HR: 14:25h
AN: B53A-04    [Abstracts]
TI: Factors Affecting the Pattern of Vegetation Biomass and Canopy Height With Elevation at Hubbard Brook Experimental Forest
AU: * Schilz, M H
EM: mariya@solo.sr.unh.edu
AF: University of New Hampshire, Department of Natural Resources, Complex Systems Research Center, 39 College Road, Durham, NH 03824 United States
AU: Hurtt, G C
EM: george.hurtt@unh.edu
AF: University of New Hampshire, Department of Natural Resources, Complex Systems Research Center, 39 College Road, Durham, NH 03824 United States
AB: Understanding patterns of carbon stocks and fluxes on the land surface is important for studies of terrestrial ecology, the carbon cycle, and climate change and is an increasingly high priority for environmental policymakers. This need is especially relevant in areas of mountainous terrain, where methodological challenges limit the usefulness of atmospheric methods such as eddy covariance. At the Hubbard Brook Experimental Forest (White Mountains, New Hampshire), both field data and remote sensing data demonstrate that forests exhibit decreased height and biomass with elevation. In particular, aboveground biomass (AGB) values decline from an average of 280 mg/ha at 250 meters elevation to 145 mg/ha at 910 meters elevation. Correspondingly, average canopy height declines from 28 meters to 15 meters within the same elevational range. Although this trend is well documented by field and LiDar data, the relative influence of various causal factors has not been well established. Potential mechanisms include increased rates of disturbance and mortality, decreased rates of growth and changes in tree allometry. These factors may in turn be influenced by changes in water and nutrient availability, edaphic factors, and climate. This study examines the relative importance of these mechanisms through 2 objectives; statistical analysis of existing Hubbard Brook data and collection and analysis of additional field data. Our analysis of 1999 LiDar data indicates that differences in slope and aspect do not explain the AGB and height trend. Analysis of ground based measurements of tree diameters (DBH) and remote sensing measurements of tree height suggest that allometric changes are not responsible for the observed trends. To evaluate the remaining hypothesis of growth, mortality, and disturbance, we obtained and analyzed 371 previously collected tree cores. Using a stratified random sampling design based on LiDar data, 108 additional tree cores have been collected to better establish rates of growth and mortality along an elevational transect at Hubbard Brook. Analysis of these cores establishes the relative importance of growth rates, mortality, and disturbance on tree height and AGB at elevation. Results from this study will add more detail to the pattern of AGB and height decline with elevation at Hubbard Brook and improve understanding of carbon stocks and fluxes.
DE: 0428 Carbon cycling (4806)
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0476 Plant ecology (1851)
SC: Biogeosciences [B]
MN: Fall Meeting 2005