Demography of Pometia pinnata and Canarium indicum in tropical rain forest – impacts of anthropogenic disturbance from subsistence agriculture
The long-term effects of subsistence (shifting) agriculture on the composition and structure of tropical forest communities has been extensively studied. However, its impacts on the demography of individual tree species are less well documented. This study examined two tropical forest species that are commonly used as resources on Lihir Island, Papua New Guinea. The demographies of Pometia pinnata and Canarium indicum are described from a study encompassing 4.5 ha and 3.75 ha respectively in tropical lowland rain forest on Lihir over a two year period. Study sites were assessed as experiencing high or low disturbance levels based on the current land practice of Lihirians. Sample populations of each tree species were enumerated and classified by size for height (seedlings < 1.0 m, saplings < 5.0 m) and diameter (juveniles < 15 cm, subcanopy < 30 cm, canopy > 30 cm) and remeasured after one year. In sites of low disturbance, P. pinnata seedlings, saplings and juveniles grew at a significantly lower rate than those in high disturbance sites. Canarium indicum subcanopy trees also exhibited significantly higher growth rates in high disturbance sites. The finite rate of increase for P. pinnata indicated a positive response to high disturbance levels, however, other parameters contradict this result. Population growth rate of C. indicum suggests a higher rate of growth in less disturbed areas, consistent with results for other parameters.