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).