Diversity and frequency of Acacia spp. in three regions in the Kingdom of Saudi Arabia

Abstract

This study was carried out to assess the diversity and frequency of Acacia spp. and to determine the effect of soil texture on the frequency of Acacia spp. The study sites were selected after field visits to the Al Madinah, Aseer and Al Baha areas. The selection was done on the basis of the natural distribution and density of Acacia spp. Both Aseer and Al Baha are in the semiarid zone, and Al Madinah is in the arid zone according to Emberger. Measurements of trees were carried out inside 0.1 ha sample plots. Diameter frequency histograms were drawn for all locations as a measure of stand structure. There were great differences between species in relation to diameter distribution. The study shows the scarcity of large diameter trees and also in some cases, medium and small trees, which necessitated urgent intervention by transplanting and protection during regeneration periods to attain sustainability. A. ehrenbergiana and A. tortilis were the species common to all the three regions studied. A. origena, A. etbaica, A. asak and A. gerrardii were restricted to Al Baha and Aseer, possibly due to differences in climate (semi-arid) as compared to Al Madinah (arid). There were significant differences in soil texture associated with the various species, with some apparently preferring sandy soils and others clay rich soils.

Key words: Acacia, diversity, soil texture, diameter at breast height (DBH) classes.