Abstract
Grazing is one of the main human disturbance factors in alpine grassland on the Qinghai-Tibet Plateau (QTP), which can directly or indirectly influence the community structures and ecological functions of grassland ecosystems. However, despite extensive field grazing experiments, there is currently no consensus on how different grazing management approaches affect alpine grassland diversity, soil carbon (C), and nitrogen (N). Here, we conducted a meta-analysis of 70 peer-reviewed publications to evaluate the general response of 11 variables related to alpine grassland ecosystems plant diversity and ecological functions to grazing. Overall, the results showed that grazing significantly increased the species richness, Shannon–Wiener index, and Pielou evenness index values by 9.89% (95% CI: 2.75–17.09%), 7.28% (95% CI: 1.68–13.62%), and 3.74% (95% CI: 1.40–6.52%), respectively. Aboveground biomass (AGB) and belowground biomass (BGB) decreased, respectively, by 41.91% (95% CI: −50.91 to −32.88%) and 17.68% (95% CI: −26.94 to −8.52%). Soil organic carbon (SOC), soil total nitrogen (TN), soil C:N ratio, and soil moisture decreased by 13.06% (95% CI: −15.88 to −10.15%), 12.62% (95% CI: −13.35 to −8.61%), 3.27% (95% CI: −4.25 to −2.09%), and 20.75% (95% CI: −27.89 to −13.61%), respectively, whereas, soil bulk density and soil pH increased by 17.46% (95% CI: 11.88–24.53%) and 2.24% (95% CI: 1.01–3.64%), respectively. Specifically, moderate grazing, long-durations (>5 years), and winter grazing contributed to increases in the species richness, Shannon–Wiener index, and Pielou evenness index. However, AGB, BGB, SOC, TN, and soil C:N ratios showed a decrease with enhanced grazing intensity. The response ratio of SOC was positively associated with AGB and BGB but was negatively related to the Shannon–Wiener index and Pielou evenness index. Furthermore, the effects of grazing on plant diversity, AGB, BGB, SOC, and TN in alpine grassland varied with grazing duration, grazing season, livestock type, and grassland type. The findings suggest that grazing should synthesize other appropriate grazing patterns, such as seasonal and rotation grazing, and, furthermore, additional research on grazing management of alpine grassland on the QTP is needed in the future.
Highlights
Grassland is an important component of terrestrial ecosystems, accounting for approximately 20% of the total global land surface (Scurlock and Hall, 1998)
Across all the observations compiled in this study, our metaanalysis showed that grazing significantly increased all the grassland diversity indices: the species richness, Shannon– Wiener index, and the Pielou evenness index increased on average by 9.89%, 7.28%, and 3.74%, respectively (Figure 2)
Among the different grazing intensities, MG had the largest impact on both species richness and the Shannon–Wiener index, increasing these values by 18.79%
Summary
Grassland is an important component of terrestrial ecosystems, accounting for approximately 20% of the total global land surface (Scurlock and Hall, 1998). Grasslands play vital roles in supporting living and grazing conditions and in mitigating the effects of both local and global climate change (Zhang et al, 2015; Ren et al, 2016; Yan et al, 2020). Because of human overuse and climate change, the alpine grassland has degraded seriously in recent decades, resulting in a loss of biodiversity and the degradation of ecosystem functions (Li et al, 2017; Liu et al, 2018). The main purpose of these programs is to reverse the negative effects of overgrazing and rebuild the ecological functions of degraded grassland areas. Since grazing management has become a widely effective strategy to help prevent grassland degradation and maintain sustainable grazing on the QTP (Lu et al, 2017; Liu X. et al, 2021)
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