Study On The Carbon Dynamic Of Metasequoia Glyptostroboides Plantation Ecosystems In Chongming Island, Shanghai

Carbon sequestration of forest ecosystem per year represents about two-thirds of terrestrial ecosystems, and occupies more than 86% of global vegetation carbon pools. Forest ecosystem has an irreplaceable role in regulating global carbon balance, reducing green house gases concentrations and maintaining global climate change. Water fir (Metasequoia glyptostroboides) is a unique relict plant in China. Duo to fast-growing and adaptable features and beautiful tree shape, water fir is widely distributed in China's tropical and temperate areas. Moreover, water fir is one of the major afforestation and greening species in south of the Yangtz River. Thus, in the climate change situation, the study of carbon dynamics of water fir plantation has an important theoretical significance.This study was taken in Dongping Forest Farm (Dongping National Forest Park), which is located in Chongming Island, Shanghai, Eastern China. The three stands (8, 16 and 30 year-old stands in 2009) were selected to represent different age classes: young, middle-aged, and mature stands. A sample plot (20 m ? 20 m) was set up in each stand in which tree height (H) and the diameters at breast height (DBH) were measured in April, 2009 and May, 2011, respectively. Allometric equations were used to estimate carbon stocks and annual carbon increment. A static chamber/gas chromatography method was used to collect and analysis greenhouse gases samples. Integrating with climatic data and environmental factors in Chongming Island, we studied on carbon dynamics of M. glyptostroboides plantation ecosystem.The major findings were in the following areas:1) The aboveground carbon storage of young, mid-aged and mature stands were 13.11, 29.76 and 64.93 t ha^-1, respectively. As the stand age growing, carbon storage increased with the stand age. After comparative analysis, site conditions is the major reason of different biomass and carbon storage of M. glyptostroboides plantations in different regions. And precipitation difference is the main factor.2) The annual carbon increment of young, mid-aged and mature stands were 4.31, 2.83 and 2.54 t C hm^-2 yr^-1, respectively, and annual carbon increment decreased.3) According to day and night observation, M. glyptostroboides plantations soil is CO₂ and N₂O source, and CH4 sink. CO₂ emission flux strengthened along with increasing temperature. N₂O and CH4 emission presented low fluxes in daytime and high fluxes in night.4) According to home position observation during June to December in 2011, three kind of greenhouse gases flux difference in different aged M. glyptostroboides plantations soil was small. CO₂, N₂O and CH4 fluxes in young stand were 363.09 mg·m^-2?h^-1, 13.65μg·m^-2?h^-1 and - 0.05 mg·m^-2?h^-1, respectively. And in mid-aged stand, three greenhouse gases emission were 369.26 mg·m^-2?h^-1, 13.83μg·m^-2?h^-1 and - 0.06 mg·m^-2?h^-1. Greenhouse gases fluxes in mature stand soil were a little higher than young and mid-aged stands, CO₂ 387.88 mg·m^-2?h^-1, N₂O 19.37μg·m^-2?h^-1, and CH4 -0.08 mg·m^-2?h^-1.5) The temperature and the soil organic carbon content are important factors effecting CO₂ emission flux. And CH4 flux was easily affected by temperature. As stands growing, soil organic carbon content gradually played an important role in CH4 flux. But soil moisture influenced little in CO₂ and N₂O fluxes. N₂O content is the least in three kind of greenhouse gases, and is fluctuated obviously by the temperature, the soil moisture and the soil organic carbon content. There was a remarkable correlational relationship between CO₂ and N₂O fluxes.The main characteristic of this study was using three age state M. glyptostroboides plantations as study object, from two sides, aboveground annual carbon increment and soil greenhouse gases emission, to analysis carbon dynamic in M. glyptostroboides plantation ecosystems.