Rainfall exclusion changes the sapwood of eucalyptus wood in humid and dry sites

Abstract

The height, diameter, and leaf area of trees influence the anatomical structures because rapid growth requires maintenance of the water conduction in sapwood, despite environmental variations that may limit water supply. Our objective was to evaluate the influence of water availability conditions on the soil in humid and dry sites, on the percentage of sapwood along the trunk, and on the hydraulic properties of the wood of eucalyptus clones. The experimental plantings were carried out in Brazil in humid and dry sites. Six-year-old E. urophylla and E. grandis × E. camaldulensis clones were evaluated under 100% water (W) at each site considering local precipitation and 33% rainfall exclusion (WE) conditions. The wood was evaluated for heartwood and sapwood percentage, apparent sapwood density, diameter, wall thickness and vessel area, potential hydraulic conductivity, and Huber value. Rainfall exclusion at the dry site promoted an increase of 9% of sapwood when compared to the humid site, with an impact on diameter, area, wall thickness and vessel composition index, and lower Huber value for E. grandis × E. camaldulensis wood. The rainfall exclusion increased the sapwood percentage and reduced the growth of E. urophylla. E. grandis × E. camaldulensis had a higher sapwood apparent density at the dry site, while E. urophylla had a higher density at the humid site. The genetic diversity of the clones was expressed in the tree growth and in the sapwood content and was modified by humid and dry sites, which demonstrates different rusticity levels of the clones.