Crescimento inicial e respostas fotossintéticas de três espécies leguminosas arbóreas submetidas à adubação verde e química em um plantio florestal na Amazônia

Abstract

Currently 20% of the Amazon is degraded or altered. The need to restore these ecosystems becomes greater every day, once we recognize the services provided by the forest. Knowing the silvicultural needs of native species, and their ecophysiological responses to different methods of fertilization, is of great importance for the development of forest plantations, that can better use the resources available. In this sense, we evaluated the influence of different fertilization treatments on the growth, photosynthetic and nutritional responses, and biomass production of three leguminous trees, native of the Amazon region, in a mixed forest plantation. The experiment was conducted in a degraded area in the vicinity of the Balbina Hydroelectric Power Plant (UHE - Balbina) in the county of Presidente Figueiredo, AM. The fertilization treatments were: T1 = no fertilizer, T2 = manure pit, T3 = chemical fertilization, T4 = green manure, and T5 = green manure more chemical fertilization. We also assessed the performance of three species Dipteryx odorata, Inga edulis and Schizolobium amazonicum. Thus, we determined the percentage of survival, growth rates absolute and relative, in height and diameter, biomass production, nutrient content and chloroplastidic pigments in the leaves, gas exchange and chlorophyll fluorescence. D. odorata had 100% survival in all treatments. The lowest survival rate for I. edulis was found in the T5, and S. amazonicum in T2 and T4. The highest rates of absolute growth in height were obtained at T5 for the species I. edulis and S.amazonicum, 23.02 cm month-1 and 20.11 cm month-1 respectively. The species D. odorata had the highest height growth in T3 months 10.16 cm month-1. The same behavior was observed in the rates of absolute growth in diameter. In general, the species I. edulis had the highest absolute growth rates compared to other species. The relative growth rates were higher in the S. amazonicum both in height and diameter. The species I. edulis produced more biomass than other species in all treatments. The biggest difference between species for total biomass was found in T4, where I. edulis biomass produced 23 times more than D. odorata and 7 times more than S. amazonicum. The best treatment of fertilization in biomass production for I. edulis (7350.27 g) and S.amazonicum (1877.60 g) was T5, and the species D. odorata presented values very close on the T3 (455.00 g) and T5 (443.83 g). The high productivity of the species reflected the high photosynthetic rates found in the T5 treatment for the three species D. odorata (13.08 mmol CO2 m-2 s-1), I. edulis (20.65 mol CO2 m-2 s-1) and S.amazonicum (18.24 mol CO2 m-2 s-1). The highest rates for stomatal conductance and transpiration were obtained for the species I. edulis, in all fertilization treatments. With respect to chlorophyll fluorescence, the highest values of FV / FM were found in the T5 treatment for the species S. amazonicum (0.80), the lowest values occurred for the species I. edulis on T1. For the performance index the highest values were also observed for the species S. amazonicum on treatment T5, and the lowest values were determined in T1 and T2 for the species D. odorata and I. edulis, respectively. The highest total chlorophyll levels were found in T3 (1.74 mmol g-1) and T5 (1.82 mmol g-1) for D. odorata and I. edulis respectively. We conclude then the necessity to restore soil fertility prior to the establishment of forest plantations in degraded areas. It is also recommended the development of new research with native species, in the area of tropical forestry, to develop new planting techniques for reforestation in the Amazon.