HR: 0830h
AN: B11D-0723    [PDF]
TI: Impacts of Forest Management, Climate, and Productivity on Soil CO$_{2}$ Efflux from Loblolly Pine ({\it Pinus Taeda} L.) Stands Located on the Virginia piedmont and the South Carolina coastal plain
AU: * Gough, C M
EM: gough.21@osu.edu
AF: The Ohio State University, Department of Evolution, Ecology, and Organismal Biology 318 W. 12th Avenue, Columbus, OH 43210 United States
AU: Seiler, J R
EM: jseiler@vt.edu
AF: Virginia Tech, Department of Forestry 228 Cheatham Hall, Blacksburg, VA 24061 United States
AU: Wiseman, P E
EM: pwisema@clemson.edu
AF: Clemson University, Department of Forest and Natural Resources 265 Lehotsky Hall, Clemson, SC 29634 United States
AB: Managed loblolly pine ({\it Pinus taeda} L.) forests occupy over 13 million hectares or nearly 1.5% of the total land area in the United States. Typically, over 70% of stored carbon (C) in forests resides in soils, emphasizing the need to better understand the impact forest management has on belowground processes affecting C storage. We measured soil CO$_{2}$ efflux (E$_{c}$) from loblolly pine stands located on the Virginia piedmont (VA$_{p}$) and SC coastal plain (SC$_{cp}$) in efforts to quantify soil C loss from sites differing in climate, productivity, and common management practices. VA$_{p}$ sites were less productive and subjected to a cooler climate than SC$_{cp}$ sites. VA$_{p}$ sites were burned prior to planting as a form of weed and slash reduction while SC$_{cp}$ sites were bedded to raise planting rows above the water table. E$_{c}$ was measured monthly for one year in four replicated age classes (1 to >20 years) on both VA$_{p}$ and SC$_{cp}$ sites using a closed dynamic chamber. Spatial variability for a given site was accounted for by taking measurements both near the base of the tree and between rows. Concurrent with E$_{c}$ measurements, soil temperature (top 10 cm), soil moisture (top 10 cm), stand age, and site index were recorded. Empirical models were developed for the VA$_{p}$ and SC$_{cp}$ sites to assess the relationship between E$_{c}$ and potential drivers. Soil temperature (top 10 cm) was the major E$_{c}$ driver on both VA$_{p}$ and SC$_{cp}$ sites, explaining half or more of the variance. Stand age was positively correlated with E$_{c}$ on VA$_{p}$ sites, but we observed no relationship between stand age and E$_{c}$ on the SC$_{cp}$ sites. Using the empirical models developed from small chamber measurements, we scaled up soil C losses to the stand level for a 20-year rotation. We estimate a total efflux rate of 278.6 Mg C/ha over a 20-year rotation for SC$_{cp}$ and 210.9 Mg C/ha over the same time period for VA$_{p}$. The contribution of heterotrophic respiration to E$_{c}$ was greatest early in the rotation on the SC$_{cp}$ sites, where soils were tilled and organic matter was integrated into the mineral soil. The more minor soil disturbances on VA$_{p}$ sites had less of an impact on heterotrophic respiration early in the rotation. Our results indicate that management intensity impacts soil C efflux by affecting microbial driven C turnover. In a collaborative effort, empirical models developed from small chamber measurements will be incorporated into process-based models currently being developed to predict net C fluxes in response to a variety of management regimes. Further efforts are ongoing to remote sense input variables.
DE: 0315 Biosphere/atmosphere interactions
DE: 0322 Constituent sources and sinks
DE: 1610 Atmosphere (0315, 0325)
DE: 1615 Biogeochemical processes (4805)
SC: Biogeosciences [B]
MN: 2003 Fall Meeting