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United States Department of Agriculture

Agricultural Research Service

Research Project: GLOBAL CHANGE: RESPONSES AND MANAGEMENT STRATEGIES FOR SEMI-ARID RANGELANDS
2006 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? Why 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 research is aligned with National Program 204, Global Change. The main experiment of the project 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 by year the currently approved milestones (indicators of research progress)
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 (2004) Modeling of SGS and TGP CO2-enrichment studies (2004, 2005) Assess legume inter-planting methods (2005) Baseline soil and root biomass sampling (2005). Final testing of FACE system; installation (2005) Establish plots and transplant legumes (May, 2005) Seed plots with weed species (September, 2005) Results on modeling water relations/forage responses reported in manuscripts (2006, 2007) Annual and seasonal measurements (2006-2010) Data summary/synthesis of Bowen Ratio CO2 flux, send to El Reno (2007) Analysis, synthesis, and manuscript development and submission for 1st 3 years of project (2008, 2009) Collaborate with 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) Baseline soil sampling of Browder Ranch and McGuire Ranch Studies (2004) Bi-weekly assessment of alfalfa establishment McGuire Ranch study (2004, 2005) Trace gas measurements at HPGRS and Smith (2004, 2006-2008) 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) Repeat soil sampling and analyses of McGuire Ranch Study (2006, 2009) Repeat soil sampling and analyses from above (2009) Repeat soil sampling and analyses of Browder Ranch Study (2009)


4a.List the single most significant research accomplishment during FY 2006.
Consequences of high atmospheric CO2 concentrations on root systems in a native semi-arid grassland. Increasing levels of atmospheric CO2 are known to cause significant changes in ecosystem structure and function, but little information is available on the consequences for native plant root systems. In a recent report from an Open Top Chamber experiment conducted in north-eastern Colorado, standing root biomass, and root length and diameter were evaluated in dominant grasses exposed to a doubling of atmospheric CO2 over present-day concentrations. Atmospheric CO2 had no significant consequences for total standing root biomass, although there was a 37% increase in fine root length in the upper 10-cm soil layer. The fine root length increases may have been caused by increased recruitment of an important site dominant species, needle-and-thread grass (Stipa comata). These findings, which address the Agricultural Ecosystem Impacts Component of ARS’ National Program 204, Global Change, suggest that the balance of increased root growth and root death, which was reported to occur in an earlier paper from this experiment, will tend to conserve root biomass and not necessarily lead to large root biomass increases as atmospheric CO2 concentrations increase. The 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 research accomplishment(s), if any.
Soil microbes and enzymes in a native Colorado grassland prove sensitive to transient changes in ambient concentrations of carbon dioxide. Rising atmospheric carbon dioxide is predicted to alter growth, development and plant species change in native ecosystems, but little is known about how CO2 and climate change will affect the biology of soil organisms. Yet the responses of soil organisms to global change is important as they determine in large part the cycling and release of soil nutrients that plants rely on. Research was therefore undertaken to determine the microbial response to 5 years of CO2 enrichment in a field experiment conducted in the Colorado shortgrass steppe, plus the reversibility of the microbial responses following cessation of CO2 enrichment. Elevated CO2 increased important enzyme activities in the upper soil layers, but did not change microbial biomass during the 5-year CO2 enrichment. Activities of soil enzymes increased after the conclusion of the experiment, although there were no differences in activities later that same year, suggesting that the increased C inputs that resulted earlier elevated CO2 atmospheres mainly entered the fast cycling carbon pool and contribute little to long-term carbon storage. These findings, which address the Agricultural Ecosystem Impacts Component of ARS’ National Program 204, Global Change, suggest that despite the enhancement of plant growth due to rising atmospheric CO2, long-term soil C sequestration may not be enhanced by rising atmospheric CO2 in semi-arid grasslands like the shortgrass steppe.


4c.List significant activities that support special target populations.
None.


