| Through the study of soil respiration and carbon balance of the Chinese fir (Cunninghamialannceolata) plantation in Dagangshan, Jiangxi province, this dissertation has accuratelyevaluated the Carbon Sink of Chinese fir plantation and discussed the rules of the carbonbalance of Central Subtropical Chinese fir plantation ecosystem, and is expected to providetheoretical bases for the forest exercise in order to exert the carbon sequestration ability ofplantation to the utmost extent.This research is based on a major type of plantation, Chinese fir plantation in Jiangxi Province.In the experiments, the soil CO2 emission rate was measured in two consecutive growingseasons, Apr～Oct 2005 and Apr～Oct 2006, using LI-6400 portable photosynthesismeasurement system and its fitting, 6400-09, and the rules of soil respiration were studied. Thebiomass of the Chinese fir plantation ecosystem and NPP were calculated, based on standingbiomass inventory. And combined with the carbon content of each component, the annualcarbon fixation of ecosystem was calculated. The results of this research show that:1. Both diurnal and seasonal dynamic variations of soil respiration rate are single peak curveshaped. In the diurnal time scale, soil respiration rate forms good regression relationshipsagainst surface air temperature and 0～10 cm soil temperature. The regression formula isRs=3.313e0.012Ta (R2=0.640) and Rs=0.925e0.066Ts(R2=0.829), respectively. In the seasonal timescale, the regression relationships between soil respiration rate and surface air temperature/0～10 cm soil temperature are further enhanced. However, it is inappropriate to explain thevariance of soil respiration rate using the variation of soil water containing rate alone indifferent time scales. The determination coefficient reaches 0.880 when using 0～10 cm soiltemperature and 0～10 cm deep soil water containing rate to make the multiple linear regressionon soil respiration rate. Therefore, the double-factor model better explains the variance of soilrespiration rate than the single-factor model.2. The biomass of the Chinese fir plantation ecosystem of different growing stages is39.923～175.974 t·hm-2, where the biomass of arbor layer takes up 92.57～94.94％. Thisindicates that arbor layer is the major component of the biomass of Chinese fir plantation. Thebiomass of understory layer takes up about 2％of the community biomass. It is less than thelitter layer, which takes up 3.02～4.78％of the community biomass.3. The annual biomass increase of Chinese fir plantation ecosystem is 4.832～17.832 t·hm-2·a-1, where arbor layer takes up 45.03～68.50％. The annual biomass return of the litter is just nextto the NPP of arbor layer. Hence it is an important component of the community NPP. Theunderstory layer has little contribution to the increase of the community biomass. It takes uponly 6.53％of NPP even in its young plantation (YP) stage, in which it contributes the most tothe community NPP.4. The average carbon content of arbor layer, understory layer, and litter layer is 49.37～51.89％, 40.89～45.44％, and 47.39～50.27％, respectively. For each individual layer, there are significantvariances between the average carbon content of different growing stages, the average carboncontent ranking as: Middle-Aged Plantation (MAP)＞Premature Plantation (PP)＞MaturePlantation (MP)＞Past-Aged Plantation (PAP)＞Young Plantation (YP). In each growing stage, there are also variances between the average carbon content of different organs, the averagecarbon content ranking as: leaf＞stem＞root＞branch. As these plants grow, the variances ofthe average carbon content between different organs decrease gradually.5. The annual carbon fixation of the Chinese fir plantation ecosystem is 2.329～9.088 t·hm-2·a-1, where the annual carbon fixation of arbor layer, understory layer, and litter takes up46.22～69.91％, 3.42～5.54％, and 24.55～49.46％, respectively. For each individual layer, theannual carbon fixation of different growing stages ranks as: PP＞PAP＞MP＞MAP＞YP, which is the same as the NPP ranking. The variation of annual carbon fixation betweendifferent growing stages is mainly caused by arbor layer and litter layer.6. According to the exponent model, Rh=a·ebTs, combined with the 0～10 cm soil temperaturedata, it is calculated that the root-free soil respiration rate of Middle-Aged Plantation (MAP) ofthe Chinese fir plantation ecosystem is 0.889μmol·m-2·s-1, the annual carbon emission ofroot-free soil respiration is 3.395 t·hm-2·a-1, and the net annual carbon fixation of MAP of theChinese fir plantation ecosystem in Dagangshan, Jiangxi, is 2.672 t·hm-2·a-1, which indicatesremarkable Carbon Sink capability.
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