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Logging leaves a fingerprint on the number, size, spatial configuration and geometry of tropical forest canopy gaps

Accepted version
Peer-reviewed

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Article

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Authors

Zhang, B 
Fischer, FJ 
Coomes, DA 

Abstract

Recent advances in remote sensing such as airborne laser scanning have revolutionised our ability to accurately map forest canopy gaps, with huge implications for tracking forest dynamics at scale. However, few studies have explored how canopy gaps vary among forests at different successional stages following disturbances, such as those caused by logging. Moreover, most studies have focused exclusively on the size distribution of gaps, ignoring other key features such as their spatial distribution and shape. Here we test a series of hypotheses about how the number, size, spatial configuration and geometry of gaps vary across a logging disturbance gradient in Malaysian Borneo. As predicted, we found that recently logged forests had much higher gap fraction compared to old-growth forests, a result of having both a greater total number of gaps and a higher proportion of large gaps. Regrowing forests, on the other hand, fell at the opposite end of the spectrum, being characterised by both fewer and smaller gaps compared to nearby old-growth forests. Across all successional stage gaps were found to be spatially clustered. However, logging significantly diluted the degree of spatial aggregation and led to the formation of gaps with much more complex geometries. Our results showcase how logging and subsequent regrowth substantially alter not just the number and size of gaps in a forest, but also their spatial arrangement and shape. Linking these emergent patterns to their underlying processes is key to better understanding the impacts of human disturbance on the structure and function of tropical forests.

Description

Keywords

airborne laser scanning, canopy height models, canopy structure, forest degradation, forest dynamics, remote sensing, selective logging

Journal Title

Biotropica

Conference Name

Journal ISSN

0006-3606
1744-7429

Volume Title

Publisher

Wiley
Sponsorship
Natural Environment Research Council (NE/K016377/1)
. The acquisition of the ALS data was funded through a grant awarded to the BALI consortium through NERC's Human Modified Tropical Forests Programme (grant code: NE/K016377/1). TJ was supported by a NERC Independent Research Fellowship (grant code: NE/S01537X/1) and through a Research Project Grant from the Leverhulme Trust which also funded FJF (grant code: RPG-2020-341). BZ was funded by a Scholarship from the China Scholarship Council (grant code: 202008320276).