基于生态系统恢复力的干旱区植被生态需水阈值计算方法与应用

本文以石羊河流域中下游为研究区,采用考虑生态系统恢复力(latitude of ecosystem resilience, LER)的月尺度生态需水评估方法计算1982-2020年植被月适宜生态需水量、最小生态需水量以及相应的生态缺水量,并与土壤水分特征值法(characteristic value of soil water, CVSW)进行比较,分析不同类型植被生长期的水分盈亏关系。结果表明:LER法和CVSW法计算结果相近,但LER法具有更大的生态需水阈值区间;天然降水基本可以满足植被的基本生存,但无法满足正常生长需求;LER法的适宜需水条件下,各植被生长期总体处于缺水状态,缺水严重程度排序为灌木林＞其他林地＞疏林地＞高覆盖度草地＞中覆盖度草地＞有林地,全部植被生长期总适宜生态需水量为3.7×10⁸ m³,亏缺水量为1.2×10⁸ m³,同一植被亏缺水量基本符合春秋多、夏季少的规律;最小需水条件下,只有其他林地存在生长期缺水情况,全部植被生长期总最小生态需水量为0.8×10⁸ m³;在缺乏土壤水分数据的干旱地区,LER法具有良好的适用性。研究结果可为石羊河流域水资源高效利用和干旱区生态系统的恢复与重建提供理论参考。

Calculation method and application of ecological water demand threshold for vegetation in arid areas based on ecosystem resilience

This paper calculated the suitable ecological water demand, minimum ecological water demand, and corresponding ecological water deficit of vegetation from 1982 to 2020 by using a monthly-scale ecological water demand assessment method that considered the resilience of the ecosystem (Latitude of Ecosystem Resilience, LER) in the middle and lower reaches of the Shiyang River Basin. It compared these results with the Characteristic Value of Soil Water method (CVSW) and analyzed the water surplus and deficit relationship during different vegetation growth periods. The results showed that the LER method and CVSW method had similar calculation results, but the former one had a larger ecological water demand threshold range; natural precipitation could meet the basic survival needs of vegetation but could not meet the requirements for its normal growth. Under suitable water demand conditions, the overall vegetation growth periods were in a water-deficient state, with the severity of water deficiency ranking as follows: shrubland > other forests > sparse forests > high coverage grassland > medium coverage grassland > forested areas. The total suitable ecological water demand for all vegetation growth periods was 3.7×10⁸ m³, with a water deficit of 1.2×10⁸ m³. The water deficit of the same vegetation generally followed the pattern of higher in spring and autumn and lower in summer. Under the minimum water demand conditions, only other forests experienced water deficiency during the growth period, with a total minimum ecological water demand for all vegetation growth periods of 0.8×10⁸ m³. The research results indicated that the LER method, which considerd the resilience of the ecosystem, was applicable in arid areas. These findings can provide theoretical references for the efficient utilization of water resources in the Shiyang River Basin and the restoration and reconstruction of ecosystems in arid regions.