Long-Term Patterns of Peat Accumulation and Organic Matter Decomposition in Costa Rican Peatlands
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Authors
Mitchell, Hannah Lynn
Issue Date
2025
Type
Thesis
Language
en_US
Keywords
Carbon Storage , Ecosystem Dynamics , Peatlands , Tropical
Alternative Title
Abstract
Tropical peatlands, compared to their boreal counterparts, are vastly understudied despite these ecosystems acting as a significant terrestrial carbon (C) sink, sequestering 100-300 gigatons of carbon. Within tropical ecosystems, Central and South American peatlands are even more overlooked, with most research stemming from Southeast Asia and new emerging data from the Congo Basin. Likewise, although modeling and global predictive studies have been performed on the future of tropical peatland carbon dynamics, there is an alarming lack of field-based studies, again particularly affecting Latin America. For instance, very little is known about the characteristics of peat soils and their carbon stocks. We also lack a mechanistic understanding of why peat develops in certain areas but not in others, both in terms of peat initiation conditions as well as the factors that enable peat to subsist over centuries and millennia. In the face of rapid environmental land-use changes, the carbon-sink capacity of peatlands could be weakened, or even reversed, which would lead to further climate warming through the release of greenhouse gases into the atmosphere. Here, I present extensive, high-resolution laboratory datasets from peat cores that were gathered from four distinct peatland types found within Costa Rica (high-elevation, riverine, coastal palm swamp, and mangrove). A multi-proxy palaeoecological approach was employed to shed light on the successional pathways and past conditions that have allowed these peatlands to form, as well as provide a first estimate of their carbon stock. The performed analyses include radiocarbon dating, loss-on-ignition, carbon and nitrogen content, and plant macrofossils. Fourier transform infrared spectroscopy (FTIR) was additionally utilized to characterize changes in organic matter quality across sites and over time, and the role of recalcitrant material in tropical peat accumulation. This research provides the basis for understanding long-term carbon accumulation within Caribbean tropical peatlands and is critical to advancing knowledge of the structure of tropical peatland ecosystems.