Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China.
Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Hangzhou 310058, China.
Sci Total Environ. 2018 Sep 1;634:1157-1164. doi: 10.1016/j.scitotenv.2018.04.117. Epub 2018 Apr 12.
Nitrifying microbes are of critical importance in regulating efficient nitrogen (N) cycling, which plays a crucial role in plant productivity and maintaining soil sustainability. Long-term different intensities of grazing can strongly influence the microbial communities, while our understanding of the complex nitrifying community in the grazed grassland soil environment is still limited. To investigate whether and how long-term grazing with different intensities influence soil nitrifying communities, high-throughput sequencing and quantitative PCR analyses were performed on soil samples from permanent grassland soils under four grazing intensities: 0 (G0), 1.5 (G1), 6 (G2) and 9 (G3) sheepha. Results showed that the G3 treatment significantly reduced the soil nutrient content and increased the soil bulk density, changes that are not sustainable in the long run. The G1 treatment, on the other hand, significantly increased the soil nutrient content and would improve soil fertility. Some functional microbes were specifically enriched after long term grazing, like Nitrospirae (phylum) to Nitrospira (class) in the G2 samples and Chromatiales (order) to Nitrosococcus (genus) in the G3 soils. The numerically dominant Nitrosococcus watsonii lineage of ammonia oxidizing bacteria (AOB) was observed in this grassland soil. The redundancy analysis (RDA) together with the structural equation modeling (SEM) analysis showed that grazing intensity was important in mediating the distribution of soil microorganisms and affected nitrifying communities by impacting soil physicochemical characteristics (e.g., bulk density, NH-N). These results showed the shifts of nitrifying communities across different grazing intensities, and could aid in the determination of an optimal grazing intensity for these grazed grassland soils.
硝化微生物在调节高效氮（N）循环中至关重要，氮循环对植物生产力和维持土壤可持续性起着关键作用。长期不同强度的放牧强烈影响微生物群落，而我们对放牧草地土壤环境中复杂硝化群落的理解仍然有限。为了研究长期不同强度放牧是否以及如何影响土壤硝化群落，我们对四种放牧强度（0（G0）、1.5（G1）、6（G2）和 9（G3）只羊/公顷）下的永久草地土壤的土壤样品进行了高通量测序和定量 PCR 分析。结果表明，G3 处理显著降低了土壤养分含量并增加了土壤容重，这些变化从长远来看是不可持续的。相比之下，G1 处理显著增加了土壤养分含量，将改善土壤肥力。长期放牧后，一些功能微生物被特异性富集，如 G2 样品中硝化螺旋菌（门）到硝化螺旋菌（纲）和 G3 土壤中 Chromatiales（目）到 Nitrosococcus（属）。在这片草地土壤中，发现了数量上占优势的氨氧化细菌（AOB）Nitrosococcus watsonii 系。冗余分析（RDA）和结构方程模型（SEM）分析表明，放牧强度是调节土壤微生物分布的重要因素，并通过影响土壤物理化学特性（如容重、NH-N）影响硝化群落。这些结果显示了不同放牧强度下硝化群落的变化，并有助于确定这些放牧草地土壤的最佳放牧强度。
