不同土地覆被格局情景下多种生态系统服务的响应与权衡——以雅砻江二滩水利枢纽为例

在二滩水库集水区,按照当地生态政策发展以坡度为指标构建了10种未来土地覆被格局情景,研究生态系统减轻水库泥沙淤积、减轻水库面源污染、产水发电服务及价值对未来覆被格局的响应程度,并兼顾相关产业收益的变化,权衡各种情景格局的服务效益,优选利益相关方福祉提升幅度最大的情景格局。结果表明:1)现有土地覆被格局对减轻水库泥沙淤积功效的发挥不合理,而以退耕还林政策指导区域土地覆被格局变化,对集水区减轻河道和水库泥沙淤积具有较好功效。10种情景下,保沙价值的高低关系同入库泥沙量正好相反,遵循"随地表林地和草地面积比例的增加,保沙价值增加"的规律。随产沙总量的增加,高产沙强度像元呈现从水库周边逐渐向中上游蔓延的趋势。2)退耕还林政策单纯以坡度作为指标,指导土地覆被的转化,对集水区减轻水环境磷素非点源污染功效较差。除了全为未利用地覆被的情景10,余下9类情景模拟的入库磷素量及过滤磷素经济价值的高低关系完全一致,呈农田草地林地的规律。随入库磷素总量的增加,高强度磷素输出像元从雅砻江流域源区和大河湾区,逐渐蔓延扩散至集水区整个水网。3)随着集水区地表林地覆盖面积比例的减少,集水区生态系统总发电净利润值增加,且高净利润像元呈现从冕宁和喜德县的东部逐渐向整个集水区东南部乃至整个下游蔓延的趋势。4)从减轻对环境的负效应以及提升利益相关方福祉的角度,以坡度6°上下划分林地和耕地的情景5和以坡度15°和6°为阈值划分林草农的情景3为除极端的情景外,综合指标提升最高的两种情景。

Responses and weigh of multi-ecosystem services and its economic value under different land cover scenarios: a case study from Ertan water control pivot in Yalong River

10 different future land cover pattern scenarios with slope criteria were built based on local ecological policies in the watershed of Ertan reservoir. The responses of 3 different ecosystem regulating services which were avoiding reservoir sedimentation, avoiding nonpoint source pollution of aquatic environment and water supply and energy produced and its economic value to future land cover pattern were studied. The service benefit of various pattern scenarios was weighed by integrating the change of income of agriculture, forestry and animal husbandry. The scenario which let the well-being of related groups to maximal increase was selected. The results showed: 1) The existing land cover pattern was incongruous to exerting the ability of avoiding reservoir sedimentation. The land cover pattern changed according to the national policies for returning farmland to forests was in favor of avoiding riverway and reservoir sedimentation. The value of sediment retention's ranks was contrary to sediment delivery. The value of sediment retention followed the rules of "the area percent of forest and grassland increasing as the value of sediment retention". Along with the increase of total sediment delivery, the high sediment delivery cells spread out from the region around the reservoir to the middle and upper reaches of Yalong river. 2) The national policies for returning farmland to forests guided the land cover changes were based on the slope ranks. It was unsuitable to avoiding phosphorus nonpoint source pollution of aquatic environment in watershed. The ranks of phosphorus delivery were completely in line with the value of filtering phosphorus pollution except scenario 10 which was all covered by unused land. The law was farmland>grassland>forest. Along with the increase of total phosphorus pollution delivery, the high phosphorus pollution delivery cells spread out from the source region and big river bend of Yalong river basin to the whole network of rivers of watershed except scenario 10. 3) Along with the increase of the forest area percent, the total net present value (NPV) of energy produced in watershed decreased. Along with the increase of total net present value (NPV) of energy produced, the high NPV cells spreaded out from the eastern of Mianning and Xide county to the southeast of whole watershed and the lower reaches of Yalong river. 4) From the viewpoint of lightening the negative effect to environment and letting the well-being of related groups be maximal increase, The quantity of aggregative indicator on scenario 5 that 6° slope was a threshold in determining farmland and forest cover and scenario 3 that 6° and 15° slope were threshold in determining farmland, grassland and forest cover increased at the highest extent except the extreme scenarios.