甘肃省天然林碳汇现状及其动态变化分析

Analysis on Status and Dynamic Changes of Natural Forest Carbon Sink in Gansu Province

基于甘肃省森林资源连续清查第5次复查以来的3期调查数据,利用不同森林类型蓄积量与生物量之间的回归关系来估算甘肃省天然乔木林的生物量,分析甘肃省天然林总体及分龄组、树种(组)和林种的面积、碳储量、碳密度现状和动态变化。结果表明,(1)甘肃省天然林面积为383.2×104 hm^2,主要分布在甘肃南部、东部和祁连山;全省天然林碳储量由2006年的63.59TgC增加到2016年的74.57TgC,碳储量呈线性均匀增加,10年间累计增加10.99TgC,年均增长率为1.06%;(2)林龄结构中幼龄林、中龄林、近熟林、成龄林、过熟林面积依次占比为21.85%、31.18%、20.69%、17.57%和8.71%,中龄林比例较高,呈单峰左偏山状曲线,林龄结构较差,需人工促进更新;(3)防护林和特用林的碳储量相差不明显,但防护林幼龄林面积增加的趋势明显,较符合自然生态环境脆弱的甘肃省需要;(4)天然乔木林碳储量主要集中在栎类、阔叶混交林、冷杉、云杉和其他硬阔类。其中阔叶混的面积和碳储量增长量最大并远大于其他树种(组),且加速增长的趋势明显,使得甘肃省天然林树种组成在向混交林演变,生物多样性和森林质量等都在提高。同时,不同森林类型碳密度差异较大,其中,栎类碳密度最大,华山松碳密度最小。

Based on the three periods of forest inventory data since the fifth review of Gansu Province,the research estimated the biomass of natural arbor forests by using the regression relationship between the volume of different forest types and biomass,analyzed the status and dynamic changes of areas,carbon storage and carbon density from overall natural forest,age groups,tree species(groups)and forest categories.The results showed that:(1)The area of natural forests is 3.832 million hm^2,and mainly distributed in southern,eastern Gansu and Qilian Mountains;The carbon storage of natural forests increased from 63.59TgC in 2006 to 74.57TgC in 2016,which increased linearly and evenly with an average annual growth rate of 1.06%,it has increased by 10.99TgC in 10 years.(2)The forest-aged structure is that the area of the young forest,half-mature forest,near-mature forest,mature forest and over-mature forest respectively is 21.85%,31.18%,20.69%,17.57%,and 8.71%,and the proportion of half-mature is too high,in that showed a single-peak left-biased curve.The structure of the forest age is poor,and it needs to be artificially promoted.(3)There is no obvious difference between the carbon storage of shelter forest and special forest,but the young forest area of shelter forest showed an increasing trend,which is more in line with the fragile natural ecological environmental requirements of Gansu Province.(4)The natural arbor forest carbon storage are mainly concentrated in Quercus spp.,mixed broad leaf forest,other hard broad leaf,Picea spp.and Abies spp.and so on species(groups),among them,the area and carbon storage growth of mixed broad leaf forest is the largest and far greater than other tree species(group).The trend of accelerating increase is obvious,which makes the natural forest species evolving into mixed forests,the biodiversity and forest quality are improving.Meanwhile,the carbon density of different species(groups)is quite different.Among them,the carbon density of Quercus spp.is the largest,and Pinus armandi is the smallest.