Department of Range and Watershed Management, Faculty of Agriculture and Natural Resources, Lorestan University, Khorramabad, Lorestan, Iran.
Department of Environmental Science and Engineering, Faculty of Natural Resources, University of Jiroft, Jiroft, Kerman, Iran.
Environ Monit Assess. 2022 Mar 26;194(4):299. doi: 10.1007/s10661-022-09972-z.
It is important to choose an indicator that can optimally demonstrate the effects of drought intensity on soil moisture access, evapotranspiration and the changes in vegetation cover at a regional scale. Therefore, herein, SEDI was developed by the fit of the experimental distribution of Gringorten on evapotranspiration deficit based on TerraClimate data at the time scales of 1, 3, 6 and 12 months, and its relationship with Standardized Precipitation-Evapotranspiration Index (SPEI), Standardized Precipitation Index (SPI), Standardized Soil Moisture Index (SSMI), Normalized Ecosystem Drought Index (NEDI) and Normalized Difference Vegetation Index (NDVI) were investigated. The results indicated that SEDI has the highest significant correlation (above 95%) with NEDI and SPEI, especially for the 1-month time scale. This index also revealed the lowest correlation (less than 25%) with SPI on short-term time scales. The relationship between SEDI and SSMI indicated the high sensitivity of SEDI to the cumulative reduction of low amounts of soil moisture. According to the findings, the 6-month SEDI with NDVI showed the highest correlation with a 1-month delay (r = 0.64) and the best fit between them occurred in wet months. However, in the dry months, the relationship between SEDI with NDVI was affected via water availability stresses, grazing intensity and pest infestation. Finally, the use of SEDI at a regional scale, especially in arid and semi-arid regions like Lorestan, could be recognized as an important index in depicting the effects of drought on vegetation cover, due to the use of the actual evapotranspiration factor.
选择一个能够在区域尺度上最优地展示干旱强度对土壤水分获取、蒸散和植被覆盖变化影响的指标非常重要。因此，本研究通过在 1、3、6 和 12 个月时间尺度上基于 TerraClimate 数据，将 Gringorten 实验分布拟合到蒸散亏缺上，开发了 SEDI，并研究了它与标准化降水蒸散指数（SPEI）、标准化降水指数（SPI）、标准化土壤湿度指数（SSMI）、归一化生态干旱指数（NEDI）和归一化差异植被指数（NDVI）的关系。结果表明，SED 与 NEDI 和 SPEI 具有最高的显著相关性（高于 95%），尤其是在 1 个月时间尺度上。该指数与 SPI 之间在短期时间尺度上的相关性最低（低于 25%）。SED 与 SSMI 的关系表明，SED 对土壤水分少量累积减少具有很高的敏感性。根据研究结果，具有 NDVI 的 6 个月 SEDI 与 1 个月的延迟表现出最高的相关性（r=0.64），且它们之间的拟合效果最好出现在湿润月份。然而，在干旱月份，SED 与 NDVI 之间的关系受到水可用性压力、放牧强度和虫害侵袭的影响。最后，SED 在区域尺度上的应用，特别是在像 Lorestan 这样的干旱和半干旱地区，可以被视为描绘干旱对植被覆盖影响的一个重要指标，因为它使用了实际蒸散因子。
