我国东北天然林保护工程区森林植被的碳储量

以东北天然林保护工程区森林生态系统为对象,通过对其主要森林类型进行调查,探讨天保工程经营区划对森林植被固碳现状的影响,并结合已有的东北林区生物量与蓄积量数据库,建立了东北林区主要树种组的生物量-蓄积量回归模型,然后以第7次森林资源清查为基础,对东北天保工程区森林植被碳储量进行估算,以期为全国森林生物量的估算和天保工程的评估提供参考。结果表明,不同经营区之间(重点公益林、一般公益林和商品林)森林植被碳密度的差异并不显著,这可能与天然林保护工程实施初期经营区划的标准、样地的选择以及天保工程实施过程中粗放的管理方式有关。东北天保工程区森林植被碳储量为1045 Tg C,占东北、内蒙古三省森林植被总碳储量的68%;工程区以天然林为主,占工程区总植被碳储量的97%。工程区森林植被平均碳密度为41 Mg/hm2,较东北、内蒙古三省平均植被碳密度高14%;工程区植被碳密度随林龄的增加逐渐增大,由幼龄林的13 Mg/hm2到过熟林的63 Mg/hm2。因此,继续加强天然林保护工程的实施,提高其林分质量,这对未来我国森林碳汇潜力的增加和森林的可持续发展都具有重要的意义。

Carbon storage of forest vegetation under the Natural Forest Protection Program in Northeast China

The Natural Forest Protection Program (NFPP), which aims at protecting ecological resources and achieving sustainable forest management, has been implemented for 10 years in Northeast China. Under the program forest ecosystems in the region have been divided into three management areas-Key conservation, General conservation and Commercial forest. Each of these three types of forest land is subject to different management measures (protecting or logging). Estimating carbon storage of forest vegetation in these areas is important both for understanding the capacity of forests in the Northeast region for carbon sequestration and as an aid to assessing the effectiveness of the NFPP in meeting its goals. To address this important need, this study selected five major forest types in the Northeast forest region-larch forest, birch forest, coniferous mixed forest, broadleaved mixed forest, coniferous and broadleaved mixed forest. Each forest type was divided into four age classes-young, mid-aged, premature and over mature forest. Tree biomass was calculated through species-specific allometric equation models based on field measurement in the Daxing''anling, Xiaoxing''anling and Changbai mountains. At the same time, an dataset on biomass and volume of the main forest types in the Northeast forest region was established based on existing data from former studies. Since some studies have found that the relationship between forest biomass and volume fits relatively well within a liner regression framework, this study utilized this two data sources noted above to establish biomass-volume line regression models of the main tree species groups in the Northeast, focusing primarily on the five major forest types identified above. Forest biomass carbon storage in areas under the NFPP in the Northeast region was subsequently estimated based on data from the 7th National Forest Resource Inventory. Results showed that forest biomass carbon storage based on field measurement did not varied significantly with management areas, which likely reflects both the classification standard for the management areas and the relatively short period since the NFPP have been implemented. On the other hand, forest biomass carbon storage of lands under the NFPP was 1045 TgC, which accounted for 68% of total forest biomass carbon storage in the Northeast provinces of Jilin, Heilongjiang and Inner Mongolia. Moreover, forest biomass carbon density of lands under the program (41 Mg/hm²) exceeded that of the average biomass carbon density in Northeast provinces (36 Mg/hm²). Simultaneously, in the lands of the NFPP, forest biomass C density increased with forest age class, from 16.4 Mg/hm² in young to 63.0 Mg/hm² in over mature forest, thus the relative large areas of young and mid-aged forests (together accounted for 61% of total forest area), implying its great C sequestration potential in the future. In addition, forest biomass carbon storage was dominated by natural forest, which accounted for 97% of total biomass carbon storage under the NFPP. On an overall basis, the Natural Forest Protection Program acts an important role in the Northeast forest region, and it should be played an increasingly important role in forest ecosystem carbon sequestration and sustainable forest management in the next implemented decade.