Effects of grazing on spatiotemporal variations in community structure and ecosystem function on the grasslands of Inner Mongolia, China

Abstract

Grasslands worldwide are suffering from overgrazing, which greatly alters plant community structure and ecosystem functioning. However, the general effects of grazing on community structure and ecosystem function at spatial and temporal scales has rarely been examined synchronously in the same grassland. Here, during 2011-2013, we investigated community structure (cover, height, and species richness) and aboveground biomass (AGB) using 250 paired field sites (grazed vs. fenced) across three vegetation types (meadow, typical, and desert steppes) on the Inner Mongolian Plateau. Grazing, vegetation type, and year all had significant effects on cover, height, species richness, and AGB, although the primary factor influencing variations in these variables was vegetation type. Spatially, grazing significantly reduced the measured variables in meadow and typical steppes, whereas no changes were observed in desert steppe. Temporally, both linear and quadratic relationships were detected between growing season precipitation and cover, height, richness, or AGB, although specific relationships varied among observation years and grazing treatments. In each vegetation type, the observed community properties were significantly correlated with each other, and the shape of the relationship was unaffected by grazing treatment. These findings indicate that vegetation type is the most important factor to be considered in grazing management for this semi-arid grassland.

Figure 1

Locations of the 250 paired (fenced and grazed pairs) study sites in Inner Mongolia. (A), Meadow steppe (B), typical steppe (C), desert steppe. Map created using ArcGIS 9.3 software. (Environmental Systems Research Institute (ESRI), Redlands, CA, USA).

Figure 2

Variation in vegetation cover, height, richness and aboveground biomass (AGB) among three vegetation types (MS: meadow steppe; TS: typical steppe; DS: desert steppe) in 2011–2013.

Figure 3

Spatial pattern of grazing-induced response in vegetation cover, height, species richness and AGB among three vegetation types (MS: meadow steppe; TS: typical steppe; DS: desert steppe) in 2011–2013.

Figure 4

Relationship between vegetation cover, height, richness, aboveground biomass (AGB) and growing season precipitation at both fenced (F) and grazed (G) sites. *P-value < 0.05, **P-value < 0.01, ***P-value < 0.0001. MS: meadow steppe; TS: typical steppe; DS: desert steppe.

Figure 5

Relationships between aboveground biomass (AGB) and vegetation cover, height, richness at both fenced (F) and grazed (G) sites. *P-value < 0.05, **P-value < 0.01, ***P-value < 0.0001. MS: meadow steppe; TS: typical steppe; DS: desert steppe.