Influence of environmental, root, and stand parameters on soil surface CO2 efflux in a Populus euphratica of desert forest in extreme arid region
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Spatial variation in soil surface CO2 efflux was measured in a stand of Populus euphratica in the Ejina Oasis of desert riparian forest in the extreme arid region in northwestern China from April 2007 through October 2007. Measurements were taken with a gas-exchange analyzer linked to a soil-respiration chamber. The mean soil CO2 efflux in the stand was 2.71?μmol/(m2·s) during the growing season and 1.38?μmol/(m2·s) in the nongrowing season. The seasonal maximum (end of May through early June) and minimum (October) CO2 efflux were 3.38 and 0.69 μmol/(m2·s), respectively. The diurnal fluctuation of CO2 efflux was relatively small (< 20 percent), with the minimum appearing around 05:00 and the maximum around 15:00. Linear regression analysis showed soil-surface CO2 efflux to be most highly correlated with soil temperature (R2=0.435) and soil moisture (R2=0.213). When all variables were considered simultaneously, only soil temperature (R2=0.378), soil moisture (R2=0.147), and root volume density (R2=0.021) explained a significant amount of variance in soil surface CO2 efflux. Stand volumes were not correlated with soil CO2 efflux on our sites.
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