Carbon and Nitrogen Isotopic Survey of Flora of Mt. Pangasugan in Leyte, the Philippines

Stable isotope surveys provide valuable insights into nutrient cycling, food web dynamics, and forest ecosystem functioning, aiding in tracing nutrient sources, assessing carbon sequestration and climate change impacts, and understanding plant-water relations. In the Philippines, studies on carbon and nitrogen isotopic surveys or any other stable isotopic survey are very limited. Here, we aimed to survey the carbon and nitrogen isotopes component of the flora in Mt. Pangasugan at various altitudes. Leaves from three individuals from each species were collected and combined into one sample per species and analyzed using isotope ratio mass spectrometry for δ13C and δ15N signatures. A total of 104 plants coming from 82 species and 44 families were sampled. The result shows that the average foliar δ13C of the altitudinal sampling points sampled ranged from – 33.53‰ to – 35.84‰ while that of δ15N ranged from 0.80‰ to – 2.88‰. No clear trend was observed for foliar δ13C across elevation while that of δ15N showed decreased depletion with an increase in altitude. No correlation was observed for foliar δ13C and δ15N with any of the environmental parameters measured. The lack of correlation between foliar δ13C and δ15N with environmental parameters could be influenced by several factors like genetic factors, sampling scale, lag effects, and local adaptation of plants. By providing an overview of the isotopic baselines of the plants from Mt Pangasugan, this study fills in some of the gaps in the scarce research and data for stable isotopic profiling of the majority of the country's forest species.