The impact of lianas on radiative transfer and albedo of tropical forests
- 1Computational and Applied Vegetation Ecology, Ghent University, Ghent, Belgium
- 2Department of Earth and Environment, Boston University, Boston, MA, USA
- 3Joint Global Change Research Institute, Pacific Northwest National Laboratory, College Park, MD, USA
- 4Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, 08544, USA
Forest albedo changes with vegetation dynamics, ecosystem demography and succession as different plant species can be characterized by contrasting leaf traits, as well as different allocation strategies. In tropical ecosystems, lianas (woody vines) strongly impact the forest biogeochemical cycles by competing with co-occurring trees for above- and below-ground resources. In addition to the particular location of their foliage (often at the top of the canopy), lianas were shown to contrast with tropical trees in terms of biochemical and structural leaf properties, as well as allocation strategies. As a consequence, liana spectral signature differs in several regions of the leaf spectrum (visible, near infrared and shortwave infrared) from tree’s one. At larger scale, the forest canopy reflectance spectrum is also affected by the relative abundance of lianas.
To evaluate the impact of lianas on the radiative transfer and albedo of tropical forests, we collected all published reflectance spectra of liana and co-occurring tree leaves as well as the canopy reflectance spectra characterized by high and low liana coverage. We then calibrated both a leaf (PROSPECT-5) and a canopy (ED2-RTM) radiative transfer model on those data to reproduce the spectral signatures together with their differences, for each single study and site. The Bayesian framework that we used generated leaf biochemical and structural trait distributions, as well as allocation pattern strategies that could be compared between both growth forms.
Collected spectra could be fairly well reproduced at both leaf and canopy levels by the selected mechanistic models. In most studies, calibration led to significantly lower chlorophyll and carotenoid contents, higher relative water content, and larger specific leaf areas for liana leaves, which allowed reproducing observed higher leaf reflectance values in the visible and shortwave infrared and the lower ones in the near infrared. We then validated our findings with independent field data on leaf chemistry and structure from the same studies.
These calibrated radiative transfer models are tools that can be used in future research to investigate the liana impact on the global energy budget of tropical forests, as well as to monitor spatial and temporal liana abundance.
How to cite: Meunier, F., Shiklomanov, A., Dietze, M., Visser, M., and Verbeeck, H.: The impact of lianas on radiative transfer and albedo of tropical forests, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22268, https://doi.org/10.5194/egusphere-egu2020-22268, 2020.
