2008 Annual Report
1a.Objectives (from AD-416)
Evaluate how management practices and disturbance processes interact to influence A) transitions/thresholds in ecological phases and states, B) plant community heterogeneity and nesting habitat for grassland birds, C) mechanisms and risk of weed invasion, and D) temporal dynamics of key ecological indicators of rangeland health. Subobjective A. Determine the influences of season and intensity of grazing, season and frequency of prescribed burning, and shifts in stocking rate on plant species composition, plant diversity, biomass production, animal gains and nesting habitat of a bird species of concern. (Augustine 0.2, Blumenthal 0.2, Derner 0.5). Subobjective B. Evaluate the influences of fire X grazing interactions (i.e., patch burning) and prairie dog disturbances on within-pasture cattle grazing distribution, consequences for plant community heterogeneity and nesting habitat for a bird species of concern (Augustine 0.5, Derner 0.2, Morgan 0.2). Subobjective C. Determine how disturbance interacts with enemy release (the loss of specialized herbivores and diseases in the exotic range of a plant species) to influence weed invasion and the success of biological control. (Blumenthal 0.4, Morgan 0.1). Subobjective D. Assess the temporal dynamics of key ecological indicators of rangeland health (plant cover and bare ground) for entire pastures in sagebrush and shortgrass steppe. (Booth 0.8).
1b.Approach (from AD-416)
The planned research is designed to integrate contemporary goals of both livestock production and conservation in semiarid rangelands. Research will be conducted in shortgrass steppe, northern mixed-grass prairie and sagebrush steppe. Two experiments are replicated across three ARS locations (Miles City, MT; Nunn, CO; Woodward, OK) to determine ecological consequences of fire seasonality, return interval and grazing interactions along a north-south gradient in the western Great Plains. Rangeland monitoring efforts at two ARS locations with contrasting vegetation (grass-dominated shortgrass steppe, Nunn, CO; shrub-dominated sagebrush steppe, DuBois, ID) will use newly-developed techniques involving very large-scale aerial photography to assess plant cover and bare ground, and incorporate this information into a recently developed index to assess landscape function. Understanding the mechanisms that control disturbance effects on plant communities and animal responses will contribute to the development of innovative management strategies that optimize livestock production and conservation goals. In addition, because state-and-transition models function as a means for organizing current understanding of the processes resulting in stability and change in ecological systems, findings from these experiments will be incorporated into revised state-and-transition models of plant community dynamics that more accurately accommodate multiple successional pathways and stable states.
Our efforts in the prior CRIS (5409-12630-001-00D, expired February 2008) resulted in several major accomplishments involving key collaborators. Livestock and vegetation production responses to stocking rate and grazing systems were completed from long-term research projects on both northern mixed-grass prairie and the shortgrass steppe. Stocking rate was the management factor influencing both livestock and vegetation responses, with grazing system having no effect, and these findings were included in a world-wide synthesis of the effects of grazing systems on rangelands conducted by scientists in the Unit and across many other countries that was published in the January 2008 issue of the prominent journal Rangeland Ecology and Management. Long-term research findings on livestock management, land-use history, primary production, and cattle grazing on shortgrass steppe were recently synthesized and published in the book “Ecology of the Shortgrass Steppe” by Oxford Press. Second, carbon dioxide (CO2) and water flux data from Bowen ratio tower systems installed on grazing treatments in shortgrass steppe were used to evaluate how grazing management affects the carbon and water balance of semi-arid rangelands. In related research, a comparison between different CO2 and water vapor flux measurement methodologies (eddy covariance and Bowen ratio) has been completed to reconcile differences between these two dominant measurements systems. Third, technological advances have been made to increase the precision and accuracy of very large-scale aerial (VLSA) photography, and associated interpretative software developments for determinations of bare ground and plant cover, two key ecological indicators of rangeland health. Resolution of aerial images is <1mm, assessments have been conducted on over 1 million acres of western rangelands in many different ecosystems, developed software has been downloaded by persons in over 15 countries. Fourth, increased snowfall is a primary mechanism of weed invasion in northern mixed-grass prairie, with success of invasive species enhanced providing more accurate predictions of which types of invasive plants will be most successful. Efforts in the new CRIS (5409-22660-002-OOD) involved new patch-burning (grazing X fire interaction) experiments across 3 ARS locations (Miles City, MT–northern mixed-grass; Nunn, CO–shortgrass; and Woodward, OK–southern mixed-grass) including instrumentation of soil thermocouples, TDR probes, tipping rain-gauges and two channel radiometers (for estimates of green phytomass), and assessments of animal movement patterns by Lotek GPS collars outfitted on several yearling steers. Also Unit scientists are involved in literature assessments and monitoring efforts regarding the effectiveness of major conservation practices employed on private lands through the USDA-Natural Resources Conservation Service (NRCS) Rangeland Conservation Effects Assessment Program (CEAP). This research primarily addresses NP215 Pasture Forages, Rangeland Systems Component 1-Rangeland Management Systems to Enhance the Environment and Economic Viability.
