Global temperature is keeping increasing because of human activities. In the meantime, many studies suggest that species shift upward in migration and these patterns are not only in temperate area but also in tropical area. How about the forest in the border zone which is between tropical and subtropical area? The Nanjenshan ecology conservation area is in Kenting National Park, southern Taiwan, and the Nanjenshan transect was established in 1995 which elevation ranges from 200 to 476 meter with 500 meter in length and 20 to 40 meter in width. It is often visited by typhoons in summer and affected by northeast monsoon wind in winter. There were 72 quadrats (10 x 10 m2) of woody trees and 90 subquadrats (1 x 2 m2) of woody seedlings in 1995. All the woody plants (DBH ≥ 1 cm) and seedlings (DBH < 1 cm) have been tagged, identified and measured. The woody plants have been recensused in 2013 and so did seedling in 2015. We analyzed the data of woody plant species and seedlings for their distribution change.
Results/Conclusions
During the two census year, individuals in woody plant increased by 19.6%, but the seedling decreased by 35.1%. The results in species migration that the woody plant were overall downward migration (0.48 m yr-1). Almost half species did not change significantly and some species (22.3%) were upward migration (0.49 m yr-1). The others were downward migrated average 1.24 meter every year. On the contrary, the seedling overall migrated to higher elevation (0.58 yr-1). A total of 35% species were upward migration and 30% species were downward migration. The others 35% species stayed at the same elevation range. The rate of species migration in Nanjenshan transect were slower than global researches probably because of the high beta diversity or the northeast monsoon wind which cause species can not migrate to higher elevation easily. We also propose that one of the downward reasons may be the gaps which happened in lower elevation so that the intolerant tree could grow up quickly. In summary, the species migration is not significant in Nanjenshan transect due to the special environment which affected by the long-term northeast monsoon wind, but now it is steady declining. How will the species distribution change in the future? We need to keep monitoring the woody plant and seedling in Nanjenshan transect and maybe we can find out the answers.