Understanding the Vegetation Dynamics of Tropical Rainforests and Drylands Using Solar-induced Chlorophyll Fluorescence (SIF)

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Tropical ecosystems, including rainforests and drylands, are of vital importance in sequestering CO2 and mitigating climate change as well as providing great socioeconomic values. However, the future trajectory of these ecosystems remains highly uncertain due to a lack of accurate quantification of their carbon fluxes and a limited understanding of their sensitivities to climatic conditions. While solar-induced chlorophyll fluorescence (SIF) has emerged as a promising proxy for quantifying photosynthesis, original satellite SIF retrievals have various limitations (e.g., coarse spatial resolution, incomplete spatial coverage, short time span, unresolved diurnal cycle), which hinder revealing vegetation dynamics in response to climate variations. My dissertation aims to fill this knowledge gap by first developing global high-resolution long-term time series of SIF and then applying it to elucidate the climate sensitivity of carbon fluxes in tropical ecosystems.In Chapter 1, I give an overall introduction of the background, i.e., a brief review of carbon monitoring and climate sensitivity evaluation of the terrestrial carbon cycle, followed by descriptions of methods and main conclusions in Chapters 2 – 5 (i.e., four individual research papers, published or to be published). Specifically, in Chapters 2 and 3, I focused on the methodological development of the reconstructed SIF products, in order to resolve the limitations in the original SIF retrievals. The reconstructed products faithfully reproduced the spatiotemporal patterns of original satellite retrievals (but with enhanced characteristics, e.g., higher spatial or temporal resolutions) and showed great consistency with independent ground measurements. In Chapters 4 and 5, I employed the reconstructed SIF data products to study the climate sensitivities of tropical drylands and rainforests, respectively. I found that the relationship between carbon uptake and climate may not be consistent among different seasons or different regions (even with the same vegetation type). In Chapter 4, I found an asymmetric sensitivity of vegetation growth to different water availability proxies (e.g., precipitation and soil moisture) during the two rainy seasons at a tropical dryland site, due to differences in soil water storage prior to the two rainy seasons. In Chapter 5, I also found a differential sensitivity to water availability between Amazon and Congo rainforests, which cannot be fully captured by the state-of-art terrestrial biosphere models (TBMs). These evaluations can provide great insights on tropical vegetation responses to climate and inform model predictions for the future. Finally, Chapter 6 summarizes the major findings of this dissertation work and discusses the future research directions.

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284 pages


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climate change; interannual variability; solar-induced chlorophyll fluorescence; terrestrial carbon cycle; tropics; vegetation dynamics


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Sun, Ying

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Goodale, Christine
Albertson, John

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Soil and Crop Sciences

Degree Name

Ph. D., Soil and Crop Sciences

Degree Level

Doctor of Philosophy

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Government Document




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dissertation or thesis

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