Zhong Yangquanwei, Sorensen Patrick O, Zhu Guangyu, Jia Xiaoyu, Liu Jin, Shangguan Zhouping, Wang Ruiwu, Yan Weiming
School of Ecology and Environment Northwestern Polytechnical University Xi'an P.R. China.
Earth and Environmental Sciences Lawrence Berkeley National Laboratory Berkeley California USA.
Imeta. 2022 Apr 5;1(2):e18. doi: 10.1002/imt2.18. eCollection 2022 Jun.
Microorganisms of the soil-root continuum play key roles in ecosystem function. The Loess Plateau is well known for its severe soil erosion and thick loess worldwide, where mean annual precipitation (MAP) and soil nutrients decrease from the southeast to the northwest. However, the relative influence of environmental factors on the microbial community in four microhabitats (bulk soil, rhizosphere, rhizoplane, and endosphere) in the soil-root continuum along the environmental gradient in the Loess Plateau remains unclear. In this study, we investigated 82 field sites from warm-temperate to desert grasslands across the Loess Plateau, China, to assess the bacterial diversity, composition, community assembly, and co-occurrence networks in the soil-root continuum along an environmental gradient using bacterial 16S recombinant DNA amplicon sequencing. We discovered that the microhabitats explained the largest source of variations in the bacterial diversity and community composition in this region. Environmental factors (e.g., MAP, soil organic carbon, and pH) impacted the soil, rhizosphere, and rhizoplane bacterial communities, but their effects on the bacterial community decreased with increased proximity to roots from the soil to the rhizoplane, and the MAP enlarged the dissimilarity of microbial communities from the rhizosphere and rhizoplane to bulk soil. Additionally, stochastic assembly processes drove the endosphere communities, whereas the soil, rhizosphere, and rhizoplane communities were governed primarily by the variable selection of deterministic processes, which showed increased importance from warm-temperate to desert grasslands. Moreover, the properties of the microbial networks in the rhizoplane community indicate more stable networks in desert grasslands, likely conferring the resistance of microbial communities in higher stress environments. Collectively, our results showed that the bacterial communities in the soil-root continuum had different sensitivities and assembly mechanisms along an environmental gradient. These patterns are shaped simultaneously by the intertwined dimensions of proximity to roots and environmental stress change in the Loess Plateau.
土壤 - 根系连续体中的微生物在生态系统功能中发挥着关键作用。黄土高原以其严重的土壤侵蚀和全球范围内深厚的黄土而闻名，其年平均降水量（MAP）和土壤养分从东南向西北递减。然而，沿着黄土高原环境梯度，环境因素对土壤 - 根系连续体中四个微生境（土壤、根际、根表和内生菌）中微生物群落的相对影响仍不清楚。在本研究中，我们调查了中国黄土高原从暖温带至荒漠草原的82个野外站点，利用细菌16S重组DNA扩增子测序评估沿着环境梯度的土壤 - 根系连续体中的细菌多样性、组成、群落组装和共现网络。我们发现微生境解释了该区域细菌多样性和群落组成变化的最大来源。环境因素（如MAP、土壤有机碳和pH）影响土壤、根际和根表细菌群落，但随着从土壤到根表靠近根系程度的增加，它们对细菌群落的影响减小，且MAP扩大了根际和根表与土壤微生物群落的差异。此外，随机组装过程驱动内生菌群落，而土壤、根际和根表群落主要由确定性过程的可变选择控制，从暖温带至荒漠草原，这种选择的重要性增加。此外，根表群落中微生物网络的特性表明荒漠草原中的网络更稳定，这可能赋予了微生物群落在更高压力环境下的抗性。总体而言，我们的结果表明，沿着环境梯度，土壤 - 根系连续体中的细菌群落具有不同的敏感性和组装机制。这些模式是由黄土高原根系距离和环境压力变化的交织维度同时塑造的。
