Carbon Sequestration And Balance In Pure Plantations Of Cunninghamia Lanceolata And Schima Superba

The increased greenhouse gas concentration such as CO₂ are the main reason caused the global climate change, so reduction of greenhouse gas concentration is a great challenge for next decades and forest ecosystems might play an important role in mitigating the rise of atmospheric CO₂ concentration, because they are the largest carbon pool in the the terrestrial ecosystem. There is 530million hectare plantation in our country now, but there are few studies on carbon sequestration and carbon balance in plantations, especially in the mid-subtropics.The process of forest carbon balance is carbon input and output. The carbon sequestration of plantation is through photosynthesis and carbon inputs from litterfall, root turnover in soil. The carbon output is soil respiration. To provide potential implications of species selection for carbon plantation, differences in carbon sequestration pattern and net ecosystem production (NEP) were determined between two plantations of Schima superba and Cunninghamia lanceolata (Cunninghamia lanceolata) in Jianou, Fujian. Major conclusions were summarized as follows:1) The total carbon stocks of Cunninghamia lanceolata and Schima superba forests were up to173．11 t·hm^-2 and 166．59 t·hm^-2 , of which 35．91% and 64．09% and 40．03% and 59．97% were occupied by biomass carbon stock and soil organic carbon stock, respectively.2) Mean annual total litterfall of observations were 2312．12 kg·hm^-2·yr^-1 in Chinese fir forest and 4496．37 kg·hm^-2·yr^-1 in Schima superba forest; of total litterfall, the leaf constituted 73．6% and 87．8% respectively, twigs constituted 21．1% and 5．0% respectively. Annual carbon returns through litterfall in Chinese fir and Schima superba forests were 1．15 t·hm^-2 and 2．14·hm^-2 respectively.3) The soil respiration showed distinct seasonality, being summer> spring> autumn>winter. The maximum was in July for Cunninghamia lanceolata and in May for Schima superba, and the minimum was in December for Cunninghamia lanceolata and in January for Schima superba. There were better relainoships between soil temperature and soil respiration for the two forests. Soil temperature could explain 93．17% and 81．69% of variation in total soil respiration rates by exponential models in Cunninghamia lanceolata and Schima superba forests, respectively. Annual soil CO₂ effluxes of Chinese fir and Schima superba forests were 12．44 and 15．16 tC·hm^-2·y^-1 ,respectively; annual C effluxes from root respiration were 6．66and 6．82tC·hm^-2·y^-1 , and from the heterotrophic respiration were 5．78 tC·hm^-2·y^-1 and 8．34 tC·hm^-2·y^-1 , respectively.4) Annual net carbon sequestration was 8．29 and 12．04tC hm^-2 y^-1 , respectively, in Cunninghamia lanceolata and Schima superba forests, among which the annual biomass C increment and the litterfall production constituted 30．21% and 69．79% (Cunninghamia lanceolata) and 30．71% and 69．29% (Schima superba forest), respectively. Carbon balance analysis showed there were a positive net ecosystem production (C sink), 2．51 and 3．70t C hm^-2 yr^-1 , for the Cunninghamia lanceolata and Schima superba forest, respectively.