Characterizing an in-situ fraction of Photosynthetic Active Radiation product for implementation in the validation of MODIS-derived fraction of Photosynthetic Active Radiation products using continuous-wavelet transforms

• Author / Creator

  Sharp, Iain

• The goal of this thesis is to address the need to improve forestry monitoring and satellite validation techniques to better contextualize the effects that human-induced climate change is having on tropical dry forests (TDFs). Climate change is expected to change regional and global precipitation patterns, intensifying and punctuating precipitation events, lengthening drought periods and shortening growing season length for photosynthesizing vegetation. Anthropogenically focused land use policies impose a top-down control of ecosystems by altering the disturbance regimes of ecosystems and determining the ability of ecosystems to regenerate based on its anthropogenic value. Understanding the interplay between the top-down anthropogenic control and bottom-up climate forces on TDF ecosystem functionality, resilience, and productivity is ailing, and remedying that ailment is the drive for this thesis. Therefore, the thesis aims to test previously established findings about the influences that increase the variance of an in-situ fraction of Photosynthetic Active Radiation (fPAR) product and establish the influences that are unique to TDFs for the creation of this product. Another purpose of this study is to bring to light the utilization of near-surface optical wireless sensor networks for the purpose of validating satellite-derived products and to monitor the health, productivity, and ecological functionality of TDFs. By passively observing the photosynthetic dynamics of TDFs, while collecting subsequent environmental data this study reveals the benefits of using wireless sensor network technology to monitor and assess leaf phenology, phenological drivers and how these can be used to validate the observations from satellite-derived fPAR products with a case study from the tropical dry forest located in Costa Rica’s, Santa Rosa National Park Environmental Monitoring Super-Site (SRNP-EMSS).
  Chapter one is used as an introduction into the motivation behind the methodologies presented in this thesis. Chapter two confirms that environmental and methodological influences that exist in the northern hemispherical deciduous broadleaf forests also influence the creation of an in-situ fraction of Photosynthetic Active Radiation (fPAR) product in tropical dry forests. The scope of influence that solar zenith angle, sky condition, wind speed, network configuration and mechanical PAR sensor calibration have on in-situ 2-flux fPAR is defined and isolated for each phenological phase that tropical dry forests undergo. Results from this chapter indicate that utilizing data captured when wind speeds are less than 5 m/s, when solar zenith angles are between 27° and 60°, and which are captured under diffuse sky conditions with seven or more sensors present results in the smallest degree of variance for the in-situ 2-flux fPAR product. Utilizing the findings from chapter two, chapter three slightly alters and then employs the in-situ fPAR product produced to test and validate if the MODIS-derived fPAR products are capable of accurately capturing the timing, length, and magnitude of phenological events and trends observed in the TDF of Costa Rica’s SRNP-EMSS. Conclusions from chapter three indicate that while MODIS-derived fPAR products are capable of capturing broad phenological trends, they
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  are incapable of capturing the magnitude of change that occurs in photosynthesizing vegetation throughout a phenological year, and that they are incapable of accurately capturing the timing of phenological patterns, such as the yearly, bi-annual peaking, or onset of green-up or senescence. Chapter four provides the conclusive statement to the thesis, reviewing the significance of these results and how the contributions of this thesis may further research in the fields of remote sensing and forest phenology. The results presented here may be specific to tropical dry forests and the MODIS satellite system, but the methodologies are not, and their implementation in other forest ecosystems should be considered when considering the standardization of satellite-validation procedures and environmental monitoring as they can improve our understanding of the limitations or problems of satellite techniques and how vegetation seasonality is rapidly changing globally.

• Subjects / Keywords

  • Remote Sensing
  • MODIS
  • tropical dry forests
  • wavelets
  • fPAR
  • satellite validation

• Graduation date

  Spring 2020

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-wakd-ph44

• License

  Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.