Effects of Different Grazing Disturbances on the Plant Diversity and Ecological Functions of Alpine Grassland Ecosystem on the Qinghai-Tibetan Plateau

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.

Grazing lowers soil multifunctionality but boosts soil microbial network complexity and stability in a subtropical grassland of China

“…This study found that grazing evidently elevated the SH ( Shan et al, 2011 ; Zhang et al, 2019 ; Li et al, 2021 ; Liu et al, 2021 ), BD, pH ( Blank et al, 2006 ; Ajorlo et al, 2011 ; Rong et al, 2022 ), ACa, AMg ( Jusoff, 1988 ; Blank et al, 2006 ), ßGC, ACP, and C limitation ( Goenster-Jordan et al, 2021 ), but decreased the WC and AP ( Niu et al, 2016 ; Sigcha et al, 2018 ; Chen et al, 2021 ; Fenetahun et al, 2021 ; Rong et al, 2022 ; Figure 1 ). The buffalo squeezed the soil pores that include those pores originally storing water and air, through treading, which caused soil compaction ( Ludvíková et al, 2014 ), elevated the bulk density ( Li et al, 2008 ; Zhan et al, 2020 ; Fenetahun et al, 2021 ; Wade et al, 2022 ) and soil hardness, and reduced soil water infiltration ( Daniel et al, 2002 ).…”

“…Grazing could decrease soil porosity ( Tang et al, 2019 ) and increase soil bulk density ( Binkley et al, 2003 ; Davidson et al, 2017 ; Zhang et al, 2018b ; Sun et al, 2019 ; Lai and Kumar, 2020 ; Fenetahun et al, 2021 ). These could result in a decline in the air and water permeability ( Daniel et al, 2002 ; Zhang et al, 2018b ) and soil moisture ( Hou et al, 2014 ; Li et al, 2021 ; Liu et al, 2021 ). However, grazing also increased soil pH ( Binkley et al, 2003 ; Hao and He, 2019 ; Fenetahun et al, 2021 ; Li et al, 2021 ).…”

“…These could result in a decline in the air and water permeability ( Daniel et al, 2002 ; Zhang et al, 2018b ) and soil moisture ( Hou et al, 2014 ; Li et al, 2021 ; Liu et al, 2021 ). However, grazing also increased soil pH ( Binkley et al, 2003 ; Hao and He, 2019 ; Fenetahun et al, 2021 ; Li et al, 2021 ). Since soil pH, O 2 , and water were most crucial driving forces of soil microorganisms ( Fierer, 2017 ), and grazing compressed the living niche for soil microbiome ( Chai et al, 2019 ; Proesmans et al, 2022 ) and negatively affected the growth of microbes ( Zhan et al, 2020 ), we speculated that the changes caused by grazing may have a far-reaching impact on the attributes of soil microorganisms.…”

Distinct Elevational Patterns and Their Linkages of Soil Bacteria and Plant Community in An Alpine Meadow of the Qinghai–Tibetan Plateau

“…Plants’ diversity patterns have been attributed to spatial factors, climate factors, abiotic factors, or biotic factors in previous studies, and these patterns generally exhibit either monotonically declining or hump-shaped diversity patterns with increased elevation [ 49 , 50 , 51 ]. Plant alpha diversity had no strong relationship with soil bacterial alpha diversity and other environmental factors in the current study, although it may be affected by human disturbances [ 52 ]. Soil bacterial Shannon index was closely related with climate factors (elevation, MAT, and MAP) and soil nutrients (soil moisture, pH, and SOC).…”

Editorial: Patterns, functions, and processes of alpine grassland ecosystems under global change

“…In alpine meadow, N and P addition significantly affect t plant communities ( Ma et al., 2021 ), soil microbial community and enzyme activities ( Zi et al., 2022 ), and microbial functional genes ( Xiao et al., 2022 ). In alpine steppe, N and P application led to an increase in aboveground biomass ( Li et al., 2021b ), and increased intensity of bacteria and fungi ( Li et al., 2021c ), also affected the plant functional traits ( Li et al., 2022d ). Meanwhile, grazing increased herbage respiration in summer, presumably through stimulation of gross photosynthesis ( Yuan et al., 2022 ), and changed plant community composition and reduced stochasticity of soil microbial community assembly of alpine grasslands ( Li et al., 2022a ).…”