Abstract:

It is well known that soil elemental stoichiometry, strongly dependent on soil water contents, plays an important role in shaping soil microbial diversity, which in turn is important for promoting aboveground biodiversity. However, it is not yet clear how soil water contents-mediated changes in elemental stoichiometry may affect microbial diversity. In this study, we sampled 1287 soil cores from a 20 hm² subtropical forest dynamic plot in Zhejiang Province to elucidate how resource quantity (OC, TN and TP) and elemental stoichiometry (C:N, C:P and N:P ratios) affected soil microbial community under different soil water contents that were the relatively “high” (75.5%-34.8%) level vs. the relatively “low” (34.8%-4.83%) level. Illumina high-throughput sequencing technology was used to analyze soil microbes. Results showed that soil water contents altered soil elemental stoichiometry, thereby microbial diversity. Our specific results included that (1) soil water contents significantly affected the α diversity of soil microbes. Compared with that under high water contents, the α diversity of bacterial and fungal communities under low water contents was significantly increased by 0.830% and 2.62%, respectively. (2) The dominant microbial phyla responded differently to high vs. low water contents. Compared with low water contents, high water contents significantly increased the relative abundance of five bacterial phyla (Proteobacteria, Actinobacteria, Planctomycetes, WPS and Cyanobacteria) and two fungal phyla (Rozellomycota and Zygomycota) by 6.50%-97.4% and 0.530%-39.7%, respectively. Conversely, the relative abundances of seven bacterial phyla (Acidobacteria, Verrucomiocrobia, Bacteroidetes, Chloroflexi, Gemmatimonadetes, Patescibacteria and Elusimicrobia) and two fungal phyla (Ascomycota and Glomeromycota) were significantly decreased under high water contents, with decreases of 6.90%-39.7% and 7.09%-7.33%, respectively. (3) The resource quantity (OC, TN and TP) and elemental stoichiometry (C:N, C:P and N:P) were significantly and positively correlated with soil water contents. (4) The C:N, C:P and N:P were significantly and negatively correlated with microbial diversities, regardless of soil water contents. These findings combined indicate that soil elemental stoichiometry is critical for shaping soil microbial diversity and soil water contents do not alter the trend. Our study that tested the effect of soil water contents on soil elemental stoichiometry may contribute to improving our understanding of how the microbial diversity would respond to the change in soil water contents caused by global warming.

Key words: climate change, soil water content, elemental stoichiometry, microbial diversity

摘要：

土壤元素化学计量特征在塑造微生物多样性方面起着至关重要的作用，而元素化学计量受到土壤含水量的影响。为探究不同土壤水分条件下，有机碳（OC）、全氮（TN）、全磷（TP）及其元素化学计量特征（C:N、C:P和N:P）如何影响土壤微生物多样性，在浙江省20 hm²亚热带森林动态监测样地内共采集1287份土壤样品。利用Illumina高通量测序技术测定了土壤细菌和真菌的群落组成，并结合土壤理化性质，分析了不同土壤水分下元素和元素化学计量与微生物群落的关系。结果表明，土壤水分能改变元素化学计量特征，进而塑造细菌和真菌群落的多样性。其中，（1）土壤水分显著影响微生物群落的α多样性。相较于高土壤水分，在低土壤水分下，细菌和真菌群落的α多样性分别显著提高了0.830%和2.62%。（2）细菌和真菌的主要门类对土壤水分表现出差异化响应。相较于低土壤水分，高土壤水分显著提高了细菌5个门类和真菌2个门类的相对丰度；并且显著降低了细菌7个门类和真菌2个门类的相对丰度。（3）土壤元素含量和元素化学计量特征与土壤水分呈显著正相关关系。（4）元素化学计量C:N、C:P和N:P与微生物多样性呈显著负相关关系，其相关性不受土壤含水量的影响。综上所述，土壤元素化学计量塑造微生物多样性，且土壤水分的高低并不改变其整体变化趋势。该研究验证了土壤水分对元素化学计量的影响，有助于提高微生物多样性如何响应全球气候变暖引起的土壤水分变化的理解。

关键词: 气候变化, 土壤水分, 元素化学计量, 微生物多样性