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United States Department of Agriculture

Agricultural Research Service


Location: Rangeland Resources Research

2005 Annual Report

1.What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? What does it matter?
Increases in atmospheric CO2 and other trace gases, primarily N2O and CH4, are implicated in climate change and other global change weather phenomena. In addition to the potential impacts of climate change on world economies and the environment, climate change is predicted to have important and lasting impacts on both agricultural and native ecosystems. Further, the more direct effects of CO2 on specific plant species and their ecosystems are likely to be as important as their responses to climate change. Numerous experiments have evaluated how various ecosystems might respond to increases in CO2 or temperature alone, but almost no field experimentation has been undertaken to investigate how combined warming and rising CO2 will impact ecosystem structure and function. Such multiple-factor global change experiments are needed as the interactions among the various environmental components of global change are not well understood, although there is good reason to suspect that factors like increased concentrations of CO2, warming, and altered precipitation patterns will interact in complex ways that are difficult to predict. The problem of understanding how global change will impact native ecosystems is especially germane to the problem of weed invasions. Despite multiple reasons to expect that increases in CO2 will exacerbate weed invasion, little data exists on CO2-invasion interactions. CO2 facilitation of individual invaders has been observed in two field experiments. Other studies have found CO2 to facilitate growth of invaders such as Pueraria montana (kudzu), Centaurea solstitialis (yellow-star thistle), and Bromus tectorum (cheatgrass). Despite potential mechanisms and some data suggesting that increasing CO2 may exacerbate invasion, we have very little information on whether any of those mechanisms result in systematic differences between native and invasive responses to CO2. Finally, our current knowledge of C and N cycling and the land-atmosphere exchange of greenhouse gases (GHG) emissions in rangeland ecosystems are insufficient for recommending or developing new management practices for reducing their emissions. Such new management practices are needed if the agricultural sector is to play a significant role in our nation’s reduction in GHG emissions.

To address the challenges of a changing environment, due in part to the release of GHGs into the atmosphere, we will assess/project changes in the structure and functioning of Great Plains grasslands due to the interactive effects of elevated CO2 and warming on primary production, N and C cycling, and plant community dynamics, including invasive weeds. This will be done in a field Free Air CO2 Enrichment (FACE) and warming experiment conducted in a native northern mixed grass prairie, with some areas inter-planted to locally important perennial weeds. Some controlled environment studies will be conducted to evaluate specific mechanistic responses, like plant recruitment or N cycling. Modeling exercises will also be conducted from previous CO2 field enrichment experiments to predict long-term responses of Great Plains grassland ecosystems to global change. The management question related to reducing GHG emissions will be addressed in additional experiments evaluating legume inter-seeding into grasslands as a tool to increase carbon storage, and grazing practices. In particular, we will be investigating how legume inter-seeding affects N cycling among associated plants and the microbial community in an effort to determine the impact on the land-atmosphere GHG exchange as well as on carbon storage. We will also be evaluating the effects of different stocking rates on C and N cycling.

2.List the milestones (indicators of progress) from your Project Plan.
Objective 1. Assess/project changes in the structure and functioning of Great Plains grasslands due to the interactive effects of elevated CO2 and legume N on primary production, N and C cycling, and plant community dynamics, including invasive weeds.

Build and test FACE system prototype (July-Oct, 2004) Assess legume inter-planting methods (April-June, 2005) Final testing of FACE system; installation (2005) Establish plots and transplant legumes (May, 2005) Seed plots with weed species (September, 2005) Annual and seasonal measurements (2006-2010) Analysis, synthesis, and manuscript development and submission for 1st 3 years of project (2008, 2009) Modeling of SGS and TGP CO2-enrichment studies (2004, 2005) Results on modeling water relations/forage responses reported in manuscripts (2006, 2007) Data summary/synthesis of Bowen Ratio CO2 flux, send to ARS El Reno (2007) Collaborate with ARS El Reno on modeling weather-driven CO2 fluxes, develop manuscript (2008) Submit manuscript on weather-driven CO2 fluxes (2009)

Objective 2. Develop management strategies that optimize responses of semi-arid rangeland to global change and minimize emission of greenhouse gases (GHGs).

