HR: 0800h
AN: B11D-0782    [Abstracts]
TI: Impacts of prescribed fire on ecosystem C and N cycles at Fort Benning Installation, Georgia
AU: * Zhao, S
EM: szhao@usgs.gov
AF: ERT, contractor to U.S. Geological Survey (USGS) Center for Earth Resources Observation and Science (EROS), 47914 252nd Street, Sioux Falls, SD 57198, United States
AU: Liu, S
EM: sliu@usgs.gov
AF: SAIC, contractor to USGS Center for EROS, Sioux Falls, SD 57198. Work performed under USGS contract 03CRCN0001, 47914 252nd Street, Sioux Falls, SD 57198, United States
AU: Tieszen, L
EM: Tieszen@usgs.gov
AF: USGS Center for EROS, 47914 252nd Street, Sioux Falls, SD 57198, United States
AB: A critical challenge for the land managers at military installation is to maintain the ecological sustainability of natural resources while meeting the needs of military training. Prescribed ground fire as a land management practice has been used to remove the ground layer plants at Fort Benning for two purposes: to facilitate access for military training, and to maintain and restore fire-adapted longleaf pine communities that are critical habitat for the federally endangered red-cockaded woodpecker (Picoides borealis). Nevertheless, the impacts of prescribed fire on ecosystem processes and health are not well-understood and quantified at the plot to regional scales. Frequent fire may result in ecosystem nitrogen (N) deficiency due to repeated N loss through combustion, volatilization, and leaching, threatening ecosystem sustainability at Fort Benning. On the other hand, N loss may be offset by enhanced symbiotic N2 fixation since fire favors herbaceous legumes by scarifying legume seeds and stimulating germination. Quantifying the impacts of prescribed fire on ecosystem carbon (C) and N cycles is further complicated by interactions and feedbacks among burning, nitrogen inputs, other land use practices (e.g. tree thinning or clear-cutting), and soil properties. In this study, we used the Erosion-Deposition-Carbon Model (EDCM), a process-based biogeochemical model, to simulate C and N dynamic at Fort Benning under different combinations of fire frequency, fire intensity, nitrogen deposition, legume nitrogen input, forest harvesting, and soil sand content. Model simulations indicated that prescribed fire led to nitrogen losses from ecosystems at Fort Benning, especially with high intensity and high frequency fires. Forest harvesting further intensified ecosystem nitrogen limitation, leading to reduced biophysical potential of C sequestration. The adverse impacts of prescribed fire and forest harvesting on C and N cycles were much higher in more sandy soil than in less sandy soil. N inputs from nitrogen deposition and legume N fixation helped replenish N losses to some extent. However, N losses due to fire and harvesting were not balanced or exceeded under current atmospheric N deposition and legume N input rates, suggesting additional N input (e.g., fertilization) may be needed to maintain the sustainability of current ecosystem states and management practices at Fort Benning.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0466 Modeling
DE: 0469 Nitrogen cycling
SC: Biogeosciences [B]
MN: 2007 Fall Meeting