Assessing tree diversity and carbon density of a riparian zone within a protected area in southern Philippines.
Riparian zones are a small portion of a watershed but hold a diverse and important ecosystem functioning. We assessed diversity and carbon density of pole (5-10 cm DBH) and canopy (>10 cm DBH) trees along a riparian zone in Pasonanca Natural Park, southern Philippines. We identified 66 species, which included 41 canopy and 54 pole tree species, and comprised 46 indigenous, 18 Philippine endemics, and two exotic species. We recorded eight vulnerable (VU) and two endangered (EN) species under the Philippine Red List, whereas five VU, three EN, and six critically endangered (CR) species were recorded under the IUCN Global Red List. We estimated the Hill number of canopy trees at 60.91 ± 12.14 species and the Shannon diversity H' was 49.57 ± 5.15, whereas the pole tree was 77.87 ± 12.60 species with diversity H' of 33.07 ± 3.77. The estimated carbon density was 128.42 ± 39.04 MgC ha-1, majority from canopy trees (101.51 ± 63.52 MgC ha-1). We found an asymptotic and strong positive relationship (R2 = 0.81; p = <0.001) between species dominance and carbon density. Our result highlighted the role of dominant species in maintaining ecosystem function, which can be considered when managing riparian ecosystems as they perform better in storing and sequestering carbon.