Discocarpus pedicellatus is an endemic tree species in the Atlantic Forest. It presents natural regeneration from seedling banks and populations with patches of high-density of adult trees in the semideciduous forests of southern Bahia, Brazil. Two studies were conducted, in the field and under greenhouse conditions, aiming to analyze seedling survival and the effects of shade on growth and on photosynthetic characteristics of D. pedicellatus saplings. In the field, the density of seedlings was very high at the beginning of the study, in some cases exceeding 700 seedlings m-2. After two years of observations, density values were between 5 and 190 seedlings m-2 and few individuals showed the first true leaves. In greenhouse, the results obtained for light-saturated net photosynthetic rate (Amax), the compensation irradiance (Ic), the dark respiration rate (Rd), the relative growth rate (TCR) and the net assimilation rate (TAL), suggest that this species presents slow growth, typical of species that regenerate in the understory of mature forests under closed canopies. Also, in response to increase in shading there was a significant decrease in Rd, indicating that the survival in the forest understory may be associated to low metabolic and growth rates. The results indicate that the regeneration strategy by seedling banks and the ability to adjust their metabolism in response to the low available light radiation are important factors that explain the establishment of high-population density patches of D. pedicellatus in the semideciduous forests of southern Bahia, Brazil.
Atlantic rainforest; hemispherical photographs; shade tolerance
