人工造林对森林覆盖率的贡献分析

根据全国森林资源历次清查和全国历年造林面积统计公布数据,详细分析了不同时期的造林贡献率:1950—1962年、1963—1976年、1977—1981年、1982—1988年、1989—1993年、1994—1998年和1999—2003年间造林贡献率分别为:15.0%、33.1%、19.3%、47.1%、46.0%、53.9%和46.9%;1950—1981年、1982—1993年和1994—2003年3个时段造林贡献率平均为24.9%、46.8%和50.1%;1950—2003年的54a间,造林至少增加森林覆盖率9.38个百分点,而其中被采伐和征占用等消耗达41.83%,保存面积占59.17%,54a造林贡献率平均为37.33%,但保存面积仅占造林总面积的22.1%。另一方面,我国森林采伐利用数量较大,1950—2003年森林采伐蓄积总量达130.57亿m3,按平均每公顷蓄积量85m3计算,折合森林覆盖率约16个百分点。即,建国初的森林全部被采伐过一次,有的地方甚至多次择伐。可见,人工造林在稳定和提高森林覆盖率方面发挥了重大作用,1962—2003年,人工造林成林面积占期间森林面积增加值的78.43%。但经长期采伐利用,我国森林质量变低,林相状况变差,到2003年,森林的平均郁闭度仅为0.54,平均胸径仅为13.8cm,与1962年比,单位面积蓄积量由98.87m3/hm2下降到84.73m3/hm2,下降14.3%;近成过熟林面积比例由46.84%下降到32.14%,下降31.4%。指出:随着我国生态安全和生产生活对森林资源需求的不断增长,在稳定和扩大人工造林数量的同时,应提高造林质量,彻底解决重造轻育、忽视森林资源经营问题,并重视人工造林在碳汇交易、绿色GDP测算等各个方面的作用。

Analysis on Contribution of Artificial Afforestation to Forest Coverage

The contribution ratio of artificial afforestation to forest coverage is analysed in detail based on all previous forest inventory data and planting area of each year in China. Results indicate that the contribution ratios in the periods from 1950 to 1962, 1963 to 1976, 1977 to 1981, 1982 to 1988, 1989 to 1993, 1994 to 1998, and 1999 to 2003 are 15.0%, 33.1%, 19.3%, 47.1%, 46.0%, 53.9% and 46.9%, respectively. The ratios in the periods from 1950 to 1981, 1982 to 1993 and 1994 to 2003 are 24.9%, 46.8% and 50.1%, respectively. In the past 54 years from 1950 to 2003, the forest coverage has increased by 9.38%, while forest harvesting and occupation account for 41.83% and the preserved areas occupy 59.17%. The average contribution ratio is 37.33% for the past 54 years, however the rate of preserved area accounts for 22.1% of the planting area. On the other hand, the amount of forest harvesting and consumption is relatively large, and the total forest cutting volume reached 130.57 billion m3. Suppose the volume per hectare is 85 m3, the forest cutting area will occupy 16% of the forest area, which indicates that the total forest has been cut once, and it may be selectively cut several times in some places. It is obvious that artificial afforestation plays an important role in stabilizing and improving forest coverage, for example, the established artificial forest area occupied 78.43% of the forest increasing area from 1962 to 2003. Because of forest harvesting and consumption, the forest quality in China is becoming lower, and the forest form is becoming poor, for example, in 2003, the average crown density was 0.54, and the average diameter at breast height was 13.8 cm, and compared with the forest in 1962, the volume per hectare decreased from 98.87 m3 to 84.73 m3 and decreased by 14.3%, the near-mature, mature and over-mature forest areas reduced from 46.84% to 32.14% and reduced by 31.4%. Therefore, with the ever-increasing demands for national ecological safety as well as production and living, some necessary measures should be adopted on the basis of stabilizing and extending artificial afforestion amount, including improving planting quality, completely solving the problems of emphasizing planting and ignoring cultivation and forest management, and emphasizing the afforestation effects on carbon exchange and green GDP account.