HR: 1340h
AN: B43D-0301    [Abstracts]
TI: Carbon Dioxide and Energy Exchange Dynamics: the Interaction of Ashe Juniper Encroachment Onto Grassland/Live Oak Savannas on the Edwards Plateau
AU: * Kjelgaard, J F
EM: jkjelgaard@ag.tamu.edu
AF: Soil and Crop Sciences, Texas A&M University 2474 TAMU, College Station, TX 77843 United States
AU: Heilman, J L
EM: j-heilman@tamu.edu
AF: Soil and Crop Sciences, Texas A&M University 2474 TAMU, College Station, TX 77843 United States
AU: McInnes, K J
EM: KMcInnes@ag.tamu.edu
AF: Soil and Crop Sciences, Texas A&M University 2474 TAMU, College Station, TX 77843 United States
AU: Owens, M K
EM: m-owens@tamu.edu
AF: Texas Agricultural Research Station, 1619 Garner Field Road, Uvalde, TX 78801 United States
AU: Litvak, M E
EM: mlitvak@mail.utexas.edu
AF: The University of Texas at Austin, Section of Integrative Biology, 1 University Station C0930, Austin, TX 78712 United States
AU: Dreiling, L
EM: LDreiling@ag.tamu.edu
AF: Soil and Crop Sciences, Texas A&M University 2474 TAMU, College Station, TX 77843 United States
AU: Bendivas, M
EM: MBendevis@ag.tamu.edu
AF: Soil and Crop Sciences, Texas A&M University 2474 TAMU, College Station, TX 77843 United States
AU: Thijs, A
EM: annthijs@mail.utexas.edu
AF: The University of Texas at Austin, Section of Integrative Biology, 1 University Station C0930, Austin, TX 78712 United States
AU: Cramer, N
EM: NCramer@ag.tamu.edu
AF: Soil and Crop Sciences, Texas A&M University 2474 TAMU, College Station, TX 77843 United States
AB: The Edwards Plateau (Texas Hill Country) is a large (93,000 km2), distinct ecoregion in south and west central Texas that is a biological crossroads for three major biomes of North America (grassland, desert, deciduous forest). Extensive portions of the Plateau are dominated by live oak/ashe juniper savannas with increasing encroachment by invasive junipers over the underlying grasslands. A multi-year, multi-disciplinary study was begun in 2004 to quantify fluxes, source and sinks of atmospheric CO2 on the Edwards Plateau, and to determine how encroachment by ashe juniper alters CO2 fluxes and CO2 source/sink relationships. Flux towers utilizing eddy covariance measurements of CO2 exchange were installed in a typical savanna dominated by grasses (both C3 and C4) and forbs, and in a live oak/ashe juniper forest representing the worst case scenario of juniper encroachment. Measurements at the savanna began on 29 April `04 and at the forest on 18 July `04. The first year of the study was unusually wet, while 2005 was drier than normal through much of the year. The savanna was a net carbon sink during the spring and early summer during both years, and a net source the remainder of the year. Net gain of carbon on an annual basis was near zero. The forest was a net sink for carbon throughout the year because live oak and ashe juniper, the dominant species, are evergreen and the winter was warm. Light response curves showed that the forest was as responsive to drought as the savanna, in spite of root systems capable of penetrating the limestone bedrock and extracting water stored in cracks and fissures.
UR: http://jimheilman.tamu.edu/texmec/index.htm
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0495 Water/energy interactions (1878)
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
SC: Biogeosciences [B]
MN: Fall Meeting 2005