The shortgrass steppe: The region and research sites. The historical account of research conducted primarily at the USDA-ARS Central Plains Experimental Range, the primary site for the Shortgrass Steppe Long Term Ecological Project (LTER), is this introductory chapter to the book Shortgrass Steppe: A Long-Term Perspective. This overview chapter tells the story of how grassland scientists have approached and addressed the management challenges of the shortgrass steppe, and how that and related research has led to a sound ecological understanding of the region’s ecology. Perhaps more importantly, the authors explain how the research interests of basic and applied rangeland scientist have converged over the years and resulted in a strong and relevant present-day partnership. This synthesis report supports the “Need for economically viable rangeland management practices, germplasm, technologies and strategies to conserve and enhance rangelands ecosystems”, Problem Statement A of National Program 215: Rangeland, Pasture, and Forages.
Net primary production in the Shortgrass Steppe. A synthesis of collaborative research involving ARS and the Shortgrass Steppe Long Term Ecological Project (LTER) Project focused on the climatic attributes which control net primary production, discussed spatial and temporal patterns in net primary production, and speculated on how future global change may influence net primary production in the Shortgrass Steppe over the next 25 to 50 years. Temporal patterns of plant production were reported to be determined in large part by seasonality of temperature and precipitation. Inter-annual variability in precipitation was identified as the key determinant of inter-annual availability of soil water, which has the most fundamental control on annual net primary production. Other factors that can affect temporal variability of net primary production include landscape effects, soil nitrogen, and atmospheric CO2. This research supports the “Need for economically viable rangeland management practices, germplasm, technologies and strategies to conserve and enhance rangelands ecosystems”, Problem Statement A of National Program 215: Rangeland, Pasture, and Forages.
The future of the Shortgrass Steppe. Although approximately half of the shortgrass steppe region of the Western Great Plains remains today in native or semi-natural grassland, the region is rapidly changing due to human population growth and shifts. In this synthesis book chapter, grassland ecologists and range scientists speculate on the future of this important grassland, based on their knowledge and experience of the region from research conducted primarily over the past quarter century. The authors conclude that the shortgrass steppe tends to be a resilient ecosystem, and with the exception of dramatic changes (urbanization, cultivation management, combined with drought and wind), native portions of this grassland will tend to respond slowly to environmental changes. However, some of the most important fundamental changes in its ecology will be hidden from view, occurring below the soil surface, in the roots of plants and the soil biota which in large part control its ecology. This research supports the “Need for economically viable rangeland management practices, germplasm, technologies and strategies to conserve and enhance rangelands ecosystems”, Problem Statement A of National Program 215: Rangeland, Pasture, and Forages.
