Long-Term Forest Growth in a North Carolina Piedmont Forest: Examination of Recent Growth Trends Using Individual Tree Growth and Mortality Data
Studies show evidence of recent biomass increases across various forest types, including temperate forests. Some studies suggests that these trends are due to increased forest growth rates attributable to effects of climate change and fertilization effects from increased atmospheric CO2. Using a dataset of tree growth and mortality collected over the previous 80 years from 34 permanent sample plots in Duke Forest, we examine trends of biomass accumulation and tree growth in a temperate piedmont forest. We hypothesize that growth rates will exhibit above-expected increases the last 30 years, and that the trend is correlated with increased temperature and atmospheric CO2. Individual measurements of tree growth and death across all of the Duke Forest plots allow us to track broad, region-wide successional change. Individual tree height growth records provide better calculations of forest growth than estimates using diameter growth alone. Further, individual-tree mortality data allows us to determine the extent that observed trends in biomass accretion are due to shifts in mortality rates versus changes in growth rates. Additionally, knowledge of the successional age and disturbance history of the plots allows us to determine expected growth levels attributable to normal recovery processes in order to determine if growth rates are exceeding expected values. Finally, we collect regional weather and atmospheric CO2 measurements from the previous 80 years to determine if a strong correlation exists between the measured forest growth rates and observed climatic trends. Observed correlations may be a possible explanation for higher than expected levels of biomass accretion.
1 Curriculum for the Environment & Ecology, University of North Carolina at Chapel Hill, Chapel Hill, NC; 2 Dept of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC
171 • Elizabeth Martin, Beverly Collins
Paleoecological History of a High Elevation Valley in the Blue Ridge Mountains of North Carolina
Panthertown is a high-elevation valley in the Nantahala National Forest, and is one of few sites in western North Carolina with natural wetlands. Radiocarbon dating of multiple cores at a Panthertown valley wetland has returned basal dates of 8,000+ yr BP with nearly constant sedimentation rates. This is the oldest continuous record in the region; as such, this wetland is uniquely suited to provide information on vegetation dynamics and climatic regimes of the Holocene in the region. Using standard palynological techniques, pollen was extracted from sediment core samples and identified to genus or family at 400x; the resulting pollen percentages were used to describe the environmental history of Panthertown valley. Presence of Alnus, Salix, Asteraceae, and ferns throughout indicate a consistent open, moist site. The early to mid-Holocene (8.5-6.5 yr BP) forest appears to have been dominated by Castanea and Quercus, with minor contributions by Betula, Carya, Acer, and Pinus. The mid-Holocene (6.5-3.5 yr BP) is characterized by severe decreases in Castanea and Pinus, with increases in Quercus and Poaceae,and, to a lesser extent, ferns, Asteraceae, and Betula; these increases coincide with a δ13 isotope record, supporting the idea of a warmHypsithermal (8-4 yr BP). Elements of both a wetter and drier flora are present during this time. The late Holocene (3.5 yr BP -present) assemblage shows a more diverse forest, with significant contributions from Castanea, Quercus, Betula, Pinus, and Tsuga.
Dept of Biology, Western Carolina University, Cullowhee, NC
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172 • Emily C. Adams, Frank P. Day
Blue Carbon in Coastal Freshwater Marshes on the Barrier Islands of Virginia: Aboveground Carbon Pools
Blue Carbon is a relatively new concept describing carbon distributed tidally and sequestered via net production within coastal ecosystems, including sea grass beds, mangrove forests and salt-water marshes. These systems sequester carbon at least 10 times faster than terrestrial systems. Freshwater wetlands that receive irregular tidal influence due to overwash and storm events have not been typically studied as blue carbon systems. Our objective was to quantify carbon sequestered within 4 interdunal freshwater marshes on Hog Island, VA to determine their relationship to other blue carbon systems. Marshes 1 and 2 are farthest from the ocean, below and above a berm respectively. Marshes 3 and 4 are closest to the ocean, below and above a berm respectively. Aboveground primary production was determined via harvests throughout 2013. Peak biomass in August indicated marsh 2 was highest (612 g/m2) followed by marshes 1 (550 g/m2), 4 (435 g/m2) and 3 (406 g/m2). These values are similar to biomass in salt-water marshes (80 - 860 g/m2). Peak belowground biomass was from cores taken to 1 m depth in August. Marsh 2 had more biomass (0.014 g/cm3) than marsh 1 (0.01 g/cm3) and significantly more than marshes 3 and 4 (0.008 g/cm3; 0.007 g/cm3). Decomposition was measured with litterbags collected throughout the year. All marshes exhibited slow exponential decay (k = 0.0000004, 0.002, 0.001, 0.001). Soil carbon data are being finalized, but aboveground production and decomposition rates suggest these marshes are sequestering carbon at rates similar to other blue carbon systems.
Dept of Biology, Old Dominion University, Norfolk, VA
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173 • Howard S. Neufeld, Alyssa Teat
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