Key Laboratory of Agro-ecological Processes in Subtropical Region & Changsha Research Station for Agricultural and Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Hunan, 410125, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Microb Ecol. 2021 Feb;81(2):425-436. doi: 10.1007/s00248-020-01591-w. Epub 2020 Sep 8.
Biological nitrogen (N) fixation as a source of new N input into the soil by free-living diazotrophs is important for achieving sustainable rice agriculture. However, the dominant environmental drivers or factors influencing N fixation and the functional significance of the diazotroph community structure in paddy soil across a climatic gradient are not yet well understood. Thus, we characterized the diazotroph community and identified the ecological predictors of N fixation potential in four different climate zones (mid-temperate, warm-temperate, subtropical, and tropical paddy soils) in eastern China. Comprehensive nifH gene sequencing, functional activity detection, and correlation analysis with environmental factors were estimated. The potential nitrogenase activity (PNA) was highest in warm-temperate regions, where it was 6.2-, 2.9-, and 2.2-fold greater than in the tropical, subtropical, and mid-temperate regions, respectively; nifH gene abundance was significantly higher in warm-temperate and subtropical zones than in the tropical or mid-temperate zones. Diazotroph diversity was significantly higher in the tropical climate zone and significantly lower in the mid-temperate zone. Non-metric multidimensional scaling and canonical correlation analysis indicated that paddy soil diazotroph populations differed significantly among the four climate zones, mainly owing to differences in climate and soil pH. Structural equation models and automatic linear models revealed that climate and nutrients indirectly affected PNA by affecting soil pH and diazotroph community, respectively, while diazotroph community, C/P, and nifH gene abundance directly affected PNA. And C/P ratio, pH, and the diazotroph community structure were the main predictors of PNA in paddy soils. Collectively, the differences in diazotroph community structure have ecological significance, with important implications for the prediction of soil N-fixing functions under climate change scenarios.
生物固氮（N）作为自由生活的固氮生物将新的 N 输入土壤的一种方式，对实现可持续的水稻农业至关重要。然而，驱动固氮作用的主要环境因素或因子，以及在气候梯度上稻田中固氮生物群落结构的功能意义尚不清楚。因此，我们对中国东部四个不同气候带（中温带、暖温带、亚热带和热带稻田）的固氮生物群落进行了特征描述，并确定了固氮潜力的生态预测因子。通过综合 nifH 基因测序、功能活性检测以及与环境因子的相关分析进行了估计。在暖温带地区，潜在氮酶活性（PNA）最高，分别比热带、亚热带和中温带高 6.2、2.9 和 2.2 倍；nifH 基因丰度在暖温带和亚热带地区显著高于热带或中温带地区。在热带气候带，固氮生物多样性显著较高，而在中温带地区则显著较低。非度量多维标度和典范对应分析表明，四个气候带之间稻田固氮生物种群存在显著差异，主要归因于气候和土壤 pH 的差异。结构方程模型和自动线性模型表明，气候和养分通过分别影响土壤 pH 和固氮生物群落，间接影响 PNA，而固氮生物群落、C/P 以及 nifH 基因丰度直接影响 PNA。C/P 比、pH 和固氮生物群落结构是影响稻田 PNA 的主要预测因子。总体而言，固氮生物群落结构的差异具有生态意义，对预测气候变化情景下的土壤固氮功能具有重要意义。
