不同视角下InVEST模型的土壤保持功能对比

土壤保持是生态系统的重要服务功能之一。黄土高原是世界上水土流失最严重的地区,黄河中游地区是黄河泥沙的主要来源,继续开展黄河中游地区土壤保持研究,对于当地的水土保持、土地利用结构调整、退耕还林、生态补偿以及水库管理具有重大意义。以黄河一级支流无定河的源头(营盘山库区)为研究区,采用生态系统服务和交易的综合评估模型InVEST(Integrated Valuation of Ecosystem Services and Trade-offs),从水文和土地利用两个角度出发,对研究区地块截留能力、输出能力和保持能力进行对比研究,重点探讨哪种角度的结果更科学合理,并进一步研究清淤情境下2010年营盘山库区的土壤保持能力及其空间格局特征。结果表明：① 基于子流域边界和土地利用边界的计算结果差异悬殊,水文学意义的子流域边界可以保证沉积物沿水文路径迁移过程的完整性,评价结果更科学合理;InVEST沉积物模型应该采用水文意义上的自然流域边界,而不宜将土地利用边界作为子流域单元进行评价。② 2010年营盘山库区在清淤情境下的沉积物截留总量为586482.60 t,输出总量为129868.61 t,平均输出量为12.93 t/hm²,保留总量为1559198.40 t,平均保留量为151.57 t/hm²。③ 地块的沉积物截留能力从上游至下游逐渐增强,而沉积物输出能力却刚好相反。无定河西侧支流的土壤保持能力比东侧支流偏高,两大支流平均土壤保持量低值区均出现在河流上游地区。

Comparative study on the soil conservation function of InVEST model under different perspectives

Soil conservation is one of the important service functions of ecosystem. The Loess Plateau is the most serious soil erosion area in the world, and the middle reaches of the Yellow River Basin is the main source of silt. Therefore, it is of great significance to conduct further studies on the soil conservation in the middle reaches of the Yellow River, especially in the aspects of soil and water conservation, land use structure adjustment, conversion of farmland to forests, eco-compensation as well as reservoir management.By taking the Yingpanshan Reservoir region, the source of Wuding River which is the primary tributary of the Yellow River, as an example, this paper uses the Sediment Retention Model of InVEST to compare the capacity of trapping sediment of land parcel, sediment output and sediment retention from the perspective of hydrology and land use, and try to figure out which result is more scientific, and to reveal the ability of soil conservation for Yingpanshan Reservoir region and its spatial pattern in 2010. The results are shown as follows: (1) The boundary of subwatershed in hydrological perspective can ensure the integrity of the removal of sediment by vegetation along hydrologic flowpaths, which makes the evaluation result more scientific and reasonable, since the evaluation results are significantly different under different perspectives. Therefore, the Sediment Retention Model of InVEST should choose natural basin boundary in the sense of hydrology as the sub-basin unit to evaluate the soil conservation function, instead of choosing the inputting boundary of land use. (2) When dredging for reservoir is considered, the total sediment retained, the total sediment export, the mean sediment export the total amount of sediment retained from sediment originating upstream, and the mean amount of sediment retained are 586482.60 t, 129868.61 t, 12.93t/hm², 1559198.40t, and 151.57 t/hm², respectively. (3) The sediment retention capacity of land parcel increases gradually from upstream to downstream, while the capability of sediment output has a contrary tendency. The sediment retention ability of west tributary of the Wuding River is more stronger than that of the east tributary. In addition, the low-value areas of soil conservation in the two major tributaries are both observed in the upstream.