Carbon in the Desert
In recent decades, a worldwide trend of increasing woody plant abundance in grasslands and savannas has been reported. This proliferation of trees and shrubs move affects livestock production, wildlife habitat, water availability. At the same time their presence changes the way the ecosystem processes carbon and nitrogen, two important elements linked to climate change. SNRE professor Steve Archer is interested in understanding how carbon and nitrogen stocks in ecosystems change as the systems shift from grassland to shrubland.
Dr. Archer's research ultimately will lead to some answers about how much carbon gets sequestered, or tied up, and for how long, in various types of vegetation and under different land management practices. This is important for carbon credit programs being considered in some parts of the United States. Such programs compensate landowners and land managers for promoting vegetation growth or restoring degraded range and pasture land, to increase carbon sequestration in the soil.
This is a potential win-win situation because carbon credits could be a source of capital for range improvement practices that have many spin-off benefits, such as increasing soil organic matter and improving water-holding capacity and fertility. The biodiversity of grassland ecosystems, the capacity for the soil to retain water and the ability of the land to sustain wildlife and livestock are some of the issues at stake.
Conferences:
Conservation management and woody plant encroachment: the yin/yang of tree-grass interactions in grazing lands. In: Wild Rangelands: Conservation in the World's Grazing Ecosystems, Regents Park, London, UK
Land cover, climate and management of rangelands. In: Earth system feedbacks: vulnerability of the carbon cycle to drought and fire. Canberra, Australia, June 2006
Carbon cycle dynamics on grazed rangelands. In: SCOPE/FAO "Livestock in a changing landscape" workshop. FAO Headquarters, Rome, March 2006
International Forum on Soils, Society and Global Change (Reykjavik, Iceland, Sep 2007)
Grasses, shrubs and the functional consequences of ecosystem state changes. In: Current Ecological Issues n Grassland Science Symposium, Society for Range Management Annual Meetings, Louisville, KY (Jan 2008).
Grasslands in transition: emerging issues and challenges in the western USA. In: Symposium on "Assessing the Multi-Functionality of Grasslands-Future Research Priorities to Address Global Change", SA-CSSA-SSSA Annual Meetings,Houston, Texas (Oct 2008)
Funding sources:
National Science Foundation Ecosystems Program
NASA Carbon Cycle Science
USDA Managed Ecosystems
Key Collaborators:
Rebecca McCulley (University of Kentucky)
Heather Thoop (New Mexico State University)
Carol Wessman (University of Colorado)
References:
Archer, S, TW Boutton, KA Hibbard. 2001. Trees in grasslands: biogeochemical consequences of woody plant expansion, pp. 115-137. In: Global Biogeochemical Cycles in the Climate System (E-D Schulze, SP Harrison, M Heimann, EA Holland, J Lloyd, IC Prentice, D Schimel, eds.). Academic Press, San Diego.
Wheeler, CW, SR Archer, GP Asner, CR McMurtry. 2007. Climate and edaphic controls on soil carbon-nitrogen response to woody plant encroachment in desert grassland. Ecological Applications 17:1911-1928.
Huang, C., S. E. Marsh, M. P. McClaran, and S. R. Archer. 2007. Post-fire stand structure in a semi-arid savanna: cross-scale challenges estimating biomass. Ecological Applications 17: 1899-1910.
Knapp AK, Briggs JM, Archer SR, et al. 2008. Shrub encroachment in North American grasslands: shifts in growth form dominance rapidly alters control of ecosystem carbon inputs. Global Change Biology 14:615-623.
Throop, H., SR. Archer. 2008. Shrub (Prosopis velutina) encroachment in a semi-desert grassland: spatial-temporal changes in soil organic carbon and nitrogen pools. Global Change Biology: 14:1-12 .
Browning, DM, SR Archer, GP Asner, MP McClaran, CA Wessman. 2008. Woody plants in grasslands: post-encroachment stand dynamics. Ecological Applications: 18: 928-944.
Bai, E., T. Boutton, F. Liu, X. Wu, S. Archer. 2008. Variation in woody plant δ13C along a topoedaphic gradient in a subtropical savanna parkland Oecologia 156:479-489.
Ryan, M, Archer, S. 2008 & Contributors. Land Resources: Forests and Arid Lands. In: The Effects of Climate Change on Agriculture, Land Resources, Water Resources, and Biodiversity (P. Backlund, A. Janetos, D. Schimel, eds.). Synthesis & Assessment Product 4.3, US Climate Change Program, Washington, DC. http://www.sap43.ucar.edu/
Boutton,TW, JD Liao, TR. Filley,SR Archer. In Press. Belowground carbon storage and dynamics following woody plant encroachment in a subtropical savanna. In: Soil Carbon Sequestration and the Greenhouse Effect (R. Lal and R. Follett, eds.). Soil Science Society of America, Madison, WI.
Asner, G., and S. Archer. In Press. Livestock and the Global Carbon Cycle.in H. Mooney, H. Steinfeld, F. Schneider, and L. E. Neville, editors. Livestock in a Changing Landscape: Drivers, Consequences and Responses. Island Press, Washington, D.C.
Throop, HL, SR Archer. 2008. Resolving the dryland decomposition conundrum: some new perspectives on potential drivers. Progress in Botany: In Press.
