Aboveground Carbon Stocks and Soil Carbon–Nutrient Characteristics Across Edge, Intermediate, and Core Spatial Zones in Kaya Kauma Sacred Forest, Kenya

Abstract

Sacred forests contribute to biodiversity conservation and forest carbon storage, yet quantitative information on their carbon and nutrient characteristics remains limited. This study quantified standing aboveground biomass (AGB) and aboveground carbon (AGC) stocks and characterized soil carbon–nutrient concentrations across Edge, Intermediate, and Core spatial zones in Kaya Kauma Sacred Forest, coastal Kenya. Forest inventories from ten permanent 20 × 20 m plots containing 384 trees representing 42 indigenous species were used to estimate AGB and AGC. Soil samples collected at four depths (0–10, 10–20, 20–50, and 50–100 cm) were analysed for total organic carbon (TOC), total nitrogen (TN), soil organic matter (SOM), soil inorganic carbon (SIC), and calcium carbonate (CaCO3). Mean AGB and corresponding AGC were 204.2 ± 38.2 Mg ha−1 and 96.0 ± 18.0 Mg C ha−1, respectively. No statistically significant zonal difference in AGB was detected under the present sampling design (Kruskal–Wallis, H = 2.373, p = 0.305). Because AGC was derived directly from AGB using a fixed carbon fraction of 0.47, its zonal pattern was mathematically identical. Descriptively, TOC, TN, and SOM generally decreased with increasing soil depth, while no significant zonal differences were detected for TOC or TN. Litter TN was the only litter, deadwood, or regeneration-material variable showing a significant overall zonal effect (H = 6.873, p = 0.032). Exploratory regressions detected no statistically significant relationships between AGC and TOC, TN, or CaCO3. These findings provide baseline information on standing aboveground carbon stocks and soil carbon–nutrient characteristics that can support future monitoring and conservation of Kaya Kauma Sacred Forest.