Forest biomass and biomass dynamics were used in this study of forest structure and environmental assessment as one of the most important criteria in order to understand forest ecosystem status and forest equilibrium. This research approach evaluated the effects of topographic indices consisting of elevation, slope aspect, slope inclination and index of convexity (IC) on the live-tree, aboveground biomass (AGB), biomass dynamics and species diversity of 5-year, inter-census intervals in a lower montane forest of a 15 ha forest dynamics plot at Doi Inthanon. Spatial variation of biomass dynamics was drawn up using 20 x 20 m subplots (n=375) and then estimating the biomass and biomass dynamics consisting of the AGB increment, AGB of ingrowth, AGB loss and AGB change of each subplot. Differences in biomass, biomass dynamics and species diversity among topography classes were analyzed using ANOVA. The results of this research revealed that elevation had a significant effect on the mean AGB, mean AGB of recruitment rate and mean AGB of increment rate. Slope aspect had a significant effect on the mean AGB recruitment rate and mean AGB loss rate. Slope inclination only had a significant effect on the AGB recruitment rate while IC had a significant effect on the mean AGB recruitment rate and mean AGB of increment rate. Changes in the species diversity index were significantly different based on topographic variables except for the slope aspect. The results suggested that the evaluation of forest biomass, biomass dynamics and changes in species diversity of the tropical lower montane forest should be based on data from various topographic sites. The relationship between the mean AGB, biomass dynamics, species diversity and topography may be mediated by differences in the stand turnover rates, which must be related to topography.
Keywords: forest biomass, forest dynamic, tropical lower montane forest, topography index, species diversity