Soil‐atmospheric exchange of CO₂, CH₄, and N₂O in three subtropical forest ecosystems in southern China

Abstract

The magnitude, temporal, and spatial patterns of soil-atmospheric greenhouse gas (hereafter referred to as GHG) exchanges in forests near the Tropic of Cancer are still highly uncertain. To contribute towards an improvement of actual estimates, soil-atmospheric CO 2 , CH 4 , and N 2 O fluxes were measured in three successional subtropical forests at the Dinghushan Nature Reserve (hereafter referred to as DNR) in southern China. Soils in DNR forests behaved as N 2 O sources and CH 4 sinks. Annual mean CO 2 , N 2 O, and CH 4 fluxes (mean AE SD) were 7.7 AE 4.6 Mg CO 2 -C ha À1 yr À1 , 3.2 AE 1.2 kg N 2 O-N ha À1 yr À1 , and 3.4 AE 0.9 kg CH 4 -C ha À1 yr À1 , respectively. The climate was warm and wet from April through September 2003 (the hot-humid season) and became cool and dry from October 2003 through March 2004 (the cool-dry season). The seasonality of soil CO 2 emission coincided with the seasonal climate pattern, with high CO 2 emission rates in the hot-humid season and low rates in the cool-dry season. In contrast, seasonal patterns of CH 4 and N 2 O fluxes were not clear, although higher CH 4 uptake rates were often observed in the cool-dry season and higher N 2 O emission rates were often observed in the hot-humid season. GHG fluxes measured at these three sites showed a clear increasing trend with the progressive succession. If this trend is representative at the regional scale, CO 2 and N 2 O emissions and CH 4 uptake in southern China may increase in the future in light of the projected change in forest age structure. Removal of surface litter reduced soil CO 2 effluxes by 17-44% in the three forests but had no significant effect on CH 4 absorption and N 2 O emission rates. This suggests that microbial CH 4 uptake and N 2 O production was mainly related to the mineral soil rather than in the surface litter layer.

Effects of land use conversion and fertilization on CH4 and N2O fluxes from typical hilly red soil

“…However, this was in contrast with the finding from a similar study by Tang et al (2006), who only reported a reasonable correlation between soil moisture and N 2 O emissions. In our study, statistical positive relationship between N 2 O emissions and soil moisture were detected in orchard plots, which were in line with the former studies (Tang et al 2006;Liu et al 2008). Nevertheless, the stimulation of soil moisture on N 2 O fluxes may be significant at dry soils and wet soils (Lin et al 2012).…”

“…Generally, temperature regulated the N 2 O emissions through its influence on nitrifying and denitrifying activity (Burger et al 2005). However, this was in contrast with the finding from a similar study by Tang et al (2006), who only reported a reasonable correlation between soil moisture and N 2 O emissions. In our study, statistical positive relationship between N 2 O emissions and soil moisture were detected in orchard plots, which were in line with the former studies (Tang et al 2006;Liu et al 2008).…”

Seasonal dynamics in nitrous oxide emissions under different types of vegetation in saline-alkaline soils of the Yellow River Delta, China and implications for eco-restoring coastal wetland

“…Correlation analysis in the current study showed that there did not exist a significant relationship between air or soil temperatures and N 2 O emissions in P. australis community, but the significant relationship between N 2 O emissions and temperature was found in other three positions. Tang et al (2006) suggested that soil temperature did not have a strong effect on N 2 O emissions, which was consistent with results reported in tropical, agricultural soils (Crill et al, 2000;Kiese and Butterbach-Bahl, 2002). On the other hand, some studies showed that N 2 O fluxes were strongly correlated with soil temperature.…”

Seasonal dynamics of soil CO2 efflux in a conventional tilled wheat field of the Loess Plateau, China

“…5), and more than 60.4% and 68.2% of the seasonal variability covering all four periods in 2006 and 2007, respectively. Such a strong temperature dependence of SCE has also been reported in other studies of subtropical forest ecosystems (Tang et al 2006;Saiz et al 2006;Sheng et al 2010), temperate semiarid grassland (Jin et al 2009b) and agro ecosystems (Han et al 2007;Meijide et al 2010). In these ecosystems, the SCE exhibited a distinct seasonal variation that paralleled the seasonality observed in soil temperature (Saiz et al 2006); the peak values could be explained by temperature.…”