Effects of stem anatomical and structural traits on responses to stem damage: an experimental study in the Bolivian Amazon

Persistence of tree species in a habitat depends on their ability to avoid and respond to disturbance-related damage. Responses to stem damage vary among species but typically include bark wound closure and prevention of xylem decay spread. These responses are associated with anatomical, structural, and physiological traits. This study explores how xylem (vessel size and (or) abundance, parenchyma abundance, ray width, and wood density) and phloem (bark thickness, proportion of live inner bark, ray width and (or) dilation, inter-ray distance, and tissue density) traits relate to responses to stem damage in seven species from the Bolivian Amazon. Rates of bark wound closure and radial xylem decay penetration were compared 2 years after experimental damage. A species that closed bark wounds rapidly (100% in Chorisia speciosa A. St.-Hil.) was not efficient at constraining xylem radial decay spread (1.7 mm). The opposite was true for Pseudolmedia laevis (Ruiz & Pav.) J.F. Macbr., a species that closed wounds slowly (30%) but efficiently controlled decay spread (0.5 mm). The relationship between anatomical and (or) structural traits and damage response variables revealed that species with favorable traits for rapid wound closure (e.g., widely dilating rays) had traits that favored xylem decay spread (e.g., low wood density). It is plausible that this apparent trade-off is based on physiological and phylogenetic constraints.