HR: 10:35h
AN: B41E-02    [PDF]
TI: Temporal variability in 13C of respired CO2 in a pine and a hardwood forest subject to similar climatic conditions
AU: * Mortazavi, B
EM: mortazavi@ocean.fsu.edu
AF: Florida State University, Dept of Oceanography, Tallahassee, FL 32306-4320 United States
AU: Chanton, J P
EM: chanton@ocean.fsu.edu
AF: Florida State University, Dept of Oceanography, Tallahassee, FL 32306-4320 United States
AU: Prater, J
EM: prater@ocean.fsu.edu
AF: Florida State University, Dept of Oceanography, Tallahassee, FL 32306-4320 United States
AU: Oishi, C
EM: andrew.oishi@duke.edu
AF: Duke University, Nicholas School of the Environment and Earth Sciences LSRC, Box 90328, Durham, NC 27708 United States
AU: Oren, R
EM: ramoren@duke.edu
AF: Duke University, Nicholas School of the Environment and Earth Sciences LSRC, Box 90328, Durham, NC 27708 United States
AU: Katul, G
EM: gaby@duke.edu
AF: Duke University, Nicholas School of the Environment and Earth Sciences LSRC, Box 90328, Durham, NC 27708 United States
AB: The temporal variability in the 13C of ecosystem („Cr), soil („Cs) and foliage („Cf) respired CO2 were contrasted in a 18 m tall evenly aged loblolly pine forest and in a 35 m tall unevenly aged mature second growth deciduous mixed hardwood forest in North Carolina, USA, over a two year period. These two sites are located within a kilometer of each other and are subject to identical climatic and edaphic conditions. „Cr varied in response to time lagged vapor pressure deficit (VPD) at both forests. However, the response of „Cr to VPD was more dynamic at the pine relative to the hardwood. „Cr at the pine forest varied from -31.0 to -26.4 per mill and at the hardwood forest from -26.0 to -27.0 permill during the growing season. „Cr at the hardwood forest was 13C enriched during the growing season, on average, by 1.4 permill relative to „Cr at the pine forest for the same time periods. Three factors influence these results. Canopy height and composition were different between the two sites, and also at the pine forest „Cr values generally were more similar to „Cf values, while at the hardwood forest, „Cr values were more similar to „Cs values. At the hardwood forest, the temporal variability in „Cs was less that of „Cf and buffered changes in the „Cr. The results indicate that within a forest mosaic the vegetation structure needs to be considered for predicting realistic „Cr values. Inclusion of a temporally and spatially variable „Cr into the atmospheric inversion models will lead to a more realistic estimate of the partitioning of the global carbon uptake into oceanic and terrestrial sinks. Because „Cr within each ecosystem varies in response to VPD in a predictable fashion, a variable „Cr can be incorporated to better constrain atmospheric inversion models.
DE: 1615 Biogeochemical processes (4805)
DE: 1704 Atmospheric sciences
DE: 1851 Plant ecology
DE: 4870 Stable isotopes
SC: Biogeosciences [B]
MN: 2003 Fall Meeting