INVASIVE BEHAVIOUR OF Myroxylon balsamum AT UDAWATTAKELE FOREST RESERVE

H.P. Wedathanthri and H.M.G.S.B. Hitinayake

Department of Crop Science, Faculty of Agriculture,
University of Peradeniya.

Udawattakele forest is a national heritage of Sri Lanka which has rich flora and fauna. There are about 460 plant species including 135 tree species and 11 liana species, of which 9 species are endemic to Sri Lanka. When considering floristic composition of Udawattakele it is dominated by Swietenia macrophylla (mahogany), Michelia champaca (gini-sapu), Mesua ferrea (na) and Myroxylon balsamum (katta kumanchal). Senadhera (1997) has reported that Myroxylon balsamum has become invasive in some parts of the forest. The objectives of this investigation was to estimate the invasive behaviour of Myroxylon balsamum at Udawattakele forest reserve.

Plots of 10 m x 15 m were used for sampling of overstory vegetation and 10 m x 10 m plots were used for understory. Plots were located randomly in Myroxylon balsamum dominant regions in the forest and measurements taken were number of individuals and their species, tree height (m), stem diameter (m) at breast height (1.3 m above ground level) and crown diameter (m) in order to evaluate species diversity and dominance. Germination of Myroxylon balsamum seeds were evaluated under four different light levels (full sunlight, 70% and 35% light and complete dark conditions). A map was prepared to show the distribution and density of Myroxylon at various parts of Udawattakele forest reserve.

Results showed that Myroxylon has dominated the understory even when a few mother plants were available in the overstory. This could be attributed to prolific seed production capacity, its ability to germinate under wide range of light conditions, favourable micro-climatic conditions presenting in the understory and absence of any seed pest or pathogen. Further results clearly showed that Myroxylon invasion had resulted in the decline of species diversity of the forest.
If no control measures are applied, there is a possibility that this species could invade the other parts of the forest in the long term. Therefore necessary action must be taken immediately to control Myroxylon balsamum. This could be done by uprooting seedlings, collecting and destroying seeds and thinning some mother trees. Further understanding of the efficiency of key physiological processes of Myroxylon including water use efficiency and stomatal conductance could be useful in deciding measures to control the invasion.

Further examinations of the dynamics of the Myroxylon seedling bank and competition taking place at some parts of the forest between mahogany, Myroxylon and na for the dominance could be useful in the management and maintenance of the species diversity of Udawattakele forest reserve.

Department of Forestry and Environmental Science,
University of Sri Jayewardenepura,Sri Lanka. 1995-2000. All rights reserved.