| Abstrakt: |
Assessing the long-term exchange of trace gases and energy between terrestrial ecosystems and the atmosphere is an important priority of the current climate change research. In this regard, it is particularly significant to provide valid data on simultaneous fluxes of carbon, water vapor and pollutants over representative ecosystems. Eddy covariance measurements and model analyses of such combined fluxes over a subalpine coniferous forest in southern Wyoming (USA) are presented. While the exchange of water vapor and ozone are successfully measured by the eddy covariance system, fluxes of carbon dioxide (CO2) are uncertain. This is established by comparing measured fluxes with simulations produced by a detailed biophysical model (FORFLUX). The bias in CO2 flux measurements is partially attributed to below-canopy advection caused by a complex terrain. We emphasizethe difficulty of obtaining continuous long-term flux data in mountainous areas by direct measurements. Instrumental records are combinedwith simulation models as a feasible approach to assess seasonal andannual ecosystem exchange of carbon, water and ozone in alpine environments. The viability of this approach is demonstrated by: (1) showing the ability of the FORFLUX model to predict observed fluxes over a9-day period in the summer of 1996; and (2) applying the model to estimate seasonal dynamics and annual totals of ozone deposition and carbon, and water vapor exchange at our study site. Estimated fluxes above this subalpine ecosystem in 1996 are: 195 g C m-2 year-1 net ecosystem production, 277 g C m-2 year-1 net primary production, 535 mm year-1 total evapo-transpiration, 174 mm year-1 canopy transpiration, 2.9g m-2 year-1 total ozone deposition, and 1.72 g O3 m-2 year-1 plant ozone uptake via leaf stomata. Given the large portion of non-stomatal ozone uptake(i.e. [ABSTRACT FROM AUTHOR] |
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