HR: 12:05h
AN: B52B-08    [Abstracts]
TI: Correlations of Soil C and N With Vegetation and Soil Attributes and Their Spatial Scaling in a Subtropical Savanna Landscape
AU: * Liu, F
EM: asherliu@tamu.edu
AF: Texas A&M University, Department of Rangeland Ecology and Management, College Station, TX 77843-2126 United States
AU: Bai, E
EM: ebai@tamu.edu
AF: Texas A&M University, Department of Rangeland Ecology and Management, College Station, TX 77843-2126 United States
AU: Wu, B
EM: xbw@tamu.edu
AF: Texas A&M University, Department of Rangeland Ecology and Management, College Station, TX 77843-2126 United States
AU: Archer, S
EM: sarcher@ag.arizona.edu
AF: University of Arizona, School of Renewable Resources, Tucson, AZ 85721 United States
AU: Boutton, T
EM: boutton@tamu.edu
AF: Texas A&M University, Department of Rangeland Ecology and Management, College Station, TX 77843-2126 United States
AB: Invasion of woody plants into grass-dominated ecosystems has occurred worldwide. At present, there is no clear consensus as to whether soil carbon (C) and nitrogen (N) pools increase, decrease, or remain unchanged following shifts from grass to woody plant domination. The purpose of this study was to quantify correlations of soil C and N with soil and vegetation parameters and their spatial scaling properties along a topoedaphic gradient in a subtropical savanna in the Southern Great Plains (Texas) where woody cover is known to have increased over the past 100 years. Variables measured along a 309 m upland-to-lowland catena gradient included soil bulk density, soil particle size distribution, grass and forb biomass, shrub and tree basal diameter, litter and root biomass, and soil C and soil N (0-15 cm). Results indicated that vegetation cover was an important determinant of soil C and N, and that soil C and N mass have increased since woody plant invasion. Mantel tests showed that soil C and N are spatially autocorrelated. Based on correlation analyses with a modified t-test that corrected for autocorrelation, litter and root biomass had strongest correlation with soil C and N. Soil bulk density, shrub basal area, and tree basal area are also significantly correlated with soil C and N. Relationships between grass biomass and soil C and N differed in herbaceous vs. woody dominated patches. The scale of the spatial patterns of soil C and N was about 45m based on quadrat variance methods and corresponded approximately to the distance between the centers of dominant woody patches and the adjacent herbaceous patches. Soil C, N, litter, root biomass, shrub and tree basal area exhibited similar scaling characteristics and differed from those of grass biomass and soil bulk density. Spatial scaling of soil C and N was more strongly related to that of litter and root biomass than to the basal area of neighboring trees and shrubs. This suggests increases in near surface soil C and N accompanying woody plant encroachment is related to production and turnover of litter and root biomass. These, in turn, are likely related to local leaf biomass which increases logarithmically with basal area. This knowledge of scaling and correlations will facilitate efforts to extrapolate point estimates of ecosystem properties to landscapes and regions.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
DE: 0476 Plant ecology (1851)
SC: Biogeosciences [B]
MN: Fall Meeting 2005