近40年来黄土高原植被变化趋势及其生态效应

Vegetation Trends and Ecological Effects on the Loess Plateau,China in the Last Forty Years

1999年起我国实施了退耕还林还草政策,黄土高原植被覆盖状况与土地利用结构发生了明显变化,植被覆盖大幅增加,生态质量显著改善。然而,植被覆盖的时空变化趋势却很不确定,对于其生态效应综合评估方面的研究相对薄弱。基于此,在分析归一化植被指数(NDVI)与植被覆盖度(FVC)两种指标的基础上,综述了近40年来退耕还林还草政策实施前后黄土高原植被覆盖及分布的变化情况。结果表明:①通过分析比较记录植被覆盖动态变化的5种常见数据集,发现数据源在一定程度上影响生态环境效益评价结果的真实性;②黄土高原多年来整体植被覆盖呈波动式增加,且增速随着退耕还林还草政策的实施而增大,空间分布自东南向西北方向递减,并受到生态系统格局、土地利用类型及气候变化等因素的影响;③随着植被覆盖面积增长,黄土高原生态系统水土保持效应与固碳能力逐渐增强,二者均与植被覆盖变化高度耦合。针对黄土高原生态环境治理及粮食生产水平现状,建议加强高标准农田建设,缓解退耕还林还草政策导致的耕地紧缺问题,同时加快推动生态价值转化和生态补偿力度,让“绿水青山”真正成为“金山银山”。

Since 1999,China has implemented the Grain for Green Project(GFGP),which has significantly changed the vegetation coverage status and land use structure of the Loess Plateau.As a result,vegetation coverage and ecological quality have been greatly improved.However,the spatio-temporal trend of the vegetation coverage is very uncertain,while the comprehensive assessment of its ecological effects has been relatively weak.To this end,two vegetation indices,including normalized difference vegetation index(NDVI)and fractional vegetation cover(FVC),were analyzed,and the changes in vegetation coverage and distribution on the Loess Plateau before and after the implementation of GFGP in the past forty years were reviewed.The results show that①comparing five common data sets that record the dynamic changes of vegetation coverage,it is found that the data sources affect the authenticity of the eco-environmental benefits evaluation results to a certain extent;②the overall vegetation coverage of the Loess Plateau has been increasing in a fluctuating manner over the years,whose growth rate has surged due to the implementation of the project;its spatial distribution decreases from southeast to northwest,and is influenced by the ecosystem pattern,land use type,climate change,etc.;③with a rise of vegetation coverage,the water and soil conservation,and carbon sequestration capacity of the Loess Plateau ecosystem also gradually make a build-up,both of which are highly coupled with vegetation changes.According to the current situation of eco-environment management and food production level,it is recommended to strengthen the construction of high-standard farmland to alleviate the problem of arable land shortage caused by GFGP.Meanwhile,it is necessary to accelerate the promotion of ecological value transformation and eco-compensation,so that the lucid water and lush mountains can truly become invaluable assets.