Effects Of Sphagnum On Soil Carbon Exchange In Subalpine Peatland Of Southwest Hubei Province

Peatland is a special marsh wetland,which absorbs CO₂ in the air for a long time and plays an important role in regional carbon cycle.The study of carbon exchange in peatland plays an important role in revealing the carbon budget of peatland in subtropical.In this study,two peatlands in southwest hubei province were selected as the study area.Carbon exchange of peatlands with and without sphagnum coverage were compared during the growing season?May-October?.Meanwhile,the effects of growth and decomposition of sphagnum and degradation of sphagnum on soil organic carbon were observed.The effects of sphagnum on soil carbon exchange and the contribution of sphagnum to soil carbon were discussed to make up the deficiency of the study on the carbon cycle of peatlands in subtropical regions.The main conclusions of this study are as follows:?1?Under natural conditions,the average growth rate of sphagnum for 12 months was 0.07mm day^-1.Habitat had no significant effect on the height growth and biomass growth of sphagnum,but had significant effect on the growth process.The decomposition rate of sphagnum was slow,and the average residual rate was 92.28%after 12 months.The decomposition rate of sphagnum is different in different time periods.?2?Compared with the control treatment,after the removal of sphagnum,the emission trend of CH₄ in peatland during the growing season?from May to October?showed little change,but the emission intensity was significantly higher than that of peatland without sphagnum coverage.Its daily mean CH₄ emission rate,monthly cumulative emissions and growth season cumulative emissions increased by 311.90%,270%and 322.99%,respectively.?3?During the growing season,under light conditions,average net CO₂ exchange rate of the control peatland was 109.07 mg C m^-2h^-1,which showed carbon absorption.And average net CO₂ exchange rate after peat moss removal was 53.30 mg C m^-2h^-1,wihich showed carbon release.Compared with the control treatment,after the removal of sphagnum,the daily mean respiratory rate,monthly cumulative respiratory volume and cumulative respiratory CO₂ emission during the growing season in peatland decreased by 62.88%,65.83%and 65.92%,respectively.?4?Soil organic carbon content and density in natural peatlands and degraded peatlands decreased with soil depth vertically.After the degradation of sphagnum,soil organic carbon content and organic carbon density in peatlands decreased by 69.16%and 34.96%respectively.?5?Temperature is the main non-biological factor affecting the carbon exchange of peatlands,and the growth dynamics of sphagnum is the main biological factor affecting the carbon exchange of peatlands.The existence of sphagnum directly determines the source-sink relationship of the carbon exchange in peatlands.