A comprehensive understanding of allelopathy and resource availability mechanisms is critical for protecting rare and endangered species, biodiversity and ecosystems. We treated 20 major plant species with a gradient of three aqueous extracts of Dacrydium pierrei litter and irrigation/nutrients to compare the relative importance of allelopathy and resource availability on roots, stem growth and seed germination using bioassays. The results showed that the height, ground diameter and aboveground biomass of individuals increased more quickly in the early stage, and rate of increase tends to slow down in the later. The allelopathy was species specific (inhibitory, neutral or promotive), and the survival rate and growth rate of saplings changed significantly along a resource treatment gradient (P< 0.05), indicating that the native species diversity was reduced by lower or higher resource availability in natural forests. The effect of allelopathy on trees was relatively weak during the treatments, and that of resource availability was relatively strong. Resource availability is relatively more important than allelopathy in mediating the reduction in plant biodiversity. Therefore, water and nutrient availability and the species and number of allelochemicals released by plants have substantial influences on the survival and growth of plant species in a natural Dacrydium forest.