退耕还林还草工程对干旱区内陆河流域生态系统服务的影响

Effects of the Grain for Green Program on the ecosystem services of inland river basin in arid area

探讨人类活动尤其是大型工程、政策对生态系统服务的影响是国际上地理学和生态学研究的前沿与热点领域。利用土地利用数据、气象数据、遥感数据等,结合InVEST产水量模型、CASA模型和RUSLE模型,对石羊河流域退耕还林还草工程实施期间的生态系统产水、净初级产品生产和土壤保持服务进行精准测度,分析其演变特征,并进一步细化对比了工程实施区与非工程实施区生态系统服务变化的差异。结果表明:(1)石羊河流域退耕还林还草工程实施期间(2000—2015年),林、草地面积有所增加,耕地和未利用地面积有所减少;面积变化比例最大的土地转化类型为“未利用地—草地”、“未利用地—林地”、“耕地—草地”和“耕地—林地”。(2)石羊河流域在退耕还林还草工程实施期间整体生态系统产水服务和土壤保持服务有不同程度衰退,但是NPP有较为明显增加;各服务在空间分布上具有一致性,均呈现出南高北低,由西南向东北阶梯递减的趋势。(3)石羊河流域“退耕区”产水、NPP和土壤保持总量和平均量均呈现出明显的增加趋势,而“非退耕区”除了NPP总量和平均量有所增加以外,其余两类服务均有不同程度的减少;各退耕模式中,“荒地造林”区对各类服务的提升最为明显,“退耕还林”区产水总量和平均量均有所减少。

Discussing the impact of human activities,especially large-scale projects and policies,on ecosystem services is the frontier and hotspot of international geographic and ecological research.Based on land use data,meteorological data and remote sensing data,combined with InVEST water yield model,CASA model and RUSLE model,we estimated three key ecosystem services,including water yield,NPP and soil conservation,to analyze the change characteristics during the implementation of the Grain for Green program(GFGP)in Shiyang River Basin.In addition,we further compared the differences of the three key ecosystem services between the project implementation area and the non-project implementation area.The results were as follows.(1)During the implementation of the GFGP in Shiyang River Basin(2000-2015),the area of forest and grassland increased,while the area of farmland and unused land decreased.The land conversion types with the largest proportion of area change were“unused land-grassland”,“unused land-forest”,“farmland-grassland”and“farmland-forest”.(2)The water yield service and soil conservation service of the whole basin declined in varying degrees,but NPP increased significantly.The spatial distribution of the services was consistent,showing a trend of high in the South and low in the north,and decreasing stepwise from southwest to northeast.(3)The gross and average amount of water production,NPP and soil conservation in the“GFGP area”of Shiyang River Basin showed an obvious increasing trend,while the other two types of services in the“Non-GFGP area”decreased in varying degrees except NPP.Among all the conversion modes,the improvement of various services was most obvious in“conversion unused land to forest”area,and the total and average water yield in“conversion of farmland to forest”area decreased.