A Typology of Vessel Patterning in Trees with Examples from the Fossil Record

Abstract

Premise of research. The diversity of anatomical features in wood presents a challenge for understanding wood functioning and developing fossil wood as a paleoenvironmental proxy. This study focuses on the variation in vessel-related features in trees to identify environmental correlates and address questions relating to function and adaptation. Methodology. The features considered include vessel diameter and density; the occurrence, degree, and type of vessel grouping; the variable vessel diameter seen in some woods; and vessel arrangements of various types. Starting from the question of the basic or most typical type of vessel patterning in the midlatitudes versus the tropics, the analysis employs midlatitude/tropical comparisons, information in online databases, examples of modern and fossil woods, and novel ways of representing vessel patterning as a basis for interpretation. Pivotal results. A typology is presented that illustrates the range of variation in vessel patterning in trees and shows both temperature-related disjunctions between the tropics and the midlatitudes and the influence of moisture availability. The diffuse-porous woods of the tropics have a wide range of vessel diameters and densities, whereas in the midlatitudes, diffuse-porous woods have vessels only in the narrow-diameter, high-density categories and ring-/semi-ring-porous woods are also present. The posited relationship between vessel diameter and height is not so clear for the floras considered, especially for tall forest trees. Woods with variable vessel diameters are quite diverse; the complex patterns in some Eocene fossil woods may reflect increased water stress during a time of global warmth. Conclusions. Variation in vessel patterning shows clear relationships to climate and environment that can be used in interpreting paleoenvironments. However, understanding adaptive pathways requires consideration of a broader range of anatomical features and functional and developmental constraints.