Collect baseline soils data from 2 new NP205 grazing management studies (2004) Repeat soil sampling and analyses from above (2009) Repeat soil sampling and analyses from long-term grazing management studies (2004, 2007) Results on long-term grazing impacts on soil C and N cycling developed into manuscripts (2005, 2008) Baseline soil sampling on private ranches (2004) Bi-weekly assessment of alfalfa establishment in a private ranch study (2004, 2005) Repeat soil sampling and analyses in a private ranch study (2009) Repeat soil sampling and analyses in a private ranch study (2006, 2009) Trace gas measurements at HPGRS and in a private ranch study (2004, 2006-2008)

4a.What was the single most significant accomplishment this past year?
Rising Atmospheric CO2 Levels and Root Dynamics in a Native Grassland. We published a manuscript with collaborator the Dept. of Forest, Rangeland and Watershed Stewardship, Colorado State University, Fort Collins, CO, in which we reported the effects of a doubling of CO2 concentration over a native shortgrass prairie in Colorado on root system dynamics. We found that while elevated CO2 enhanced root growth of native grasses, it also enhanced the death of roots, but on balance, resulted in an increased standing root biomass. Growth under elevated CO2 also increased root diameter and the branching of roots, suggesting that roots in future CO2-enriched environments may have a morphology that increases their ability to mine nutrients and water from the soil. This may be a benefit to plants obtaining additional resources to support the higher plant growth rates predicted for future CO2-enriched environments. These results are important because they help us understand how our native grasslands will adapt to increasing levels of atmospheric CO2 concentrations.

4b.List other significant accomplishments, if any.
Scaling carbon dioxide fluxes from fields to regions. In collaborative research involving the USDA-ARS Rangeland Resources Research Unit, Fort Collins, CO; the Northern Great Plains Research Laboratory, Mandan, ND; Fort Keogh, Miles City, MT; plus the Department of Biology and Microbiology, North Dakota State University; the Department of Biology, University of Lethbridge; and the Atmospheric, Turbulence and Diffusion Division, NOAA/ARI, Oak Ridge, Tennessee, relationships were established between satellite imagery and ground-measured carbon dioxide (CO2) fluxes that have significantly advanced our ability to utilize satellite data to estimate the capacity of agricultural systems to store carbon. Semi-empirical models were used to characterize fluxes of CO2 that had been measured with micrometeorological towers placed at several grassland locations across the northern Great Plains. The model was able to translate whole-system measured CO2 fluxes into ten-day estimates of photosynthetic assimilation of CO2, and these photosynthetic estimates, in turn, were correlated to a spectral index (NDVI) developed from remotely sensed satellite imagery. This statistical connection between satellite imagery and ground-based determinations of grassland CO2 fluxes is an important accomplishment that brings us closer to the goal of estimating agriculture’s capacity to store carbon. Such tools are critical for understanding and managing greenhouse gas fluxes from our agricultural and native ecosystems. Synthesis of C Cycling Research in Northwestern USA and Canada. Concern over human impact on the global environment has generated increased interest in quantifying agricultural contributions to greenhouse gas fluxes. As part of a research effort called GRACEnet (Greenhouse Gas Reduction through Agricultural Carbon Enhancement Network), three scientists from the RRRU served as co-authors on a review paper that summarized available information concerning management effects on soil organic carbon (SOC), and greenhouse gas fluxes in croplands and rangelands in northwestern USA and western Canada. Rates of C sequestration measured in recent studies were comparable to estimates used by the Intergovernmental Panel on Climate Change (IPCC) for net annual change in C stocks from improved cropland management practices. The high variability in SOC sequestration potential of rangelands underscores the need for additional long-term C cycling research on rangelands. This paper elucidates the large voids in our knowledge of trace gas flux from cropland and rangeland in the northwestern USA and western Canada, as well as the need to integrate such data to determine the net effect of agricultural management on radiative forcing of the atmosphere.

Plant Growth and Forage Quality Responses to UV Radiation. Collaborative research was undertaken with the Dept. of Forest, Rangeland and Watershed Stewardship, Colorado State University, Fort Collins, CO; the Dept. of Soil, Water, and Climate, University of Minnesota; the Dept. of Biological Sciences, University of Northern Colorado; the USDA UV-B Monitoring and Research Program, Colorado State University; and the ARS Soil-Plant-Nutrient Research Unit, Fort Collins, CO, to manipulate UV radiation in a natural field setting to determine the effects of increasing surface UV radiation on vegetation. UV levels were manipulated by constructed structures over native shortgrass prairie that either passed or blocked wavelengths shorter than 370 nanometers. The overall effects of UV radiation were to decrease forage quantity but to increase quality. Such UV-induced changes in forage quality could speed up organic matter decomposition, thereby altering carbon dynamics such that the ecosystem’s ability to store C is reduced. Significant species differences in biomass sensitivity to UV were also apparent, and the species with the greatest sensitivity is one that is important in stabilizing the system. The results suggest that increased surface UV radiation will have important consequences on ecosystem nutrient dynamics and community species composition that must be considered in evaluations of climate change impacts on native grassland ecology.

4c.List any significant activities that support special target populations.

