Assessing the influence of elevational gradient and soil properties on forest diversity in a low tropical hill of Malaysian Sarawak, Southwestern Borneo

Abstract

This study investigates tree species diversity on a low tropical hill, Teramuo Hill, in Bau District, Sarawak. Although conservation efforts have maintained the vegetation, elevational patterns and soil ecological functions remain underexplored. The study aimed to (1) quantify tree species diversity along the elevational gradient, (2) determine soil property variation along the gradient, and (3) assess the relationship between elevation, soil properties, and tree species diversity. Twenty eight sampling plots were established along six vertical transects spanning 45–105 m above sea level. A hump-shaped pattern of diversity was observed, with peak diversity at mid-elevation (61–75 m). Soil texture varied systematically, with clay-rich soils dominating lower elevations and sandier soils occurring at higher elevations. Soil moisture content generally declined with increasing elevation. Generalized Linear Model results showed that elevation and soil moisture content had significant negative effects on tree species diversity, while sandy clay loam soils were associated with significantly higher diversity. These findings demonstrate that even modest elevational gradients (< 100 m) can structure tree species diversity through interacting topographic and edaphic factors. The study provides important insights for conservation planning and sustainable forest management in low-elevation tropical landscapes.