Rapid assessment on tree diversity of Nickel Mining sites in Carrascal, Surigao del Sur, Philippines

Abstract

An examination of the tree species diversity of the mined and slightly disturbed nickel mining sites of Carrascal, Surigao del Sur was carried out using quadrat and transects techniques. The general assessment of the site revealed that it falls under a mixed secondary forest type over an ultramafic soil. In spite the fertility limitations of the area substrates being ultramafic, it still have a disproportionately high number of tree species and mostly are endemic and/or rare. A total of 48 taxa belonging to 30 genera and 20 families were recorded. The dominant families were Dipterocarpaceae and Fabaceae having 6 species each, and the dominant genus was Shorea with 4 species. The area has a composite Shannon-Weiner diversity index of 2.2872 which is considered low. As an ultramafic ecosystem, 46 species (96%) of the 48 total identified species are found to be indigenous (native) to the Philippines and of which 24 (50%) are endemic or exclusively found in the country. Conservation status of these taxa according to IUCN Red List of Threatened Species and the Philippine Red List showed that about 15 endangered species was encountered. Noteworthy species include Xanthostemon verdugonianus – the iron wood of the Philippines, and some premium timber producing species under the Dipterocarpaceae family. Though mining sites are considered less productive for timber production, the conservation of this ultramafic environment is highly necessary in order to stabilize ecosystem dynamics, protect biodiversity, and prevent potential impacts of natural calamities such as landslides and flooding on lower areas.