Abstract
Drought is a significant challenge to semiarid Mediterranean grasslands, Increasing the accuracy of monitoring allows improving the conservation and management of these vital ecosystems. Meteorological drought is commonly monitored by the Standard Precipitation Index (SPI) or the Standard Precipitation Evapotranspiration Index (SPEI). On the other hand, agriculture drought is estimated by the Vegetation Health Index (VHI). This work aims to optimise the correlation between both drought types using the best transformation of VHI and the most appropriate time scale. Two drought-vulnerable Mediterranean grasslands were selected to evaluate the performance of the drought indexes. The SPI and the SPEI were calculated using data obtained from nearby weather stations. MODIS data were used to calculate the VHI. This index was standardised, naming it as SVHI. Our results revealed that SPEI was better correlated with VHI compared to SPI. In addition, SVHI obtained better results in the critical vegetation phases than VHI. Overall, SPEI and SVHI were the best correlated indexes. The quarterly scale showed stronger relationships than the monthly scale and the most correlated time frame were Mediterranean spring and autumn. This fact suggests that SPEI and SVHI could provide a plus point for increasing the precision of vegetation monitoring during these periods.
Highlights
IntroductionThe prairie regions account for about one third of the earth surface [1,2], being the permanent grassland over 7 million hectares of the Iberian Peninsula in 2020 [3]
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This study aims to evaluate the performance of several climate droughts (SPI and Standard Precipitation Evapotranspiration Index (SPEI))
Summary
The prairie regions account for about one third of the earth surface [1,2], being the permanent grassland over 7 million hectares of the Iberian Peninsula in 2020 [3]. These ecosystems are important in providing ecological and cultural services, such as biodiversity conservation, landscape preservation and rural population fixation. Drought is an important driving force in grassland dynamics and is a limiting factor in Mediterranean areas [4] It depends on two main interacting forces, precipitation, and temperature. The amount and timing of precipitation controls grasslands productivity, inducing fluctuations in soil water content throughout the seasons [5]
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