江西省森林碳蓄积过程及碳源/汇的时空格局

森林碳蓄积是研究森林与大气碳交换以及估算森林吸收或排放含碳气体的关键参数,不同年龄森林的碳源/汇功能差异则体现出森林生态系统碳蓄积过程的时间特征。以森林资源清查的样方数据作为数据源,通过刻画主要树种的林分蓄积生长曲线、林龄与净初级生产力(NPP)之间的关系,驱动区域碳收支模型(InTEC)模拟江西省1950—2008年的森林碳蓄积过程,了解山江湖工程实施以来的森林碳源/汇状况。结果表明,20世纪80年代以前,江西省森林年平均NPP波动于450—813 gCm-2a-1之间,年净增生物量碳26.55—36.23 TgC/a,年净增木质林产品碳0.01—0.3 TgC/a;80年代初,NPP和年净增生物量碳分别降至307.39 gC m-2a-1和17.31 TgC/a,而年净增木质林产品碳却高达0.6 TgC/a,说明森林被大量砍伐进入林产品碳库;1985年山江湖工程实施后,大面积造林使得年净增碳蓄积呈现急剧上升趋势,生物量和木质林产品碳蓄积分别上升至目前的42.37 TgC/a和0.79 TgC/a,而平均NPP值增加缓慢、碳汇功能降低,说明林分质量有待提高;90年代后碳汇功能开始稳步增强,说明造林面积的迅速增加是引起江西省森林碳增汇的主要驱动因素,但未来森林增汇潜力应源于森林生长和有效的经营管理。

Forest carbon sequestration and carbon sink/source in Jiangxi Province

Forest carbon sequestration is one of the key parameters in research of carbon exchange between forest and atmosphere,also in estimation of the carbonaceous gas that absorbed or released by forest.The variation of forest carbon source and sink patterns presented the temporal charactors of forest carbon sequestration.The study applied regional carbon budget model(InTEC),and scale transformation from plot to region,based on forest inventory data,to depict the growth curve of main tree species and the relationships among forest age and net primary production(NPP),and to simulate and analyze the carbon sequestration of forest biomass,soil organic carbon and wood products from 1950 to 2008 in Jiangxi Province,considering forest age and disturbances.Furthermore,the spatial and temporal patterns of forest carbon sink and sources during the period of 1980—2008 were estimated,since the implementation of Mountain-River-Lake Program were revealed to assess the ecological effectiveness of the program,and to promote forest ecosystem restoration and conservation in Jiangxi Province.The results showed that forest annual average NPP,annual net increased carbon sequestration of biomass and wood products were estimated to ranges of 450 — 813 gC m-2 a-1,26.55— 36.23 TgC/a and 0.01—0.3 TgC/a before 1980s respectively.And the annual average NPP and annual net increased biomass carbon sequestration declined rapidly to lowest value of 307.39 gC m-2 a-1 and 17.31 TgC/a respectively,however,the annual net increased carbon sequestration of wood products reached to highest value of 0.6 TgC/a.Since the beginning of the Mountain-River-Lake Program in 1985,annual net increased carbon sequestration of biomass and wood products both increased rapidly to 42.37 TgC/a and 0.79 TgC/a due to massive forest planting project,however,the increasing rate of annual average NPP showed slower compared than that before.Furthermore,the forest ecosystem in Jiangxi province was a relatively strong carbon sink at the beginning of 1980,and then it decreased because of the lower volume of plantations and most residual secondary natural forests.Since 1990s,the carbon sinks increased steadily responding to the rapidly increasing forest area.Of course,there remained some uncertainties in our estimations of carbon sources and sinks in Jiangxi′s forests.The improved inventory-based estimates of forest carbon stocks presented in this paper would help to constrain uncertainties from ecological modeling.In addition,most estimates of forest carbon stocks have neglected or seldom considered the effects of economic forest,bamboo and understory etc.,which led to underestimate.However,the limited forest land reminded that forest growth and efficient management would be effective to potential carbon gains in the future.Therefore,we should focus on the effects of forest management,to solve the demand of increased terrestrial carbon sinks.Furthermore,forest carbon management raises some interesting questions for us.For example,is carbon management compatible with utilization of forest resources? How does carbon management enhance or detract from other ecosystem services such as water conservation and biodiversity? Besides deepening our understanding of increasing carbon sinks by forestation,the limitations and negatives of forestation projects should be realized,and new technologies for forestation and enhancement of carbon stocks should be exploited.