5.Describe the major accomplishments to date and their predicted or actual impact.
In the first year of the project (2005), we developed and tested a new type of FACE (Free Air CO2 Enrichment) 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. In late 2005-early 2006, we successfully tested and installed a ring-type FACE system, comprised OF rings of an intermediate size (3 meters in diameter) compared to field CO2 enrichment systems built previously. The experiment, called the High Plains Global Change Experiment, began in mid-April, 2006, when CO2 injection into the rings began. In this first year of the HPGCE, we are already seeing increases in net CO2 assimilation, soil CO2 levels, and net primary production when CO2 is elevated over a native northern mixed-grass prairie from current atmospheric concentration of 370 ppm CO2 to 600 ppm CO2, a level we expect by the later part of this century. Collaborator Dr. Bill Parton is using the well-known DAYCENT model to predict the long-term consequences of elevated CO2 on grassland ecology, a test of that model that will be evaluated against the experiment results over the next several years. The HPGCE is but one of a handful of such experiments, and the only one being conducted in native rangelands in North America that is evaluating the combine effects of rising atmospheric CO2 and warming (system to be installed in 2007) on the ecology and productivity of semi-arid grasslands. These initial experimental and modeling results will be featured in an invited manuscript to be submitted to the New Phytologist later this year in a special issue edition featuring new progress in global change experiments. The results will build on earlier results from the Colorado Open Top Camber experiment which evaluated how rising atmospheric CO2 increases forage production, but causes changes in the plant community and reduces forage quality. Research from this project addresses the Agricultural Ecosystem Impacts Component of ARS’ National Program 204, Global Change. The primary clients of this work are scientists, particularly ecologist interested in global change biology; and also governmental organization and policy makers who base their decisions on policy relevant to greenhouse gas emissions in part on results from such experiments. Scientists from this project continue to be consulted by national and international global change organizations for their expertise in global change synthesis and policy matters, including the International Geosphere Biosphere Programme (IGPB) and the Intergovernmental Panel on Climate Change (IPCC).


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 in FY 2006 are:

Dr. Blumenthal, April 2006, presented an invited lecture on causes of plant invasion, including discussion of altered precipitation, N and CO2 as drivers of invasion, for a University of Wyoming Rangeland Restoration Course. The audience consisted primarily of range-science students.

Dr. Morgan, October 2005, attended the GraceNet workshop in Fort Collins, CO, helped organize a network of research activities involving over fifty ARS scientists on trace gas fluxes and C sequestration, and gave an overview of current research, “GraceNet Research of the Rangeland Resources Research Unit” to the workshop attendees, other scientists mostly.

Dr. Morgan, December 2005, traveled to Phoenix, AZ to develop collaborative research with the USDA-ARS research unit stationed at Maricopa, and gave a seminar entitled, “The High Plains Global Change Experiment” to staff and scientists at Maricopa.

Dr. Morgan, Jan. – August, 2006, served as an invited expert reviewer for the 4th Assessment Report of the Intergovernmental Panel on Climate Change. The audience for the report will be primarily scientists, the general public, various environmental NGOs, and world government policy makers.

Drs. Morgan, Derner, Blumenthal and Booth, January 2006, met with their customer focus group, a group consisting of private ranchers, public land managers, university professors, NGOs representing diverse interest groups from ranching to conservation, and governmental interests, to discuss research priorities for the RRRU, including the latest research findings and research needs on how western rangelands are responding to global change.

Dr. Morgan, May 2006, met with Dr. Joel Brown, NRCS, Las Cruces, NM, to discuss global change research priorities for USDA-ARS, and opportunities for collaborating with NRCS’ global change program.

Dr. Morgan, July 2006, organized tours and poster presentations for the Crops Research Lab dedication, held to celebrate the completions of the Crops Research Lab renovation project, Ft. Collins, CO. The audience was mostly the general public, but included university and private agricultural collaborators, plus government scientists and administrators.

Dr. Morgan, August 2006, reported a review of the book Climate Change and Managed Ecosystems for the Journal of Environmental Quality. The audience for this review are educators, students, scientists, policy folks, and administrators involved in agriculture and global change interests.


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).
Dr. Morgan, 2005, published an invited book chapter entitled “Rising atmospheric CO2 and global climate change: Management implications for grazing lands.” for an FAO Publication Grasslands: Developments Opportunities Perspectives, FAO and Science Pub. Inc., pp. 245-272 (S.G. Reynolds and J. Frame, eds)

Dr. Morgan (author) and Derner, Andales, Dunn (co-authors), April, 2006, gave an invited presentation, “Water relations and management of semi-arid grasslands: Current status, future critical research, and the useful role of model,” as an invited speaker to the 36th Biological Systems Simulation Conference, Ft. Collins, CO. The audience were scientists and technicians involved in agricultural research.

