RESPONSES TO PHOSPHORUS OF CONTRASTING SUCCESSIONAL TREE-SEEDLING SPECIES FROM THE TROPICAL DECIDUOUS FOREST OF MEXICO

1. We compared the growth responses of three early successional specie s, Cochlo-spermum vitifolium, Cordia alliodora and Heliocarpus pallidu s, and the late successional Caesalpinia eriostachys, Caesalpinia plat yloba, Jacquinia pungens and Recchia mexicana tree-seedling species to four concentrations (0, 2, 10 and 41 ppm) of phosphorus. The experime nt was conducted over 50 days in pure silica sand inside growth chambe rs. 2. Mature-forest species had low relative growth rates and net ass imilation rates, and showed little or no response, in growth and bioma ss allocation, to different P concentrations. 3. Early successional sp ecies had small seeds and higher responses in biomass allocation, grow th and net assimilation rates to P availability, as well as a higher p hosphorususe efficiency when P supply was low. 4. Species and treatmen t differences in,growth rate generally corresponded more closely with patterns of net assimilation rate than with biomass allocation. The re sponsiveness of growth to P availability was negatively correlated wit h seed mass and P dependency.