2026-04-08 中国科学院（CAS）
中国科学院応用生態研究所の研究チームは、温帯林における菌根タイプ別樹種の分布を15年以上の長期データで解析し、土壌肥沃度が決定的要因であることを示した。菌根にはAM（アーバスキュラー菌根）とEcM（外生菌根）があり、肥沃な土壌ではAM樹種が成長率向上・死亡率低下を示す一方、貧栄養土壌ではEcM樹種が優勢となる傾向が確認された。結果は、環境条件が種の分布を規定する「環境フィルタリング仮説」を強く支持した。一方、樹木が土壌を改変して優占を維持する仮説は分布形成には主要因でないと結論づけられた。さらに、落葉の栄養バランスが植物‐土壌相互作用に重要であることも示され、生態系の養分循環理解に貢献する成果となった。
Conceptual framework illustrating two hypotheses for the distribution of AM- and EcM-associated tree species along a soil fertility gradient (Image by ZHU Meihui)
＜関連情報＞
- https://english.cas.cn/newsroom/research-news/202604/t20260408_1155406.shtml
- https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2745.70298
環境フィルタリングが、温帯林における土壌肥沃度勾配全体にわたる菌根樹の優占を促進する Environmental filtering drives mycorrhizal tree dominance across a soil fertility gradient in a temperate forest
Meihui Zhu, Zhichao Xu, Nicolas Fanin, Mengxu Zhang, Ji Ye, Fei Lin, Zikun Mao, Xugao Wang
Journal of Ecology Published: 16 March 2026
DOI:https://doi.org/10.1111/1365-2745.70298
Abstract
- Trees associated with arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) fungi are commonly thought to dominate in nutrient-rich and nutrient-poor environments, respectively. However, the mechanisms underlying this pattern remain poorly understood. Here, two potential drivers were evaluated: (i) environmental filtering, where soil fertility shapes tree species dominance by regulating growth and mortality; and (ii) tree-mediated regulation, where trees modify soil conditions in ways consistent with their mycorrhizal strategy.
- The importance of these drivers was tested using a comprehensive 15-year dataset for a 25-ha temperate forest dynamics plot, including data on individual trees, soil properties, leaf litter production and leaf litter nutrient content. Generalized linear mixed models were employed to estimate the effects of initial soil properties on tree mortality and growth. Leaf litter disposal models and structural equation models were utilized to evaluate the effects of mycorrhizal dominance on changes in soil properties over time.
- Consistent with the environmental filtering hypothesis, EcM tree mortality increased with soil fertility, while growth declined. However, EcM dominance did not drive soil impoverishment as predicted (i.e. tree-mediated regulation hypothesis). Instead, EcM dominance was associated with the accumulation of total phosphorus and with reduced losses of available nitrogen and phosphorus over time. Furthermore, leaf litter stoichiometry rather than absolute nutrient levels mediated the effects of EcM dominance on soil physicochemical properties.
- Synthesis. These results highlight that environmental filtering largely contributes to the distribution of mycorrhizal-associated trees along a soil fertility gradient. Although tree-mediated regulation did not directly shape tree distributions, it tended to modify soils in directions opposing their associated niche. This study refines our understanding of plant–soil feedback mechanisms, highlighting that community assembly is primarily governed by local soil conditions, whereas plant-induced modifications develop more slowly through time.
