EFFECTS OF SPRING PRECIPITATION ON TOTAL AND FUNCTIONAL GROUP FORAGE PRODUCTION IN THREE SEMI-ARID RANGELAND ECOSYSTEMS

Authors: EAST, ERICA - UNIVERSITY OF WYOMING; Derner, Justin; HESS, BRET - UNIVERSITY OF WYOMING; OLSON, RICH - UNIVERSITY OF WYOMING; SCHUMAN, GERALD - RETIRED ARS-COLLABORATOR

Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2005
Publication Date: 2/11/2006
Citation: East, E.L., Derner, J.D., Hess, B.W., Olson, R.A., Schuman, G.E. 2006. Effects of spring precipitation on total and functional group forage production in three semi-arid rangeland ecosystems. Society for Range Management Meeting Abstracts. CD-ROM Rangelands To Rainforests #91.

Interpretive Summary:

Technical Abstract: Forage production in semi-arid rangeland ecosystems of the western Great Plains is largely dependent upon spring precipitation. We assessed the influence of relatively low (2004) and relatively high (2005) spring precipitation amounts on total and functional group forage production in ungrazed areas of three rangeland ecosystems: sagebrush grassland (Bossler, WY), northern mixed grass prairie (Cheyenne, WY) and shortgrass steppe (Nunn, CO). Aboveground biomass was harvested to ground level by species in mid-July/early August from 48 0.1m2 quadrats in sagebrush grassland, 12 0.18m2 quadrats in northern mixed-grass prairie, and 12 0.1m2 quadrats in shortgrass steppe, and assigned one of seven functional groups: C4 perennial grass, C3 perennial grass, C3 annual grass, perennial forb, annual forb, sub-shrub, or shrub. Total forage production was 99% greater in 2005 than 2004 in the sagebrush grassland (1172 vs. 589 kg ha-1), 75% greater in the northern mixed-grass prairie (1990 vs. 1139), and 159% greater in shortgrass steppe (1657 vs. 641). For the sagebrush grassland, forage production increases in 2005 were primarily attributable to C3 perennial grasses (811 vs. 363) and perennial forbs (220 vs. 102). Forage production increases in 2005 by C3 perennial grasses (1378 vs. 706), C4 perennial grasses (95 vs. 46), and C3 annual grasses (86 vs. 0) were largely responsible for the increased forage production in the northern mixed-grass prairie. In the shortgrass steppe, forage production increases for C3 perennial grasses (971 vs. 314), C4 perennial grasses (526 vs. 273), C3 annual grasses (57 vs. 0), and annual forbs (40 vs. 1) are mostly responsible for the observed total forage production increase. All three semi-arid rangeland ecosystems were responsive to increased spring precipitation in 2005, with the majority of the forage production increases associated with greater aboveground biomass of the C3 perennial grass functional group. These results indicate that spring precipitation amounts can be a valuable tool for land managers in forecasting forage production, and that increased forage production in these semi-arid rangeland ecosystems with wet springs results in the largest absolute increases in production by the dominant C3 perennial grasses.