Very-Large Scale Aerial Photography for Rangeland Monitoring. Ecological monitoring has been severely limited by the cost and time constraints of obtaining adequate sample sizes and distribution when using conventional ground methods. Using slow-and-low flying “Sport” airplanes with advanced digital cameras, navigational (including a Geographic Positioning System or GPS) and other technical equipment, we regularly obtain hundreds to thousands of aerial samples (images) uniformly-spaced across areas of interest, with minimal motion blur, and at resolutions as great as 1-mm (0.04") ground sample distance, or 30,000 times the resolution of Landsat images. Because we have the GPS “geocodes” for each image, each sample can be described by aspect, elevation, soils, vegetation, and other characteristics using the Geographic Information System data bases commonly available. Costs for aerial surveys are $0.03 to $0.04/acre and the methods are well adapted for monitoring extensive rangeland watersheds in the western US. This research supports the “Need for economically viable rangeland management practices, germplasm, technologies and strategies to conserve and enhance rangelands ecosystems’, Problem Statement A of National Program 215: Rangeland, Pasture, and Forages.
Digital Point Frame Facilitates Image-Based Rangeland Monitoring. A point frame is an apparatus used to systematically sample points within plots or along transects (sampling lines) for measuring vegetative cover and bare ground as part of ecological assessments. With the move toward image-based monitoring, there was a need for an accurate means for measuring cover and bare ground from images. “SamplePoint” software was developed to meet this need. It has a demonstrated accuracy greater than 90% when used with 1-mm (0.04 inch) GSD images and can save time and expense with minimal user training. The software is now used extensively in our research, by collaborators, and by Wyoming ranchers participating in agency-cooperative monitoring. “SamplePoint” has been downloaded from the ARS web site by people from around the world. This research supports the “Need for economically viable rangeland management practices, germplasm, technologies and strategies to conserve and enhance rangelands ecosystems’, Problem Statement A of National Program 215: Rangeland, Pasture, and Forages.
Aerial Surveys Reduce Small Stream Monitoring Costs on Western Rangelands. Stream and stream-side vegetation are critical habitat of US western rangelands and ecological monitoring are key aspects of sustainable management of these resources. However, monitoring of stream-related habitat is limited by manpower costs and time-consuming travel and methods. Very-large scale aerial (VLSA) surveys (low-altitude, high-resolution, intermittent aerial digital photography) were conducted in a watershed inhabited by the Lahonton Cutthroat trout, a threatened species, to measure late-summer open water width, number and location of late-summer dry channels, widths of riparian areas and willow coverage, and riparian proper functioning condition (PFC; an ecological assessment protocol for streams). PFC assessments from VLSA imagery averaged 4 staff hours per stream compared to 36 staff hours per stream for ground PFC assessments. Aerial monitoring allowed more samples to be analyzed, yet cut the costs in half. This research supports the “Need for economically viable rangeland management practices, germplasm, technologies and strategies to conserve and enhance rangelands ecosystems’, Problem Statement A of National Program 215: Rangeland, Pasture, and Forages.
Indirect effects of plague on western Great Plains rangelands: Black-tailed prairie dog management has been a contentious issue in the Great Plains because prairie dogs are central to biodiversity conservation, but also can negatively affect livestock weight gains. We compiled long-term data sets on prairie dog colony complexes in Montana, Nebraska and Colorado, and used these to quantify large-scale spatial and temporal fluctuations in the extent of prairie dog colonies related to sylvatic plague outbreaks. In northern mixed prairie, plague accelerates the temporal turnover of prairie dog colonies, but does not strongly affect their spatial distribution, whereas in shortgrass steppe, plague accelerated both temporal fluctuations and spatial movement of colonies, which in turn may dampen the effects of prairie dogs on shortgrass rangeland vegetation. Mountain plovers, a declining grassland bird, abandoned plague-affected colonies within 1 – 2 years after a plague epizootic, but returned within 1 – 2 years to areas that were recolonized by prairie dogs after plague events. These findings indicate that available plover nesting habitat associated with prairie dog colonies closely tracks the area actively occupied by prairie dogs each year. This research supports the “Need for economically viable rangeland management practices, germplasm, technologies and strategies to conserve and enhance rangelands ecosystems’, Problem Statement A of National Program 215: Rangeland, Pasture, and Forages.
