Composition and Structure of Aleppo Pine (Pinus halepensis) Communities in the Dibeen Forest Reserve, Jordan

The amount of forest cover in Jordan is estimated at about one percent of the country's land area. Land-use pressures and altered disturbance regimes have generated concern for the conservation of forests. In this context, Aleppo pine (Pinus halepensis Mill.) is a valuable forest type diminished from its historic extent. Accordingly, to gather information for conservation planning, we used systematic vegetation sampling to evaluate the composition and structure of Aleppo pine communities at the Dibeen Forest Reserve in Jordan. Permanent plot centers were established on a 200-m grid, and 72 of the grid points were selected randomly for an initial sampling of the reserve. An inventory of all live and dead trees was taken on circular plots. Due to their conservation value and growing pattern, the plot size for live Aleppo pine was enlarged to capture additional diameter samples. Relative species abundance, as determined by basal area estimates, ranged from < 1 m²/ha for five of seven tree species captured in our inventory and up to 4.6 m²/ha for P. halepensis. The majority of basal area (41.2%) occurred in diameter classes between 5 and 20 cm. Not counting recruitment trees under 5 cm in diameter, tree density ranged from 0.7 trees per hectare (TPH) for Azarole hawthorn (Crataegus azawlus L. Azarole.) to 504.5 TPH for Palestine oak (Quercus coccifera ssp. calliprinos Holmboe (syn. Quercus calliprinos Webb)). Given the importance of P. halepensis in determining the structure of Dibeen communities, basal area values were further stratified by diameter for the species, over 70% of which were concentrated in diameter classes between 20 and 55 cm. To assess succession and recruitment patterns in the pine, stem density was also stratified by diameter class and ranged from 68.9 TPH in the smallest class to 0.1 in the largest measured class, 140+ cm. The distribution of stem densities among diameter cohorts implies a selfsustaining population of P. halepensis at the reserve. Low recruitment of other seral species suggests a need to further monitor tree recruitment and consider conservation strategies.