This study was conducted at Pulau Jerejak, Penang to determine the floristic variation of its tree
communities. A 0.5-hectare study plot was established and divided into 11 subplots. A total of 587 trees
with diameter at breast height (DBH) of 5 cm and above were measured, identified and recorded. The tree
communities comprised of 84 species, 63 genera and 32 families. The Myrtaceae was the most speciose
family with 10 recorded species while Syzgium glaucum (Myrtaceae) was the most frequent species. The
Myrtaceae recorded the highest density of 306 individuals while Syzgium glaucum (Myrtaceae) had the
highest species density of 182 individuals. Total tree basal area (BA) was 21.47 m2
/ha and family with the
highest BA was Myrtaceae with 5.81 m2
/ha while at species level, Syzgium glaucum (Myrtaceae) was the
species with the highest total BA in the plot with value of 4.95 m2
/ha. The Shannon˗Weiner Diversity
Index of tree communities showed a value of 3.60 (H'max = 4.43) and Evenness Index of 0.81 which
indicates high uniformity of tree species. The Margalef Richness Index (R') revealed that the tree species
richness was 13.02. Myrtaceae had the highest Importance Value of 20.4%. The Canonical
Correspondence Analysis (CCA) showed that Diospyros buxifolia (Ebenaceae) and Pouteria malaccensis
(Sapotaceae) were strongly correlated to low pH. Dysoxylum cauliflorum (Meliaceae) and Eriobotrya
bengalensis (Rosaceae) were correlated to phosphorus (P) and calcium ion (Ca2+), respectively.
Therefore, the trees species composition at Pulau Jerejak showed that the biodiversity is high and
conservation action should be implemented to protect endangered tree species.