Climbing strategies determine light availability for both vines and associated structural hosts

Abstract

This study investigated biomass allocation traits and shading impact of vines (ground-rooted climbing plants) on their hosts in a tall open forest understorey community (Blue Gum High Forest) in Sydney, Australia. Eighty-six vine individuals from 11 species (7 natives and 4 exotics) were recorded and sampled on 26 individuals from 5 host species. All host species sampled were <3 m in height. Each recorded climber was assigned to one of the five established climbing strategies: tendril climber, petiole climber, stem twiner, scrambler or root climber. No root climbers were recorded. Each species was also recorded as native or exotic. We measured shading effects of the different climbing strategies by removing vines from their hosts and measuring the change in canopy openness (diffuse non-interceptance, DIFN) above the host. Vines had significantly greater specific leaf area than their hosts. The most abundant climbing strategy was stem twining, followed by scrambling, petiole twining and tendril climbing. Leaf mass fraction (leaf mass per total aboveground biomass) did not differ among climbing strategies or between natives and exotics. Vines reached taller heights on taller hosts and the percentage of host’s shoot height reached differed significantly among climbing strategies: petiole twiners and scramblers reached the largest percentage host shoot height (97% and 92%, respectively) whereas stem twiners and tendril climbers reached 68% and 61%, respectively. Total relative shading of the host increased significantly with increasing vine biomass. There were significant differences between climbing strategies in the shading imposed on hosts. In the context of average canopy openness above the understorey for this site (24%), scramblers reduced light availability to their hosts by nearly 25%, compared with petiole-tendril twiners (14%) and stem twiners (8%). Thus, climbing strategies differentially shape the light environment available to their structural hosts.