Mechanism of grazing and climate interaction on vegetation
diversity
Grazing and climatic factors have interactive effects on vegetation
diversity in arid and semi-arid regions, that is, one driver can change
the effect of the other driver on the state variable. We discuss the
mechanisms and causes of the discovered interaction effects from the
perspective of vegetation community stability. With climate change,
grazing may reduce vegetation stability. However, under no grazing and
low grazing intensity, vegetation coverage was higher, and surface
plants were able to fully reduce water loss due to temperature rise.
Grasslands with higher vegetation coverage have stable water retention
capacity and are more resistant to climate change, especially warming.
Under the background of high intensity grazing, the surface vegetation
is overeaten, the vegetation coverage is greatly reduced, and the water
holding capacity of the grassland is reduced. Factors such as soil
exposure and temperature increase will accelerate surface water
evaporation, reducing the available water for plants. An increase in
precipitation does not effectively increase surface water supply to
plants. By affecting water supply, high-intensity grazing makes
vegetation more sensitive to temperature changes and reduces the
stability of vegetation communities.
In addition to the environment, the characteristics of plants are also
important internal factors that determine their survival. The survival
and anti-interference ability of plant species were different under
different climate patterns. For example, in arid climates,
high-individual plants were more significantly affected by grazing,
indicating that high-individual plants were less resistant to grazing
disturbance when the climate was drier. In addition, in humid DL and HL,
grasses were more sensitive to grazing. Although the coverage of grasses
decreased significantly, the coverage of low-height plants did not
decrease, and high-height plants were least affected by grazing in this
climate model (Figure 7). The results showed that humid climate was
conducive to niche succession among species. Although the number of tall
grass plants decreased, other tall plant populations quickly occupied
the niche, which reflected the higher stability of plant communities in
humid climate. The results show that the increase of precipitation in
the rainy season plays a greater role in maintaining vegetation
stability, while the role of temperature change is very limited.
Moreover, a severely dry climate would weaken the resistance of plant
communities to grazing and amplify the negative effects of grazing,
while a transition to a wetter climate model would increase the
stability of plant communities and make them less susceptible to
grazing.