Tree Population Mortality, Recruitment and Growth During a 15-Year Period of Secondary Succession in Tropical Montane Rainforests at Jianfengling, Hainan Island, China
Abstract:Trees greater than 7.0 cm DBH were censused from 1984 to 1999 in two permanent plots in secondary-growth tropical montane rainforests to determine tree mortality, recruitment, and basal area growth. The two plots are regrowth from large-(Plot 8401) and small-scale cuts (Plot 8402). The 248 trees tagged in 1984 were grouped into two species types: common (≥5 trees/0.2 hm2) and uncommon, and were sorted according to DBH into three size groups: small, medium and large. Plot 8401, which suffered greater damage from typhoons and disturbance from human activities, showed higher species diversity than did Plot 8402. Tree density decreased by 0.3 % per year in Plot 8401, but increased by 0.9% in Plot 8402. The common species contributed to 10.7% and 10. 6% of recruitment, but accounted for 82.4% and 90.0% of mortality in Plot 8401 and Plot 8402, respectively. Tree mortality tended to decrease with tree size. Mortality of large trees (≥17.7 cm DBH) was significantly lower than for the all other trees. When different census periods were considered, there was a positive and significant relationship between the number of trees recruited and the number of trees that died, suggesting that tree recruitment was more frequent at times of greater tree mortality. Growth in total basal area was mainly affected by mortality of the common species and the rate of replacement that took place in the plots. The annual growth rate of total basal area was higher in Plot 8402 than in Plot 8401. We conclude that tree mortality, recruitment, and growth appeared to be dependent on the species type as defined. Population studies confined only to trees of dominant or pioneer species would probably fail to detect some important successional effects, such as we found in this study.