CRESCIMENTO, ESTADO NUTRICIONAL E CARACTERÍSTICAS FOTOSSINTÉTICAS DE Bertholletia excelsa SOB TRATAMENTOS DE ADUBAÇÃO EM ÁREA DEGRADADA NA AMAZÔNIA CENTRAL

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Human activities on forest ecosystems can result in the removal of forest cover followed by impoverishment of the soil physical, chemical and biological properties. Throughout time, these areas without forest coverage can turn in to degraded areas. In face of this, for the revegetation of these areas with forest species different methods have been applied for the recovery of the soil properties. Moreover, have been used species able to develop in under limiting environmental conditions regarding the availability of primary resources (light, water and nutrients). In this sense, this research aims to investigate the responses of growth, gas exchange, photosynthetic performance and nutritional status of young plants of Bertholletia excelsa, growing in a forest plantation under different fertilization treatments, established to restore a degraded area in the county of Manaus, AM (60 01 07 W and 03 05 08 S). The treatments were: T0 = control (without fertilization), T1 = fertilization with green fertilizer (branches and leaves) and T2 = chemical fertilization (Ouromag). It was also analyzed the influence of the different fertilizer treatments on the recovery of the soil fertility. For this, soil particle sizes and the concentrations of nutrients were also analyzed. In plants of B. excelsa were evaluated the growth in height and diameter, as also the leaf nutrient contents, gas exchange, leaf chloroplastid pigment contents, chlorophyll a fluorescence, leaf water potential, and specific leaf area. For the soil fertility, it was observed that in the treatments T1 and T2 the soils presented higher concentrations of the nutrients C, N, K, Ca and Mg, when compared to T0. These changes in the soil fertility provided also higher nutrient contents of the leaves. Most of the foliar nutrients contents were higher in treatment T1, excepted for K, Ca and Mg, which presented higher values in T2. The N content in the leaves of treatment T1 presented values 41 and 37% higher than in treatments T0 and T2, respectively. The net photosynthetic rates varied between 4.8 and 13.2 μmol CO2 m-2 s-1, with values of treatment T1 177 and 65% higher than treatments T0 and T2, respectively. For the photosynthetic nutrient use efficiency, the treatment T1 presented values 135, 57, 57, 255, 147, 363, 100 and 76% higher than T0 for the nutrients N, P, K, Ca, Mg, Fe, Zn and Mn, respectively. In the period of this study, the variables height and diameter did not presented absolute growth rates differences between treatments T0 and T2. On the other side, treatment T1 presented 10.2 cm mês-1 and 2.4 mm mês-1 in height and diameter, respectively. This values were 12 times higher than in treatment T0. In the evaluation of the maximum photochemical efficiency (Fv/Fm) the plants of B. excelsa in treatment T1 (0.75) did not presented differences when compared with the individuals of treatment T2 (0.68). However, between T1 and T0 (0.64) they presented lower values of stress when the ratio Fv/Fm was analyzed. For the chloroplatid pigment contents, the values of chlorophyll b (chl b) and carotenoids (cx+c) did not presented differences between treatments T1 (chl b = 2.3 μmol g-1 and cx+c = 0.8 μmol g-1) and T0 (chl b = 1.9 μmol g-1 and cx+c = 0.6 μmol g-1). The values for the leaf water potential varied during the day, with treatment T2 presenting higher values at midday (Ψmd = -2.42 MPa) followed by the treatments T0 (-2.64 MPa) and T1 (-2.79 MPa). The specific leaf area (SLA) presented values between 78.0 and 91.0 cm2 g-1, treatments T0 and T2 presented values 16 and 15% higher, respectively, when compared with treatment T1. The application of fertilizer treatments, especially T1, promoted high increases of net photosynthetic rates, which compensate the higher transpiration rates, reflecting an increase of the water use efficiency (WUE). These values were 66 and 38% higher in treatments T1 and T2, respectively, as in treatment T0. Therefore, it is ended that is important reestablishing a priori soil fertility in degraded areas destined for reforestation, as also the importance of physiological, nutritional and growth research as a basis for the development of reforestation programs aiming the restoration of degraded areas in Amazonia.

ASSUNTO(S)

restauração florestal nutrição florestal castanheira-da-amazônia. recursos florestais e engenharia florestal fertilidade do solo fotossíntese

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