net primary production (NPP) of AM trees increased but EcM trees decreased, largely because AM trees are more effective in acquiring nitrogen and phosphorous. Specifically, with diversity increase, AM trees enhance both nutrient resorption and litter decomposition, while there is a tradeoff between litter decomposability and nutrient resorption in EcM trees. These results provide a mechanistic understanding of why and how AM trees dominate in vast tropical and subtropical forests, which would enable better prediction of ecosystem productivity in changing climates.

菌根（Mycorrhizae）是陆生植物与真菌之间形成的共生联合体，真菌以获取植物光合产物为代价，为宿主植物提供养分。然而目前学界仍未明确不同类型的菌根如何调控其宿主的种间互作与群落生产力。本研究依托一项设置了丛枝菌根（arbuscular mycorrhizae，AM）与外生菌根（ectomycorrhizal，EcM）树木多样性梯度的长期定位实验，结果证实菌根类型是决定多样性对生产力影响效应的核心调控因子。随着物种多样性水平提升，丛枝菌根树木的净初级生产力（net primary production，NPP）显著升高，而外生菌根树木的NPP则呈下降趋势，这一差异主要源于丛枝菌根树木在氮、磷养分获取方面具有更优的效率。具体来看，随着多样性增加，丛枝菌根树木可同时增强养分回收与凋落物分解过程；而外生菌根树木则在凋落物分解性与养分回收之间存在权衡关系。本研究结果为丛枝菌根树木为何能在广袤的热带与亚热带森林中占据生态主导地位提供了机制层面的解释，同时也将助力更精准地预测气候变化背景下的生态系统生产力。