Document: DOU-3-76-6
Impacts of livestock herbivory on woody species in a central Arizona riparian area.
GREEN, D.* 1, P.FENNER 2 and T.WILLARD 2
Arizona State University East, Mesa, AZ 85212 1
U.S. Forest Service 2
Abstract:
Maintaining riparian functions and values is a key goal of many public land management agencies. Woody species form an important component of many riparian systems. In April 1999 we initiated a study to assess the impact of livestock on community dynamics of Salix gooddingii and Populus fremontii. The study site is located along the Verde River in central Arizona. Livestock are grazed on this reach as part of a winter grazing program and are generally removed by April of each year. Utilization limits of woody riparian species is set at 40% for the grazable meristems. We tagged a total of 410 trees located in 10 greenline communities. We measured tree height, diameter, utilization, and distance from the tag to the sediment surface. Utilization averaged 31.6% of grazable meristems for P. fremontii and 15.2% for S. gooddingii. Between April and October growth of P. fremontii averaged 39.4 cm for grazed and 34.3 cm for ungrazed. During the same time period growth of S. gooddingii averaged 35.6 cm for grazed and 32.1 cm for ungrazed individuals. Differences in growth were not significant for either species. Correlations between growth and percent utilization ranged form 0.07 to 0.80 for P. fremontii and from 0.18 to 0.36 for S. gooddingii. All correlations were significant at the 0.05 level. Our results indicate that the amount of livestock grazing in this river system is not significantly impacting height growth of P. fremontii or S. gooddingii.
Keywords: riparian, herbivory, livestock grazing, Populus fremontii, Salix gooddingii, Arizona
This abstract is being presented at: 10:30 AM in session:
RIPARIAN ECOLOGY