Abundance of climbing plants in a southern temperate rain forest: host tree characteristics or light availability?

Question In a southern temperate rain forest, we addressed three questions: (1) Does the abundance of climbing plants increase with light availability? (2) Do host tree species differ in their susceptibility to vine infestation? (3) How does the relationship between host tree trunk diameter and relative abundance of vines vary with their climbing mechanism? Location Two sites in the temperate evergreen rain forest of southern Chile: Puyehue (40 degrees 39'S, 72 degrees 09'W; 350 m a.s.l.) and Pastahue (42 degrees 22'S, 73 degrees 49'W; 285 m a.s.l.). Methods We sampled vines in 60 25-m2 plots, with 20 plots in each of three light environments: mature forest, forest edges and canopy gaps. In each plot, for every tree >= 1.50-m tall of any diameter we counted and identified all climbing plant individuals at a height of 1.30 m. We also counted, measured (trunk diameter at 1.30 m) and identified all these trees, and determined prevalence of vine infestation for each tree species. Results Light availability in forest plots did not affect vine abundance when the number and size of host trees was taken into account. Overall, vine abundance increased with host tree trunk diameter. Tree species did not differ in the prevalence of vine infestation. The relative abundance of stem twiners and adhesive climbers decreased and increased with trunk diameter, respectively. The densities of stem twiners and adhesive climbers were negatively correlated across the forest. Conclusion We provide further evidence that the pattern of vine abundance is independent of light availability in southern temperate rain forests, in contrast to results commonly reported for tropical rain forests. We also show that support suitability across the forest varies with the mechanism by which vines climb, probably due in part to biomechanical constraints and in part to vine interspecific competition, a virtually unexplored ecological factor.