Abstract
Assessment of population structure provides necessary information about the status and disturbance of the forest key supporting indicator for forest management and conservation interventions. In this study, current Acacia tortilis community status in Makkah Region was assessed in term of population structure and regeneration pattern. To carry out vegetation survey we selected three main areas (Al-Qunfudah, Al-Leith and East Makkah) in Makkah Region. Further, within each area the data was collected from three different sites. Population structure was analyzed and classified according to tree height and crown area size class distribution. In order to determine the potential effects of other factors in the population we evaluated status of new regeneration, stand density, tree diameter, height, crown area, canopy cover percentage, associated trees and shrubs in addition to fluctuations in Emberger Aridity Index. The results of individual trees frequency distribution based on height size classes produced a bell-shaped curve in all the three populations with the highest density in 2-4 meters class. In regards to crown area the three populations revealed a reverse J-shaped pattern with most of the individuals falling in 0-20 m2 class. In Al-Leith the combination of poor natural regeneration, low stand density, higher proportion of big trees and invading of exotic Prosopis juliflora indicating deterioration in this community. While in East Makkah the higher density of smaller trees and lowest canopy cover percentage may reflect the presence of selective cutting of big trees. Despite the good natural regeneration, nevertheless, the arid climate and very high year to year variation in dryness recorded as well as land use change may highlight the vulnerability of this species in Makkah region.