Aims A major challenge in studies of tropical forest successional dynamics is to reveal the relative importance of deterministic versus stochastic processes affecting species composition, spatial distributions and their rates of change. Here, we tested succession trajectory of tropical secondary forests follow equilibrium or non-equilibrium dynamics by evaluating community reassembly for tropical lowland rainforest recovery on the abandoned shifting cultivation lands on Hainan Island of south China. Methods We explored species composition and dominance of different size classes (seedlings, saplings and adult trees) of communities along a chronosequence of secondary forest plots ranging from 15 to 60 years since abandonment after shifting cultivation. We included two old-growth forest plots for comparison. Important findings Both species diversity for the three size classes and the species similarity index among size classes in old-growth forests were significantly higher than in secondary forests. However, the proportion of dominant species in old-growth community was lower than that of secondary forests. Species similarity between secondary forests and old-growth forests increased with forest recovery, supporting the view of equilibrium succession dynamics. In each recovery stage, the number of individuals, species richness and abundance-based coverage estimator of seedlings were lower than those of both saplings and adult trees. Moreover, the species composition of seedlings in secondary forests differed significantly from that of both saplings and adult trees, suggesting that seedling recruitment might be an unpredictable process. Our results highlighted that the community assembly processes during secondary forest recovery are driven simultaneously by stochastic and deterministic processes.

In this study,we examined the ecological effect of palms on tree seedlings regeneration in a tropical lowland rain forest plot in Bawangling,Hainan Island. The results showed that there were 1 288 palm plants which belonged to 5 species in a 1 hm2 plot,and Calamus faberii contributes 82.7% to the total palm plants. The mean individual crown area differed among 5 species and Livistona saribus was significantly larger than other 4 species. The palm number in each subplot showed a normal distribution. The palms abundance of the subplot was significantly negative correlated with the number of trees DBH<10 cm,but not with that of the large trees. The species richness of large seedlings,saplings,and small trees significantly decreased with increase of the palm abundance in each subplot,but no relationship was found between the richness of small seedlings and large trees with the palm abundance. The palm coverage reduced the seedlings density and there were only 18% seedlings recruited under the palms. Compared to the micro-sites with no palms cover,more small seedlings under palms recruited than large seedlings did. There were respectively 53% and 97% of species recruited in the micro-site with and without palms coverage. The short-lived pioneer species distributed exclusively in sites without palms cover. There was 11.6% and 19.8% of long-lived pioneer species seedlings and late species seedlings regenerated under palms cover,respectively.

2008年5月,8月与2009年1月分别对海南岛霸王岭国家级自然保护区卷萼兜兰的生境进行了调查研究.结果显示:卷萼兜兰自然分布区植物群落丰富,群落科,属组成成分较为分散和多样;分布在海拔1000～1260m范围,在林下植被密度中等且坡度较缓处较为密集;卷萼兜兰为浅根性植物,生长在富含腐殖质的腐叶土层上的卷萼兜兰生长旺矗,有较强的无性繁殖能力,但其致危机制还需要进一步研究.