Abstract

Aims

Grassland degradation represents a major challenge in the maintenance of grassland productivity. This process has dramatic impacts on energy flows and soil nutrient dynamics, thus directly or indirectly influencing soil microbes. Here, we aim to (i) examine changes in soil microbial composition, diversity and functionality in response to different levels of grassland degradation (i.e. non-degraded, moderately and severely degraded) in a temperate grassland in Inner Mongolia, and (ii) elucidate biotic and abiotic factors that are responsible for these changes.

Methods

The composition structure of soil microbial community was determined by high-throughput sequencing. The functionality of bacterial communities was examined using the tool of FAPROTAX, and functional guilds of fungal communities were quantified using the FUNGuild pipeline.

Important Findings

Grassland degradation significantly decreased soil bacterial diversity but it did not affect fungal diversity. Belowground biomass, soil organic carbon and total nitrogen were positively related to changes in diversity of bacterial community. Grassland degradation significantly increased the relative abundance of Chloroflexi (from 2.48% to 8.40%) and decreased Firmicutes (from 3.62% to 1.08%) of bacterial community. Degradation also significantly increased the relative abundance of Glomeromycota (from 0.17% to 1.53%) and decreased Basidiomycota (from 19.30% to 4.83%) of fungal community. The relative abundance of pathogenic fungi (Didymella and Fusarium) was decreased significantly by degradation. In addition, degradation had a significant impact on putative functionality of soil bacteria related to soil carbon and nitrogen cycling. Our results suggest that soil bacterial community is more sensitive than fungal community in response to degradation in the temperate grassland.

中文翻译：

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温带草原退化后土壤微生物群落结构和功能的变化

摘要

目的

草地退化是维持草地生产力的主要挑战。这个过程对能量流和土壤养分动态有巨大影响，因此直接或间接影响土壤微生物。在这里，我们的目的是（i）研究内蒙古温带草原对土壤微生物组成，多样性和功能的响应，以应对不同程度的草地退化（即未退化，中度和严重退化），以及（ii）阐明造成这些变化的生物和非生物因素。

方法

通过高通量测序确定土壤微生物群落的组成结构。使用FAPROTAX工具检查了细菌群落的功能，并使用FUNGuild管道对真菌群落的功能协会进行了定量。

重要发现

草原退化显着降低了土壤细菌的多样性，但并未影响真菌的多样性。地下生物量，土壤有机碳和总氮与细菌群落多样性的变化呈正相关。草地退化显着增加了绿藻的相对丰度（从2.48％降低到8.40％），并降低了细菌群落的硬毛虫（从3.62％降低到1.08％）。降解还显着增加了真菌群落的球藻的相对丰度（从0.17％降低到1.53％），降低了担子菌的比例（从19.30％降低到4.83％）。病原真菌的相对丰度（迪迪米拉和镰刀菌）由于降解而显着降低。此外，降解对与土壤碳和氮循环有关的土壤细菌的推定功能具有重大影响。我们的结果表明，在温带草原退化中，土壤细菌群落比真菌群落更敏感。