Lianas have more acquisitive traits than trees in a dry but not in a wet forest

Abstract

Abstract Lianas are increasing in relative abundance and biomass in many tropical forests. We tested the hypothesis that lianas conform to the fast and acquisitive end of the continuum of plant strategies, allowing lianas to acquire resources faster than trees. We assessed functional traits representative of the leaf (LES) and wood economics spectrum (WES), including plant hydraulics, in 16 liana and 16 tree species in the canopy of two tropical forests at the extremes of the climatic and geological gradient across the Isthmus of Panama. For both forests, we observed a trade‐off between the construction of more productive leaves with rapid turnover and expensive leaves with slower turnover. We also found trait variation associated with wood and hydraulic traits. These two axes were orthogonal, suggesting that trade‐offs at the leaf and stem, including plant hydraulics, operate independently. For the dry forest, lianas had cheaper and more efficient leaves than trees. For the wet forest, lianas and trees overlapped in leaf and stem characteristics. Moreover, the duration of green foliage highly explained the variation between dry forest species, reflecting different adaptations to drought. In the wet forest, fast‐growing species benefited from a higher return on investments of leaf vascular tissues than slow‐growing species and they had a higher capacity to transport water through the leaf. A higher capacity to construct more productive leaves and display leaves with lower costs may favour lianas over trees in light interception, photosynthetic rates, and growth under high light and nutrient availability in dry forests. Synthesis. Lianas in a dry tropical forest had a more acquisitive strategy than trees, characterized by more productive leaves and more efficient display for light interception. In dry environments, lianas appear to benefit from high‐light and nutrient‐rich soils and thus take advantage of higher resource conditions compared to trees. By contrast, in a wet tropical forest, lianas and trees overlapped in leaf and stem characteristics and lianas were not more acquisitive than trees. In wet environments, low light availability and nutrient‐poor soils in a context of low water limitation may constrain variation in resource acquisition strategies between lianas and trees.