Vegetation on ultramafic edaphic ‘islands’ in Kinabalu Park (Sabah, Malaysia) in relation to soil chemistry and elevation

Abstract

Kinabalu Park is the world’s most species-rich hotspot with over 5000 plant species recorded for an area 1200 km2. The aim of this study was to characterise the vegetation on ultramafic edaphic ‘islands’ in relation to soil chemistry and elevation. In total 87 non-permanent vegetation plots were established covering 12 ultramafic edaphic ‘islands’ from 474 to 2950 m asl in which 2854 plant species in 742 genera and 188 families were recorded from 14 662 collections. The results show that plant diversity decreases with elevation, but a mid-elevation (circum 1500 m asl) ‘hump’ occurs for some plant groups (orchids, pteridophytes) as a result of the presence of cloud forests. Six main vegetation classes with associated soil types were discerned: (i) Sub-Alpine Scrub; and (ii) Graminoid Scrub, both associated with Hypermagnesic Cambisols (‘hypermagnesian soils’); (iii) Montane Cloud Forest, associated with Cambisols often with accumulation of humus; (iv) Mixed Dipterocarp Forest, associated with deep Ferralsols (‘laterites’); (v) Pioneer Casuarina Scrub; (vi) Mature Mixed Casuarina Forest, both associated with Hypermagnesic Leptosols. We hypothesised that ‘adverse’ soil chemistry would exacerbate vegetation stunting, and the results confirmed that stunted vegetation and elevational floristic compression occurs on chemically adverse soils (mainly hypermagnesian soils). However, no clear correlation with plant diversity was found, as some of the most ‘adverse’ soils on the summit of Mount Tambuyukon had up to 132 species per 250 m2.