Abstract
Aim of the study: To evaluate the growth performance, wood density and anatomical features of four drought-tolerant Eucalyptus spp. clones, at 4 years, and to examine the relationships between these characteristics and some functional parameters. Area of study: The analyzed trees were from a clonal test installed in a region characterized by seasonal drought stress in central-western Brazil. Methods: Trees were felled, followed by obtaining dendrometric parameters and wood disk sampling to determine wood bulk density by x-ray densitometry, and morphometric parameters of fibers and vessels in order to evaluate the xylem hydraulic architecture. Lumen fraction (F), vessel composition (S) and hydraulic conductivity (Ks) were estimated. Results: Clone D (E. urophylla x E grandis) presented the highest growth rates, which was related to anatomical characteristics such as low relative frequency of wide vessels. High theoretical Ks does not necessarily imply higher growth rates and were related to lower wood densities. It is possible to infer that the better xylem adjustability of Eucalyptus trees in response to drought stress conditions is associated with increased vessel composition to the detriment of higher hydraulic conductivity. Research highlights: Vessel composition showed a greater variation among Eucalyptus genotypes and was positively associated with growth performance. Keywords: wood anatomy; dendrometry; X-ray densitometry; water stress; hydraulic conductivity. Abbreviations used: F: lumen fraction; S: vessel composition; Ks: theoretical xylem-specific hydraulic conductivity.
Highlights
Water deficit is one of the most limiting growth factors in Eucalyptus plantations (Martins et al, 2018)
The present study evaluated the growth performance and wood features of four Eucalyptus spp. elite-clones (E. pellita x E. grandis; E. camaldulensis x E. tereticornis; E. grandis x E. urophylla x E. tereticornis; E. urophylla x E. grandis) at four years old from a breeding program located in a region of seasonal drought stress in central-western Brazil
The four elite Eucalyptus clones presented high edaphic-climatic suitability growing under seasonal drought-stress, highlighting the E. pellita x E. grandis and E. urophylla x E grandis hybrids
Summary
Water deficit is one of the most limiting growth factors in Eucalyptus plantations (Martins et al, 2018). Drought stress conditions promote stomata closure to avoid water losses, and this mechanism prevents desiccation and xylem cavitation, it restricts CO2 supply for photosynthesis, leading to a decrease in the tree productivity (Chaves et al, 2009; Sperry & Love, 2015). In the Brazilian scenario, the extension of Eucalyptus cultivation to new regions with drier climate conditions has demanded superior drought-tolerant genotypes to compose commercial plantations (Pita-Barbosa et al, 2016). This demand is related to the growing concern with respect to climate change and the risk for more intense and frequent droughts all over the world (Lagergren & Jönsson, 2017) which is expected to affect forestry even in regions which are currently productive forests.
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