HR: 1340h
AN: B23C-1505    [Abstracts]
TI: Spatial Heterogeneity and Sources of Soil Carbon in Southern African Savannas
AU: Macko, S
EM: sam8f@virginia.edu
AF: University of Virginia, 291 McCormick Rd, Department of Environmental Sciences, Charlottesville, VA 22904, United States
AU: * Wang, L
EM: Lixin@virginia.edu
AF: University of Virginia, 291 McCormick Rd, Department of Environmental Sciences, Charlottesville, VA 22904, United States
AU: Okin, G
EM: okin@ucla.edu
AF: University of California, Los Angeles, Department of Geography, 1255 Bunche Hall, Los Angeles, CA 90095, United States
AB: Soil organic carbon (SOC) is one of the largest and most dynamic reservoirs of C on Earth, with nearly twice as much C stored in SOC than in the biosphere and atmosphere combined. SOC storage in global tropical savannas constitutes approximately 56 Gt of C, which rises to 216 Gt of C (i.e., about 17% of the terrestrial non- agricultural SOC), when woodlands, shrublands, and desert scrub are included. Savannas cover about 20% of the global land surface, including about one-half of Africa, Australia and South America. The shared dominance of trees and grasses in savannas, the dominant physiognomy in southern Africa, add more complexity to soil C pool partitioning and dynamics than is found in landscapes with a single physiognomy. Here, the spatial variability of the soil C pool was investigated with particular emphasis on understanding the contribution to SOC from trees and grasses at two savanna sites of the Kalahari Transect, one wet and the other dry. Using a combination of stable isotope techniques and geostatistics, the results showed that spatial patterns of soil δ¹³ C exist and were related to the distributions of woody (C₃) and herbaceous (C₄) vegetation at both sites. Heterogeneity of the sources of SOC, as well as heterogeneity in the amount of SOC, was greater at the dry site relative to the wet site. At the dry site, the grasses were the major contributor to soil C whereas in the wet site, woody vegetation was the major contributor, regardless of the location with respect to woody canopies.
DE: 0428 Carbon cycling (4806)
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0486 Soils/pedology (1865)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting