基于能值理论的三江源区生态系统服务物质当量研究

Estimation of Substance-Equivalent of Ecosystem Services in the Three-River Headwaters Region based on Emergy

鉴于生态系统服务的多样性和评估方法的复杂性使得生态系统服务研究难于纳入到政府决策和政绩考核的问题,以三江源区为例,提出生态系统服务物质当量的概念,并发展了基于能值理论的物质当量估算方法;进而通过构建用于调节生态系统类型之间与生态系统内部差异的均衡因子和调整因子,发展了生态系统服务快速核算方法.结果表明:三江源区主导生态系统服务(包括水源涵养、土壤保持和生态系统固碳)所具有的能值量为2.74×1022sej/a,标准物质当量(即物质当量单位)的能值基准值为1.58×1017sej/(km^2·a),由此估算的物质当量为173 618.80当量/a,单位面积物质当量为0.56当量/(km^2·a),其中,水源涵养、土壤保持和生态系统固碳服务的物质当量所占比例分别为52.72%、28.14%和19.14%.三江源区主导生态系统服务物质当量的空间分布特征表现为从东南向西北逐渐递减的变化趋势;分县(乡)估算的主导生态系统服务物质当量的空间分布与其单位面积物质当量存在较大差异,前者的高值区主要位于治多县、曲麻莱县和杂多县,后者则主要位于尖扎县、同仁县、久治县和班玛县.基于直接评估法估算的各县(乡)单位面积物质当量与基于快速核算方法估算结果的决定系数为0.72,均方根误差为0.25当量/(km^2·a).研究结果有助于实现生态系统服务的快速评估.

Due to the diversity of ecosystem services and the complexity of evaluation methods,it is difficult to be applied in government decision-making and performance examination. To resolve this problem, a substance-equivalent concept for ecosystem services and introduction to its estimation approach based on emergy were proposed. A method was subsequentlydeveloped to quickly estimate ecosystem services through building an equivalence factor and an adjustment factor,which were separately used for balancing and adjusting the differences among inter- and intra-ecosystems. In this paper,the Three River Headwaters Region was chosen as a case study. The results showed that the emergy of the dominant ecosystem services,including water conservation,soil conservation and carbon sink,in the Three River Headwaters Region was 2. 74 × 10^22sej/a. The standard substance-equivalent of ecosystem services（ i. e.,unit of substance-equivalent） was 1. 58 × 10^17sej/（ km^2·a）. The further estimated substance-equivalent of ecosystem services was 173,618. 80 equivalent/a,and its value in per unit area was 0. 56 equivalent/（ km^2·a）,with the water conservation,soil conservation and carbon sink accounting for 52. 72%,28. 14% and 19. 14%,respectively. The spatial pattern of substance-equivalent of ecosystem services generally decreased from the southeast to the northwest. There were discrepancies between the substance-equivalent of ecosystem services per county（ township） and the corresponding values in the unit area. The higher values of the former were located in Zhiduo,Qumalai and Zhaduo,while those of the latter were located in Jianzha,Tongren,Jiuzhi and Banma. The coefficient of determination between the substance-equivalent of ecosystem services in unit area per county（ township） derived from the above direct estimation and that derived from the quick estimation was 0. 72,and the root mean square error was 0. 25 equivalent/（ km^2·a）. The above results are beneficial for quick ecosystem services estimation.