TITLE:
Assessment of Cork Oak Decline Using Digital Multispectral Imagery in Relation with in Situ Crown Condition
AUTHORS:
Soumia El Ahmadi, Hassan Ramzi, Abderrahman Aafi, Nejm Eddine Jmii, Taoufik Aadel
KEYWORDS:
Dieback, Cork Oak Forest, Mâamora, Satellite Images, Crown Condition
JOURNAL NAME:
Open Journal of Forestry,
Vol.13 No.1,
January
31,
2023
ABSTRACT: Cork oak in Maamora forest is experiencing the dieback phenomenon. The
evaluation of the latter in this forest has gained the importance over time and with the solicitation of managers to
objectify its phytosanitary situation. Aiming at prioritizing management
actions, remote sensing seems to be an effective tool to inquire about stands’
health conditions and their evolution. To this end, this study aims at mapping
and validating health status of cork oak stands in Maamora. Sentinel 2 images
in 2015 and 2020 were processed to calculate the differential normalized
difference water index (NDWI), revealing
vegetation moisture variation caused by drought. A statistical method based on thresholds was used to map cork oak
dieback stands, those with no changes and those recovered. Results have
shown that 54.63% of cork oak in Maamora forest have not changed in terms of
phytosanitary situation between 2015 and 2020, 31.10% of oak stands are
afflicted by a slight decline and 12.97% by a severe decline. Areas with slight
or strong recovery remain minimal and represent 1.04% and 0.25% respectively.
Ground data indicated that the map generated displayed a good distinction
between stands severely and slightly declined with a global accuracy of 66.66%.
Therefore, further research elaborating an advanced vegetation index reflecting
the various factors of dieback would be of much importance.