Abstract
Climbing plants are a key component of rainforests, but mechanistic approaches to their distribution and abundance are scarce. In a southern temperate rainforest, we addressed whether the dominance of climbing plants across light environments is associated with the expression of ecophysiological traits. In mature forest and canopy gaps, we measured leaf size, specific leaf area, photosynthetic rate, and dark respiration in six of the most abundant woody vines. Mean values of traits and their phenotypic change (%) between mature forest and canopy gaps were predictor variables. Leaf size and specific leaf area were not significantly associated with climbing plant dominance. Variation in gas-exchange traits between mature forest and canopy gaps explained, at least partly, the dominance of climbers in this forest. A greater increase in photosynthetic rate and a lower increase in dark respiration rate when canopy openings occur were related to the success of climbing plant species. Dominant climbers showed a strategy of maximizing exploitation of resource availability but minimizing metabolic costs. Results may reflect phenotypic plasticity or genetic differentiation in ecophysiological traits between light environments. It is suggested that the dominant climbers in this temperate rainforest would be able to cope with forest clearings due to human activities.
Highlights
Rainforests are heterogeneous ecosystems in terms of light availability [1,2] and show as a distinctive feature a considerable abundance of climbing plants [3,4,5,6,7,8,9]
Not all climbing plant species exhibit an even density throughout canopy gaps, secondary forest and mature forest; some species behave as light-demanding pioneers and some proliferate in the shaded understory of mature forests [3,4,9,10]
In order to calculate the overall dominance across the entire light gradient for each species, and given the distribution of understory light environments in this site, dominance values were weighed by 60%, 30%, and 10% for mature forest, secondary forest and canopy gaps, respectively, and averaged
Summary
Rainforests are heterogeneous ecosystems in terms of light availability [1,2] and show as a distinctive feature a considerable abundance of climbing plants [3,4,5,6,7,8,9]. This research question is of interest from a basic perspective, i.e., Do climbing plants show strategies of adaptation to light heterogeneity similar to those exhibited by trees?, considering that vines may account for 40% of species diversity in tropical forests [4], are present in more than 130 plant families [16], and the climbing habit is associated with increased diversification in plant lineages [17] This question is of interest to estimate the response of a key component of rainforest communities to changes in climate or land-use [8,18,19], considering evidence that woody climbers are increasing in dominance, relative to trees, in several forests worldwide [20,21,22,23]. We report results of a field study in a temperate rainforest showing a significant association between the dominance of climbing plant species across light environments and changes in ecophysiological traits between forest understory and canopy gaps
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