Structure and Function in Degraded Forests in the Amazon from Multi-source Remote Sensing

Rangel Pinagé, Ekena

Structure and Function in Degraded Forests in the Amazon from Multi-source Remote Sensing

Rangel Pinagé, Ekena

Permalink

Publication Type:: Thesis
Issue Date:: 2021

Open Access

Copyright Clearance Process

Recently Added
In Progress
Open Access

This item is open access.

Adobe PDF

Download contents and abstractAdobe PDF (496.08 kB)

Adobe PDF

Download thesisAdobe PDF (11.86 MB)

View statistics

Full metadata record

Field	Value	Language
dc.contributor.author	Rangel Pinagé, Ekena
dc.date.accessioned	2021-11-05T04:52:27Z
dc.date.available	2021-11-05T04:52:27Z
dc.date.issued	2021
dc.identifier.uri	http://hdl.handle.net/10453/151370
dc.description	University of Technology Sydney. Faculty of Science.	en_US.UTF-8
dc.description.abstract	Tropical forests provide critical ecosystem services for global climate and biodiversity, and sustain the livelihoods of millions of people. Yet, they have become hotspots of land-use change. The Southern border of the Brazilian Amazon has been a focus of land development with large swaths of tropical forests converted to agriculture. Degradation of forests by selective logging and fires has accompanied the advance of the frontier and has resulted in significant impacts on Amazonian ecosystems. While the agricultural use in the region is well quantified, forest degradation is more challenging to study. Given that changes in tree cover and structure have large impacts on forest function, there is an urgent need to quantify these properties for degraded forests. The overarching goal of this thesis is to investigate the functional and structural linkages in degraded forests in the Amazon and assess whether forest structure mediates forest responses to disturbance. To achieve this goal, I (1) compared phenological patterns of intact and degraded forests using time-series of spectral indices; (2) examined the relationship between forest structure and photosynthesis across a gradient of forest degradation, by integrating structural variables and solar-induced fluorescence (SIF) data; and finally, (3) investigated the influence of forest structure on evapotranspiration and land surface temperature. These broad thesis objectives were accomplished using multi-source remote sensing (MODIS, Landsat and TROPOMI SIF satellite data combined with airborne and orbital lidar observations) and statistical methods. My results showed that fires had a stronger effect than selective logging on ecosystem functioning (e.g., stronger phenological shifts and alterations in evapotranspiration and land surface temperature) and caused more dramatic changes in forest structure (e.g., lower forest canopy and leaf area index, more abundant understory). I also found that shifts in ecosystem functioning related to forest degradation were exacerbated by the dry season in the study region. Finally, I found that the most heavily disturbed forests presented strong structure-function relationships that do not hold in the least disturbed forests, suggesting that forest structure acts as a mediator of forest recovery. My findings help to elucidate the effects of human-induced disturbances in ecosystem fluxes and can inform public policy related to forest management and land use planning. Besides, my results provide inputs regarding the role of phenology and forest structure in degraded forests for ecosystem demography models. The importance of this research is underscored by the recent surge in deforestation in the Brazilian Amazon and associated forest fires.	en_US.UTF-8
dc.format	Thesis (PhD)
dc.language.iso	en_US	en_US.UTF-8
dc.relation	https://opus.lib.uts.edu.au/bitstream/10453/151370/2/02whole.pdf
dc.rights	The author owns the copyright in this thesis including all reproduction and reuse rights for the work. The work may not be altered without the permission of the copyright owner. Attribution is essential when quoting or paraphrasing from this thesis.
dc.rights	au.edu.uts.lib/ppc
dc.rights	info:eu-repo/semantics/openAccess
dc.title	Structure and Function in Degraded Forests in the Amazon from Multi-source Remote Sensing	en_US.UTF-8
dc.type	Thesis
utslib.copyright.status	open_access	*

Abstract:

Tropical forests provide critical ecosystem services for global climate and biodiversity, and sustain the livelihoods of millions of people. Yet, they have become hotspots of land-use change. The Southern border of the Brazilian Amazon has been a focus of land development with large swaths of tropical forests converted to agriculture. Degradation of forests by selective logging and fires has accompanied the advance of the frontier and has resulted in significant impacts on Amazonian ecosystems. While the agricultural use in the region is well quantified, forest degradation is more challenging to study. Given that changes in tree cover and structure have large impacts on forest function, there is an urgent need to quantify these properties for degraded forests. The overarching goal of this thesis is to investigate the functional and structural linkages in degraded forests in the Amazon and assess whether forest structure mediates forest responses to disturbance. To achieve this goal, I (1) compared phenological patterns of intact and degraded forests using time-series of spectral indices; (2) examined the relationship between forest structure and photosynthesis across a gradient of forest degradation, by integrating structural variables and solar-induced fluorescence (SIF) data; and finally, (3) investigated the influence of forest structure on evapotranspiration and land surface temperature. These broad thesis objectives were accomplished using multi-source remote sensing (MODIS, Landsat and TROPOMI SIF satellite data combined with airborne and orbital lidar observations) and statistical methods. My results showed that fires had a stronger effect than selective logging on ecosystem functioning (e.g., stronger phenological shifts and alterations in evapotranspiration and land surface temperature) and caused more dramatic changes in forest structure (e.g., lower forest canopy and leaf area index, more abundant understory). I also found that shifts in ecosystem functioning related to forest degradation were exacerbated by the dry season in the study region. Finally, I found that the most heavily disturbed forests presented strong structure-function relationships that do not hold in the least disturbed forests, suggesting that forest structure acts as a mediator of forest recovery. My findings help to elucidate the effects of human-induced disturbances in ecosystem fluxes and can inform public policy related to forest management and land use planning. Besides, my results provide inputs regarding the role of phenology and forest structure in degraded forests for ecosystem demography models. The importance of this research is underscored by the recent surge in deforestation in the Brazilian Amazon and associated forest fires.

Please use this identifier to cite or link to this item:

http://hdl.handle.net/10453/151370