Zhao Aihua, Liu Lei, Xu Tianle, Shi Leilei, Xie Wei, Zhang Wei, Fu Shenglei, Feng Haiyan, Chen Baodong
State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.
University of Chinese Academy of Sciences, Beijing, China.
Front Plant Sci. 2018 Dec 11;9:1842. doi: 10.3389/fpls.2018.01842. eCollection 2018.
Nitrogen (N) deposition and precipitation could profoundly influence the structure and function of forest ecosystems. However, conventional studies with understory additions of nitrogen and water largely ignored canopy-associated ecological processes and may have not accurately reflected the natural situations. Additionally, most studies only made sampling at one time point, overlooked temporal dynamics of ecosystem response to environmental changes. Here we carried out a field trial in a mixed deciduous forest of China with canopy addition of N and water for 4 years to investigate the effects of increased N deposition and precipitation on the diversity and community composition of arbuscular mycorrhizal (AM) fungi, the ubiquitous symbiotic fungi for the majority of terrestrial plants. We found that (1) in the 1st year, N addition, water addition and their interactions all exhibited significant influences on AM fungal community composition; (2) in the 2nd year, only water addition significantly reduced AM fungal alpha-diversity (richness and Shannon index); (3) in the next 2 years, both N addition and water addition showed no significant effect on AM fungal community composition or alpha-diversity, with an exception that water addition significantly changed AM fungal community composition in the 4th year; (4) the increment of N or water tended to decrease the abundance and richness of the dominant genus and favored other AM fungi. (5) soil pH was marginally positively related with AM fungal community composition dissimilarity, soil NH -N and N/P showed significant/marginal positive correlation with AM fungal alpha-diversity. We concluded that the effect of increased N deposition and precipitation on AM fungal community composition was time-dependent, mediated by soil factors, and possibly related to the sensitivity and resilience of forest ecosystem to environmental changes.
氮（N）沉降和降水会深刻影响森林生态系统的结构和功能。然而，以往在林下添加氮和水的常规研究很大程度上忽略了与树冠层相关的生态过程，可能并未准确反映自然状况。此外，大多数研究仅在一个时间点进行采样，忽视了生态系统对环境变化响应的时间动态。在此，我们在中国一片落叶混交林中进行了一项为期4年的野外试验，通过树冠层添加氮和水，以研究增加的氮沉降和降水对丛枝菌根（AM）真菌多样性和群落组成的影响，AM真菌是大多数陆生植物普遍存在的共生真菌。我们发现：（1）在第1年，添加氮、添加水及其相互作用对AM真菌群落组成均有显著影响；（2）在第2年，仅添加水显著降低了AM真菌的α多样性（丰富度和香农指数）；（3）在接下来的2年中，添加氮和添加水对AM真菌群落组成或α多样性均无显著影响，但有一个例外，即添加水在第4年显著改变了AM真菌群落组成；（4）氮或水的增加倾向于降低优势属的丰度和丰富度，并有利于其他AM真菌。（5）土壤pH与AM真菌群落组成差异呈微弱正相关，土壤铵态氮和氮/磷与AM真菌α多样性呈显著/微弱正相关。我们得出结论，增加的氮沉降和降水对AM真菌群落组成的影响具有时间依赖性，受土壤因素介导，并且可能与森林生态系统对环境变化的敏感性和恢复力有关。
