3年高氮添加对黄山松土壤真菌网络稳定性的影响

The impact of reduced by three⁃year high nitrogen addition on stability of soil fungal network of Pinus taiwanensis

土壤真菌群落对维持生态系统功能至关重要,然而氮沉降等环境变化如何影响其稳定性尚不清楚。利用高通量测序和网络分析,探究了连续三年不同氮添加水平对土壤真菌群落特征的影响,并通过计算“内聚力”量化连通性以预测真菌网络的稳定性。结果表明,真菌多样性及其群落稳定性对氮添加的响应存在明显的时间效应。相比于前2年,第3年氮添加改变了真菌β多样性,且低氮添加显著提高了0—10 cm土层真菌Chao1和Shannon指数。网络分析发现,随着氮添加量的增加真菌网络正连接比例增加,平均聚类系数和模块性降低。内聚力分析表明,第3年高氮添加显著降低了两个土层的真菌负:正内聚力的绝对值,而低氮添加提高或不改变两者的比值。这说明高剂量氮添加将通过破坏真菌群落的稳定性影响其生态系统服务功能。研究为评价不同水平氮添加下森林土壤真菌群落稳定性提供了新的见解,对评价氮沉降的生态效应具有科学意义。

Soil fungal communities are crucial for maintaining ecosystem functions,but it remains unclear that how environmental changes such as nitrogen deposition affect their stability.In this study,by using high⁃throughput sequencing and network analysis,we investigated the effects of different nitrogen addition levels on soil fungal community characteristics for three consecutive years.The connectivity was quantified by calculating″cohesion″to predict the stability of fungal networks.The results showed that there was a significant time effect on the response of fungal diversity and community stability to nitrogen addition.Compared to the previous two years,nitrogen addition altered the fungal beta diversity in the third year,and low nitrogen addition significantly increased the Chao1 and Shannon indexes of fungi in the 0—10 cm soil layer.Network analysis revealed that the proportion of positive connections in the fungal network increased and the average clustering coefficient and modularity decreased as the amount of added nitrogen increased.Cohesion analysis showed that high nitrogen addition significantly reduced the absolute value of negative:positive cohesion of fungi in both soil layers in the third year,while low nitrogen addition increased or did not change the ratio.This suggests that high⁃dose nitrogen addition can affect the ecosystem service function of fungal communities by destroying the stability of fungal communities.This study provides new insights for evaluating the stability of soil fungal communities in forest under different levels of nitrogen deposition,which is of scientific significance for evaluating the ecological effects of nitrogen deposition.