Stocking rates and grazing systems influence cattle gains in northern mixed-grass prairie: The effects of stocking rate and grazing system on gains of yearling beef cattle grazing rangelands have largely been addressed in short-term (<10 yr) studies. Average daily gains (pounds/head/day) across all years (1982-2006) decreased 12-16% with increasing stocking rate and grazing pressure in northern mixed-grass prairie, whereas beef production (pounds/acre) increased with increasing stocking rate and grazing pressure. Cattle gains were reduced by 6% with short-duration rotation compared to season-long grazing over the study period, with differences between systems observed in years with average, but not dry or wet, spring (April+May+June) precipitation. The influence of spring precipitation on cattle gains suggests that incorporation of these relationships into modeling efforts for strategic planning and risk assessment will assist land managers in better matching forage and animal resources for greater sustainability in this highly variable environment. This research supports the “Need for economically viable rangeland management practices, germplasm, technologies and strategies to conserve and enhance rangelands ecosystems’, Problem Statement A of National Program 215: Rangeland, Pasture, and Forages.
Grazing system influence on cattle gains and vegetation cover in shortgrass steppe. We compared effects of time-controlled rotational grazing versus season-long continuous grazing, at the same moderate stocking rate on animal gains, and foliar and basal cover of functional groups (C4 and C3 perennial grasses, C3 annual grasses, perennial and annual forbs, litter and bare ground) in both lowlands and uplands of shortgrass steppe from 1995 to 2003. Gains per unit land area (pounds/acre) did not differ between grazing systems in any year. Grazing system did not affect basal or foliar cover of any functional group in either upland or lowland topographical positions. Land managers in shortgrass steppe will not benefit from the implementation of rotational grazing as a management practice as animal and vegetation responses were similar compared to those under traditional continuous, season-long grazing, at least with the moderate stocking rates used in this investigation. This research supports the “Need for economically viable rangeland management practices, germplasm, technologies and strategies to conserve and enhance rangelands ecosystems’, Problem Statement A of National Program 215: Rangeland, Pasture, and Forages.
Spring precipitation influence on forage production and vegetation cover across 3 semiarid rangeland ecosystems. 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. We compared 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). Responses of forage production were more responsive (75-159%) than basal (8-35%) or foliar (2-29%) cover to increasing spring precipitation. Forage production increases were largely attributable to greater production by C3 perennial graminoids in each ecosystem suggesting that 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. This research supports the “Need for economically viable rangeland management practices, germplasm, technologies and strategies to conserve and enhance rangelands ecosystems’, Problem Statement A of National Program 215: Rangeland, Pasture, and Forages.
World-wide synthesis of rotation grazing on rangelands. The preponderance of experimental grazing research documents that weather variation and stocking rate affect vegetation and animal responses independently of grazing system. Experimental evidence does not support implementation of rotational grazing to enhance either production or environmental goals on rangelands, but this evidence does not effectively address all potential management benefits arising from rotational grazing systems because they have seldom been investigated as a component of the entire ranch enterprise. The continuation of conventional grazing systems research will yield little additional information if it is unable to disentangle the confounding effects of management objectives and capabilities, as well as personal goals and values (i.e., human dimensions), from the associated ecological effects. Rangeland managers and policy makers need to recognize that the potential benefits of grazing systems are derived from sound management models, rather than from ecological phenomena. This research supports the “Need for economically viable rangeland management practices, germplasm, technologies and strategies to conserve and enhance rangelands ecosystems’, Problem Statement A of National Program 215: Rangeland, Pasture, and Forages.
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|Number of Non-Peer Reviewed Presentations and Proceedings||5|
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Lauenroth, W.K., Burke, I.C., Morgan, J.A. 2008. Chapter 1. The shortgrass steppe: The region and research sites. In: W.K. Lauenroth and I.C. Burke (eds.). Ecology of the shortgrass steppe: A long-term perspective. Oxford University Press, Oxford, England. pp. 3-13. Book Chapter.
