B116-0008
High-resolution drone LiDAR reveals ecological drivers of decadal canopy tree crown growth on Barro Colorado Island, Panama

Wednesday, 16 December 2020
Poster
Carlos Celes, Smithsonian Tropical Research Institute, Balboa, Panama, Raquel Araujo, Smithsonian Tropical Research Institute, Panama City, Panama, Eben N Broadbent, University of Florida, School of Forestry Resources and Conservation, Gainesville, FL, United States, Angelica M Almeyda Zambrano, University of Florida, Ft Walton Beach, MA, United States and Helene C Muller-Landau, Smithsonian Tropical Research Institute, Balboa, Ancon, Panama
Abstract:
  • Growth in height and crown area are critical to determining an individual tree’s carbon capture and competitive success, and thus to forest dynamics.
  • However, the vast majority of tree growth studies consider only trunk diameter growth, because measurement errors in ground-based measurements of tree height and crown area are large relative to growth.
  • We use high-resolution airborne and drone-based LiDAR data from 2009 and 2019 for a 50-ha tropical forest dynamics plot in Barro Colorado Island, Panama, together with ground-based tree census data to precisely quantify height and crown area growth of 401 individual canopy trees of 69 species and evaluate their relationships with crown illumination and neighborhood competition.
  • If variation in canopy tree growth is primarily driven by variation in resource supply, then we expect higher growth in trees with higher illumination.
  • In contrast, if variation in canopy tree growth is primarily driven by the potential payoff of growth, then we expect higher growth in trees experiencing higher neighborhood competition, that is, in those having taller neighbors.
  • We found that one quarter of canopy trees shrank in height and/or crown area.
  • Among trees that grew, height growth increased with neighborhood competition and decreased with crown illumination, suggesting that height growth variation among canopy trees is explained by payoffs (demand) rather than resources (supply).
  • In contrast, diameter and crown area growth were unrelated to crown illumination and neighborhood competition.
  • Interspecific variation in growth patterns aligned with shade-tolerance, with light-demanding species showing stronger responses to neighborhood competition.
  • These results demonstrate that height and crown area growth patterns differ qualitatively from diameter growth patterns, and highlight the limitations of current approaches to modeling tree growth.
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