Intensities of human disturbance dictate the floral diversity in tropical forest: the case of a secondary forest in Benguet, Philippines

This study inventoried the floral diversity of a secondary forest in Tuba, Benguet, Philippines as affected by different intensities of human disturbance. This study is unique from other land use studies in Southeast Asia in having conventional farms as the most disturbed land use while other sites have oil palm plantations. A total of 267 species belonging to 222 genera and 78 families was documented. Results showed that the level of human disturbance is the major factor affecting the floral diversity while the effect of elevation is secondary. The level of human disturbance is significantly associated with species richness, species composition, dominant species and biodiversity indices. Greater human disturbance, as in the case of conventional farms, results in lower species richness, predominantly weed composition, dominant weed species and lower biodiversity indices. On the other hand, lesser human disturbance (as in the case of secondary forest) leads to higher species richness, greater native species composition, dominance of indigenous species, and higher diversity indices. The most disturbed land use experienced the greatest loss of species richness, change in floristic composition and vegetation structure, as well as a shift from native to alien-dominated plant communities. These results showed that the effect of land use change is not limited to species richness but also to species composition, dominant species and biodiversity indices. Locally, the study is an important baseline data for biodiversity conservation of the Marcos Highway Watershed Forest Reserve.