我国竹林面积占全世界的1/3 左右,其中毛竹(Phyllostachy edulis)林约387万公顷,占我国竹林总面积的72%,主要分布在南方,其碳储量约为409Tg,占我国森林碳储量的2.4%。由于毛竹林生长快、更新周期短,在长期尺度上碳储量潜力很大。土壤微生物驱动了竹林系统的碳循环过程,其中细菌主要分解简单有机物(碳水化合物、有机酸和氨基酸),而真菌分解难降解有机物,细菌和真菌群落演变协同影响了竹林土壤碳转化和碳汇潜力。目前,我国毛竹林土壤微生物的地理分布格局和形成规律仍不清楚,尤其是土壤微生物群落结构演变影响竹林碳代谢的机制缺乏系统研究。

我室孙波课题组针对我国南方毛竹主产区(福建、浙江、湖南、江西),通过野外采样和高通量测序方法,发现在不同地点毛竹林土壤真菌与细菌群落有显著差异,细菌群落b多样性主要受扩散限制影响,而真菌群落受到较强环境选择影响;真菌网络交互作用显著高于细菌网络,对毛竹林土壤碳源代谢的影响更大。研究结果表明,细菌中酸杆菌门(Acidobacteria)占主导,真菌中子囊菌门(Ascomycota)占主导;只有细菌群落在区域尺度上表现出显著的距离-衰减关系,说明扩散限制是影响细菌b多样性的重要生态过程;细菌群落b多样性受到年均降雨量的直接影响和间接影响(土壤碳储量),而真菌群落b多样性主要受年均温和年均降雨量的直接影响;在区域尺度上真菌b多样性解释了土壤碳代谢图谱的17.7%,显著高于细菌(解释了约2.6%);真菌生态网络的网络密度比细菌更高,且物种间的交互作用更密切,显著影响了土壤碳代谢过程。总体上,与细菌群落相比,真菌受到较少的扩散限制作用和较强的环境选择作用,具有较高的生态网络密度,在含有木质素较高的竹林凋落物碳代谢过程中起到更重要的作用。上述研究为在区域尺度上升揭示竹林土壤微生物群落结构和功能的协同演变机制提供了新视角。

这一成果得到了中国科学院重点部署项目和国家重点基础研究发展计划项目的资助。

Xiao X, Liang YT, Zhou S, Zhuang SY, Sun B. Fungal community reveals less dispersal limitation and potentially more connected network than that of bacteria in bamboo forest soils. Molecular Ecology, 2018, 27: 550-563

Abstract

A central aim of this microbial ecology research was to investigate the mechanisms shaping the assembly of soil microbial communities. Despite the importance of bacterial and fungal mediation of carbon cycling in forest ecosystems, knowledge concerning their distribution patterns and underlying mechanisms remains insufficient. Here, soils were sampled from six bamboo forests across the main planting area of Moso bamboo in southern China. The bacterial and fungal diversities were assessed by sequencing 16S rRNA and ITS gene amplicons, respectively, with an Illumina MiSeq. Based on structural equation modelling, dispersal limitation had strongest impact on bacterial beta diversity, while the mean annual precipitation had a smaller impact by directly or indirectly mediating the soil organic carbon density. However, only the mean annual temperature and precipitation played direct roles in fungal beta diversity. Moreover, the co‐occurrence network analyses revealed a possibly much higher network connectivity in the fungal network than in the bacteria. With less dispersal limitation, stronger environmental selection and a potentially more connected network, the fungal community had more important roles in the soil carbon metabolisms in bamboo forests. Fungal beta diversity and the clustering coefficient explained approximately 14.4% and 6.1% of the variation in the carbon metabolic profiles among sites, respectively, but that of bacteria only explained approximately 1.7% and 1.8%, respectively. This study explored soil microbial spatial patterns along with the underlying mechanisms of dispersal limitation, selection and connectivity of ecological networks, thus providing novel insights into the study of the distinct functional traits of different microbial taxa.

我国南方毛竹林土壤微生物群落结构的演变及其对碳代谢功能的影响