Soil Respiration Characteristics Of Four Forests In Jinyun Mount Of Chongqing City

As one of the most important resouce of CO2in the atmosphere, soil respiration is getting more and more attention from scientific community with the increasingly serious global climate change. So it has important significance for better descibing regional and global carbon cycle to study the change characteristic of soil respiration over time and its response to relative impact factors, and thus estimate flux of soil respiraion. This experiment located in Jinyun Mountain National Nature Reserve, and is to study the soil respiraiton of four kinds of typical forests including broadlesf forest, mixed forest, coniferous forest and bamboo forest with the help of LI-8100soil carbon flux measurement system.(1)The diurnal viriation of soil respiration of four kinds of typical forests was expressed in a style of the shape of a undulating curve or a not very significant single peak curve. The maximum soil respiration rate generally appeared during14:00～18:00, and the minimum generally appeared during5:00～8:00, in general soil respiration rate in days were higer than that in nights. The intermonthly variation of soil respiration was significantly different with respiration rate increased from Mar. to Jul. and decreased after Jul. From Mar. to Jul., overall average soil respiration expressed as:broadleaf forest(2.65μmolm-2s-1)>mixed forest(2.34μmolm-2s-1)>bamboo forest(2.26μmolm-2s-1)>coniferous forest(2.01μmolm-2s-1). And interannual variation of soil respiration was also signicantly different, the soil respiration rate and change process from Jul. to Dec. of2011was significantly different form that in2010.(2) The relationship between soil respiration of four kinds of typical forests and air temperature and soil temperature by layers was fitted by exponential model, and the fitting result showed a highly significant correlation between them. In general, soil respiration had remarkable correlation with the temperature at5cm and15cm depths, and soil temperature could account for56.55%,62.48%,67.5%and75.95%of soil respiration change of broadleaf forest, mixed forest, coniferous forest and bamboo forest respectively, and Q10(temperature susceptibility index) of soil respiration expressed as:bamboo forest(3.67)> mixed forest(1.93)>coniferous forest(1.86)>broadleaf forest(1.67).As for its relationship with soil water, none of four typical forest’s soil respiration rate was obviously correlate with soil mositure. Comparing single factor simulation model, the composite model showed the better simulated result for all kinds of the forests except bamboo forest. Litter fall had significant effect on soil respiration rate, respiration rate without it were all smaller than that with it, and in general Q10value with litter fall were all larger than that without litter fall. Through path analysis of soil respiration rate and11terms soil physical and chemical properties, it can be found that soil organic carbon had the greatest effect on soil respiration rate.(3) During the period from Mar. to Dec, the total flux of CO2was in sequence of broadleaf forest(26.83t/hm2)>mixed forest(24.05t/hm2)>bamboo forest(23.74t/hm2)>coniferous forest(20.17t/hm2). In the same time, the release amount of CO2from litter fall expressed as bamboo forest(5.62t/hm2)>mixed forest(5.09t/hm2)>broadleaf forest(4.90t/hm2)>coniferous forest(2.62t/hm2), while that from autotrophic and heterotrophic respiration expressed as broadleaf forest(5.98t/hm2、6.90t/hm2)>mixed forest(5.06t/hm、6.08t/hm2)>bamboo(4.82t/hm2、6.00t/hm2)>coniferous forest(4.78t/hm2.5.44t/hm2).