Assessment of woody species diversity and carbon sink functions in tropical wildlife parks

Abstract:

Tropical wildlife parks across the Asia-Pacific region serve as critical refugia for woody plant diversity and provide essential carbon sink functions, yet integrated assessments of species diversity and carbon dynamics within these protected landscapes remain insuficient for evidence-based management. This research assessed woody species diversity and evaluated carbon sink functions within a tropical wildlife park in Laguna Province, Philippines. Twenty sampling plots of 20 m × 20 m were systematically established across an elevational gradient from 150 to 800 m above sea level between February and November 2023. All woody species with diameter at breast height exceeding 10 cm were enumerated and measured. Aboveground biomass was estimated using validated allometric equations for Philippine dipterocarp and non-dipterocarp species. A total of 1,078 woody individuals representing 55 species across 25 families were recorded. Moraceae and Dipterocarpaceae co-dominated with six species each. Shannon-Wiener diversity ranged from 2.55 at the highest elevations to 3.48 in midelevation forests. Radar chart analysis of ecosystem service provision revealed that the park scored highest for carbon storage capacity and biodiversity value. Mean above-ground carbon stock was 78.5 Mg C per hectare across the park, with mid-elevation forests exhibiting the highest density at 112.8 Mg C per hectare. Scater plot analysis revealed a negative relationship between elevation and Shannon diversity. Annual carbon increment analysis showed peak sequestration in stands aged 15 to 20 years. Box plot analysis of carbon distribution by size class confirmed the disproportionate contribution of large-diameter individuals. These findings establish that tropical wildlife parks in the Philippines function as significant carbon sinks whose capacity is mediated by elevation, stand age, and species diversity.