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The response of Tropical Dry Forests to meteorological drought and El Niño Southern Oscillation
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- Author / Creator
- Lidong, Zou
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As a result of economic pressures from agricultural development, timber extraction, tourism and the expansion of cattle ranching, Tropical Dry Forests (TDFs) are considered one of the most threatened and least protected ecosystems in the neotropics. Interacting with these human-induced effects, natural disturbances resulting from climate change are also affecting their capacity to provide key ecosystem services. One of the most recurrent effects associated to climate change is the increase in the frequency, and intensity of meteorological droughts driven by the El Niño-Southern Oscillation (ENSO). The former in turn leads to changes in the structure and function of these tropical ecosystems. Despite the importance that drought plays on the provision of ecosystem services, the response of TDFs to meteorological droughts is not fully understood. In this context, the utility of remote-sensing drought indices in the context of the ENSO was evaluated in this doctoral dissertation via four chapters. Chapter 1 conducts a review of droughts in the context of the ENSO. Chapter 2 evaluates the utility of three remote-sensing drought indices: the Vegetation Condition Index (VCI), the Temperature Condition Index (TCI), and the Vegetation Health Index (VHI), in a TDF located at the Santa Rosa National Park Environmental Monitoring Super site (SRNP-EMSS), Guanacaste, Costa Rica. This evaluation was done at multiple temporal scales (year, month and season). Chapter 2 findings suggests that the TCI performed best over the VCI and the VHI. Chapter 3 assesses the response of Gross Primary Productivity of the SRNP-EMSS to meteorological droughts. The former is done using a temporal correlation analysis of the Normalized Difference Vegetation Index (NDVI), Land Surface Temperature (LST), and the Standard Precipitation Index (SPI) at monthly and seasonal scales. Results indicate that the NDVI and LST are largely influenced by seasonality as well as the magnitude, duration, and timing of precipitation. The responses of the NDVI and the LST to meteorological droughts mainly reflect how greenness and evapotranspiration at the SRNP-EMSS TDFs respond to precipitation. Chapter 4 assesses the response of TDFs to Sea Surface Temperature (SST) anomalies in Niño 3.4 (a proxy for ENSO) across multiple TDFs sites in the Americas. This analysis was conducted from both, a long-term (18-years) and a short-term (1-year) perspective. Selected sites were chosen at the Chamela-Cuixmala Biosphere Reserve (CC-BR; Jalisco, Mexico); the Parque Estadual da Mata Seca (PEMS; Minas Gerais, Brazil); the Tucabaca Valley Municipal Wildlife Reserve (TV-MWR; Santa Cruz, Bolivia); and SRNP-EMSS (Guanacaste, Costa Rica). Results indicate that the Gross Primary Productivity at the SRNP-EMSS and the PEMS are negatively impacted by the long-term SST anomaly, while there is no long-term impact at the CC-BR and the TV-MWR. The long-term effect of the SST anomaly is more significant during the dry season at the SRNP-EMSS and the PEMS. Findings from a short-term perspective, suggest that the SRNP-EMSS and the CC-BR are sensitive to the ENSO warm phase, but not the other two sites. Finally, Chapter 5 addresse’s general conclusions and provides ideas for future research.
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- Subjects / Keywords
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- Graduation date
- Spring 2020
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- 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.