How long do trees resist prolonged drought? Insights from semiarid regions
Abstract
Understanding how tree species resist drought is essential for resource conservation in the context of increasing climate stress. This study quantifies the spatiotemporal dynamics of drought impacts on two land classes within the Oum Er Rbia Basin in Morocco: irrigated orchards in the plain and evergreen forests in mountainous areas. The study focuses on the prolonged drought that began in September 2019, identified using the CHIRPS monthly Standardized Precipitation Index and the TerraClimate Palmer Drought Severity Index. To extract the tree mask, separate methodologies were applied. First, the Random Forest model, trained on Sentinel-2 data with spectral indices and phenological metrics, achieved an accuracy of 95.94% for the irrigated area. Second, for the forest extraction of evergreen forests, monthly NDVI time series from 01/2017 to 12/2018 were used, and pixels with values greater than 0.25 in all months were selected to distinguish forestland areas from cropland areas. This monthly NDVI threshold is ecologically justified by the evergreen nature of the dominant forest species in the Middle Atlas Mountains. The duration of vegetation resistance to drought (DVR) was quantified by calculating the number of months with NDVI values greater than 0.25 after drought onset in September 2019. This metric captures how long vegetation maintains physiological its function despite the prolonged drought conditions, reflecting the duration of vegetation resistance to drought. The results revealed that the DVR ranges from an average of 34 months in the irrigated trees to an average of 50.6 months in the mountain forest, indicating that irrigated orchards are significantly more vulnerable to prolonged drought than natural forest ecosystems. Within the irrigated perimeters, the Tassaout region showed the shortest DVR, directly linked to the complete interruption of the irrigation water supply from 2021 onwards. Within the mountain forest areas, south and southeast facing slopes showed the lowest DVR values, reflecting their greater exposure to hot and dry conditions, while north and northeast facing slopes demonstrated greater resistance to drought stress. Additionally, GRACE data, dam water flow for irrigation, and dam water area were analysed to determine the impact of irrigation on water resources. Field validation confirmed these trends. These integrated earth observation-field methods ultimately provide operational frameworks for adaptive drought management, supporting reforestation planning, irrigation scheduling, and resilience monitoring in semiarid regions globally.
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BibTeX
@article{oussaoui2026long,
title = {{How long do trees resist prolonged drought? Insights from semiarid regions}},
author = {Sabir Oussaoui and Abdessamad Hadri and Abdelghani Boudhar and Ismaguil Hanadé Houmma and Jamal-Eddine Ouzemou and El Mahdi El Khalki and Ismail Karaoui and Kaoutar Ebbakhali and Mostafa Bousbaa and Christophe Kinnard},
journal = {Science of Remote Sensing},
year = {2026},
month = nov,
doi = {10.1016/j.srs.2026.100435},
url = {https://hal.science/hal-05850836v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - How long do trees resist prolonged drought? Insights from semiarid regions
AU - Sabir Oussaoui
AU - Abdessamad Hadri
AU - Abdelghani Boudhar
AU - Ismaguil Hanadé Houmma
AU - Jamal-Eddine Ouzemou
AU - El Mahdi El Khalki
AU - Ismail Karaoui
AU - Kaoutar Ebbakhali
AU - Mostafa Bousbaa
AU - Christophe Kinnard
PY - 2026
DA - 2026/11/03
JO - Science of Remote Sensing
DO - 10.1016/j.srs.2026.100435
UR - https://hal.science/hal-05850836v1
AB - Understanding how tree species resist drought is essential for resource conservation in the context of increasing climate stress. This study quantifies the spatiotemporal dynamics of drought impacts on two land classes within the Oum Er Rbia Basin in Morocco: irrigated orchards in the plain and evergreen forests in mountainous areas. The study focuses on the prolonged drought that began in September 2019, identified using the CHIRPS monthly Standardized Precipitation Index and the TerraClimate Palmer Drought Severity Index. To extract the tree mask, separate methodologies were applied. First, the Random Forest model, trained on Sentinel-2 data with spectral indices and phenological metrics, achieved an accuracy of 95.94% for the irrigated area. Second, for the forest extraction of evergreen forests, monthly NDVI time series from 01/2017 to 12/2018 were used, and pixels with values greater than 0.25 in all months were selected to distinguish forestland areas from cropland areas. This monthly NDVI threshold is ecologically justified by the evergreen nature of the dominant forest species in the Middle Atlas Mountains. The duration of vegetation resistance to drought (DVR) was quantified by calculating the number of months with NDVI values greater than 0.25 after drought onset in September 2019. This metric captures how long vegetation maintains physiological its function despite the prolonged drought conditions, reflecting the duration of vegetation resistance to drought. The results revealed that the DVR ranges from an average of 34 months in the irrigated trees to an average of 50.6 months in the mountain forest, indicating that irrigated orchards are significantly more vulnerable to prolonged drought than natural forest ecosystems. Within the irrigated perimeters, the Tassaout region showed the shortest DVR, directly linked to the complete interruption of the irrigation water supply from 2021 onwards. Within the mountain forest areas, south and southeast facing slopes showed the lowest DVR values, reflecting their greater exposure to hot and dry conditions, while north and northeast facing slopes demonstrated greater resistance to drought stress. Additionally, GRACE data, dam water flow for irrigation, and dam water area were analysed to determine the impact of irrigation on water resources. Field validation confirmed these trends. These integrated earth observation-field methods ultimately provide operational frameworks for adaptive drought management, supporting reforestation planning, irrigation scheduling, and resilience monitoring in semiarid regions globally.
SN - 2666-0172
ER -