Abstract:
Drought can affect forest structure and function at various spatial and temporal
scales. Forest response and recovery from drought may be a result of position within landscape.
Longleaf pine forests in the United States have been observed to reduce their carbon sequestration
capacity during drought. We collected eddy covariance data at the ends of an edaphic longleaf pine
gradient (xeric and mesic sites) over seven years; two years of normal rainfall were followed by
2.5 years of drought, then 2.5 years of normal or slightly above-average rainfall. Drought played
a significant role in reducing the physiological capacity of the sites and was compounded when
prescribed fire occurred during the same periods. The mesic site has a 40% greater basal area then the
xeric site, which accounts for its larger sequestration capacity; however, both sites show the same
range of variance in fluxes over the course of the study. Following drought, both sites became carbon
sinks. However, the xeric site had a longer carry-over effect and never returned to pre-drought
function. Although this study encompassed seven years, we argue that longer studies with greater
spatial variance must be undertaken to develop a more comprehensive understanding of forest
response to changing climate.
