PS 39-1 - Examining the structural impact of invasive trees on tropical forest canopy on the islands of Hawaiʻi and Moʻorea: An application of terrestrial LiDAR

Wednesday, August 17, 2022

5:00 PM – 6:30 PM EDT

Located in: ESA Exhibit Hall

Presenting Author(s)

TS

Tara Seely

PhD Candidate
University of California, Berkeley - Berkeley, CA
Berkeley, California, United States

Coauthor(s)

LF

Lucas Berio Fortini

PIERC-USGS, United States
DS

David Saah

Professor
University of San Francisco, United States
JM

Jean-Yves Meyer

Researcher
Délégation à la Recherche de la Polynésie française, France
JB

John Battles

Professor
University of California, Berkeley, United States

Background/Question/Methods

Invasive trees are one of the most significant drivers of ecological change in tropical forests. In island systems, forests are particularly vulnerable to invasion, which causes cascading impacts to ecosystem function. Previous research has demonstrated functional implications of invasion ranging from altering water fluxes to impacting soil characteristics. However, the underlying mechanisms of these impacts are not well understood. We investigate invasive species' effect on forest structure as a potential functional link to ecosystem changes. To assess this structural impact, we leverage advancing Light Detection and Ranging (LiDAR) technology. Terrestrial laser scanning (TLS) is an emergent method that utilizes LiDAR to capture high-resolution 3D models of forest structure. We expand the forestry application of TLS to explore how tree invasion changes the structure of tropical island forests, and its resulting functional consequences. We integrate TLS with traditional field methods to quantify functionally-important canopy structural attributes across a gradient of tree invasion on Hawai’i Island and Mo’orea. In doing so, we also determine how well TLS structural data compares to traditional field-based measurements.

Results/Conclusions

Preliminary results indicate functionally-important structural attributes such as height and rugosity vary across a gradient of invasion. However, the trends are mediated by differences in the characteristics of individual study sites. Canopy density, represented by vegetation area idex (VAI) did not significantly change as invasive species abundance increased. From these results, we can infer that invasive species cause structural changes to tropical island forests, but the magnitude of change and the functional implications are not uniform across sites. The preliminary results of our methodological assessment indicate TLS can match traditional field-based measurements within +/- 0.10 m. However, the bias between TLS and traditional methods is mediated by ecosystem attributes, such as understory characteristics. With proper calibration, TLS is a viable method for quantifying canopy structural change at high resolution. Additional research elucidating the structural impact of invasive tree species on tropical island forest ecosystems is crucial to inform future management decisions.