**3.2 Vegetative ecological characteristics after grazing exclusion**

Grassland coverage, plant species richness (number of plant species), plant density (number of plant individuals) and Shannon-Wiener index had similar variation tendencies during the three-decade restoration process (**Figure 3**). Initially, the coverage, plant richness, plant density and Shannon-Wiener index significantly increased. After 20 years' restoration, they reached peak values of 92.47%, 29.33 species m<sup>−</sup><sup>2</sup> , 161.8 individuals m<sup>−</sup><sup>2</sup> and 2.93, respectively. With grazing exclusion process continuing, the four indices' values decreased to 88.73%, 28.2 species m<sup>−</sup><sup>2</sup> , 138.7 individuals m<sup>−</sup><sup>2</sup> and 2.47, respectively (**Figure 3**).

### **3.3 Biomass changes in grassland community after grazing exclusion**

There were significant differences in aboveground biomass between four groups and between total aboveground biomass and total belowground biomass (**Figure 4**).

### **Figure 4.**

*Biomass changes of Gramineae (a), Leguminosae (B), Compositae (C), weeds (D), aboveground community (E) and belowground community (F) of grassland with grazing exclusion time at 5, 10, 15, 20, 25 and 30 years.*

*Plant Communities and Their Environment*

**3.1 Temperature and precipitation changes**

The annual mean air temperature had an increasing trend and increased by 1.17°C from 1982 to 2011(**Figure 2A**). In contrast with mean annual temperature, mean annual precipitation showed a decreasing trend and larger intra- and interannual variations in our study, indicating the warmer and drier climate. The mean annual precipitation from 1982 to 2011 was 425.42 mm, with markedly lower values

*Mean annual air temperature (a) and mean annual rainfall (B) of growing season, nongrowing season and* 

in 1986, 1991 and 1999 and with higher values in 2003 (**Figure 2B**).

**3. Results**

**140**

**Figure 3.**

**Figure 2.**

*entire year at Yunwu Mountain during 1982–2011.*

*with grazing exclusion time at 5, 10, 15, 20, 25 and 30 years.*

*Changes of coverage (a), number of plants (B), plant density (C) and Shannon-wiener index (D) of grassland* 

Aboveground biomasses of four plant groups increased with restoration time after grazing exclusion. Aboveground biomass of Gramineae and Compositae peaked at the 20th year, while that of Leguminosae peaked at the 25th year, and that of Weeds families peaked at the 15th year during restoration process after grazing exclusion. Considering the reduced biomasses of weed families, long-term grazing exclusion improved forage quality of grassland. Meanwhile, aboveground and belowground community biomasses were both increased by grazing exclusion. Since grassland mainly consisted of plants belonging to Gramineae and Compositae, peaks of the total above- and belowground community biomass both occurred at the 20th year, with aboveground community biomass of 520.5 g m<sup>−</sup><sup>2</sup> and belowground community biomass of 3240.2 g m<sup>−</sup><sup>2</sup> (**Figure 4**).
