The quantity of exudation and the viscosity of pine oleoresins are thought to influence the performance of herbivores and pathogens, but little is known about how fire events affect oleoresin properties. We tested two hypotheses regarding resin properties following a fire event: (1) exudation quantity and viscosity of resins differ between trees in burned and unburned stands, and (2) in burned stands variation in resin exudation quantity and viscosity are predictable by individual tree characteristics. We quantified constitutive resins in burned and unburned stands four months post-fire and determined mean resin exudation quantities and viscosity in a southwestern ponderosa pine (Pinus ponderosa) ecosystem. Mean resin exudation quantities were 35% higher in burned stands than unburned stands (24.267 g and 18.057 g, respectively), and mean viscosity was 22% lower in trees in burned stands than unburned stands (52.24 and 66.14 poises, respectively). In burned areas, resin exudation and resin viscosity were weakly predicted by several individual tree characteristics. Tree diameter and percentage of live crown were positively correlated with the quantity of resin exudation, but basal area was negatively correlated with exudation quantity. The percentage of live crown was the only variable related to resin viscosity. This study shows that ponderosa pine resin properties are affected by fire events, and that some individual tree characteristics may predict the expression of resin defenses in burned stands.
|Journal of the Arizona-Nevada Academy of Science
|Published - 2011