Resumo:
The efficiency in the initial growth of trees can be related to the ability of the seedlings in adapting to different light intensites in the enviroment. The objective of this work was to evaluate the influence of different levels of shading in the initial growth of Tabebuia aurea and Angico (Anadenanthera macrocarpa) in the nursery phase. The experiment was conducted at the Federal Rural University of Semiárido located in Mossoró-RN. The seeds of A. macrocarpa and T. aurea were collected from parent trees and donated by the Caatinga/ UFERSA / Petrobras Project, where, afterwards, they were processed. The composting used in the experiment was coconut fiber, after the substrate was placed in 55-cm³ tubes and organized in plastic supports. The seedlings were submitted to three levels of shade, full sun (absence of shade), shade of 50% and 80%. For the different levels of shading, mean values of the height/diameter ratio of the neck were obtained of 3.74 (A. macrocarpa) and 1.57 (T. aurea) for cultivation in full sun, 0% of shading, indicating that the growth of this cropt may have better results under these conditions. The highest values of the Dickson Quality Index (DQI) were observed in seedlings grown under a lower shade level of 0.03454 and 0.11719. The species T. aurea shows little tolerance when subjected to high levels of shading, showing that the luminosity interfere in the initial growth of the species. A. macrocarpa, also acquired a better development in full sun, showing less progress at higher levels of shading.
