Wednesday, August 5, 2009: 10:10 AM
Dona Ana, Albuquerque Convention Center
Ifang Sun, Department of Life Science, Tunghai University, Taichung, Taiwan, Yuyun Chen, National Center for Theoretical Sciences, Mathematics division, Tsinghua University, Hsinchu, Taiwan and Chang-Fu Hsieh, Institute of Ecology and Evolutionary Biology, National Taiwan University, Taipei, Taiwan
Background/Question/Methods We report dynamic data on the mortality and recruitment pattern over a 15-year interval in a
3 ha forest dynamics plot in Nanjenshan forest in southern
Taiwan. This subtropical monsoon forest located at the southern end of
Taiwan in which a wind-stress gradient (directional exposure to wind) generates and interacts with gradient of light, moisture and soil nutrients to produce a mosaic forest sharply differentiated on windward vs. leeward slopes separated by very short distance.
In 1990, a 3.0 ha plot measuring 100 x 300 m was established, all woody plants with a stem diameter of >
1 cm dbh were tagged, measured, mapped, and identified to species. The recensus was completed in 1998 and 2005, respectively. Results/Conclusions The number of species increased from 118 species in 1990 to 123 species in 2005, however, total abundance decreased during this 15 years interval, from 36570 in 1990 to 32800 in 2005. Annual mortality increased from 1.11 % in first recensus to 1.57 % in second recensus. Annual mortality varied greatly between species as well as between censuses, from the lowest of 0 % to over 42 %. However, annual mortality increased in the second recensus for most species. Among habitats, trees that occurred in creek habitat showed the highest annual mortality (3.19%), followed by leeward habitat (2.89%), intermediate habitat (2.54%) and windward habitat (2.47%). The number of new recruit varied significantly between species as well as between habitats. There is no significant relationship between species abundance and number of new recruit. In addition, when an adult tree died, the probability of conspecific new recruit occurred within 5 m radius was low for all species, and species with zero probability of replace themselves increased from 41.5% in the first recensus to 86.1% in the second recensus. The high species turnover rate, high mortality and recruitment rate suggest that Nanjenshan forest is still subject to dramatic fluctuation, showing little sign of equilibrium.
