Soil-atmosphere exchange of carbon dioxide, methane and nitrous oxide in temperate forests along an elevation gradient in the Qinling Mountains, China.

Purpose: We sought to identify the effects of elevationally (1560−2160 m) driven climate (mean annual air temperatures of + 4.0 to + 10 oC and mean annual precipitation of 900–1200 mm), forest type and soil property variations on soil greenhouse gas (GHG) fluxes in the Qinling Mountains, China. Methods: Soil GHGs were monitored at five temperate forest sites using static chambers for two full years. The related edaphoclimatic parameters were also monitored. Results: The cumulative soil CO2 and N2O emissions and the CH4 uptake from the five sites ranged between 3.82 to 7.48 t CO2-C ha−1 yr−1, 1.19 to 2.25 kg N2O-N ha−1 yr−1, and 0.89 to 5.67 kg CH4-C ha−1 year−1, respectively. Average soil CO2 emissions decreased with increasing site elevation, whereas CH4 and N2O fluxes showed no clear relationship with site elevation. All sites were net CH4 sinks. Occasionally, soils switched to net sources of CH4 during summer or autumn rainfall events at all sites. All sites were net N2O sources although short periods of soil N2O uptake were observed during freeze–thaw cycles and during summer rainfall. The source strength of N2O and CH4 differed during summer and winter and snowfall which had direct effects on soil water content. Conclusions: Site elevation could be used as a predictive variable for constructing regional soil CO2 emissions budgets, whereas soil CH4 and N2O fluxes are driven by a more complex interplay of climatic and soil biochemical variables, which are more difficult to integrate on a regional scale. [ABSTRACT FROM AUTHOR]