Demography of the threatened endemic shrub, Arbutus pavarii, in the Al-Akhdar mountainous landscape of Libya

Abstract

We sampled twenty populations of the vulnerable endemic shrub or tree, Arbutus pavarii Pampan., at different elevations and aspects within the Al-Akhdar mountainous region of Libya. Our sampling sites were at elevations ranging from 285 to 738 m above sea level, and several different habitats: vallies (locally known as wadis), north- and south-facing slopes, and mountaintops. All individuals within each quadrat were studied. Population size and structure, and plant functional traits were assessed. None of the populations had a stable distribution of size classes. Some consisted mostly of small plants, with little or no fruit production; others consisted only of mid-sized and large plants, with high fruit production, but no juvenile recruitment. There was a significant increase in percent cover with increasing elevation; reproductive output (the number of fruits per branch and total number of fruits per individual) also generally increased with elevation. In some of these populations the lack of recruitment, and in others the failure to produce fruit, together constituted serious demographic threats. In light of these results, recommendations are made for conservation of this vulnerable endemic species.