Crescimento e consumo hídrico de Pinus sp e Eucalyptus saligna Sm. em diferentes condições ambientais

Abstract

Species of the genus Pinus and Eucalyptus are among the most planted in several countries in the world. In many of these areas, forest plantations are subject to periods of water deficit of different severity, duration and recurrence, adding to this climatic events arising from climate change caused by the increase in the concentration of greenhouse gases in the atmosphere. The quantification of water consumed as well as the influence of its deficit on forest growth and production should be taken into account for a rational and ecologically responsible management not only of forest resources but also of water resources. This research had as main objective the quantification of the water consumption by trees, in two different experiments that were the basis for these results. The first one studying the water consumption of young plants P elliottii and E. saligna, submitted to different times of water deficit and its influence on growth. The essay was conducted in 20-liter vessels and used the difference-weighing technique to estimate the water consumed. This trial showed a significant difference between species in the consumption of water during the period of deficit as well as a contrasting behavior with respect to the climatic conditions in which the drought occurs. There were periods with greater loss of increment and this was related to the vapor pressure deficit of the atmosphere. The second experiment was carried out for the phenotypic differentiation of three P. radiata clones regarding water use efficiency. Continuous measurements of sap flow, as well as seasonal measurements of gas exchange, leaf area index and volumetric trunc increment of the clones were carried out in the Balmoral forest in Canterbury on the South island of New Zealand, a region with restricted precipitation. Likewise the same clones were evaluated on the same parameters in Creigeburn, West Coast, a site with very high precipitation. The results indicated that there are clones with greater total and proportional water use, leaf transpiration rates and maximum carbon dioxide assimilation were variable between the seasons and the clones presented interaction site vs. environment, showing that the plasticity of its physiological apparatus may be related to its genotype, and it is recommended to use more efficient clones in areas of more sensitive hydrology. Both experiments, even using very different techniques, have shown that it is possible to satisfactorily quantify the use of water by trees as long as it suits the desired temporal scale and physical resolution. The use of climatic variables was satisfactorily related to growth and water use in both experiments.