Relationship between edaphoclimatic attributes and productivity of loblolly pine (Pinus taeda L.) in southern Brazil

The productivity of loblolly pine in southern Brazil is one of the highest in the world, in part because of genetic breeding programs but also as consequence of the species adaptation to the edaphoclimatic conditions and of the right silvicultural management. Thus, the understanding of the relationship between wood productivity and soil attributes is very important and can serve as a basis for guiding management practices in forest plantations. This research aimed to identify which are the natural factors related to the productivity of Pinus taeda planted on different geological formations in southern Brazil. The selection of the study plots was carried out based on site productivity, altitude, soil maps and geological maps. In the selected plots, soil profiles were opened to classify and characterize the physical and chemical attributes of the soils. The soil attributes evaluated were depth of the A and B soil horizons, pH, clay content, carbon, phosphorus, basic cations and potential acidity. Mean annual precipitation and mean temperature of coldest and warmest quarter of the year were collected for all the study sites. Productivity was represented by the mean annual increment (MAI) and by the site index (SI). To identify the relationship between soil attributes and productivity, correlation analysis was performed. The plots showed MAI varying from 27.2 to 44.5 m3 ha-1 year-1, and SI varying from 9.0 and 26.6 m. Among the climatic parameters, the temperature of the warmest quarter of the year (Tmax) showed positive correlation with SI, and among the soil attributes the best correlation was between MAI and clay content. Another important result was the correlation between clay and carbon content in the whole soil profile which combination seemed to present a high influence on the loblolly productivity in southern Brazil.