The Effects of Precipitation Intensification on Salt Marsh Ecosystems and their Services
Precipitation change, and the intensification of precipitation events (droughts and storms) are expected to occur over the next century as a part of anthropogenic climate change. Changes in annual precipitation totals have the potential to alter ecosystem processes. Some of the affected processes (carbon sequestration, nutrient removal, raw material production) are valued as ecosystem services. Hollie’s hypothesis is that the predicted intensification of precipitation patterns (e.g. the redistribution of rainfall into fewer, more intense storms with longer periods of drought between) will affect ecosystem processes even if annual precipitation totals remain constant.
The first component of this project will be a field experiment in a salt marsh at the Cape Code National Seashore. In this experiment, she will manipulate the incoming precipitation to a set of 1.5 m2 plots, and measure the response of ecosystem processes including: plant growth, plant litter decomposition, biogeochemical cycling of C, N, and Si, and microbial greenhouse gas production and consumption.
The second component of this project will use sediment data gathered from these plots, and from park long-term monitoring data, to make predictions about the marsh’s ability to keep up with future sea level rise. Long-term monitoring data from several sites will be used to make a robust prediction of the effects of future sea level rise on the marsh system. Data from the treatment plots will be used to estimate how the possible future precipitation regimes may alter this prediction.
Updates:
2015
The first component of this project will be a field experiment in a salt marsh at the Cape Code National Seashore. In this experiment, she will manipulate the incoming precipitation to a set of 1.5 m2 plots, and measure the response of ecosystem processes including: plant growth, plant litter decomposition, biogeochemical cycling of C, N, and Si, and microbial greenhouse gas production and consumption.
The second component of this project will use sediment data gathered from these plots, and from park long-term monitoring data, to make predictions about the marsh’s ability to keep up with future sea level rise. Long-term monitoring data from several sites will be used to make a robust prediction of the effects of future sea level rise on the marsh system. Data from the treatment plots will be used to estimate how the possible future precipitation regimes may alter this prediction.
Updates:
2015
- March 2015: I am happy to share that NSF selected me to receive a Doctoral Dissertation Improvement Grant! With this additional funding, I’ll be able to add a new dimension to the project, and dig deeper with the greenhouse gas flux study that has been my main focus. To really get at the mechanisms driving greenhouse gas production and consumption, I will be measuring the expression of the key functional genes involved in these processes. I hope to shed light on the relative rates of important processes that happen at the same time, but work in opposite directions.
- April 2015: This field season we have relocated the project to the Rough Meadows Massachusetts Audubon Sanctuary! This new marsh has peaty, organic rich sediments that will be perfect for the new microbial work. Thanks to MAS and the Rowley Conservation Commission for allowing me to work at this beautiful site!
- May 2015: The first monthly greenhouse gas flux samplings were a success! Now comes lab work and data analysis….
- June 2015: This month we’re installing litter bags (thanks to Maria and Emma!) and doing the first round of seasonal microbial samples. New research questions, new methods, a new site… I have a lot to learn but it’s been exciting so far!
- August 2015: This month I sampled twice – once when the marsh was wet from recent spring tides, and once when the marsh was wet from rain. How will these compare? I took microbial samples both times, so I can compare the ecosystem level gas fluxes as well as the process on the gene expression level.
- October 2015: This month I am doing some work with rhodamine (a harmless non-toxic, but very pretty bright pink dye) to trace the lateral flow of water through marsh sediment. I’m doing this at both sites (the Plum Island site I’ve been working at this year, plus the Cape Cod site from last year) to characterize the rate of water flow and to compare the sites to one another. These studies will tell us if lateral flow of water into the plot is a big enough concern to interfere with the effects of the precipitation treatments.
- April 2014: The structures are in and treatments have begun!
- May 2014: We took our first greenhouse gas flux measurements! We will continue these measurements twice a month through the growing season. We also installed litter bags containing Spartina patens and Spartina alterniflora leaves. After a few months, we will see how fast they decompose!
- June 2014: This month we installed root ingrowth cores and porewater peepers to monitor belowground plant growth and biogeochemistry.
- July 2014: The samples and data are really rolling in! We have plant tissue samples for silica analysis, water samples for pH, salinity, and nutrients, samples of sediment, aboveground biomass, belowground biomass, plant litter… not to mention all the gases to run on the GC!