Ajuste e comparação de equações hipsométricas em um clone híbrido de Eucalyptus urophylla plantado em diferentes densidades populacionais, na Chapada do Araripe

Abstract

The work aims to evaluate the influence of different population densities on the adjustment and selection of hypsometric models in an experimental planting of an eight-years-old Eucalyptus urophylla hybrid located in the Gypsum Pole of Araripe-PE, indicating the one(s) that best describes (m) the height-diameter ratio for each spacing. The experiment was carried out at the Experimental Station of the Agronomic Institute of Pernambuco - IPA, located in the municipality of Araripina, with geographic coordinates 07 ° 27'37 '' S and 40 ° 24'36 '' W and altitude of 831 meters. The predominant climate according to Köppen is BSh, hot and dry low latitudes, with summer rains. The data used came from an experiment consisting of three clones C41 - Hybrid Eucalyptus urophylla, C11 - Hybrid Eucalyptus brassiana and C39 - Hybrid Eucalyptus urophylla), however, only clone C39 was used, because it is the most productive. The clone was planted in five different population densities (2m x 1m, 2m x 2m, 3m x 2m, 3m x 3m and 4m x 4m) with four replications distributed in a completely randomized design. Five hispsometric models were adjusted (Henriksen, Trorey, Prodan, Stoffels and Silva). To select the best model, four validation tests were used: Schlaegel fitting index (FI), standard error of estimate (Syx), Furnival index (IF) and the graphical distribution of residuals. In general, it was observed that all models had a good dendrometric ratio for total height as a function of diameter at breast height (DBH), in all densities studied. Schlaegel's fitting index, ranged from 0.8504 to 0.9857, explaining good correlation of the models in all spacings. The planting spacing did not significantly influence the adjustment of the models. The Prodan model was the most accurate with mean values of 0.9758 for the FI, 5.31% for the Syx% and 0.62 for the IF. Furthermore, according to the graphical analysis of the residues there was no tendentiousness in the data. Thus, the Prodan model is the most suitable for estimating the height of adult eucalyptus stands in theGypsum Pole of Araripe-PE, in all evaluated spacings.