Species Diversity, Community Structure and Carbon Stock of Mangrove Forest 3-Year Post Occurrence of Typhoon Rai (Odette):

Abstract

A healthy marine ecology is dependent on healthy mangrove forests. Mangroves provide vital ecosystem services such as coastal protection from storm damage and carbon sequestration potential that help mitigate the effects of climate change. This study aimed to assess the species diversity and structure as well as the biomass carbon stock content of mangrove vegetation in Honda Bay, Snake Island, Puerto Princesa, Palawan. Data from 2021 was compared to the data gathered in 2024, which accounts for the 3-year occurrence of Typhoon Rai (Odette). The non-destructive quadrat, the nested quadrat method was employed in the assessment to quantitatively describe the mangrove stand in a total of 17 plots. The data was analyzed to reveal if there is a difference in terms of diversity, structure, and carbon stock in the area from 2021 to 2024.

The result of the study found 7 mangrove species dominated by Rhizophora stylosa with 482 tree individuals because all of the mangrove tree planting activities that have taken place on the island in the past are more of this species and the presence of numerous mother trees facilitates its growth and survival. It has been observed that Avicennia marina and Rhizophora stylosa have the highest average basal area and DBH, giving them the highest importance value among other species with 219.85% and 38.42%, respectively. In the 2024 assessment, Plot 4 has 6 of the 7 mangrove species found on the island. This plot contains the most species and is the most diverse among the plots, with an index of 1. 0810.

Results of this study revealed that the biomass carbon stock of mangroves in Snake Island ranged from 1.59 to 257.38 MgC ha-1, or a mean of 75.56 MgC ha-1, in 2021 and 2024. They differ only at the mean biomass carbon stock of 0.21 mg/ha. In accordance with species composition, Rhizophora stylosa has the largest contribution to total biomass carbon stock in the island, with 14.26 MgC ha-1 in the 2024 assessment, while Rhizophora mucronata bore the lowest with 0.49 MgC ha-1. All of the sampling plots were under the category of adequately stocked or have highly dense forest cover, with a total density of 2,935 trees per ha computed using the data gathered in 2024.

From the 612 monitoring tree individuals before Typhoon Rai in December 2021 down to the 569 tree individuals or a total of 43 individuals monitored 3 years post-typhoon. Given the destruction caused by the typhoon throughout Palawan, the 3-year post-evaluation of Snake Island revealed only a 7.03% decrease. This is most likely due to the observation that new shoots and stems regenerated from the destroyed mangrove trees, resulting in an increase of 0.63 hectares in mangrove cover on the island. Given the stated mortality rate in the 2024 assessment, the mangrove cover rises from 18.43 hectares to 19.06 hectares through natural regeneration.

According to the statistical analysis performed on the data collected in 2021 and 2024, there is a significant difference between the plots because of the number of individuals in each plot (p = 0.001), but there is no significant difference between the data collected in 2021 and 2024 in terms of diversity.

The data from 2021 and 2024 did not reveal a significant difference between the years when comparing the biomass carbon stock (p = 0.991). Nonetheless, there was a notable difference in the number of people in each plot between them (p = <0.001).

These findings suggest that mangrove vegetation in Snake Island, Palawan, consists of an amount of carbon, implying that to help preserve and protect the area's coastal resources that rely on mangrove forests, there is a need to assess the existing mangrove area regularly. The assessment of mangroves is critical to ensuring the proper management efforts of the various concerned entities in order to sustain the area's biodiversity conservation information. This would generate data and serve as the foundation for future plans and programs.