Contribution of Lianas to Plant Area Index and Canopy Structure in a Panamanian Forest

Abstract

Lianas are an important component of tropical forests, where they reduce tree growth, fecundity and survival. Competition for light among plants may be intense; however the amount of light that lianas intercept is poorly understood. We used a large-scale liana removal experiment to quantify light interception by lianas in a Panamanian secondary forest. We measured the change in plant area index (PAI) and forest structure six weeks after cutting lianas in eight 80x80 m plots and in eight control plots, and then annually for four years. We used ground-based LiDAR to measure the 3-dimensional canopy structure before cutting lianas and annually for two years afterwards. Six weeks after cutting lianas, mean plot PAI was 20% higher in control versus liana removal plots. One year after cutting lianas, mean plot PAI was ~17% higher in control plots. The differences among treatments diminished significantly two years after liana cutting and, after four years, trees had fully compensated for the removal of lianas. Ground-based LiDAR revealed that lianas were distributed in the upper and middle parts of the canopy, and not just the upper canopy as previously suspected. Therefore, lianas attenuated ~20% of the light in the upper- and mid-canopy of the forest.