Research On Carbon Dynamic Of Larch Plantation In North Region Of Yanshan Mountain Based On CO2FIX Model

China has the world’s largest plantation which played an important role in absorbing CO2. The carbon sink function of plantation is a dynamic process, and which are effected by intermediate cutting and rotation. A comprehensive understanding of the carbon sink function in plantation and its dynamic change process has important scientific and realistic significance. In this paper, biomass carbon, soil carbon, woody forest products carbon and carbon dynamic of the larch plantation in north region of Yanshan mountain were studied. CO2FIX V.2 model was used to simulate carbon dynamic process of larch plantation in different rotations. At the same time, we also studied the effects of rotation, temperature and rainfall on carbon dynamic of the plantation. The main results are as follow:（1） Under the current rotation system in Chengde region, total carbon storage of larch plantation presents periodic changes, ranged from 150 to 200 t?hm^-2 in a 50 years rotation. In each cycle, the total carbon storage showed a“reduce-increase-reduce”trend. The contribution rates of soil carbon storage, biomass carbon storage and woody forest products carbon storage to the total were 77%, 17% and 6% respectively. But in different periods of the stands, the rates showed some differences.（2） Biomass carbon storage of the larch plantation presents periodic changes along time, ranged from 0 to 55 t?hm^-2. In each cycle, biomass carbon storage show a fluctuant trend. Soil carbon storage varied almost the same in one cycle, i.e. first reduce, then increase fluctuantly and last return to the initial level, the value ranged from 130 to 160 t?hm^-2. Carbon storage of woody forest products is gradually increasing with the extension of time. According to the carbon storage value of different woody forest products carbon pools, the order is: long-term landfill > long-term products > dump > mid-term products > energy （firewood） > short-term products.（3） In the early stage of the stand, larch plantation was carbon source, then became carbon sink between 5 to 45 years. But in its later stage （about 46-50 a）, the stand became carbon source again. From the annual net carbon balance point of view, larch plantation was obviously carbon source, annual net carbon balance was about 1.0 t?hm^-2.（4） In this region, in a 50 years rotation from secondary poplar-birch forest to larch plantation, 250t?hm^-2 carbon were sequestrated by the larch plantation. 70% of the carbon transfered into soil through the way of litter and logging slash, the other 30% transfered into woody forest products. After the rotation, about 71%（ according to the forest carbon sequestration） of the carbon released to the atmosphere through soil respiration, so that made the soil become a carbon source. And 11% of the carbon stored in the woody forest products, 19% released to the atmosphere through decomposition and energy burning. Then, the values are respectively as follow: biomass carbon storage 0t, woody forest products carbon storage 27t, soil carbon storage reduced about 2t than beginning.（5） With different rotation （ 30 years, 40 years, 50 years, 60 years and 70 years ）, the total carbon storage of larch plantation showed no obvious differences, is always about 180 t?hm^-2, but the distribution in the three carbon pools has significant difference. Extension of rotation contribute to the increase of biomass carbon storage, whereas short rotation is helpful to the carbon accumulation in woody forest products. Appropriate rotation length of soil carbon storage is about 50 years, but 40 years is the most suitable length to carbon stock in the whole stands. If we considered carbon emission from afforestation, cutting and the use of big-diameter timber products, long rotation is more favorable.（6） When temperature increased, soil carbon storage of the larch plantation would decrease while soil respiration enhanced. When rainfall increased, soil carbon storage decreased and soil respiration enhanced. The increase of temperature and rainfall caused by climate change induced soil respiration enhancement and soil carbon storage decrease. We should pay more attention to these problems.