5.Describe the major accomplishments over the life of the project, including their predicted or actual impact.
In this first year of the project, we have developed and tested a new type of FACE System, GradientFACE, which was designed to deliver a range (gradient) of CO2 concentrations across a field to implement a multi-level CO2 enrichment experiment. We gave an invited paper at a workshop in Switzerland on the system, and there was great interest among scientists who conduct research in global change. Unfortunately the system has not worked within specifications required for our experiment, so the system was abandoned. Nevertheless, the progress we made with this technology may be adapted by others in the eventual design and implementation of a successful GradientFACE system. As we are still in the initial stages of installing our FACE experiment, we do not yet have any major accomplishments at this point in the project. We are currently developing a more established ring-type FACE system, and hope to have it operational before year’s end.

6.What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end-user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products?
This project “Global Change: Responses and Management Strategies for Semi-Arid Rangelands”, has two distinct topic areas, one evaluating the impact of global change on rangelands, the other developing management strategies that either cope with global change, or help to mitigate land-atmosphere greenhouse gas emissions. Technology transfer in the area of understanding impacts of global change are mainly to scientists and policy makers. Technology transfer in research geared toward management is typically aimed principally at other scientists, technology users, and the public. Some of the more important technology transfers activities are:

Nov, 2004: invited seminar speaker to Ecology Seminar Series at the University of Nevada, Reno to discuss impact of CO2 on grassland ecology.

Feb., 2005: invited presentations at symposium entitled USDA-ARS Global Change Research on Rangelands and Pasturelands presented at SRM Annual Meeting, Fort Worth, Texas. Individual talks were - Management effects and potential for rangeland carbon sequestration; Grazing management effects on inorganic C storage in rangelands; Influence of CO2 enrichment on plant community and soils systems in semi-arid rangelands.

A summary manuscript of these and other invited talks was developed into a manuscript and submitted to Rangelands under the same title.

May, 2005: invited presentation entitled, “Using Field Experiments and Modeling to Understand how Shortgrass Steppe Vegetation Will Respond to Rising Atmospheric CO2 and Global Change” at TERACC- and Diversitas-sponsored Global Change/Biodiversity Workshop in Paris, France, to improve interactions among global change ecologists and climatologists who work at several different spatial scales.

June, 2005, co-authored with the USDA Forest Service. Oral presentation “Impact of Climate Change on Western Rangelands” at USDA Forest Service Workshop in Eugene, Oregon, Bringing Climate into Natural Resource Management.

Sept., 2005: platform lead-off speaker for “Impacts of High CO2 on Land and Ocean Ecosystems” at the Seventh International Carbon Dioxide Conference, Boulder, CO.

Two papers titled “Differences in labile pool C and N dynamics in the surface soils of two semi-arid rangeland ecosystems”, and “Contribution of grass crowns and surface soil roots to rangeland ecosystem C dynamics” at the American Society of Agronomy Annual Meeting in Seattle WA, November 1-4 2004.

Soil Resource Management Workshop, Dallas TX, February 22-25, 2005.

Mentored three Colorado State University graduate students in using the proper protocols for collecting, processing and analyzing soils from rangelands and riparian grazing areas.

Co-author on a poster “Land-use impacts on carbon and water flux on the Shortgrass Steppe in Eastern Colorado - Preliminary Results” at the Shortgrass Steppe Symposium, Fort Collins CO, January 14 2005.

Co-author on a poster “Shortgrass steppe ecosystem productivity” at the Shortgrass Steppe Symposium, Fort Collins CO, January 14 2005.

Seminars to producer groups at six locations within Wyoming on the potential of yellow-flowering (Medicago sativa ssp. falcata) alfalfa in rangeland interseeding. The seminars were organized by the University of Wyoming Extension Service, local conservation districts and the Natural Resources Conservation Service. The seminars included information on how to history of the plant subspecies, interseeding methodologies, production potential, forage quality enhancement, and enhancement of soil organic carbon storage. Significant interest has been shown by producers and land managers in the use of this subspecies to enhance rangeland production and forage quality. Commercially produced seed was available for the first time and over 9000 lbs (entire available supply) of seed was marketed within a couple of months; demonstrating the interest. ARS scientists, the rancher (supplied seed stock), and NRCS Plant Materials personnel are presently preparing a release of this material as the “Smith Ranch Alfalfa” so that a common genetic base will be established.

July, 2005, supplied reprints and input to the Dept. Environmental Science, University of Botswana, Botswana concerning grassland global change research to assist in a summary report of ecosystem responses to global change for the current Intergovernmental Panel on Climate Change (IPCC) Report. This report is expected to be released to the public within a year, and will be used by world governments and policy makers to develop global change policy.

7.List your most important publications in the popular press and presentations to organizations and articles written about your work. (NOTE: List your peer reviewed publications below).
Darst, Kevin. 2005. Carbon dioxide levels threaten prairie life. The Coloradoan, Fort Collins, Colorado, March 7, 2005.

