Abstract:

To explore the regeneration dynamics of major tree species in an evergreen broad-leaved forest in Gutianshan National Nature Reserve, a 5-ha dynamic plot was established in 2002. All woody plants with DBH (diameter at breast height) ≥1 cm were tagged, mapped, measured and identified to species. Based on data from one census each in 2002 and 2007, we analyzed the characteristics of dead and recruited individuals to estimate mortality and recruitment rates, and population change for 43 tree species. The results showed the following: (1) A total of 4,758 stems were recruited and 1,384 died during the five years, and the stem increment ratio was consequently 26.05%. (2) The amounts of recruits within three growth forms (tree, subtree or shrub, and sub-shrub) all declined as DBH size class increased; a pattern different from that observed in dead individuals. (3) The average annual mortality and recruitment rate of these 43 tree species was 2.26% and 5.90%, respectively. (4) Comparing mortality and recruitment rates in each DBH class, we found that 19 subtree or shrub species consistently had higher recruitment than mortality rates in small DBH class, and almost no difference in both middle and large DBH classes. (5) 31 out of 43 species showed population growth, while 12 species’ populations declined slightly. Populations of 10 species increased or decreased at an annual rate of >5%, indicating that they were experiencing fast turnover. Among these, Chimonanthus salicifolius (45.13%) and Itea oblonga (16.35%) had the highest increment rate in population size, whereas Loropetalum chinense (-3.10%) and Quercus serrata var. brevipetiolata (-1.86%) had the highest rate of decline. In conclusion, both recruitment and mortality rates varied among species and among DBH size classes, pointing to the unique regeneration dynamics of the 43 tree species. These differences might be associated with patterns of density dependence in addition to habitat fluctuations.

Key words: forest dynamics plot, mortality rate, recruitment rate, evergreen broad-leaved forest, Gutianshan National Nature Reserve