The Distribution and Turnover of Bacterial Communities in the Root Zone of Seven Stipa Species Across an Arid and Semi-arid Steppe

Abstract

The bacterial communities of the root-zone soil are capable of regulating vital biogeochemical cycles and the succession of plant growth. Stipa as grassland constructive species is restricted by the difference features of east–west humidity and north–south heat, which shows the population substituting distribution. The distribution, turnover, and potential driving factors and ecological significance of the root-zone bacterial community along broad spatial gradients of Stipa taxa transition remain unclear. This paper investigated seven Stipa species root-zone soils based on high-throughput sequencing combined with the measurements of multiple environmental parameters in arid and semi-arid steppe. The communities of soil bacteria in root zone had considerable turnover, and some regular variations in structure along the Stipa taxa transition are largely determined by climatic factors, vegetation coverage, and pH at a regional scale. Bacterial communities had a clear Stipa population specificity, but they were more strongly affected by the main annual precipitation, which resulted in a biogeographical distribution pattern along precipitation gradient, among which Actinobacteria, Acidobacteria, Proteobacteria, and Chloroflexi were the phyla that were most abundant. During the transformation of Stipa taxa from east to west, the trend of diversity shown by bacterial community in the root zone decreased first, and then increased sharply at S. breviflora, which was followed by continuous decreasing toward northwest afterwards. However, the richness and evenness showed an opposite trend, and α diversity had close association with altitude and pH. There would be specific and different bacterial taxa interactions in different Stipa species, in which S. krylovii had the simplest and most stable interaction network with the strongest resistance to the environment and S. breviflora had most complex and erratic. Moreover, the bacterial community was mainly affected by dispersal limitation at a certain period. These results are conducive to the prediction of sustainable ecosystem services and protection of microbial resources in a semi-arid grassland ecosystem.

Changes of Arbuscular Mycorrhizal Fungal Community and Glomalin in the Rhizosphere along the Distribution Gradient of Zonal Stipa Populations across the Arid and Semiarid Steppe

“…The region is characterized by a continental arid and semiarid monsoonal climate accompanied by abrupt changes of temperature in the middle temperate zone ( 40 , 60 ). The climate is distributed in a belt and gradually transits from a semihumid to semiarid and arid areas from east to west ( 5 ). The area is characterized by prevailing winds from multiple directions, with a northwest wind prevailing in winter and southerly and southeast winds in summer ( 61 ).…”

“…Arid and semiarid grasslands have attracted wide attention, arising from the declining forage species, soil desertification, and modifications to soil microbial communities due to global climate change (e.g., severe and frequent drought and heavy rainfall events) and anthropogenic activities (e.g., grazing) ( 1 – 4 ). Arid and semiarid grasslands in northern China have a horizontal zonal Stipa grassland community composed of Stipa as constructive species, due to their significant hydrothermal gradients ( 5 ). Stipa plants also act as an important material basis for grassland animal husbandry and can maintain grassland balance and a good ecological environment ( 6 ).…”

“…The genus Stipa is a grazing-resistant, drought-resistant, mycorrhizal, and perennial bunchgrass with sand sheaths, which can help plants tolerate abiotic stresses ( 6 , 39 ). The north-south heat difference and the east-west southeast monsoon wind system differentiate meadow grassland ( Stipa baicalensis population), typical grassland ( Stipa grandis and Stipa krylovii populations), and desert grassland ( Stipa breviflora , Stipa gobica , Stipa klemenzii and Stipa glareosa populations) in arid and semiarid grasslands ( 5 , 6 , 40 ). The study transect provides a suitable area and unique opportunity for this investigation due to the high heterogeneity of abiotic factors and geographic substituted distribution patterns of unique Stipa species ( Fig.…”