Short and long-term impacts of disturbance on the structural complexity of tropical forest canopies

Abstract

Habitat structural complexity is widely recognised as a fundamental indicator of biodiversity and plays a vital role in driving ecosystem functioning across and within biomes. Yet despite its key role in shaping ecological processes, we continue to lack a robust, standardised approach for quantifying the structural complexity of our increasingly threatened biomes. In response to this challenge, a general theoretical framework was recently proposed to characterise the 3D structural complexity of any habitat based on three key features: its height range, its surface rugosity, and its fractal dimension. Although originally developed using 3D surface models of coral reefs, this geometric theory of surface habitats was specifically designed to be widely applicable across ecosystems – something which has yet to be tested. Here I used high-resolution airborne laser scanning (ALS) data acquired in Malaysian Borneo to provide the first comprehensive assessment of the value of this new framework for quantifying the 3D structural complexity of terrestrial ecosystems and its response to both human and natural disturbances. I found that the geometric theory was able to clearly capture the short and long-term effects of logging, forest clearing, windthrows and regeneration on the 3D structure of the world’s tallest tropical forests. In particular, using both a space-for-time approach and repeat ALS data I was able to identify a distinctive structural fingerprint of severe disturbances associated with logging and forest clearing. These results demonstrate the potential of this framework for understanding how tropical forests are responding to both natural and human-driven disturbance, including identifying structural features that indicate a tipping point of habitat degradation. Furthermore, I anticipate that this approach could be used to evaluate the effectiveness of different forest restoration and management practices that aim to maximise the recovery of forest structural complexity and all of its associated ecological benefits.

Date of Award	6 Dec 2022
Original language	English
Awarding Institution	University of Bristol
Supervisor	Tommaso Jucker (Supervisor) & Chris F Clements (Supervisor)