Wild Olive Trees Extent in Al-Baha Region, Saudi Arabia According to Trees’ Age, Health, and Clustering Status

Abstract

This study provided detailed information on the attributes of wild olive species in the Al- Baha region, Saudi Arabia. The study area lay along the Sarah mountain, encompassing the districts of Al-Qura, Al-Mandaq, Al- Baha and the southern part of Baljurashi. This indicates the preference of wild olive for high foggy mountain conditions, which was pre-determined by the study to be a medium-high vegetation density zone. Information extracted from high resolution satellite imagery Pleaides revealed that there are 717,894 wild olive trees (360 trees per km2) in the study area, covering 1,991 km2 .The districts of Al-Mandaq and Al-Baha have higher wild olive density with younger and highly clustered trees, whereas Al-Qura and Baljurashi districts have lower wild olive density, with medium clustered older trees. The districts of Al-Aqiq, Qelwa and Mekhwa have the least density of wild olive with younger trees and light clustering. Clustering behavior was enumerated directly at the sampling plots and the results depicted that the majority of wild olives occur in clusters with mostly 5-10 trees per cluster. The olive tree is found naturally in Al-Baha and can reportedly maintain its populations in natural old growth forests for several hundred years. This study identified the age of wild olive trees in the study area. The results indicated that there were more (68%) of young age class (<50 years old) of wild olive trees, whereas Baljurashi showed the highest percentage of old age class (>150 years). The majority (88.6%) of the wild olive trees were healthy, while more unhealthy trees were observed in Al-Mandaq and Al-Baha districts. As observed during the groundwork, unhealthy trees particularly due to dieback, were more discerned with juniper affecting vegetation in Al-Mandaq and South Baha, with 45% and 18% respectively. Similarly, this study recorded trace of unhealthy vegetation, with 11.4% of the wild olive trees in an unhealthy condition. This information would be essential in ‘Identifying the Landscape Preference of Wild Olive in Al-Baha Region Saudi Arabia’.