Figure legends
Figure 1: The effects of grazing intensity on plant aboveground biomass, belowground biomass, plant community carbon and nitrogen content. Different lowercase letters indicate significant differences between means at p < 0.05. Error bards are ± SE, Codes of different treatments are as follows: CK, control/no grazing; LG, light grazing; MG, moderate grazing; HG, heavy grazing.
Figure 2: The effects of grazing intensity and month on plant aboveground biomass and biomass of plant functional groups. Each panel represents a different grouping of plant biomass. Different lowercase letters indicate significant differences between means at p< 0.05. Error bards are ± SE, and the lines in panels b-e show the biomass of each plant functional group during the 2020 growing season. Codes of different treatments are as follows: CK, control/no grazing; LG, light grazing; MG, moderate grazing; HG, heavy grazing.
Figure 3: The effects of grazing intensity on soil nutrients. Different lowercase letters indicate significant differences between means at p < 0.05. Error bars are ± SE. Codes of different treatments are as follows: CK, control / no grazing; LG, light grazing; MG, moderate grazing; HG, heavy grazing.
Figure 4: Monthly dynamics of ecosystem fluxes. Panels show the mean value (±SE) of net exchange of ecosystem CO2 (a, NEE), ecosystem respiration (b, ER), gross ecosystem productivity (c, GEP) and soil respiration (d, SR) in the growing season (June-October) of 2020. The inset reflects the differences between treatments in the 2020 growing season, where positive and negative values represent net carbon release and uptake by the ecosystem and do not indicate the magnitude of the values. Different lowercase letters indicate significant differences between treatments (p < 0.05), Codes of different treatments are the same as in Figure 3.
Figure 5: Biplot of ecosystem carbon exchange (NEE, ER, GEP, SR) from redundancy analysis (RDA) for plant factors (a) and soil factors (b). GLM analysis was used to study the contribution of the plant and soil factors to the net exchange of ecosystem CO2 (c, NEE), ecosystem respiration (d, ER), gross ecosystem productivity (e, GEP) and soil respiration (f, SR). a-b, Ecosystem carbon exchange is represented as red lines with arrows; plant factors (a) and soil factors (b) are represented as blue lines with arrows. The length of the line indicates the magnitude of the correlation between the explanatory variable and ecosystem carbon exchange. The angle between the lines indicates the correlation between the variables, and the angle between the red and blue arrows is less than 90° for positive correlations. Codes of different plant factors (a) are as follows: AGB, aboveground biomass; BGB, belowground biomass; PG, perennial grass biomass; AB, annual and biennial plant biomass; PF, perennial forb biomass; SS, shrub and semi-shrub biomass; PTC, plant total carbon; PTN, plant total nitrogen; C/N, the ratio of total plant carbon content to total plant nitrogen content. Codes of different soil factors (b) are as follows: TC, total carbon; TN, total nitrogen; TP, total phosphorus; SOC, organic carbon; AN, ammonium nitrogen; NN, nitrate nitrogen; AP, available phosphorus; MBC, microbial biomass carbon; MBN, microbial biomass nitrogen. c-f, Importance of individual environmental variables across models for ecosystem carbon exchange is shown for each indicator as variable importance weighted by % of R2.
Figure 6: Structural equation models (SEM) examining the standard total effects of plant and soil factors on Ecosystem carbon exchange under different grazing intensities. Boxes stand for measured variables in the model. Standardized path coefficients are given. Solid black lines represent positive paths (p < 0.05), solid red lines represent negative paths (p < 0.05), and dotted black arrows represent non-significant paths (p> 0.05).