INFLUENCE OF <em>ALSTONIA</em> <em>MACROPHYLLA</em> SPREAD ON THE RESTORATION SUCCESS OF PINE CONVERSION PROGRAMS IN SRI LANKA

Abstract

Establishment of exotic invasive species causes many negative implications in restoration programmes such as out competing native species, thereby altering the structure, composition and function of the target ecosystem. Although Alstonia macrophylla is an exotic invasive tree species in Sri Lanka, its impact on native flora is undermined due to its timber value. The influence of A. macrophylla on the composition and dynamics of new recruits in an eleven-year-old restoring pine plantation (RP) was investigated and compared to a
25–30-year-old unrestored Pine plantation (UP) in Hantana, Sri Lanka. In both stands, the dominant species and the highest densities in all life stages (seedlings, saplings and trees) of the woody plants were represented by A. macrophylla. This species survived better than the non-Alstonia species in RP, than in UP, and was well represented in all diameter at breast height (dbh) classes in RP. The negative correlation between rainfall and mortality of Alstonia and non-Alstonia was stronger in UP than that in RP. The study concludes that considering life history strategies and invasive behavior of A. macrophylla in pine conversion programmes, they must be managed at different time scales (short, mid and long term) using silvicultural techniques to achieve restoration goals in the mountainous regions of Sri Lanka.