Plant Species Diversity in Tropical Planted Forests and Implication ...

K. Kamo et al.Fig. 2. Species richness of understorey plants in the study plotsOwing to differences in plot sizes, the numbers of plant species in the plots except for A. auriculiformis and E.camaldulensis were adjusted with a species-area curve for each plot to the plot size of planted forests (575 m 2 ) .that in the I. cylindrica grassland, or 26 to 48% of that inthe natural forest.No seedlings of the plantation species had becomeestablished in the planted forests, except for Leucaenaleucocephala.Similarity indexesSimilarity indexes (Nomura-Simpson’s coefficient 14 )for all the understorey vascular plant species between thenatural forest, the planted forests and the 2 grasslands areshown in Table 2. The degree of similarity was notappreciably high between the plots. The degree of similaritywas also not very high among the tree species (Fig.3).The mean similarity index of the understorey treespecies was calculated for all the tree species found in theplanted forests, and large tree species (DBH ≥ 10 cm) andsmall tree species (DBH < 10 cm) in the sample plot ofthe natural forest (Fig. 3). The similarity index for largetree species in the natural forest was significantly higherFig. 3. Mean similarity index between the planted forestsfor understorey tree speciesTable 2. Similarity index between the study plots for all the plant speciesSite Aa Am Ec Dc Xk Pm Ic SsAm 0.54Ec 0.58 0.41Dc 0.44 0.58 0.48Xk 0.55 0.49 0.44 0.59Pm 0.46 0.51 0.45 0.57 0.52Ic 0.71 0.54 0.63 0.67 0.58 0.50Ss 0.53 0.56 0.35 0.65 0.53 0.47 0.38DEF 0.42 0.45 0.42 0.57 0.50 0.46 0.54 0.56Aa: A. auriculiformis stand, Am: A. mangium stand, Ec: E. camaldulensis stand, Dc: D. cochinchinensis stand, Xk: X. kerrii stand,Pm: P. macrocarpus stand, Ic: I. cylindrica grassland, Ss: S. spontaneum grassland, DEF: dry evergreen forest.114 JARQ 36 (2) 2002