Atributos do solo e produtividade de Eucalyptus spp. na metade sul do Rio Grande do Sul

Abstract

The use of techniques for determining the productive capacity of a forest site depends on its sensitivity to evaluate or to predict the interaction between the genetic factors of the species and the environment (climate, soil, physiography). This work was developed in the southern part of Rio Grande do Sul state and aimed to evaluate the influence of soil properties in different soil classes, with the production capacity by the dominant height (h100) for Eucalyptus saligna (clone 32864) and seminal plantations of Eucalyptus dunnii. Thus, we selected 16 inventory plots based on genetic material and dendrometric variables as the dominant height (h100), mean annual increment (MAI), volume of wood with bark (m3/ ha-1) designed for seven years. Form these 16 plots, nine plots were E. dunnii and seven plots were E. Saligna. In each selected site trenches were opened to classify the soil, to collect soil samples for chemical (pH, MO, Ca, Mg, Al, P, S, K, Zn, Cu, B, CTC,ph7, V) and physical analysis ( particle size, particle density and soil porosity, macro and microporosity, soil water retention curve , saturated hydraulic conductivity) and to collect litter. Profiles/plots showed variations in soil classes, site index, source material, morphological, chemical and physical soil characteristics and amount of litter. We analyzed four classes of representative soils of the study region: Argissolos (PVe, PVd, PBACd, PBACe, PAd), Neossolos (RRd), Luvissolos (TCo) and Cambissolos (CXbd). The dominant height (h100) showed a minimum height of 22.9 m ( Profile 13 - RRd) and maximum height of 29.3 m (Profile 10-TCo) for E. dunnii and for the clone E. saligna the IS showed a minimum height of 22.4 m (Profile 11- PAd) and maximum of 28.7 m (Profile 16-PVe). The statistical analysis between dominant height (h100) and the physical, chemical and morphological soil characteristics was performed by the use of multiple regression analysis, which aimed to verify the significance of the input variables to determine the dominant height. The equations that best correlated the dominant height to soil attributes were derived from the layers 10-20 cm and 60-80 cm when were considered both genetic materials. However, when genetic materials were evaluated separately the equations that best correlated the dominant height to soil attributes were derived from the layers 10-20 cm and 20-40 cm for E. dunnii, and from the layers 40 - 60 cm and 60 - 80 cm for clone E. saligna, which shows the different relations between the genetic material and the analyzed soil profiles. The depth of the A + B horizons, the silt, the organic matter and the concentration of boron, potassium and calcium were the attributes that gave the highest contribution in the models to explain the productive capacity of the profiles analyzed by dominant height.