Dr. Derner (author) and Morgan, Andales (co-authors), July 2006, gave the invited presentation, “Tactical and strategic difficulties in managing water-limited rangelands of the Western Great Plains” to the national meeting of the Soil and Water Conservation Society Meeting, Breckinridge, CO. The audience included scientists, government land managers, private agriculturalists, and conservation interests.

Dr. Morgan, August 2006, presented the poster “The High Plains Global Change Experiment: Semi-arid grassland responses to combined elevated CO2 and warming” at the Annual Meeting of the Ecological Society of America. Audience is mostly scientists, educators, and students.


Review Publications
Morgan, J.A., Baron, V.S., Bradford, J.A., Haferkamp, M.R., Sims, P.L., Skinner, H. 2005. Managing grassland as a co2 sink. ASA-CSSA-SSSA Annual Meeting Abstracts.

Derner, J.D., Andales, A.A., Morgan, J.A. 2006. Tactical and strategic difficulties in managing water-limited rangelands of the Western Great Plains. In: Soil and Water Conservation Society Proceedings, Rocky Mountain Rendezvous II. p. 10.

Morgan, J.A., Miglietta, F., Kimball, B.A., Parton, W.J., Lecain, D.R., Zaldei, A., Reeder, S.J., Pendall, E., Williams, D.G., Blumenthal, D.M. 2006. The high plains global change experiment: semi-arid grassland responses to combined elevated co2 and warming. Ecological Society of America Proceedings. p. 60, Poster #159.

Morgan, J.A., Derner, J.D., Andales, A.A., Dunn, G.H. 2006. Water relations and management of semi-arid grasslands: current status, further critical research, and the useful role of models. pp. 30-31. 36th Annual Biological Systems Simulation Conference. April 2006, Ft. Collins, CO.

Gilmanov, T.G., Demment, M.W., Wylie, B.K., Laca, E.A., Akshalov, K., Baldocchi, D.D., Belelli, L., Bradford, J.A., Coulter, R.L., Dugas, W.A., Emmerich, W.E., Flanagan, L.B., Frank, A.B., Haferkamp, M.R., Johnson, D.A., Meyers, T.P., Morgan, J.A., Nasyrov, M., Owensby, C.E., Pekour, M.S., Pilegaard, K., Saliendra, N.Z., Sanz, M.J., Sims, P.L., Soussana, J.F., Tieszen, L.L., Verma, S.B. 2005. Quantification of co2 exchange in grassland ecosystems of the world using tower measurements, modeling and remote sensing. In: Proceedings of the 20th International Grassland Congress. June 26 - July 1, 2005, University College, Dublin Ireland. p. 587.

Milchunas, D., Morgan, J.A., Mosier, A., Lecain, D.R. 2005. Root dynamics and demography in shortgrass steppe under elevated CO2, and comments on minirhizotron methodology. Global Change Biology. 11:1837-1855.

Lecain, D.R., Morgan, J.A., Milchunas, D.G., Mosier, A.R., Nelson, J.A., Smith, D.P. 2006. Root biomass of individual species, and root size characteristics after five years of CO2 enrichment on native shortgrass steppe. Plant and Soil Journal. 279:219-228.

Derner, J.D., Schuman, G.E., Jawson, M.D., Shafer, S.R., Morgan, J.A., Polley, H.W., Runion, G.B., Prior, S.A., Torbert Iii, H.A., Rogers Jr, H.H., Bunce, J.A., Ziska, L.H., White, J.W., Franzluebbers, A.J., Reeder, S.J., Venterea, R.T., Harper, L.A. 2005. USDA-ARS global change research on rangelands and pasturelands. Rangelands. 27(5):36-42.

Kandeler, E., Mosier, A., Morgan, J.A., Milchunas, D., King, J., Rudolph, S., Tscherko, D. 2006. Response of soil microbial biomass and enzyme activities to the transient elevation of carbon dioxide in a semi-arid dryland. Soil Biology and Biochemistry. 38(8):2448-2460.

Ganjegunte, G.K., Vance, G.F., Preston, C.M., Schuman, G.E., Ingram, L.J., Stahl, P.D., Welker, J.M. 2006. Soil organic carbon composition in a northern mixed-grass prairie: effects of grazing. Soil Science Society of America Journal. 69:1746-1756.

Last Modified: 10/20/2014
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