Growth pattern and leaf morphology of Shorea parvistipulata saplings in a tropical rain forest of Sarawak, Malaysia.

摘要

This study was conducted to evaluate the morphological plasticity of Shorea parvistipulata saplings growing under different levels of canopy openness in the Kubah National Park, Sarawak, Malaysia. All saplings of S. parvistipulata were investigated in March 1998 and March 1999. There were 80 saplings in the study plot in March 1998. The canopy openness above surviving saplings (n=64) was significantly greater than the average condition on the forest floor. The canopy openness did not differ between unbranched and branched saplings. The height of the saplings that died during the study period was not significantly different from that of unbranched that survived. Light availability had a positive effect on the survival of the saplings, though sampling size did not. Sampling size had a positive effect on branching of saplings, though light availability did not. Although leaf morphology did not change with light condition, saplings showed changes in morphological traits that could reduce self-shading corresponding to the crown form. The net increase in leaf number of branched saplings resulted from large leaf production rate and relatively small leaf loss rate. The height growth rate of unbranched saplings increased with canopy openness. In contrast, branched saplings showed no relationship between height growth rate and either canopy openness or height. Unbranched saplings grew rapidly in height and produced many leaves in the sites with greater light. Results suggest that S. parvistipulata saplings shifted the morphological strategy in light resource use with the change in leaf display from light-dependent vertical elongation whilst unbranched to site-dependent horizontal expansion once branched..