Introduction
Vegetation communities in arid and semi-arid regions are vulnerable to the effects of global climate change (Peters et al., 2012; Na et al., 2021; Li et al., 2021). Vegetation is the most important condition to maintain the ecosystem function in arid and semi-arid areas. Therefore, it is very important to maintain the diversity and stability of vegetation communities in these areas. (Jin et al.,2019). The dry-semi-arid regions in northwestern China have the world’s important pasture and the distribution area of the world’s important grass ecosystem. Due to the grassland vegetation protection system attributed to the Chinese government, most of these grass ecosystems facing artificial interference are limited to grazing activities. Some studies have pointed out that the climate model in northwestern China has undergone significant warm and humidization changes in recent decades. Therefore, it is necessary to study the mechanism of changes in the diversity of grassland vegetation in the northwest of China and semi -arid regions under the dual pressure of grazing and climate change.
Climate change and grazing are important stressors affecting grassland ecosystem stability (Li et al., 2015; Jiang et al., 2017). Precipitation is almost the only water source for inland grassland. Long-term precipitation changes will lead to obvious succession of vegetation communities, and some arid plants are more sensitive to precipitation changes (Vicente-Serrano et al., 2012). Temperature is also considered to be an important factor affecting vegetation growth and water cycle (Fensholt et al., 2012; Na et al., 2021). In addition, there is an interaction between surface vegetation and local climate. Low temperature, high biomass and high coverage vegetation can maintain a humid climate. The stability of the interaction between vegetation and climate may be weakened by the destruction of vegetation and the rise of temperature caused by external disturbances (Claussen et al., 2013). Overgrazing resulted in the loss of vegetation diversity and the reduction of community stability, resulting in the collapse of grassland ecosystem and promoting desertification。Continuous grazing activity will change the vegetation species composition of grassland, resulting in the disappearance of wet-loving vegetation and the replacement of grassland by drought-tolerant shrubland, resulting in the decline of grassland productivity and pasture carrying capacity (Vicente-Serrano et al., 2012). However, the interaction between climate change and human grazing activities on vegetation is currently unclear (He et al.,2022).
In the grassland areas in northwestern China, the local government proposed a series of strict management systems in order to avoid the irreversible damage of vegetation in arid areas. Therefore, in these areas, grazing is a controlled behavior that is constrained, while the effects of climate change on vegetation are uncontrollable and unavoidable. The role of climate in influencing vegetation diversity and maintaining vegetation-climate stability in the context of grazing intensity changes needs to be reexamined. In addition, under the global trend of long-term climate change, the ability of vegetation communities in arid areas to maintain vegetation-climate stability in response to grazing disturbance also needs more understanding. Therefore, the interaction analysis of climate and grazing activities on vegetation is needed to develop more scientific and economic grazing management strategies, and to better understand the impacts of climate change on vegetation in arid areas.
Vegetation survey was carried out on five grasslands with distinct climatic differences in arid and semi-arid regions of northwest China. The relationship between Simpson, Shannon and Pielou index of vegetation and grazing intensity, temperature and precipitation were analyzed. The effects of grazing activities and climate differences on vegetation diversity and stability were discussed. In addition, the variation trends of dominant species and individual height under the dual effects of grazing intensity and climate were analyzed, and the reasons for the interaction were explained from the species structure. Our results contribute to the understanding of vegetation change mechanisms in arid and semi-arid regions in the context of climate change and grazing management system reform.