Elevational parallels of latitudinal variation in the proportion of lianas in woody floras
Journal of Biogeography
Abstract Aim To determine if elevational variation in the proportion of lianas in woody floras parallels the variation observed on latitudinal gradients. This is to be expected if the poleward decrease in the importance of lianas is related to the vulnerability of their wide vessels to freeze embolism. Location Coastal ranges of south-central Chile (latitude 37o-40o S) and western South Island of New Zealand (41o-43o S). Methods The presence of all woody species was recorded in plots of 2500 m2 (Chile) or 100-400 m2 (New Zealand) on four elevational gradients in temperate rain forest. Each species was classified as a tree, shrub or liana. Original data were obtained from 22 plots at two sites in Chile. In New Zealand, two surveys comprising a total of 296 plots were extracted from the National Vegetation Survey data base. Results Liana species richness declined more or less monotonically on all four gradients, whereas richness of trees and shrubs showed more varied elevational patterns. The proportion of woody species contributed by the liana life-form was negatively correlated with elevation on all four gradients, falling from 15 to 35% of the woody flora at c. 200 m a.s.l. to nil well below the tree line. The elevational and latitudinal limits of liana species were marginally significantly correlated in Chile, but not in New Zealand. Main conclusions The elevational parallel of the well-documented decline in liana representation with increasing latitude is consistent with the hypothesis that cold intolerance is a strong control on the global distribution of the liana life-form.