| Autor: |
Gilmanov, Tagir G., Svejcar, Tony J., Johnson, Douglas A., Angell, Raymond F., Saliendra, Nicanor Z., Wylie, Bruce K. |
| Zdroj: |
Rangeland Ecology and Management; November 2006, Vol. 59 Issue: 6 p585-599, 15p |
| Abstrakt: |
We present a synthesis of long-term measurements of CO2exchange in 2 US Intermountain West sagebrush-steppe ecosystems. The locations near Burns, Oregon (1995–2001), and Dubois, Idaho (1996–2001), are part of the AgriFlux Network of the Agricultural Research Service, United States Department of Agriculture. Measurements of net ecosystem CO2exchange (Fc) during the growing season were continuously recorded at flux towers using the Bowen ratio-energy balance technique. Data were partitioned into gross primary productivity (Pg) and ecosystem respiration (Re) using the light-response function method. Wintertime fluxes were measured during 1999/2000 and 2000/2001 and used to model fluxes in other winters. Comparison of daytime respiration derived from light-response analysis with nighttime tower measurements showed close correlation, with daytime respiration being on the average higher than nighttime respiration. Maxima of Pgand Reat Burns were both 20g CO2·m−2·d−1in 1998. Maxima of Pgand Reat Dubois were 37 and 35g CO2·m−2·d−1, respectively, in 1997. Mean annual gross primary production at Burns was 1 111 (range 475–1 715)g CO2·m−2·y−1or about 30% lower than that at Dubois (1 602, range 963–2 162g CO2·m−2·y−1). Across the years, both ecosystems were net sinks for atmospheric CO2with a mean net ecosystem CO2exchange of 82g CO2·m−2·y−1at Burns and 253g CO2·m−2·y−1at Dubois, but on a yearly basis either site could be a C sink or source, mostly depending on precipitation timing and amount. Total annual precipitation is not a good predictor of carbon sequestration across sites. Our results suggest that Fcshould be partitioned into Pgand Recomponents to allow prediction of seasonal and yearly dynamics of CO2fluxes. |
| Databáze: |
Supplemental Index |
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