Estimating Emission of Leaves Seedlings Forest in Different Shading Levels, at Conditions of Transition Amazon-Cerrado, Brazil

Abstract

This study determined the thermal requirements of forest native seedlings (Hymenolobium petraeum and Parkia pendula) and exotic seedlings (Adenanthera pavonina and Cassia fistula) all belonging to Fabaceae family, in three shading conditions (full sun, 50% and 65% of global radiation attenuation by poliefinas black screens). Also they were estimated of leaf emergence by Phyllochron and the Wang and Engel models, on climatological conditions at Sinop (Region of Transition Amazon-Cerrado), Mato Grosso State, Brazil, for winter period (between June and August of 2012). The minimum (Tb) and maximum (TB) basal temperatures and the optimum temperature (Topt) of growth of each species were estimated by regressions between relative growth rates and minimum, maximum and average temperatures, respectively. The values of the estimated Tb were 15.0&degC, 16.4&degC, 14.5&degC and 14.6&degC; to TB were 39.7&degC, 37.1&degC, 38.6&degC and 40.1&degC; and to Topt were 24.4&degC, 24.9&degC, 24.9&degC and 25.1&degC to A. pavonina, C. fistula, H. petraeum and P. pendula, respectively. The Phyllochron model showed highest efficiency in the estimation of leaf appearance when compared to Wang and Engel method.