Revkin, Andrew C. 2004. U.S. report turns focus to greenhouse gases. The New York Times, August 26, 2004.

2005. More forage might be worth less. Agricultural Research, August 2005, p 23.

Sian Mooney, George F. Vance, Justin Derner, and Gerald Schuman. 2005. Collaborative Research-Committee Participation Furthers Carbon Sequestration Research. pp. 44-45. In: Reflections, University of Wyoming, College of Agriculture, May 2005, University of Wyoming, Laramie, WY.

134833 Morgan, J.A. 2001. Ecosystems and their goods and services, Chapter 5: Climate Change 2001. pp. 235-342. In: J.J. McCarthy, (eds). The third assessment report of the intergovernmental panel on climate change (IPCC), Cambridge University Press, Cambridge, UK.

184263 Pendall, E.L., King, J.Y., Mosier, A.R., Morgan, J.A., Milchunas, D. 2005. Stable isotope constraints on net ecosystem production under elevated CO2. pp. 182-198. In: L.B. Flanagan, J.R. Ehleringer and D.E. Pataki (eds) Stable isotopes and biosphere-atmospheric interactions: Processes and biological controls. Book Chapter. Elsevier, Inc., San Diego, CA.

170325 Follett, R.F., Schuman, G.E. Grazing land contributions to carbon sequestration. pp. 265-277. In: D.A. McGilloway (ed). Grassland: A global resource. XX Int’l. Grassland Congress, 25 June-1 July, 2005, Dublin, Irelad. Wageningen Academic Publishers, Wageningen, The Netherlands.

169125 Schuman, G.E., Derner, J.D. 2005. Management effects and potential for rangeland carbon sequestration. In: Proceedings Annual Society for Range Management meetings. CD Abstract #307. Fort Worth, TX, Feb. 2005.

170307 Norton, U., Morgan, J.A., Mosier, A.R., Derner, J.D. 2004. Trace gas emissions and soil C and N transformations following moisture pulses in sagebrush: Effects of invasive and native companion plant species. P. 358. In: Proceedings of the American Geophysical Union Fall meeting Abstracts.

170309 Norton, U., Morgan, J.A., Mosier, A.R., Derner, J.D., Stahl, P., Ingram, L.J. 2004. Trace gas emissions and soil C and N transformations following moisture pulses in sagebrush: Effects of invasive and native companion plant species. American Society of Agronomy Abstracts. Abstract 5328.

170990 Morgan, J.A. 2005. Influence of CO2 enrichment on plant community and soils systems in semi-arid rangelands. Society for Range Management meeting proceedings. Abstract #283.

176295 Reeder, S.J. 2005. Grazing management effects on inorganic C storage in rangelands. Society for Range Management Annual Meeting Abstracts. Special Symposium: Global change and rangelands/pastures: A state of the state. CDROM Abstract.

184913 Blumenthal, D.M., Chimner, R., Welker, J., Morgan, J.A., LeCain, D.R. 2005. Testing for evolution of increased competitive ability across species and functional groups. Ecological Society of America Annual Meeting Proceedings. August, Montreal, Canada. CDROM Abstract.

Review Publications
Morgan, J.A., Mosier, A.R., Milchunas, D.G., Lecain, D.R., Nelson, J.A., Parton, W.J. 2004. CO2 enhances productivity of the shortgrass steppe, alters species composition and reduces forage digestibility. Ecological Applications. 14:208-219.

Morgan, J.A. 2002. Looking beneath the surface. Science. 298:1903-1904.

Gilmanov, T.G., Tieszen, L.L., Wylie, B.K., Flanagan, L.B., Frank, A.B., Haferkamp, M.R., Meyers, T.P., Morgan, J.A. 2005. Integration of CO2 flux and remotely sensed data for primary production and ecosystem respiration analyses in the Northern Great Plains: Potential for quantitative spatial extrapolation. Global Ecology and Biogeography 14:271-292.

Milchunas, D., Mosier, A.R., Morgan, J.A., Lecain, D.R., King, J.Y., Nelson, J.A. 2005. Elevated CO2 and defoliation effects on a shortgrass steppe: forage quality versus quantity for ruminants. Agriculture, Ecosystems and Environment. 111:166-184.

Liebig, M.A., Morgan, J.A., Reeder, S.J., Ellert, B.H., Gollany, H.T., Schuman, G.E. 2005. Greenhouse gas contributions and mitigation potential of agricultural practices in northwestern USA and western Canada. Soil & Tillage Research 83:25-52.

Derner, J.D., Tischler, C.R., Polley, H.W., Johnson, H.B. 2005. Seedling growth of two honey mesquite varieties under CO2 enrichment. Rangeland Ecology and Management. 58:292-298.

Last Modified: 4/21/2014
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