Seedling growth of two pioneer tropical tree species in competition: The role of arbuscular mycorrhizae

The effects of arbuscular mycorrhizae (AM) fungi on growth and survival of two pioneer tropical plant species were studied in a greenhouse experiment for 6 months. One, an early pioneer species (Heliocarpus appendiculatus Turcz., Tiliaceae) and the second, a late pioneer species (Stemmadenia donnell-smithii (Rose) Woodson, Apocynaceae). Three growing conditions were used as competition factors--no competition, with intraspecific and interspecific competitions--along with two different conditions of AM--with and without mycorrhizal inoculum. Mycorrhizal colonization of H. appendiculatus roots was seven-fold more than in S. donnell-smithii. With AM infection, H. appendiculatus did not increase in growth, but showed greater survival in the absence of competition. S. donnell-smithii grew better in the presence of AM fungi and the effect of competition was diminished. S. donnell-smithii with AM fungi infection showed better survival and increase in biomass, making it a better competitor than H. appendiculatus.[PUBLICATION ABSTRACT]