Abstract: [Objective]Lianas are important components of tropical seasonal rainforest. Theobjective of this study are to investigate the liana diversity, to elucidate the climbing situation of lianas on co-occurring trees, and to better understand how lianas influence the regeneration, dynamics, and carbon sequestration of tropical seasonal rainforest in Xishuangbanna, Yunnan Province.[Method]Following the liana census protocol applied in Panamanian rainforest, we surveyed and identified all rooted lianas with diameter at breast height (DBH) ≥ 1 cm in 500 quadrats (20 m×20 m) in a 20 hm² tropical rainforest dynamics big plot which was established in 2007. We analyzed the liana spatial distribution, diversity, abundance, size, climbing mechanisms and situations on co-occurring trees.[Result]In the 20 hm² plot, 21 781 rooted liana individuals were recorded, with density of 1 089.1 individuals·hm^-2. 20 611 individuals from 127 species in 45 families were identified. The two most abundant families were Fabaceae and Vitaceae, accounting for 51.1% of and 24.4% of liana species, respectively. The most abundant lianas were Parameria laevigata (Apocynaceae) with 2 382 individuals in the plot, constituting 10.9% of all liana individuals. Byttneria integrifolia (Sterculiaceae) and Fissistigma polyanthum (Annonaceae) accounted for 10.3% and 4.6%. The top three liana species with the highest important values were Byttneria integrifolia, Parameria laevigata and Combretum latifolium (Combretaceae). Forty-three rare species with density ≤ 1 individual·hm^-2 were recorded, accounting for 33.6% of the total number of liana species, but only 1.4% of the liana individuals in the plot. Lianas with 1-5 cm DBH were dominant, constituting 86.6% of all liana individual, whereas lianas with DBH ≥ 10 cm only accounted for 0.7%. 58.0% of liana species employed stem twining to climb the forest canopy, followed by leaf-tendril climbers, sprawlers, and hook climbers, with each accounting for 1.0% of liana species. About 10.7% of the all co-occurring tree individuals (DBH ≥ 1 cm) were climbed by lianas, with 68.2% of the tree species being climbed. With an increase in tree size, the numbers of lianas climbing trees decreased, but the percentage of trees climbed by lianas was increased.[Conclusion]Lianas are abundant in Xishuangbanna tropical seasonal rainforest. The pioneer lianas, such as Pueraria montana (a legume liana), occur in the permanent plot, indicating that this plot was probably intensely disturbed in history. Disturbance, along with the distinct rainfall seasonality, could be the major factors shaping abundant lianas in Xishuangbanna tropical seasonal rainforest.

Key words: diversity, lianas, climber mechanisms, Xishuangbanna, 20 hm² tropical seasonal rainforest dynamics big plot