Dynamic And Factors Of Microbial Biomass Carbon And Dissolved Organic Carbon In Peatland

The dynamic and factors of active carbon(microbial biomass carbon, MBC and dissolved organic carbon, DOC) were researched by the Chloroform fumigation extraction(FE) method in five different plant communities in Jinchuan peatland which located in Jilin Longwan National Nature Reserve. The five typical plant communities are dominated by Carex schmidtii- Deyeuxia angutifolia(CD), Carex schmidtii(C),Carex schmidtii- Sphagnum(CS),Carex tenuiflora(Ct) and Phragmites australis- Carex spp.( PC),respectively. The seasonal fluctuations, vertical distribution pattern and differences between communities of MBC and DOC(dissolved organic carbon in soil, SDOC and dissolved organic carbon in water, WDOC) were revealed in growth season. The relationships between active carbon(MBC, SDOC, WDOC) and biological factors(aboveground biomass, underground biomass, total biomass, plant diversity) and environmental factors(water level, flooding frequency, surface soil temperature, water p H, total nitrogen and total phosphorus of water, redox potential, soil total organic matter, soil total nitrogen, soil total phosphorus and soil carbon nitrogen ratio) were explored and disccused. Stepwise regression analysis were also conducted for the active carbon and the above factors. The relationship between MBC, SDOC and WDOC were also analyzed and discussed.The main conclusions of this study were as followed:(1) Overall, MBC and DOC of the five herbaceous communities in Jinchuan peatland showed obviously seasonal variation at two soil layers. MBC contents was higher in spring and autumn, lower in summer at the depth of 0~20cm. A gradually increased seasonal dynamic of MBC content was found in the overall level at the depth of 20~40cm. Among wich, CS community and Ct community were gradually rising, while other communities were fluctuantly fluctuant. The content of SDOC both showed gradually decreased seasonal variation at the depth of 0~20cm and 20~40cm. But the surface fluctuation range is larger and the SDOC content appeared to increase in the end of the growing season at this layer. The WDOC contet of all community, except CS community, increased at first and then decreased, and reached the highest in July at the surface layer. However, at the depth of 20~40cm, all communities showed a gradually decreased seasonal variation trend and a rebound phenomenon in 8~10 month occurred in CD community.(2) The vertical distribution pattern of active organic carbon were as followed: For all communities, MBC content were greater in surface layer than that in the deep layer, and the vertical difference is most obvious in May and gradually reduce as the month goes on. Except CD community, the content of SDOC was higher at the depth of 0~20cm than that at 20~40cm in May. While for the other months, the vertical distribution of SDOC was almost oppsite to May. All communities’ WDOC content showed the same vertical distribution: 20~40cm is greater than 0~20cm, and the vertical differences were higher in spring and autumn, lower in summer. The vertical difference of active organic carbon mostly reached a significant level in the early growing season(May, June).(3) The differences of active organic carbon among communities showed : In the whole growing season, the content of MBC rank among the 5 communities is CD>Ct>C>PC>CS in 0~20cm layer, and CS>Ct >PC>C>CD in 20~40cm layer.The difference of MBC content between CD community and CS community was significant in the same soil layer and the position of community ranking of these two communities were quite different between the two soil layers. The community ranking of SDOC content at the depth of 0~20cm is PC>C>CD>CS>Ct, and CD>C>PC>CS>Ct at the depth of 20~40cm. Differences of SDOC content among communities were more significantly in the lower soil layer. The WDOC content kept the similar ordering among the 5vcommunities both in the surface and bottom layers. CD community always kept the significantly highest WDOC content and it also had the biggest seasonal flucuation range. Among all the communities, Ct community always kept the lowest WDOC content.(4) The results of main control factors of active organic carbon in Jinchuan peatland study were as follows: Only few external factors were found to influence the changes of microbial biomass carbon content. Factors entered into the equations can only explain 38.3%(0-20cm) and 21.2%(20-40cm) of the variation of MBC, respectively. The influence mechanism of the change of MBC content might refer to some more complex nonlinear relationship. The water total nitrogen, water p H, underground biomass, water total phosphorus and surface soil temperature is the factors affecting the content of MBC for the 0-20 cm soil in Jinchuan peatland. While for the 20-40 cm soil, the factors were water level and water total phosphorus. Among all the factors, water total phosphorus and surface soil temperature had a negative effect to MBC content and other showed a positive effect. The impact factors of SDOC content in Jinchuan peatland were p H, diversity and water total phosphorus at the depth of 0-20 cm, and soil total nitrogen, water total phosphorus and soil surface temperature at the depth of 20-40 cm. All of these factors had promoting effects on the production and maintaining of SDOC. The higher water level, longer flooding period, the lower WDOC content in the ecosystem. A higher biodiversity might decreased the amount of WDOC, while the higher N, P content and p H could promote the production and conservation of WDOC.(5) Microbial biomass carbon and dissolved organic carbon(SDOC and WDOC) showed positive correlation in the surface layer, while negative correlation in the lower layer, indicating that the consumption of DOC by microorganism is greater than its production in the lower. And the relationship between the three carbon pools were more closely in 20~40cm. What’s more, compared to WDOC, MBC had a more closely relationship with SDOC.