Details

Autor(en) / Beteiligte

• Fang, Yuantian
• He, Xunyang
• Gao, Kun
• Zhu, Zihong
• Wang, Kelin
• Li, Dejun

Titel

Increasing plant species diversity suppresses free‐living N2 fixation in litter and soil of a subtropical karst forest

Ist Teil von

• Functional ecology, 2024-02, Vol.38 (2), p.391-402

Ort / Verlag

London: Wiley Subscription Services, Inc

Erscheinungsjahr

2024

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• Free‐living N2 fixation (FNF) is an important source of bioavailable nitrogen for forests. Though increasing plant species diversity (PSD) benefits soil nitrogen accumulation, how it impacts FNF rate has not been explored. Forty‐five plots covering a PSD gradient were selected in a subtropical karst forest, southwest China. FNF rates in leaf litter and soil were measured using acetylene reduction assay calibrated with a 15N2 fixation method. Diazotrophic community, litter and soil properties were determined as well. The nifH gene abundance was not significantly altered in litter but was significantly decreased in soil by higher PSD. Diazotrophic community's Shannon diversity was significantly increased by higher PSD in both litter and soil. Increasing PSD inhibited litter FNF rate via aggravating phosphorus limitation and decreasing the relative abundance of Betaproteobacteria and Deltaproteobacteria. For the mineral soil horizon, increasing PSD suppressed FNF rate via decreasing nifH gene abundance caused by elevated N availability and lowered phosphorus and iron availability or through decreasing the relative abundance of Deltaproteobacteria but increasing that of Betaproteobacteria. Our findings, for the first time, reveal the microbial and abiotic controls on FNF in litter and soil in response to PSD, and hence benefit the prediction of nitrogen input via biological N2 fixation under changes in PSD. Read the free Plain Language Summary for this article on the Journal blog. 中文摘要 自生固氮是森林生物可利用氮的重要来源。尽管植物物种多样性增加有利于土壤氮累积，但其如何影响自生固氮速率尚不清楚。 本研究在中国西南部的亚热带喀斯特森林中利用自然形成的树种多样性梯度建立了45个样方。采用乙炔还原法结合15N2培养法测定了叶片凋落物与矿质土壤的自生固氮速率。结合固氮微生物群落和理化性质阐释了树种多样性影响自生固氮速率的机理。 树种多样性对叶片凋落物的nifH基因丰度无显著影响，但显著抑制了矿质土壤的nifH基因丰度。叶片凋落物与土壤的固氮微生物香农多样性指数均随树种多样性的增加而增加。树种多样性增加通过加剧叶片凋落物中固氮微生物的磷限制程度以及降低Betaproteobacteria和Deltaproteobacteria的相对丰度，显著抑制了凋落物的自生固氮速率。对于矿质土壤，树种多样性增加通过提升土壤氮有效性以及降低磷和铁的有效性而抑制nifH基因丰度，或通过降低Deltaproteobacteria的相对丰度及增加Betaproteobacteria的相对丰度最终抑制了土壤自生固氮速率。 本研究首次揭示了树种多样性如何通过微生物和非生物因素影响凋落物和土壤的自生固氮速率，为预测在树种多样性变化背景下森林土壤氮动态提供了科学依据。 Read the free Plain Language Summary for this article on the Journal blog.