Species-habitat associations of tree species under the northeast monsoon wind-affected tropical forest at Lanjenchi Forest Dynamics Plot, Taiwan

Species-habitat associations of tree species under the northeast monsoon wind-affected tropical forest at Lanjenchi Forest Dynamics Plot, Taiwan

The spatial distribution of tree species in the forest is key to understanding species coexistence concerning their realized niche. Previous research has shown that forest community composition differs in Lanjenchi Forest Dynamics Plot (FDP) and is likely to be caused by the strength of the northeast monsoon wind. However, relationships between species and other environmental factors are not completely understood. We investigated tree species-habitat associations in Lanjenchi asking how topographic habitat affects forest structure and composition, and we classified the plot into topographic habitat using Multivariate Regression Trees based on the forest community composition and topography. Then, based on metrics of forest structure, we used the torus translation test to evaluate the degree of tree species-habitat association. Three habitats were identified in Lanjenchi and can be classified into windward, intermediate, and leeward habitats based on wind exposure value and aspect. Moreover, 81% of species had a strong positive association with one of the three habitats. Based on the strength of habitat association, the tree species can be divided into six categories. Among these categories, windward species are most abundant in Lanjenchi but are some of the rarest species in Taiwan. These results indicated that the northeast monsoon wind is an essential factor that shapes species distribution in the Lanjenchi, especially at the windward habitats. The northeast monsoon wind creates a unique niche allowing many regionally rare species to dominate these habitats in tropical Taiwan.