Wood anatomy of 13 species from a successional tropical dry forest: description and ecological implications

Abstract

Successional tropical dry forest (TDF) species face water scarcity in the harsh dry season. Wood features provide insight into potential hydraulic stress coping mechanisms. Here, we describe the wood anatomy of 13 species occurring frequently in successional TDF. Given the marked rainfall seasonality of TDF, we expected these species to share conspicuous growth rings boundaries and drought-adapted anatomical features such as paratracheal parenchyma; although given the taxonomic and phenological diversity, a high wood diversity was also expected. Most species have diffuse-porosity. Axial parenchyma is diversely associated with vessels. Simple perforation plates are common and exclusive to all species. Different features poorly delimit growth boundaries, as previously observed in other tropical species. The main ground tissue is diverse, including nonseptate fibers, septate living fibers, or exclusively parenchyma. Axial and radial parenchyma may be scarce, abundant, or represent the main and unlignified ground tissue component. Vessel grouping ranges from solitary and 2–29 vessels per group. The mean vessel diameter range is ⩽50–200 μm; fiber walls are very thin to very thick. The anatomical features recorded among successional TDF species suggest different water stress coping mechanisms resulting from various anatomical combinations. Seven species exhibit wood features associated with drought tolerance (higher hydraulic redundancy, higher mechanical resistance, with vessel-ray connectivity likely given by banded parenchyma), whereas six species share xylem features associated with drought avoidance (taller and wider rays indicating higher water storage capacity). The complexity and multifunctionality of stem woody tissue should caution us against oversimplifying the relationship between anatomy, function, and ecological performance of TDF species.