Print PageLianas are characteristic of many tropical forests and recent evidence suggests that they are increasing in abundance relative to trees. Climate change may be driving these increases and if so these shifts in forest composition may alter forest carbon pools. We test the hypothesis that trees and lianas differ physiologically and morphologically and that these differences occur early in ontogeny during the seedling stage. Furthermore, the degree to which key soil resources limit the growth of trees versus lianas remains unknown. Because lianas allocate far less to structural support than trees, the resources that limit their growth may differ in important ways from trees. To address these questions, we evaluated the physiological performance and morphology of tree and liana seedlings using a long-term (> 10 years) nutrient enrichment experiment where macronutrients (N, P, K) were applied to large plots (40 x 40m) in a fully factorial design in a lowland tropical forest within the Barro Colorado Nature Monument in Panama.
Results/Conclusions
We found that trees and lianas differed physiologically; lianas had greater rates of electron transport (ETR), photochemical yield (FPSII), and non-photochemical quenching (qN and NPQ) compared to trees. In terms of morphology, the tree and liana seedlings only differed in that the tree seedlings showed overall greater height and canopy area. K increased the performance of lianas (ETRmax) but not trees suggesting contrasting resource limitation between these growth forms. P increased saturating photon flux density (PFDsat), NPQ and seedling height of both growth forms, while N failed to increase any measure of performance or morphology suggesting that P and K are more limiting early in ontogeny than N. These results suggest that although tree and liana seedlings are similar morphologically, key differences in their physiology and nutrient use may help to explain the success of lianas in tropical forests under global change scenarios.
