中国县域尺度生态保护的地域分异及其适宜性

鉴于中国对生态保护的投入与奖惩皆以县域为基本单元,需要开展县域尺度生态保护效果的监测评估,以期为县域生态环境质量考核提供科学依据。本文定量分析了近15年县域尺度优良生态系统面积及植被覆盖度变化,及其与生态保护项目数量的关系,进而评估生态保护措施在县域生态变化中的效果,并评价工程措施的地域适宜性。结果表明：① 中国东北地区、南方亚热带区、青藏高原东南部的县域优良生态系统面积占比多高于50%,西北地区、西南喀斯特区、华北平原等县域优良生态系统占比多低于20%。② 近几十年,生态保护重点是生态脆弱区,青海三江源、藏东南、川西、祁连山、新疆南部等西部地区的县域生态保护项目数量多大于5个,东部沿海地区则少于或等于1个。③ 2000-2015年,中国53%县域的优良生态系统面积占比提高,黄土高原、黄淮海平原、京津冀、川黔渝、两广等地区的县域植被覆盖度明显上升,而新疆北部、西藏中部、内蒙古中东部等干旱半干旱区、长三角等区域植被覆盖度下降。④ 生态保护项目数量与优良生态系统、植被覆盖度变化等反映生态状况改善的指标并未呈现正相关关系,生态保护应遵循优良生态系统分布格局,气候变化背景下造林等工程措施应遵循自然规律与地带性差异。

Spatial variation pattern of ecological conservation and its zonal suitability at the county level in China

China's investments, financial incentives and deductions on ecological conservation are based on the county level. Therefore, the monitoring and assessment on the effects of ecological conservation at the county level is significant to provide a scientific basis to the ecological and environmental quality assessment of counties. This paper quantitatively estimated the dynamics of high-quality ecosystems and the vegetation coverage in the past 15 years, and examined its relationships with the number of ecological conservation programs at the county level. Then it assessed and discussed the effects of ecological conservation measures in county's ecological changes and its regional suitability. The results showed that the proportion of high quality ecosystems higher than 50% was primarily observed in counties of Northeast China, subtropical southern China and southeastern Qinghai-Tibet Plateau, and the proportion lower than 20% was mostly found in counties of Northwest China, karst region of Southwest China and the North China Plain. In recent decades, ecological conservation focused on ecological fragile regions, so there are more than five ecological conservation programs in most counties of the Three Rivers Source Region in Qinghai Province, southeastern Tibet, western Sichuan, Qilian Mountains, southern Xinjiang and other parts of Western China, while there is one or no one found in coastal eastern China. In the past 15 years, the area proportion of high-quality ecosystems in 53% of the counties has increased. The vegetation coverage of counties in the Loess Plateau, Huang-Huai-Hai Plain, Beijing-Tianjin-Hebei region, Sichuan-Guizhou-Chongqing, and Guangdong and Guangxi provincial units has increased significantly. However, it has decreased in northern Xinjiang, central Tibet, central and eastern Inner Mongolia, Yangtze River Delta and other parts of China. The relationships between the numbers of ecological conservation programs and the indicators responding ecosystem restoration such as high-quality ecosystem and vegetation coverage do not show positive correlations. It is recommended that ecological conservation projects should be planned and implemented according to the distribution of high-quality ecosystems, and the restoration measures such as afforestation should follow natural principles and regional variations under the background of climate change.