Hydrology of a scrub-oak woodland under carbon dioxide enrichment
National Science Foundation, (1 April 1999 - 31 March 2002)
Collaborators: Jiahong Li, William Dugas, Bert Drake
Project Summary. This research integrates field experiments and models focusing
on the responses of a Florida scrub-oak ecosystem to elevated atmospheric carbon
dioxide (CO2). This research adds to an ongoing study invetigating the effects
of elevated CO2 on a naturally-occuring stand of scrub-oak vegetation. The main
goal of the ongoing project is to determine the effects of elevated CO2 on ecosystem
carbon balance. This proposal expands this research by adding an additional
goal: to determine the effects of elevated CO2 on the water cycle, including
plant transpiration, evapotranspiration, soil moisture, and water table dynamics,
as well as how differential responses of the co-dominant oaks to elevated CO2
mediate these changes.
In particular, this research will show how the responses of the two co-dominant
oak species in scrub oak mediate reductions in ecosystem water loss through
evapotranspiration, and how these water savings are partitioned between surface
soil water stores and the water table. Transpiration in oak individuals in elevated
and ambient CO2 treatments will be measured in the field, along with the stable
isotope composition of stem water in these species, which indicates the depth
in the soil from which the water is obtained. Together, these measurements will
determine by how much elevated CO2 reduces transpiration, and how that water
savings is partitioned in the soil. This information will be combined with measurements
of soil moisture, water table depth, and evapotranspiration, and synthesized
through modeling.
This research is important because it focuses on ecosystem responses to elevated
CO2 that have not been previously addressed, but that will likely represent
critical changes in a future, high-CO2 world. This will be one of the first
studies in any ecosystem to develop a detailed hydrologic budget and hydrologic
model that partitions water savings in elevated CO2 between surficial and deep
water stores in the soil, where savings will have very different biogeochemical
consequences. Additionally, this research will determine how individualistic
species responses to elevated CO2 mediate changes in system hydrology, and thus
will be relevant in predicting changes in hydrology in other systems where species
show differential responses. By exploring the interactive effects of elevated
CO2 through altered hydrology, this research will substantially advance our
knowledge of the responses of terrestrial ecosystems to rising CO2.