Effects Of Cutting Quota Management Measures On Forest Carbon Storage In China

The forest cutting quota system is one of the most basic management systems in which the state sets harvesting limits for forest trees based on the principles of rational management and sustainable use.It is important to conduct a study on the effects of this system on the dynamics of carbon stock changes in forest ecosystems to accurately assess the regional carbon sequestration capacity and subsequent forest management in China.In order to investigate the impact of harvesting quota management measures on the carbon stock of forest vegetation in China,this study used the data of five national forest inventory periods and the summary of five national harvesting quotas to estimate the carbon stock of forest vegetation in China by the continuous function method of biomass conversion factor and analyze its dynamic change trend.In addition,by establishing the regression equation of biomass and storage volume and calculating the resulting carbon stock of harvesting limit,the impact of this measure on the carbon stock of forest vegetation in China is analyzed.The results of the study can provide basic data and references for the assessment of ecological benefits of harvesting limit management measures and the estimation of forest ecosystem carbon stocks.The results of the study are as follows.(1)The overall trend of forest vegetation area,carbon stock and carbon density in China is increasing.The average annual growth rate of carbon stock of forest vegetation in China is 124.43 Tg C,with an average annual growth rate of 10.13%.During the study period,China’s forests showed carbon sink and strong carbon sequestration capacity.The carbon density showed a change process of rising and then decreasing,and it decreased by 2.88 Mg/hm2 during the ninth forest inventory period,when the decrease of carbon density was related to the increase of area,mainly due to the increase of low-density forest types.(2)Among all age groups,the area of young and middle-aged forests is larger,and the sum of the two accounts for about 60% of the total area of forest vegetation in China in the same period.The carbon stock of near-mature and mature forests increased the most,with increases of 126.26% and 81.27%,respectively.Middle-aged forests accounted for the highest proportion of the total carbon stock in the country during the same period,ranging from 29.08% to 31.94%,while young-aged forests and over-mature forests had a lower proportion of carbon stock than the former.(3)The carbon stock and carbon density of different tree species groups differed greatly.The carbon stock of broad-leaved mixed and coniferous mixed increased the most obviously,among which broad-leaved mixed not only increased the most,but also was the tree species group with the highest proportion of total carbon stock in the same period,accounting for 17.23%～33.91%.The degree of carbon density change was most obvious for wood sorrel,which nearly doubled,followed by oleander and cypress.(4)The total amount of harvested carbon stock decreased slightly during the study period,with a total decrease of 25.32 Tg C.The lowest value of China’s harvested carbon stock was recorded during the 10 th Five-Year Plan period,with a decrease of 30.76%,after which the amount of harvested carbon stock increased significantly,and during the 12 th Five-Year Plan period The total amount of harvested carbon stock increased by 87.9 Tg C during the 12 th Five-Year Plan period,and the overall distribution of harvested carbon stock in China’s forests is more in the north and more in the south.In Northeast China,the amount of harvested carbon stock decreased significantly,with a decrease of 62.76%.In South China,the amount of harvested carbon stock tends to increase significantly,with an increase of 114.58%.(5)The total amount of harvesting quota is positively correlated with the carbon stock of forest vegetation in China,and some policies in the harvesting quota management measures have imposed high-intensity control on the harvesting behavior,which to a certain extent has played a positive role in increasing the forest stock and forest area.During the study period,the carbon sequestration value brought by harvesting limits accounted for 3.51%～4.16% of the corresponding carbon sequestration value of forest vegetation in China,which is an important initiative to enhance forest value.