Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Coastal Ecosystems Research Station of the Yangtze River Estuary, Institute of Biodiversity Science, School of Life Sciences, Fudan University, 2005 Songhu Road, Shanghai 200438, People's Republic of China.
Proc Biol Sci. 2020 May 27;287(1927):20200483. doi: 10.1098/rspb.2020.0483.
Nitrogen addition affects plant-arbuscular mycorrhizal fungi (AMF) association greatly. However, although the direct effect of nitrogen addition on AMF colonization has received investigation, its indirect effect through shifts in plant community composition has never been quantified. Based on a 7-year nitrogen addition experiment in an alpine meadow of Qinghai-Tibet Plateau, we investigated the effects of nitrogen addition on plant community, AMF diversity and colonization, and disentangled the direct and indirect effects of nitrogen addition on community AMF colonization. At plant species level, nitrogen addition significantly decreased root colonization rate and altered AMF community composition, but with no significant effect on AMF richness. At plant community level, plant species richness and AMF colonization rate decreased with nitrogen addition. Plant species increasing in abundance after nitrogen addition were those with higher AMF colonization rates in natural conditions, resulting in an increased indirect effect induced by alternation in plant community composition with nitrogen addition, whereas the direct effect was negative and decreased with nitrogen addition. Overall, we illustrate the effect of nitrogen addition and plant species in influencing the AMF diversity, demonstrate how shifts in plant community composition (indirect effect) weaken the negative direct effect of nitrogen addition on community-level AMF colonization rate, and emphasize the importance of plant community-mediated mechanisms in regulating ecosystem functions.
氮添加对植物-丛枝菌根真菌（AMF）的关联有很大的影响。然而，尽管氮添加对 AMF 定殖的直接影响已经得到了研究，但它通过植物群落组成的变化产生的间接影响从未被量化过。基于青藏高原高寒草甸的 7 年氮添加实验，我们调查了氮添加对植物群落、AMF 多样性和定殖的影响，并厘清了氮添加对群落 AMF 定殖的直接和间接影响。在植物种水平上，氮添加显著降低了根系定殖率并改变了 AMF 群落组成，但对 AMF 丰富度没有显著影响。在植物群落水平上，植物物种丰富度和 AMF 定殖率随着氮添加而下降。氮添加后丰度增加的植物种是在自然条件下具有更高 AMF 定殖率的植物种，这导致了植物群落组成变化引起的间接效应的增加，而直接效应是负面的，并随着氮添加而减少。总的来说，我们说明了氮添加和植物种在影响 AMF 多样性方面的作用，展示了植物群落组成变化（间接效应）如何削弱氮添加对群落水平 AMF 定殖率的负面直接效应，并强调了植物群落介导的机制在调节生态系统功能方面的重要性。
