| The growing season in the karst hilly area of southwest China is long, and the flux of CO2 and CH4 on
the soil surface is greatly affected by the vegetation cover on the surface. To investigate the CO2 and CH4 fluxes and
their diurnal variations of soil surface covered with vegetation (with grass) and non-vegetation cover (without grass) in
the growing season of karst hilly area, the CO2 and CH4 fluxes on the soil surface in the Nanchuan karst hilly area in
Chongqing were studied by static box-gas chromatography, combined with soil temperature and humidity research.
The results showed that the surface of soil in karst hilly area showed CO2 source and CH4 sink during the growing season. The soil CO2 fluxes were significantly higher than that of grass-free CO2 fluxes, while there was no significant
difference between grass and grass-free CH4 fluxes on the soil surface. It indicates that vegetation cover on the surface
of the growing season is an important factor affecting soil CO2 flux, while vegetation cover has no significant effect
on soil CH4 flux. Soil CO2 flux and grass-free CO2 flux were 552 mg/m2·h, 352 mg/m2·h; Soil grass CH4 flux and
grass-free CH4 flux were - 80μg/m2·h,- 75 μg/m2·h（6-month average of growing season）. On the scale of the
growing season, the soil also appears as CO2 source and CH4 sink. The CO2 flux of grasses was significantly higher
than that of grass-free CO2 fluxes, and the change characteristics of the two were consistent; however, the CH4 flux
on the soil surface is less affected by vegetation cover. There is a positive correlation between soil CO2 flux and soil
temperature. That is, soil temperature increase will promote soil CO2 flux, while soil CH4 flux has no correlation with
soil temperature, so soil temperature has no significant effect on soil CH4 flux. Since the soil moisture change during
the growing season is smaller than the soil temperature, the effect of soil moisture on soil CO2 flux and soil CH4 flux is
smaller than soil temperature. |
