Soil Greenhouse Gases Fluxes And Coupling Relationships For The Natural Forests Dominated By Castanopsis Carlesii

Using manmade automatic gas sampling systems in the field in combination with gas chromatography (GC) analysis system in the laboratory, the fluxes dynamics of five soil greenhouse gases of CO2、CH4、NaO、NO and NO2as affected by meterological and pedological factors, were investigated for the natural Castanopsis carlesii forests in two locations of Jian’ou and Wuyishan nature reserves of Fujian Province respectively, and the relationships between the greenhouse gases fluxes were also further discussed. The aims of the project were to understand the fundermental greenhouse gases fluxes processes and to provide some basic data base for the regional greenhouse gases emissions assessment and modelling. Main results are as follows:(1) The soils of Castanopsis carlesii forests in Jian’ou and Wuyishan were the source of CO2, The daily variation patterns of CO2emission fluxes were not obvious for the two places. During the period of observation, the monthly variation of CO2emission fluxes showed a trend of decline from June to December, with higher levels of CO2emission fluxes in Summer and a lower levels in Autumn. CO2emission fluxes in September were significantly higher than in October for both Jian’ou and Wuyishan(P<0.05). CO2emission fluxes and soil water content, soil temperature and air temperature were significantly related. CO2fluxes were extremely significantly related with MBC, NO2--N and NH4+-N (P<0.01), and significantly related with DOC (P<0.05). CO2emission fluxes estimated from the soils of Castanopsis carlesii forests in Jian’ou and Wuyishan were2466.69g·m’2·a-1and1700.45g·m-2·a-1.(2) The soils of Castanopsis carlesii forests in Jian’ou and Wuyishan are the sink of CH4, the daily variation patterns of CH4emission fluxes appear relatively consistent for the two places. In the observation period monthly CH4fluxes reached the lowest in July, and monthly CH4fluxes in Jian’ou were significantly lower than those in Wuyishan (P<0.05). CH4fluxes in June were significantly higher than in July for both Jian’ou and Wuyishan. There existed significant relationships between CH4emission fluxes and soil temperature and air temperature(P<0.05), except soil water contents. CH4fluxes were extremely significantly related with MBC and NH4+-N (P<0.01), and significantly related with MBN, DOC and DON(P<0.05). CH4emission fluxes estimated from the soils of Castanopsis carlesii forests in Jian’ou and Wuyishan were-411.29mg·m-2·a-1and-239.66mg·m-2·a-1.(3) For the soil of Castanopsis carlesii forests in Jian’ou and Wuyishan there were mostly positive values of N2O fluxes, but negative fluxes would appear during daytime sampling in October and November. As a whole, the soils of Castanopsis carlesii forests in Jian’ou and Wuyishan were the source of N2O. The daily N2O emission fluxes changed largely and had no obvious patterns. The monthly N2O fluxes showed, in general, a trend of decline during the period of observation from June to November. For both positions there were no significant differences in N2O fluxes in each observed months. N2O emission fluxes were significantly related with soil moisture and soil temperature (P<0.01), and with atmospheric temperatures (P<0.05). N2O fluxes were extremely significantly related with N02--N (P<0.01), and significantly related with NH4+-N (P<0.05). N2O emission fluxes estimated from the soils of Castanopsis carlesii forests in Jian’ou and Wuyishan were19.49mg·m-2·a-1and20.40mg·m-2·a-1.(4) The soils of Castanopsis carlesii forest in Jian’ou and Wuyishan were the source of NO in summer, but in the most winter time shifted to the sink of NO. The daily variation of NO emission fluxes showed no obvious patterns. During the period of observation, monthly NO fluxes were roughly declined. NO fluxes in Wuyishan were significantly higher than those in Jian’ou in June(P<0.05). NO emission fluxes and soil temperature, atmospheric temperature are extremely significant correlated in Jian’ou(P<0.01); NO emission fluxes and soil water content, soil temperature are extremely significant correlated in Wuyishan (P<0.01), and with atmospheric temperatures (P<0.05). NO fluxes were significantly related with NO3--N (P<0.05). NO emission fluxes estimated from the soils of Castanopsis carlesii forests in Jian’ou and Wuyishan were9.86mg·m-2·a-1and16.67mg·m-2·a-1.(5) The soils of NO2fluxes changed wildly with positive or negative values, and showed no obvious patterns at either daily or monthly scales. NO2emission fluxes and soil temperature, atmospheric temperature are extremely significant correlated in (P<0.01), but has no obvious correlation between soil moisture content. NO2emission fluxes and soil water content are extremely significant correlated (P<0.01), have no obvious correlation between soil temperature and atmospheric temperature in Wuyishan. NO2emission fluxes estimated from the soils of Castanopsis carlesii forests in Jian’ou is-6.60mg·m-2·a-1.(6) The data of soil greenhouse gases fluxes sampled each month for Castanopsis carlesii forests of Jian’ou and Wuyishan were pooled to research into the correlations between greenhouse gas fluxes and the results showed as follows. CO2and CH4fluxes had extremely significant negative correlation with correlation coefficient of-0.308(P<0.01); CO2and N2O or NO fluxes had extremely significant positive correlation with correlation coefficient of0.563(P<0.01) and0.459(P<0.01) respectively; N2O fluxes were extremely significant positive correlation with NO fluxes with correlation coefficient of0.734(P<0.01); NO and NO2fluxes were extremely significant positive correlation and the correlation coefficient is0.303(P<0.01).