HR: 0800h
AN: B41B-0187 [Abstracts]
TI: Evaluation of Ecosystem Controls on Terrestrial Carbon Dynamics at a Sample Block Scale
AU: * Tan, Z
EM: ztan@usgs.gov
AF: South Dakota Center for Biocomplexity Studies, SDSU, Box 2202, Brookings, SD 57007
United States
AU: Johnston, C A
B41B-0187
AF: South Dakota Center for Biocomplexity Studies, SDSU, Box 2202, Brookings, SD 57007
United States
AU: Liu, S
B41B-0187
AF: SAIC, 27914 252nd ST, Sioux Falls, SD 57198
United States
AU: Tieszen, L L
B41B-0187
AF: USGS National Center for Earth Resources Observation and Science, 27914 252nd ST, Sioux Falls, SD 57198
United States
AB:
This study evaluated the controls on soil organic C (SOC) changes from 1973 to 2000 in the northwest Great Plains ecoregion.
SOC source-sink relationships were quantified using the General Ensemble Biogeochemical Modeling System (GEMS) based on 40
randomly selected 10 x 10 km2 sample blocks. These sample blocks were classified into crop-, grass-, and forestland
groups based on land cover composition within each sample block. SOC stock increased 0.40% per year for the whole ecoregion,
ranging from 0.11% for the cropland group to 0.75% for the grassland group. SOC change rates at the sample block scale
depended more upon the baseline SOC stock level and temperature regimes for forest- and cropland groups than for grassland
group. Of the described controls, annual precipitation was most critical to SOC sequestration but likely undermined by higher
baseline soil organic nitrogen (SON) stock for the grassland group. Impacts of higher baseline SOC stocks on C accumulation
in both crop- and forestland groups could be offset by higher baseline SON stocks. Conversion of cropped area to grassland
use reduced SOC depletion and tended to lead to a terrestrial C sink. A considerable unexplained variance in SOC change for
the grassland group suggests that, at the landscape to regional scale, grassland ecosystems are more complicated than others
in the ecoregion, which may be difficult to identify at a field scale.
DE: 0402 Agricultural systems
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 1632 Land cover change
SC: Biogeosciences [B]
MN: Fall Meeting 2005