Page Banner

United States Department of Agriculture

Agricultural Research Service

Title: Functional group and species responses to spring precipitation in three semi-arid rangeland ecosystems

Authors
item Derner, Justin
item Hess, Bret - UNIVERSITY OF WYOMING
item Olson, Richard - UNIVERSITY OF WYOMING
item Schuman, Gerald - ARS-RETIRED

Submitted to: Arid Land Research and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 14, 2007
Publication Date: January 2, 2008
Citation: Derner, J.D., Hess, B.W., Olson, R.A., Schuman, G.E. 2008. Functional group and species responses to spring precipitation in three semi-arid rangeland ecosystems. Arid Land Research and Management 22:81-92.

Interpretive Summary: Decision making for land managers regarding estimates of forage production in semi-arid rangeland ecosystems would be enhanced if there was a clearer understanding of the role of early spring precipitation plays in key forage species responses, functional group responses, and total forage production response. Here, we used two years with contrasting spring precipitation (below-average 2004, and above-average 2005) to determine effects on forage production across three semi-arid rangeland ecosystems (shortgrass steppe, northern mixed-grass prairie and sagebrush grassland). Total forage production was more responsive (75-159%) than basal (8-35%) or foliar (2-29%) cover to increasing spring precipitation for the three ecosystems. Absolute (1016 kg'ha-1, 641±69 vs. 1657±190 kg'ha-1, 2004 vs. 2005) and relative (159%) increases in total forage production from 2004 to 2005 were greatest for the shortgrass steppe, with forage production increases largely a result of greater production by C3 perennial graminoids. This information will be useful to land managers as well as in interpreting functional consequences of biomass production partitioning for modeling expected results, especially within the context of potential changes in precipitation patterns and amounts associated with global change.

Technical Abstract: Determining if precipitation-induced changes to forage production and basal and foliar cover in semi-arid rangelands are species-specific, functional group-specific or ubiquitous across species and functional groups will enhance decision making among producers and increase precision of forage production models. Our objective was to compare forage production and foliar and basal cover responses of plant communities, plant functional groups and individual species between years with below-average (2004) and above-average (2005) spring precipitation across three semi-arid rangeland ecosystems (shortgrass steppe, northern mixed-grass prairie and sagebrush grassland). Foliar and basal cover at time of peak standing crop were visually estimated using modified Daubenmire cover categories, and forage production by species was harvested from areas that had been excluded from large herbivores. Responses of forage production, but not foliar and basal cover, were similar for the three semi-arid ecosystems. Total forage production was more responsive (75-159%) than basal (8-35%) or foliar (2-29%) cover to increasing spring precipitation. Absolute (1016 kg'ha-1, 641±69 vs. 1657±190 kg'ha-1, 2004 vs. 2005) and relative (159%) increases in total forage production from 2004 to 2005 were greatest for the shortgrass steppe. Forage production increases were largely attributable to greater production by C3 perennial graminoids in each ecosystem; increases in basal and foliar cover for this plant functional group were observed in shortgrass steppe and sagebrush grassland, but not in northern mixed-grass prairie. Fine-scale inputs of species and plant functional group responses to spring precipitation will further the accuracy of forage prediction models in predicting both total biomass production and relative proportions of plant biomass. This information will be useful to land managers as well as in interpreting functional consequences of biomass production partitioning, especially within the context of potential changes in precipitation patterns and amounts associated with global change.

Last Modified: 8/30/2014
Footer Content Back to Top of Page