3.5
1999–2001 micrometeorological trends at the Forest-Atmosphere Carbon Transfer and Storage (FACTS-II) study site
Warren E. Heilman, USDA Forest Service, East Lansing, MI; and M. R. Holdaway, R. M. Teclaw, and J. E. Eenigenburg
The Forest-Atmosphere Carbon Transfer and Storage (FACTS-II) experiment at the Free Air Carbon Dioxide Enrichment (FACE) facility in northern Wisconsin is currently assessing the potential long-term biological and physical impacts of elevated surface carbon dioxide (CO2) and ozone (O3) concentrations on aspen, maple, and birch ecosystems. Included in this assessment is an examination of the resultant productivity, sustainability, competitive interactions, and carbon and nitrogen fluxes in ecosystems of this type that have been exposed to elevated CO2 and O3 concentrations. A critical component of the FACTS-II experiment is the examination of the indirect microclimate trends resulting from the altered vegetation characteristics induced by elevated near-surface CO2 and O3 concentrations. Forest vegetation changes in response to increasing CO2 and O3 concentrations under a changing climate have the potential for altering atmospheric environments and the dynamics of forest-atmosphere interactions in forest ecosystems.
Since January 1999, a micrometeorological monitoring network at the FACTS-II study site has been measuring near-surface atmospheric conditions and trends within and above four of the twelve 30 m diameter FACE treatment plots which were planted with aspen (Populus tremuloides), paper birch (Betula papyrifera), and sugar maple (Acer saccharum) seedlings in 1997. The twelve treatment plots represent three replicates of four plots each. Each replicate contains a control plot where CO2 and O3 concentrations are not altered, a plot with elevated CO2 concentrations, a plot with elevated O3 concentrations, and a fourth plot with elevated CO2 and O3 concentrations. Meteorological instrumentation has been installed in all four plots of one replicate as a means of sampling conditions under the different types of FACE-technology fumigation strategies. In addition, a 20 m tower at the FACTS-II study site has been instrumented to measure near-surface ambient conditions outside the treatment plots.
This paper reports on the micrometeorological trends in the instrumented plots and at the ambient tower site at the FACTS-II study site for years 1999-2001. Diurnal and monthly variations in temperature, vertical temperature gradient, relative humidity, wind speed, wind shear, net radiation, photosynthetically-active-radiation, and soil temperature are described in relation to developing vegetation characteristics in a control plot and CO2-, O3-, and CO2+O3-fumigated plots. The results to date suggest that potential increases in episodic surface O3 concentrations in conjunction with projected increases in atmospheric CO2 concentrations will not only have an impact on aspen, maple, and birch vegetation, but the increases will also impact the microclimatic conditions in birch, maple, and aspen ecosystems. These altered microclimatic conditions can, in turn, further influence tree growth and productivity.
Session 3, canopy micrometeorology
Monday, 20 May 2002, 3:30 PM-5:00 PM
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