NUTRIENT LIMITATION IN A MALAYSIAN ULTRAMAFIC SOIL

Abstract

To test the hypotheses that low nutrient levels and/or magnesium toxicity prevent the occurrence of Dryobalanops lanceolata (Dipterocarpaceae) on tropical ultramafic soils, a nutrient addition experiment was conducted. Dryobalanops lanceolata seedlings were planted in soil from Mount Tawai, an ultramafic mountain in central Sabah, Malaysia and subjected to four treatments: +P, +Ca, +NPK and +NPKCa. Addition of +P reduced the leaf mass per area but increased the leaf area ratio and foliar P concentrations. However, it did not increase the biomass or total leaf area of D. lanceolata. Additions of +NPK and +NPKCa increased the biomass, total leaf area, foliar P and K concentrations but not
foliar N concentration. Calcium additions had no effect on seedling growth, indicating that magnesium toxicity was not important. The occurrence of D. lanceolata in this tropical ultramafic soil was limited by both potassium availability and low levels of soil phosphorus.