Project Number: 5434-21630-001-00
Project Type: Appropriated

Start Date: Feb 21, 2003
End Date: Jan 30, 2008

Objective:
1. Quantify relative impacts of climatic variation and livestock grazing on sustainability of Northern Great Plains rangeland ecosystems and develop management strategies to ameliorate selected economic and ecological risks resulting from adverse impacts. a. Quantify impacts of spring drought and above average summer rainfall on primary productivity and proportion of plant species groups in the biomass. b. Quantify impacts of climatic conditions and varying livestock grazing tactics on primary productivity and plant species composition and diversity. c. Quantify impacts of grazing management strategies on soil C, CO2 flux, above- and below-ground biomass, and plant species composition. d. Quantify impacts of varying abiotic and biotic factors, particularly animal mediated impacts, on rate and extent of invasion and control of noxious weeds into rangeland dominated landscapes. e. Research and develop ecologically and economically sound rangeland restoration technologies for restoring degraded, weed infested rangeland ecosystems. 2. Quantify impacts of management tactics designed to improve the supply of quality forage in relation to nutritional needs of cattle on performance of grazing cattle and related economic indicators. a. Determine persistence and potential grazing value of experimental cultivars of seeded perennial forages on non-irrigated pastures for early spring or fall grazing, with emphasis on wheatgrasses and wildryes, b. Quantify impacts of varying seasons of calving (late winter, early spring, and late spring) on rangeland-based beef cattle production traits. c. Determine profit and associated annual risk as a function of season of calving and subsequent variations in post-weaning management strategies. 3. Evaluate in vitro gas production techniques to estimate seasonal variation in forage quality and predict performance in rangeland-based beef cow production systems.

Approach:
Field-laboratory studies will evaluate how plants respond to grazing and environmental stress. Role of rangelands and management tactics in regulating atmospheric carbon dioxide flux will be assessed by measuring temporal changes in plant biomass, soil carbon and water, and carbon dioxide fluxes with chambers. Long-term impacts of environment on ecological condition will be assessed by evaluating changes in plant species composition inside and outside livestock exclosures and evaluating changes in herbage production and rooting dynamics with short-term droughts applied with a rain-out shelter. Fundamental life history, autecolgical studies will be initiated to quantify role that varying abiotic and biotic factors play in regulating the rate and extent of invasion and control of noxious weeds. Fundamental understandings of important ecological processes will be researched, developed, expanded, and ultimately incorporated into rangeland restoration technologies. The potential role of planted forages will be studied by monitoring herbage growth dynamics, cattle diets, & weight gains. Late winter, early spring, and late spring calving seasons will be evaluated for their effect on biologic and economic measures of rangeland beef production. In vitro gas production techniques will be used to evaluate seasonal variations in forage quality and results will be evaluated for their ability to accurately predict performance of grazing cattle.