Assessing Soil Carbon Sequestration Potential of Pristine Montane Heath Forests in Imbak Canyon Conservation Area (ICCA), Sabah, Malaysia

Abstract

The carbon sequestration of soils in the Imbak Canyon Conservation Area (ICCA), Sabah, Malaysia, was evaluated in this study. The study aimed to assess the potential for carbon sequestration in the pristine montane heath forest in the designated conservation area. According to our research, the lowland dipterocarp forest along the Nepenthes trail is in transition to heath forest and is characterized by granular soil texture in the 0-20 cm depth range. Three replicates of a soil sample were extracted from each sampling location with 250 m intervals as undisturbed 20 cm-deep vertical cores using a soil auger. Total Carbon (TC), Nitrogen (TN), and Total Organic Carbon (TOC) analyses were performed on the samples. Firstly, TC and N were simultaneously measured using the LECO CN928 Combustion Analyzer. The TOC was determined using a modified Walkley-Black rapid dichromate oxidation method. The Nepenthes trail, representing the montane heath forest, was found to have exceptionally low levels of TN and TC, at 0.006% and 0.876%, respectively. Based on statistical analysis, Bulk Density (BD), Soil Organic Carbon (SOC), and the Carbon to Nitrogen ratio (C/N) exhibited statistically significant differences across all five sampling points (p < 0.05) except for the TN and TC (p > 0.05). The average BD of the soil was 1.256 g cm-³, indicating inadequate C retention. On the Nepenthes trail, the high C/N ratio of 146 may prolong decomposition and contribute to the low SOC content of the soil. The soil carbon stock in the pristine montane heath forest is estimated at 16.76 tC/ha. These findings are expected to help address potential threats to soil restoration and contribute to ICCA's land management strategies and plans.