Mortality of woody plants in tropical monsoon rainforests of Bawangling National Nature Reserve on Hainan Island, South China
海南岛霸王岭热带季雨林树木的死亡率

Aims We examined the mortality of woody plants in different functional groups, different diameter classes and different site conditions to understand the status and variation of woody plant mortality in the tropical monsoon rainforest (TMRF) communities on Hainan Island. Methods We established 15 plots (50 m × 50 m) in old-growth TMRF in Bawangling Nature Reserve of Hainan Island. Each plot was divided into 10 m × 10 m subplots to measure the height, diameter at breast height (DBH) of individuals with DBH ≥ 1.0 cm and live or dead status by species. Site conditions, such as slope gradient, slope aspect, slope position and distance to the rivers were recorded. We categorized woody plants into different functional groups, and stems into different diameter classes. Important findings Overall mortality rate of woody plants ranged from 3.42% to 18.71% (mean of 7.60%). The mortality rate was higher for trees than shrubs, for deciduous species than evergreen species and for unarmed species than spinescent species. The mortality rate of the TMRF community was > 10% for 5–30 cm DBH and was highest for 5–10 cm DBH. Within the 1–5 cm same diameter class, mortality of deciduous species was higher than evergreen species, and no significant differences were found in other diameter classes. No significant difference was found between mortality of spinescent and unarmed species in any diameter class. Tree mortality rate and distance to the rivers were directly correlated. Mortalities of deciduous species and unarmed species were correlated with slope position, with the mortality rates on upper slope position higher than at mid-slope position. The closest relationships were between mortality rate and community habitats, and drought was one of important causes of mortality.