CO2 emission response to different water conditions under simulated karst environment
2015
Yuqing, Huang | Yanyu, Li | Guangping, Xu | Chengxin, He | Ling, Mo | Zhongfeng, Zhang | Jianhua, Cao | Daxing, Gu | Chunlai, Zhang | Yigang, Wei | Fang, Wen
Habitat degradation has been proven to result associated with drought in karst region in south China. However, how this drought condition relates to CO₂ efflux is not clear. In this study, we designed a simulated epikarst water–rock (limestone)–soil–plant columns, under varying water levels (treatment), and monitored CO₂ concentration and efflux in soil in different seasons during 2011. The results showed that increased soil water greatly enhanced CO₂ concentrations. With which treatment with epikarst water (WEW) had higher CO₂ concentration than without epikarst water (WOEW). This was particularly high in low soil water treatment and during high temperature in the summer season. Under 30–40 % relative soil water content (RSWC), CO₂ concentration in WEW treatment was 1.44 times of WOEW; however, under 90–100 % RSWC, this value was smaller. Comparatively, soil surface CO₂ efflux (soil respiration) was 1.29–1.94 μmol m⁻² s⁻¹ in WEW and 1.35–2.04 μmol m⁻² s⁻¹ in WOEW treatment, respectively. CO₂ efflux increased with increasing RSWC, but it was not as sensitive to epikarst water supply as CO₂ concentration. WEW tended to weakly influence CO₂ efflux under very dry or very wet soil condition and under low temperature. High CO₂ efflux in WEW occurred under 50–80 % RSWC during summer. Both CO₂ concentrations and CO₂ efflux were very sensitive to temperature increase. As a result, at degraded karst environment, increased temperature may enhance CO₂ concentration and CO₂ emission; meanwhile, the loss of epikarst and soil water deficiency may decrease soil CO₂ concentration and CO₂ emission, which in turn may decrease karst corrosion.
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