基于RS/GIS的重庆缙云山自然保护区植被及碳储量密度空间分布研究

对森林植被类型和碳储量密度空间分布的研究,可以为森林生态系统服务功能和价值的提高、充分发挥"增汇减排"的碳库经营和管理工作提供重要的基础数据。利用缙云山高分辨率影像(WorldView-2)解译植被专题图和1∶10 000地形图生成数字高程模型,结合野外样方调查、文献中植被生物量回归(经验)模型和碳含量数据资料,在ArcGIS支持下对缙云山自然保护区植被和碳储量密度空间分布进行研究。研究显示,缙云山植被以针叶林为主(30%),人为干扰程度较高的灌木林也占有相当大的比例(21%),地带性顶级植被——常绿阔叶林面积较小(6%);碳储量密度为针阔混交林(74.23 Mg/hm2)>针叶林(62.97 Mg/hm2)>常绿阔叶林(62.65 Mg/hm2)>针竹混交林(59.84 Mg/hm2)>慈竹林(48.72 Mg/hm2)>毛竹林(47.88Mg/hm2)>灌木林(10.66 Mg/hm2),平均碳储量密度高于全国和同地区的平均值,达到了50.45 Mg/hm2;在空间分布上,针叶林在中高海拔(>500 m)和斜坡(>15°)以上优势明显,灌木林则相反,针阔混交林、常绿阔叶林的优势随着海拔升高或坡度增大而增加,植被的碳储量密度也随海拔的增高或坡度增大而增势明显。结果表明缙云山积累和存贮了较多的碳,"库"的功能强;而处于演替阶段初期的针叶林及灌木林明显占优,表明其在碳的积累上还有很大的提升空间,具有"汇"的潜能。此外,在较高海拔和较大坡度上的高碳储量密度,与人类的活动频度较小和对植被干扰较轻相关。因此可以推测,随着自然演替和保护区的封育改造、退耕还林及择伐补阔等森林管理措施的进行,将利于森林植被的保护、发育和更新,促使缙云山森林生态系统的碳储量密度进一步增大,碳"汇"潜能进一步增强,生态服务功能和价值得到进一步提高。

Spatial distribution of vegetation and carbon density in Jinyun Mountain Nature Reserve based on RS/GIS

Forest ecosystem,as a major body of terrestrial ecosystem,holding 85% of terrestrial biomass plays an irreplaceable role in the global carbon cycle and consequently in global climate change.Although China has the smallest forest area among mid-latitude nations,it contains a relatively large forest vegetation carbon pool and high forest carbon density as a result of intensive forestation programs and forest managements.Thus,natural reserves are the most effective areas for forest management,and they often complement some environmental goals including protection of carbon sink,and should not be ignored in regional carbon researches.In former studies,the capability,distribution and changing of carbon resource and sink are basic scientific issues in regional carbon sequestration researches,and these issues are closely related to vegetation distribution,composition,carbon density and other forest statuses.Jinyun Mountain is one of the national natural reserves in China.As the mountain holds well-protected subtropical evergreen broad-leaved forest(EBF) accompanied by coniferous forest(CF),mixed coniferous and evergreen broad-leaved forest(MCB),etc.,it has been concerned by many researchers.Consequently,studying the spatial distribution of vegetation and carbon density of Jinyun Mountain Nature Reserve can provide important basic data for forest ecosystem operation,carbon pool management and even regional carbon sequestration researches. In this study,high-resolution remote sensing image and 1 ∶ 10 000 relief maps were used to generate Jinyun vegetation map and digital elevation model respectively,combining with non-destructive method to acquire forest biomass by field investigation and the data of carbon content and biomass regression models from the published papers.And then,the spatial characteristics of vegetation and carbon density in Jinyun Mountain Natural Reserve were analyzed by ArcGIS.The results showed that CF was the dominating forest stand,followed by SH(shrub).The vegetation area ranged as CF(30%) > SH(21%) > MCB(16%) > NS(neosinocalams stand,11%) > EBF(6%) > MCN(mixed coniferous and neosinocalsms stand,5%) > MBS(moso bamboo stand,4%).The average vegetation carbon density in Jinyun Mountain was 50.45 Mg/hm2,which was higher than the average level in China,ranged as MCB(74.23 Mg/hm2) > CF(62.97 Mg/hm2) > EBF(62.65 Mg/hm2) > MCN(59.84 Mg/hm2) > NS(48.72 Mg/hm2) > MBS(47.88 Mg/hm2) > SH(10.66 Mg/hm2).Moreover,vegetation and carbon density had clear spatial variations with altitude,slope and aspect.CF dominated in altitude higher than 500 m and slope > 15°,but the shrub was the other way around.The carbon density of MCB and EBF increased with the increasing of altitude and slope.EBF had a large area in the northwest aspect,and MCB had a large distribution in the north,northwest,east and southeast aspects.NS and MCN were the dominating forest stand in the south relatively.CF,dominated with Pinus lanceolata,and SH were at primary stage of forest recovery succession in the Jinyun Mountain.The results indicate that the actual carbon sequestration of Jinyun Mountain is still much lower than the potential value of the zonal climax vegetation in this subtropical area.As we find the carbon storage and density are negatively correlated with human disturbance,forest reserve managements,such as enclosure of forest region,might contribute to conserve and sequester carbon in Jinyun Mountain.