Interacting effects of climate change and livestock grazing on semi-arid grassland ecosystems
have not been well studied, especially on a long-term basis. This paper analyzes changes in plant community
composition in relation to grazing intensity and climate change based on repeated monitoring along longterm
grazing intensity gradients in three Mongolian ecological zones over 20 yr.We synthesized our findings
into state-and-transition models of vegetation change, contributing to our understanding of ecological
dynamics in relation to management and environmental change, and to the development of tools for resilience-
based rangeland management. In the mountain steppe (MS), community composition was driven
largely by climate, and transitions from one community to another were associated with climate change or
combined climate and grazing effects. The MS experienced the largest number of long-term transitions (14 of
15 plots) over 20 yr. In the steppe (ST), grazing intensity was the strongest influence on community composition,
but transitions between communities from the early 1990s to 2013 were most strongly correlated with
climate change. Ten of the 15 ST plots transitioned to other communities over 20 yr. Community composition
in the desert steppe (DS) was unrelated to either grazing intensity or climate change and only six of 15 plots
transitioned permanently over 20 yr. The MS appears most vulnerable to climate-induced community
change, as others have suggested. Some degraded ST communities are resilient to climate change, while ST
communities on drier sites are vulnerable to grazing-induced community changes. Our findings illustrate
the utility of state-and-transition models as a means to synthesize and depict plant community dynamics in
relation to climate and management factors. These models identify communities that may be growing rarer
or more common under the combined effects of climate change and grazing, and highlight species and communities
that may be useful conservation targets or indicators of climate- or grazing-induced change.
