Grazing Intensity Effects on the Plant Functional Group Productivity and Plant Community Carbon and Nitrogen Content
We found that both aboveground (Fig. 1a) and belowground (Fig. 1b) biomass was influenced by the grazing treatment. All grazing treatments had lower aboveground and belowground biomass than the control treatment with no grazing. Aboveground biomass was lowest in the heavy grazing treatment while there were no differences between the two lower grazing intensity treatments (Fig. 1a), belowground biomass was incrementally lower with each increased grazing intensity treatment (Fig. 1b). When we analyzed differences in nutrient content, we found that the total carbon content of the plant community was lowest in the heavy grazing treatment (Fig. 1c), while the total nitrogen content of the plant community was lowest in the moderate grazing treatment (Fig. 1d). Aboveground biomass differed significantly between months, though the difference was not significant for the interaction between month and grazing intensity (Table 1). When we divided plants into functional groups (Fig. 2b-e), we found that most groups strongly declined with increasing grazing, particularly shrubs and semi-shrubs (Fig. 2c), as well as perennial forbs (Fig. 2d). Perennial grasses, in fact, had greater biomass in the moderate grazing treatment (Fig. 2b) We performed repeated measures ANOVAs for different plant functional groups and found that most functional groups differed significantly by month, grazing intensity, and the interaction between month and grazing intensity. This was especially true for the perennial forbs, shrubs and semi-shrubs. Annuals and biennials did not differ significantly by the interaction between month and grazing intensity, and perennial grasses did not significant significantly by month, grazing intensity or the interaction between month and grazing intensity (Table 1, Fig. 2b-e).