Tree ring analysis for growth pattern and age structure of the subtrophic broad-leaved forest in Taiwan

In this study, age structure, dynamics and growth pattern of subtropical forest located in central Taiwan were analyzed. The existence of annual rings in the wood of trees was proven by cross-dating and tree ring analysis. 218 individuals which belong to 27 species were investigated in the 0.71 ha plot of Shenmu evergreen broad-leaved forest. It indicates that the age of the trees correlates not strongly with the diameter and the height, while the mean diameter growth rates vary between 0.48 cm per year in understory tree species and 0.76 cm per year in emergent species. Compared with the main canopy tree species in Costa Rica's tropical forest, the mean annual diameter growth rate 0.66 cm is greater than that of 0.42 cm. Stand dynamic of DBH and age structure fitted by Weibull function indicate that they are in medium status of forest regeneration, but the age's shape parameter r=1.2 is much close to 1 which stands for the limit boundary of very good regeneration status. The mean age for all individuals is 61 years. According to the age, height distribution and growth rate of the trees, we classify four major types of life strategies and the growth pattern of specie cohorts. These findings lead to the assumption that the investigated stand can be classified as a very late secondary stand in transition to a mature forest. The results also reveal that it is a valuable tool for estimations of growth rate and pattern by using tree ring analysis in subtropical evergreen forest ecology.