INFLUENCE OF TOPOSEQUENCE ON LEAF AND WOOD CHARACTERISTICS OF EUCALYPTUS CLONES: ADAPTIVE RESPONSES TO WATER AND LIGHT AVAILABILITY

Abstract

Background: In Brazil, the production of wood derivatives is mainly based on planted eucalyptus forests, often established in areas marginal to agriculture, such as steep terrain. However, intra-site variability in these plantations is still poorly explored, especially in operational silviculture contexts. Topographic gradients can modify the availability of water and light, influencing plant performance
and wood quality. In this context, this study aimed to evaluate the effect of topographic variation along a toposequence on the morphological and anatomical characteristics of leaves, as well as on the anatomical and chemical properties, basic density, and higher heating value of the wood, in a clonal plantation of Eucalyptus spp.

Results: Position in the toposequence significantly influenced several characteristics (p < 0.10). Trees located at the base of the slope exhibited, on average, higher leaf water content (1.37 g. g⁻¹), larger leaf area (47.95 cm²) and lower total extractive content in the wood (3.47%). The leaves of trees in the middle of the slope had the lowest water content (1.16 g. g⁻¹). At the top of the slope, where the trees with the lowest height growth were found (15.26 m), the leaves had a higher proportion of palisade and spongy parenchyma (0.62), one of the smallest leaf areas (28.9 cm²) and higher total extractive content (7.20%).

Conclusion: Topographic variation promotes integrated adjustments in leaf and wood characteristics, reflecting adaptive strategies to local resource availability conditions. These results reinforce the importance of considering intra-site variability in forest management and in the selection of genetic materials better adapted to heterogeneous environments.