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. 2023 Sep 6:14:1257521.
doi: 10.3389/fmicb.2023.1257521. eCollection 2023.

Symbiotic diazotrophs in response to yak grazing and Tibetan sheep grazing in Qinghai-Tibetan plateau grassland soils

Shengnan Sun  1   2 , Yi Zhao  1 , Quanmin Dong  2 , Xiaoxia Yang  2 , Yuzhen Liu  2 , Wentao Liu  1 , Guang Shi  2 , Wenting Liu  2 , Chunping Zhang  2 , Yang Yu  2
Affiliations

Symbiotic diazotrophs in response to yak grazing and Tibetan sheep grazing in Qinghai-Tibetan plateau grassland soils

Shengnan Sun et al. Front Microbiol. .

Abstract

Grazing by local livestock is the traditional human practice in Qinghai-Tibetan Plateau grassland, and moderate intensity grazing can maintain high productivity and diversity of alpine grassland. Grazing ecosystems are often nitrogen-limited, but N2-fixing communities in response to yak grazing and Tibetan sheep grazing in Qinghai-Tibetan Plateau grassland have remained underexplored. In this study, we applied quantitative PCR quantitation and MiSeq sequencing of nifH under yak grazing and Tibetan grazing through a manipulated grazing experiment on an alpine grassland. The results showed that the grazing treatments significantly increased the soil ammonium nitrogen (AN) and total phosphorus (TP), but reduced the diazotrophs abundance. Compared with no grazing treatment, the composition of diazotrophs could be maximally maintained when the ratio of yak and Tibetan sheep were 1:2. The foraging strategies of grazing livestock reduced the legumes biomass, and thus reduced the diazotrophs abundance. Data analysis suggested that the direct key factors in regulating diazotrophs are AN and TP, and the changes of these two soil chemical properties were affected by the dung and urine of herbivore assemblages. Overall, these results indicated that the mixed grazing with a ratio of yak to Tibetan sheep as 1:2 can stabilize the soil diazotrophsic community, suggesting that MG12 are more reasonable grazing regimes in this region.

Keywords: Tibetan plateau; alpine grassland; grazing patterns; nifH gene; soil microbes.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Effects of grazing patterns on the nifH gene abundance in different soil depth.
Figure 2
Figure 2
Effects of grazing patterns on the OTU numbers in 0–10 cm of soil surface.
Figure 3
Figure 3
Relative abundances of diazotroph community response to different grazing patterns in the soil at the order level.
Figure 4
Figure 4
Relationships between variables related to soil diazotroph community, soil characteristics and plant functional community biomass. TC, soil total carbon; TN, soil total nitrogen; AN, soil ammonium nitrogen; TP, soil total phosphorus.
Figure 5
Figure 5
Relationships between the OTU numbers and soil AN or TP. AN, soil ammonium nitrogen; TP, soil total phosphorus.
Figure 6
Figure 6
Relationships between soil properties and diazotroph community as shown by redundancy analysis (RDA).
Figure 7
Figure 7
Relationships between plant functional community biomass and diazotroph community as shown by redundancy analysis (RDA).
Figure 8
Figure 8
Structural equation model (SEM) describing the effects of grazing on soil diazotroph community.
See this image and copyright information in PMC

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