Growth responses of tropical deciduous tree seedlings to contrasting light conditions

Summary

The growth responses of seedlings of Amphipterygium adstringens, Caesalpinia eriostachys, and C. platyloba, species associated with undisturbed parts of the tropical deciduous forest in México, and Apoplanesia paniculata and Heliocarpus pallidus, two gap-requiring pioneer species, were determined under contrasting light conditions in a growth chamber experiment. The high (400 μmol m⁻² s⁻¹) and low (80 μmol m⁻² s⁻¹) light treatments correspond to the light available in a medium size gap and underneath the vegetation canopy in the deciduous forest during the rainy season, respectively. Following four destructive harvests the biomass production, relative growth rate, root/shoot ratio, specific leaf area, net assimilation rate, leaf area ratio and light dependency were determined for all species. In the high light treatment all species achieved higher relative growth rates and net assimilation rates than when growing at low light intensity. However, the two pioneer species showed the highest light dependency and were the species more affected by the low light treatment in biomass production. The two Caesalpinia species showed similar growth responses, but C. platyloba was the most shade tolerant species. Plastic adjustments in terms of the specific leaf area were more evident in the two pioneer species.