Heavy Grazing Altered the Biodiversity–Productivity Relationship of Alpine Grasslands in Lhasa River Valley, Tibet

Abstract

Grazing is a crucial anthropogenic disturbance on grasslands. However, it is unknown how livestock grazing affects the relationship between biodiversity and productivity of alpine grasslands in Tibet. We carried out a grazing-manipulated experiment from 2016 to 2019 with grazing intensity levels of null (control, grazing exclusion, C.K.), moderate grazing [1.65 standardized sheep unit (SSU) per hectare, M.G.], and heavy grazing (2.47 SSU per hectare, H.G.) on a typical alpine grassland in the Lhasa River Basin, central Tibet. We measured aboveground biomass (AGB), species assembly (alpha and beta diversity indices), and soil nutrients’ availability. The results showed that grazing differently affected plant community in different treatments. Notably, the total dissimilarity value between C.K. and H.G. is 0.334. Grazing decreased the Shannon–Wiener index, increased the Berger–Parker index from 2016 to 2018 significantly, and decreased AGB and total soil nitrogen (STN) significantly. Our results also showed that the grazing affected the relationship between AGB and diversity indices and soil nutrients, including soil organic carbon (SOC) and total soil phosphorus (STP). Specifically, AGB decreased with increasing SOC and STP in all treatments, and heavy grazing changed the positive relationships between AGB, STP, and Shannon–Wiener index to negative correlations significantly compared with grazing exclusion. There was a significant negative correlation between Berger–Parker and Shannon–Wiener indices under each treatment. The general linear models showed that H.G. altered the relationship between diversity and productivity of grassland in central Tibet, and AGB and Shannon–Wiener index positively correlated in C.K. but negatively correlated in H.G. Our study suggests that H.G. caused a negative relationship between plant diversity and productivity. Therefore, sustainable grazing management calls for a need of better understanding the relationship between biodiversity and productivity of alpine grassland in central Tibet.

Impact of Grazing on Diversity of Semi-Arid Rangelands in Crete Island in the Context of Climatic Change

“…Our results support the hypothesis that species turnover decreases with altitude only at the higher altitudinal zone. The lower species turnover in highlands could be attributed to the presence of sparse vegetation in mountainous areas generally [ 79 ], and probably, species turnover correlates with different rangeland management [ 84 ].…”

Soil bacterial and fungal communities are linked with plant functional types and soil properties under different grazing intensities

“…The availability of soil resources supports vegetation growth (Xu, Zhang, et al, 2019), changes plant community productivity (Xiang et al, 2021) and influences the composition of plant communities (García-Palacios et al, 2013). In our study, both G3 (heavy grazing) and G4 (overgrazing) significantly reduced soil OC and total N concentrations, and their low stocks, in turn, contributed negatively to plant productivity in the typical steppe.…”

Sustainable Development of Energy, Water and Environment Systems (SDEWES 2021)

“…Addington et al [35] reported that the stomatal apparatus controls Ψ in a way that the tension on the water column created by decreasing Ψ did not cause extreme xylem cavitation. Several studies suggested that high VPD reduces g s , consequently affecting assimilation rate and growth [84,85]. On the contrary, it has been argued that the impact of high VPD on g s may not possess any impact on assimilation rate and growth [86].…”

“…Nevertheless, the impact of VPD on g s and/or assimilation rate varies amongst plant species [82]. In addition, the stomatal anatomy and structure affect water loss and carbon assimilation, demonstrating the evolution and adaptations of the plants to environmental conditions [84,87].…”