Lauenroth, W.K., D.G. Milchunas, O.E. Sala, I.C. Burke, and J.A. Morgan. 2008. Chapter 12. Net primary production in the shortgrass steppe: A long-term perspective. Oxford University Press, Oxford, England. pp. 270-305. Book Chapter.
Burke, I.C., Lauenroth, W.K., Antolin, M.F., Derner, J.D., Milchunas, D.G., Morgan, J.A., Stapp, P. 2008. Chapter 19. The future of the shortgrass steppe. In: W.K. Lauenroth and I.C. Burke (eds.). Ecology of the shortgrass steppe: A long-term perspective. Oxford Univeristy Press, Oxford, England. pp. 484-510. Book Chapter.
Blumenthal, D.M., Hufbauer, R. 2007. Increased plant size in exotic populations: A common graden test with 14 invasive species. Ecology 88:2758-2765.
Blumenthal, D.M., Booth, D.T., Cox, S.E., Ferrier, C.E. 2007. Large-scale aerial images capture details of invasive plant populations. Rangeland Ecology and Management 60:532-528.
Hardy, E.M., Blumenthal, D.M. 2008. An efficient and inexpensive system for greenhouse pot rotation. International Journal of Horticultural Science 43:965-966.
Augustine, D.J., Cully, J.F., Johnson, T.L. 2007. Influence of fire on black-tailed prairie dog colony expansion in shortgrass steppe. Rangeland Ecology and Management 60:538-542.
Augustine, D.J., Matchett, M.R., Toombs, T.P., Cully, J.F., Johnson, T.L., Sidle, J.G. 2007. Spatiotemporal dynamics of black-tailed prairie dog colonies affected by plague. Landscape Ecology 23:255-267.
Augustine, D.J., Dinsmore, S.J., Wunder, M.B., Dreitz, V., Knopf, F. 2008. Response of mountain plovers to plague-driven dynamics of black-tailed prairie dog colonies. Landscape Ecology 23:689-697.
Booth, D.T., Cox, S.E., Meikle, T., Zuuring, H.R. 2008. Ground-cover measurements: Assessing correlation among aerial and ground-based methods. Environmental Management DOI 10.1007/s00267-008-9110-x.
Booth, D.T., Cox, S.E. 2008. Image-based monitoring to measure ecological change in rangelands. Frontiers in Ecology and the Environment 6(4):185-190.
Sivanpillai, R., Booth, D.T. 2008. Characterizing rangeland vegetation using Landsat and 1-mm VLSA data in central Wyoming, USA. Agroforestry Systems 73:55-64.
Hart, R.H., Derner, J.D. 2008. Cattle grazing on the shortgrass steppe. In: W.K. Launeroth and I.C. Burke (eds.). Ecology of the shortgrass steppe: A long-term perspective. Oxford University Press. pp. 447-458. Book Chapter.
Derner, J.D., Hart, R.H. 2007. Livestock and vegetation responses to rotational grazing in shortgrass steppe. Western North American Naturalist 67:359-367.
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.
Derner, J.D., Hart, R.H., Smith, M., James, W.W. 2008. Long-term cattle gain responses to stocking rate and grazing systems in northern mixed-grass prairie. Livestock Science 117:60-69.
Briske, D.D., Derner, J.D., Brown, J.R., Fuhlendorf, S.D., Teague, R.W., Havstad, K.M., Gillen, R.L., Ash, A.J., Willms, W.D. 2008. Rotational grazing on rangelands: Reconciliation of perception and experimental evidence. Rangeland Ecology and Management 61:3-18.
Weston, T.R., Derner, J.D., Murrieta, C.M., Rule, D.C., Hess, B.W. 2008. Comparison of catalysts for direct transesterification of fatty acids in freeze-dried forage samples. Crop Science 48:1636-1641.