中国森林植被碳库的动态变化及其意义

利用1949年至1998年间7次森林资源清查资料，结合使用森林生物量实测资料，采用改良的生物量换算因子法，推算了中国50年来森林碳库和平均碳密度的变化，分析了中国森林植被的CO2源汇功能，结果表明，70年代中期以前，主要由于森林砍伐等人为作用，中国森林碳库和碳密度都是减少的，碳储量减少了0．62PgC（Pg＝10^15g)，年均减少约0．024PgC。之后，呈增加趋势。在最近的20多年中，森林碳库由70年代末期的4．38PgC增加到1998年的4．75PgC，共增加0．37PgC，年平均增加0．022PgC。这种增加主要由人工造林增加所致。20多年来，由于人工林增加导致碳汇增加0．45PgC，年平均增加吸收0．021PgC／a。人工林的平均碳密度也显增加，共增加了约一倍。这除了人工成林增多外，气温上升和CO2浓度施肥也可能是促进森林生长的重要因子。

Dynamic Forest Biomass Carbon Pools in China and Their Significance

An improved biomass estimation method that converts timber volume to total forest biomass was used to estimate forest biomass carbon storage and its changes over to the past 50 years in China, by using inventory data of seven periods from 1949 to 1998 and forest biomass data obtained from direct field measurements. By the mid-1970s, forest carbon decreased by 0.62 Pg C (Pg=10 15 g), with a decreasing rate of 0.024 Pg C per year. Since then the biomass carbon showed a significant increase, from 4.38 Pg C by the end of 1970s to 4.75 Pg C by 1998, with an increasing rate of 0.022 Pg C per year, due mainly to the increased reforestation and afforestation. During the last two decades, planted forests have sequestered 0.45 Pg of carbon, with an annual rate of 0.021 Pg C. The average carbon density of plantations showed a significant increase from 15.3 Mg/hm 2 in the mid-1970 to 31.1 Mg/hm 2 in 1998, suggesting that the rising global temperature and CO 2 fertilization may enhance this increasing uptake as well as expansion of planted forests.