A systematic review of leaf and wood traits in the Neotropics: environmental gradients and functionality

Key message

Resource-limited environments showed a tendency towards conservative and coupled leaf and wood traits, while displaying an acquisitive and decoupled pattern in resource-rich ones. Water and elevation were the most studied gradients.

Abstract

In the Neotropics, spatial and temporal environmental gradients subject plants to distinct abiotic conditions, requiring functional adjustments. This promotes changes in trait expression, resulting in individual trait variation or covariation. We have systematically reviewed the literature focusing on leaf and wood traits in the Neotropics along major abiotic gradients (water, irradiance, temperature, soil fertility, and elevation), and assessed their spatial and temporal variation and covariation trends. Thus, we compiled 141 published papers from 2010 to 2022. Most of the studies of leaf and wood traits were related to: (1) the gradients of water avalability and elevation, (2) leaf traits at the expense of wood traits, with specific leaf area and wood density the most studied traits, respectively, (3) the morphological leaf traits to a greater extent than to biochemical, ecophysiological, or anatomical ones. In general, more conservative traits were observed in environments with lower resource availability. Although there is still no consensus, coupling was predominantly linked to water balance during periods of water restriction or in dry ecosystems, and papers have focused on single ecosystems rather than making comparisons across multiple ecosystems. This systematic review highlights the tendency for systems with fewer resources to show a bias towards greater coordination between leaf and wood traits compared to systems with more resources. This review also adresses how traits are expressed based on the integration of more than one environmental driver and the qualitative variation of these resources. Finally, we emphasize the importance of analyzing different aspects of trait expression when assessing species’ responses to environmental gradients, especially in megadiverse regions such as the Neotropics.