INVASIVE BEHAVIOUR OF Myroxylon balsamum AT UDAWATTAKELE FOREST RESERVE

Abstract

Udawattakele forest is a national heritage of Sri Lanka which has rich flora and fauna. Thereare about 460 plant species including 135 tree species and 11 liana species. of which 9species are endemic to Sri Lanka. When considering floristic composition of Udawattakclcit is dominated hy Swictenia macrophvlla (mahogany), Michelin c/WIIIP({('{{ (gini-sapu),Mesua [errea (na) and Mvroxvlon balsamum (kana kumanchal). Senadheru (1997) hasreported that Myroxylon balsanium has become invasive in some parts of the forest. Theobjectives of this investigation was to estimate the invasive behaviour of Mvroxvlonbulsanium at Udawattake!c forest reserve.

Plots of 10 m x 15 m were used for sampling of ovcrsrory vegetation and 10 rn x 10 III plotswere used for understory. Plots were located randomly in Mvroxvlon balsatuum dominantregions in the forest and measurements taken were number of individuals and their species.tree height (rn), stem diameter (m) at breast height (1.3 m above ground level) and crowndiameter (rn) in order to evaluate species diversity and dominance. Germination ofMvroxvlon balsaniuni seeds were evaluated under four different light levels (full sunlight.7()'1r and 35% light and complete dark conditions). A map was prepared to show thedistribution and density of Mvroxylon at various parts of Udawattakele forest reserve.

Results showed that Mvroxvlon has dominated the understory even when a [cw mol herplants were available in the overstory. This could he attributed to prolific seed productioncapacity. its ability 10 germinate under wide range of light conditions. favourable microclimaticconditions presenting in the understory and absence or any seed pest or pathogen.Further results clearly showed that Mvroxvlon invasion had resulted in the decline of speciesdiversity of the forest.

If no control measures are applied. there is a possibility that this species could invade theother parts or the forest in the long term. Therefore necessary action must be takenimmediately to control Mvroxvlon balsamum. This could he done by uprooting seedlings.collecting and destroying seeds and thinning some mother trees. Further understanding ofthe efficiency of key physiological processes of Mvroxvlon including water use efficiencyand stomatal conductance could he useful in deciding measures to control the invasion.Further examinations of the dynamics of the Mvroxylon seedling bank and competitiontaking place at some parts of the forest between mahogany. Mvroxvlon and na for thedominance could be useful in the management and maintenance of the species diversity ofUdawauakclc forest reserve