Abstract:

Caryota obtusa forests are characterized as showy vegetation with rich species diversity and a unique habitat in the Honghe region of China. Due to its food and horticulture value, mature Caryota obtusa individuals have become more rare in the field. Here, we sampled six plots in a deep karst valley of the Honghe region of Yunnan, China. In each 20 m × 20 m plot, our examination focused on species composition of trees via the measure of any trees with DBH ≥ 4 cm. Importance values were produced from datasets of their relative abundance (RA), relative frequency (RF), and relative prominence (RP). On one hand, we analyzed the composition and geographical affinity of the tree species in Caryota obtusa forests based on the two patterns of geographic distributions (areal-type and natural geographic unit), respectively. On the other hand, we selected the top 5 dominant tree species based on importance value and illustrated their distributions to confirm the position of sampled vegetation in the background of the entire distribution of the target species. The above survey and analysis revealed that there were 67 tree species contained in the sampled vegetation, which was a Caryota obtusa + Streblus macrophyllus community and the geographic affinity of the vegetation belonged to the geographic unit of IndoChina Peninsula with some strong karst background. Our study implies that the vegetation sampled here reached its northernmost distribution and deserves to be prioritized in conservation as it is a biodiversity hotspot in IndoChina Peninsula.

Key words: northernmost tropic, karst valley, palm, relic habitat, tropic vegetation