Structure and Composition of Ankarafa Forest, Sahamalaza-Iles Radama National Park, Madagascar: Implications for the Frugivorous Endemic Blue-Eyed Black Lemur (Eulemur flavifrons)

Abstract

The composition, structure and distribution of forest trees in Ankarafa Forest in the Sahamalaza-Iles Radama National Park, Madagascar, were evaluated to determine the influence of their fruiting on the seasonal feeding/foraging ecology of the mainly frugivorous, endemic blue-eyed black lemur (Eulemur flavifrons). Plots were sampled within the forest core and on the forest edges. A total of 848 live trees belonging to 42 species, 39 genera and 28 families were recorded. Ankarafa Forest is dominated by Mangifera indica (an exotic), Garcinia pauciflora, Sorindeia madagascariensis, Grangeria porosa, bamboo spp. and Mascarenhasia arborescens. More than 20% of the stems counted were exotic, long-lived species which has a negative consequence for future forest dynamics. In particular the predominance of the exotic M. indica has negative implications for fruit availability at the end of the dry season and during the wet season. Canopy height was lower than most tropical forests but similar to other Malagasy forests with an average tree height of 10 ± 3.6 m and a mean diameter at breast height of 13.8 ± 11.7 cm. Height and diameter of trees differed significantly between the edge and core of the forest. However, most trees were between 5 and 15 m high, and most of smaller diameter, both at the edge and core, suggesting it is a complex system. Along the forest edge, many trees were burnt by uncontrolled fire. Trees felled by cyclones were recorded both on the edge and in the core of the forest. Fruit availability was similar throughout the forest on a spatial scale, but differed temporally. Being relatively high in tree species diversity, Ankarafa Forest needs to be protected to continue to support its endemic fauna, particularly those with restricted distribution such as the blue-eyed black lemur. In particular, further forest degradation and fragmentation needs to be avoided.