Divergent Changes in Plant Community Composition under 3-Decade Grazing Exclusion in Continental Steppe

Abstract

An understanding of the factors controlling plant community composition will allow improved prediction of the responses of plant communities to natural and anthropogenic environmental change. Using monitoring data from 1980 to 2009, we quantified the changes in community composition in Leymus chinensis and Stipa grandis dominated grasslands in Inner Mongolia under long-term grazing-exclusion and free-grazing conditions, respectively. We demonstrated that the practice of long-term grazing exclusion has significant effects on the heterogeneity, the dominant species, and the community composition in the two grasslands. The community composition of L. chinensis and S. grandis grasslands exhibited directional changes with time under long-term grazing exclusion. Under free grazing, the L. chinensis community changed directionally with time, but the pattern of change was stochastic in the S. grandis community. We attributed the divergent responses to long-term grazing exclusion in the S. grandis and L. chinensis grasslands to litter accumulation and changes in the microenvironment after grazing exclusion, which collectively altered the growth and regeneration of the dominant species. The changes in the grazed grasslands were primarily determined by the selective feeding of sheep during long-term heavy grazing. Overall, the responses of the community composition of the Inner Mongolian grasslands to long-term grazing exclusion and heavy grazing were divergent, and depended primarily on the grassland type. Our findings provide new insights into the role of grazing in the maintenance of community structure and function and therefore have important implications for grassland management.

Nitrogen enrichment and grazing accelerate vegetation restoration in degraded grassland patches

“…Zhao et al (2008) have demonstrated that the combination of N addition and grazing promotes revegetation, and triggers the compensatory growth of plants by accelerating the N cycle and eliminating N accumulation. N addition significantly affects the restoration process of degraded grassland patches and might be augmented by moderate grazing, and the combination of these methods should be considered as a new approach for grassland restoration (He et al, 2011).…”

Relationship of plant diversity with litter and soil available nitrogen in an alpine meadow under a 9‐year grazing exclusion

“…combined impact on grassland plant diversity. For example, He et al (2011) showed that plant diversity in different grassland types has diverse responses to litter that accumulates under grazing exclusion. Therefore, to explore the mechanisms that underlie changes in the plant diversity of grasslands, it is necessary to obtain a better understanding of how grazing exclusion affects plant diversity in grasslands with different types of vegetation, climate, nutrients, and other factors.…”

Field <sup>13</sup>CO<sub>2</sub> pulse labeling reveals differential partitioning patterns of photoassimilated carbon in response to livestock exclosure in a <i>Kobresia</i> meadow

“…Livestock exclosures have a potential value in assessing the effects of grazing upon vegetation and C sequestration in the grasslands (Bock et al, 1984;Cheng et al, 2011;He et al, 2011;Li et al, 2012;Su et al, 2003). Exclosures appear to favor higher community diversity and productivity compared with grazing in the arid grasslands (Bock et al, 1984;Cheng et al, 2011).…”

“…Furthermore, grazing exclosures are widely used as a management practice to restore degraded grasslands Su et al, 2003). However, recent studies on a fenced Leymus chinensis grassland in northern China demonstrated that the outcomes from exclosure were related to the community types of the grasslands, with responses to litter accumulation dependent on plant density (He et al, 2011). Generally, there were cascade effects on C sequestration in the plant-soil system from variations of the community structure and other factors related to exclosure Su et al, 2003).…”