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STEEP-CF: Storm Treatment Effects on Ecosystem Processes of Coastal Forests

Active Dates 9/1/2022-8/31/2025
Program Area Environmental Systems Science
Project Description
Coastal forests and other coastal ecosystems are influenced by complex hydro-biogeochemical processes that are heavily impacted by  climate change. Increased frequency and intensity of storm events and sea-level rise (SLR), already occurring and predicted to accelerate due to climate change, affect biogeochemical processes that ultimately shape ecosystem resiliency and can push these ecosystems into an alternative stable state. The result is that areas of coastal forests worldwide are transitioning from upland to wetland leaving behind “ghost forests” with an evident decline in aboveground carbon (C). That said, how these disturbances will affect less evident ecosystem processes, such as belowground C dynamics, is unclear. This lack of understanding is due to relatively less research on belowground processes, particularly at the ecosystem-scale, and the complex interplay between multiple biogeochemical pathways affected by altered hydrodynamics.

We propose to improve integrated understanding and predictive capacity of ecosystem changes, feedbacks, and subsequent responses to different types of flood disturbances in coastal forests. Our overarching objective is to improve the understanding and process-based modeling of complex feedbacks between flooding events and soil C dynamics in a coastal temperate forest. We will use field and mesocosm experiments to improve biogeochemical modeling of flooding events in coastal temperate forests using a Model Experimental (ModEx) approach.

We will take advantage of the ongoing DOE-funded TEMPEST (Terrestrial Ecosystem Manipulation to Probe the Effects of Storm Treatments), a large-scale manipulation experiment that has been established (but treatments have not started) to test flood disturbances of brackish and freshwater pulse events in a temperate coastal forest. We will additionally provide mechanistic understanding of the processes affected by these disturbance events by performing controlled mesocosm experiments on large intact soil columns obtained from the field site, where flooding events can be carefully manipulated and monitored. We will follow a ModEx approach, testing two different, cutting-edge biogeochemical models (one with emphasis on soil organic carbon (SOC) and the other on methanotrophs) to inform the coupled field-mesocosm experiments that will provide insights for future model refinement.

We will address four knowledge gaps and four associated hypotheses. The knowledge gaps include: a) Feedbacks between hydrologic disturbance events & belowground processes; b) Mineral-mediated C release after flooding disturbances; c) Successive hydrologic disturbance impacts on soil CO2 and CH4 flux magnitudes and metabolic pathways; and d) Limitations of soil biogeochemical models under flooding scenarios. We will test our hypotheses on these knowledge gaps in our field and mesocosm experiments with a diverse array of techniques such as: automated measurements of CO2 and CH4 fluxes and stable isotopes, characterization of organo-mineral associations using NEXAFS-STXM at DOE synchrotron light sources, and using the Millennial model to simulate SOC, and the Soil Methanotrophy Model with respect to soil CH4 dynamics. We will follow a ModEx approach where information of current model assumptions will be used to define the methods and experiments, and then information from our experiments will be used to refine the models as part of the ModEx framework.
Award Recipient(s)
  • University Of Delaware Newark (PI: Vargas, Rodrigo)