Explaining the Distribution and Dominance of Lianas and Tree Species – A Test of the Dry Season Advantage Hypothesis (NSF DEB-0845071)


One of the most notable recent changes in tropical forests is the increase in liana abundance and biomass. This change to tropical forests is important because recent evidence suggests that lianas are major contributors to ecosystem processes and tree community coexistence. Increasing lianas will reduce tree growth, increase tree mortality, and likely change soil nutrient dynamics – thus changing tropical forest carbon, water, and nutrient fluxes. Lianas also may impede the growth and regeneration of tree species with high wood density more than species with lower wood density, which would further reduce forest carbon stocks and fluxes. We are testing the community and ecosystem level effects of lianas in 16 long-term experimental forest plots. We started the study in 2007, where we established 16, 60×60 m plots in which we permanently tagged, spatially mapped, measured the diameter, and identified all trees > 1 cm diameter. In total, we are following more than 20,000 individual trees. In 2011, we removed all of the lianas in 8 of the plots and we are now measuring both short- and long-term changes in carbon dynamics, soil nutrient and water availability, and tree responses to the presence and absence of lianas.

This project is the first large-scale, long-term experimental study to quantify the role of lianas in both community- and ecosystem-level processes, and it will provide a benchmark for predicting future tropical forest changes with changing liana abundance. Additionally, the project provides the experimental infrastructure for a plethora of additional collaborations.

    Current Collaborations
  1. The effect of lianas on tropical invertebrate communities – Dr. Steve Yanoviak, University of Arkansas – Little Rock. The main emphasis of the project is to examine how lianas influence tropical arboreal invertebrate communities by providing both structure and resources. Lianas connect tree crowns together and provide a more structurally complex habitat that allows species to coexist.
  2. The effect of lianas on small arboreal mammals – Dr. Thomas Lambert (Frostburg State University) and Dr. Greg Adler (University of Wisconsin-Oshkosh). In this study, we are testing whether lianas increase arboreal mammal density and diversity, presumably by providing predator-free, safe sites in liana tangles, as well as providing escape paths for small mammals to escape their hosts. We are using live traps in the experimental and control plots (both pre- and post-liana removal) to estimate small mammal abundance and diversity. Most of the animals that we have found are rodents, which can have a huge effect on forest dynamics by seeds. In 2010, we discovered a Woolly Mouse Opossum in one of our traps, a species that has never been found in this region of Panama
  3. The effect of lianas on terrestrial mammals – (STRI), Dr. Patrick Jansen (STRI). Here we are testing whether lianas increase terrestrial mammal density and diversity using camera traps. To date, we have photographed Ocelots, Peccary, Agouti, Paca, and coatimundi in the plots.
  4. The effect of liana structure on bird communities – Nicole Michel (Tulane University) and Dr. Douglas Robinson (Oregon State University). The goal of this project is to determine the effect of lianas on forest bird communities. Lianas provide a complex 3-dimensional structure to tropical forests that provide habitat to birds and may be a large determinant of bird community composition. Bird surveys in the 16 plots before and after liana removal will allow us to test this hypothesis
  5. The effect of lianas on forest structure – Dr. Gil Bohrer (Ohio State University) and Dr. Greg Asner (Stanford University). We are using both plane-based and ground-based lidar to quantify forest structure before and after liana removal. This study will allow us to carefully quantify the contribution of structure by lianas and will be used in a variety of the above collaborations.

We welcome additional collaboration (please contact either Stefan Schnitzer (S1@uwm.edu) or Jennifer Powers (Powers@umn.edu).


Submissions from 2011


Increasing liana abundance and biomass in tropical forests: emerging patterns and putative mechanisms, Stefan A. Schnitzer and Frans Bongers


Community and ecosystem ramifications of increasing lianas in neotropical forests, Stefan A. Schnitzer, Frans Bongers, and S. Joseph Wright