Drivers and Mechanisms of Peat Collapse in Coastal Wetlands

Abstract

It's been a long journey, and there are many people to thank who helped me get to this point. I would like to first and foremost thank my two wonderful advisors, Dr. Tiffany Troxler and Dr. Jennifer Richards, for taking a chance on me and allowing me the freedom to craft my research. Their constant guidance and feedback helped develop not only this dissertation but my character as well. I want to especially thank one member of my committee, Dr. John Kominoski. John took me into his lab from day one and has contributed immensely to my growth as a scientist. Long discussions with John and constant feedback from him accelerated the advancement of my work. I would also like to that the members of my committee: Dr. Steve Oberbauer and Dr. Len Scinto. Without their helpful comments on my project and use of their instruments, I would not have been able to complete my dissertation. A one last special shout out to my unofficial committee member, Dr. Evelyn Gaiser. Evelyn's constant positivity and insights guided so much of my research and decisions. There are a few graduate students who I have been working closely with during my time at FIU: Sean Charles, Viviana Mazzei, Nick Schulte, and Shelby Servais. We all started at the same time and have been providing each other with project guidance, emotional support, and an ear to voice endless rants. It is their motivation that has kept me going. Long conversations in the lab had led to many new research insights. The research I conducted was part of a very large collaborative effort among many organizations, and it would impossible for me to not thank them.

Phosphorus alleviation of salinity stress: effects of saltwater intrusion on an Everglades freshwater peat marsh

“…Although we found little impact of GEP or ANPP with continuous exposure to elevated salinity, we found a decrease in live root biomass, although this effect was not significant when comparing the Salt + P to the Fresh treatment. This result supports other experiments in the Everglades that show that live root biomass in the soil significantly decreases with elevated salinity (Wilson ; Wilson et al., 2018 a , b). A decrease in live roots could result in less root binding of soil and less live root mass to replace senesced roots and overall compression of the soil matrix causing the soils to begun to slump and collapse (Delaune et al.…”

“…). Another study conducted on the same mesocosm monoliths used in this study found that there was a ~2‐cm in elevation loss after only one year in the Salt + P compared to the Fresh treatment (Wilson ). Therefore, even though aboveground productivity and NEP increased with Salt + P, soil structure and integrity appeared to be negatively affected by salt and thus vulnerable to collapse.…”

“…A decrease in live roots could result in less root binding of soil and less live root mass to replace senesced roots and overall compression of the soil matrix causing the soils to begun to slump and collapse (Delaune et al 1994). Another study conducted on the same mesocosm monoliths used in this study found that there was a~2-cm in elevation loss after only one year in the Salt + P compared to the Fresh treatment (Wilson 2018). Therefore, even though aboveground productivity and NEP increased with Salt + P, soil structure and integrity appeared to be negatively affected by salt and thus vulnerable to collapse.…”

“…However, when saltwater intrudes into karstic ecosystems, such as the Everglades, freshwater wetlands are simultaneously exposed to both a physiological stressor in the form of elevated salinity and direct supply and desorption of a limiting nutrient, P (Price et al 2006, Flower et al 2017. Understanding how marsh vegetation responds to the coupled subsidy-stress saltwater intrusion is crucial given that vegetation in these ecosystems directly control organic matter input and determine the stability of the marsh (Delaune et al 1994, Nyman et al 2006, Wilson et al 2018. In our study, the sawgrass marsh responded in different ways to the two aspects of saltwater intrusion.…”

“…Therefore, even though aboveground productivity and NEP increased with Salt + P, soil structure and integrity appeared to be negatively affected by salt and thus vulnerable to collapse. This finding would explain the presence of live sawgrass "pedestals" in the brackish portions of the Everglades (ambient salinity~10 ppt), where it appears that the surrounding soil has collapsed (Wilson et al, 2018 a, b). Although saltwater intrusion into freshwater karstic wetlands may initially stimulate primary productivity through a P subsidy, the trade-off of P subsidy and stress of elevated salinity on root productivity and soil structure may ultimately be what matters to the survival or collapse of these marshes.…”