Primary Production in Grazed and Ungrazed Desert Communities of Eastern Idaho

Abstract

The harvest method; was employed to study primary production in two plant communities, one of which had heen continuously grazed for about 70 years while the other had been protected from grazing for a period of 11 years. Exclosures were constructed around both study areas to protect them from livestock grazing during the 2 years of the study.There was 45% more top growth in the protected area but only 68% as much root mass; consequently, average annual net production was at least 12% greater in the grazed area. Irrigation with 9 em water increased top-growth yield 41.4%. Although over 30 species of plants were present in each community, two species contributed over half of the annual production in both areas. In the protected community 65% and in the grazed community 80% of the plant mass was underground. Proportion of plant mass underground ranged from 55% to over 98% in individual plants excavated whole. Following harvesting of the tops, dry weight of the roots decreased 1.6% during the first week, 22.1% during the first month, and 31.3o/o during the first 8 months. To measure seasonal trends in productivity, six plots, each 1 m2 in area, were harvested every week during two growing seasons. Artemisia tridentata, the principal shrub present, seemed to be most productive during the fall and early spring while Stipa comata, the principal grass, was most productive during late spring and early summer.

Root Dynamics of a Shortgrass Ecosystem

“…However, in a study of a gras s-sage brush community in eastern Idaho, Pearson (1965) found that grazed areas had more roots than ungrazed areas. He attributed this to ( 1) differences in species composition of the two areas or (2) root growth stimulated by grazing.…”

“…(Schuster 1964;Lorenz and RogIer 1967;Biswell and Weaver 1933;Cook, Stoddart and Kinsinger 1958;and Jam.eson a.nd Huss 1959); the only reported increase was that de scribed by Pearson (1965). Schuster (1964) Research has shown that gras s roots stop growing when the aerial portions are clipped.…”

A Preliminary Model to Predict Rainfall Use Efficiency of Pastures on Open-Cut Coal Mines in Central Queensland, Australia

“…Heavy grazing reduces RUE by reducing photosynthetic area and ground cover, thereby reducing rainfall retention and infiltration (Grigg et al, 2000). Pearson (1965) reported lower RUE values for moderately grazed paddocks in comparison to ungrazed paddocks in Eastern Idaho.…”

Special Analysis of Transuranic Waste in Trench T04C at the Area 5 Radioactive Waste Management Site, Nevada Test Site, Nye County, Nevada, Revision 1

“…A grassland dominated by cheatgrass may be another possible future state. Pearson (1965) found that the aboveground biomass of an Artemisia tridentata Shubland was partitioned as 65 percent Artemisia tridentata, 6.4 percent Chrysothamnus viscidiflorus (green rabbitbrush), and 29 percent grasses and forbs. Boindini et al (1985) found that Artemisia tridentata comprised from 60 to 80 percent of the canopy of an Artemisia tridentata Shubland.…”

“…shrub-steppe communities or semi-arid grassland communities from the western United States (Pearson 1965;Webb et al 1978;Sims et al 1978a, b;Gholz 1982;Law and Waring 1994;Hansen et al 2000;Knapp and Smith 2001). Selected grassland communities were limited to those with MAT from 8 to 12ºC and MAP less than 400 mm yr -1 .…”