My dissertation research examines how biogeochemical cycles may change in response to long-term ecosystem recovery from acid precipitation. I examine these cycles in temperate hardwood forests and the freshwater ecosystems that drain them. While acid rain has significantly abated in the last thirty years, many ecosystems remain severely impaired by the legacies of a hundred years of anthropogenic acid deposition. Symptoms of this impairment include decreased soil cationic nutrient fertility, depressed soil pH, decreased plant resilience to stressors, and increased toxic soluble aluminum in soil solution and streams. Recovery from these symptoms are expected to take decades to centuries.
I examine possible future trajectories of ecosystem recovery through the lens of a whole-watershed acid rain remediation experiment at Hubbard Brook Experimental Forest in the White Mountains of New Hampshire. In this experiment, researchers added powdered calcium silicate to a watershed to increase base cation fertility and modestly elevate soil pH. This unexpectedly caused dramatic changes to the biogeochemistry of carbon and nitrogen in the ecosystem. Soil organic matter (SOM) stocks declined by ~40% and inorganic N export from the watershed increased approximately thirtyfold. My research seeks to understand the mechanisms behind these startling perturbations to these element cycles.
I examine possible future trajectories of ecosystem recovery through the lens of a whole-watershed acid rain remediation experiment at Hubbard Brook Experimental Forest in the White Mountains of New Hampshire. In this experiment, researchers added powdered calcium silicate to a watershed to increase base cation fertility and modestly elevate soil pH. This unexpectedly caused dramatic changes to the biogeochemistry of carbon and nitrogen in the ecosystem. Soil organic matter (SOM) stocks declined by ~40% and inorganic N export from the watershed increased approximately thirtyfold. My research seeks to understand the mechanisms behind these startling perturbations to these element cycles.
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Mechanisms of SOM stabilization
I am interested in how changes in soil acid-base status alter the stability and persistence of SOM. I examine how altered soil pH and calcium status change SOM solubility, SOM complexation with aluminum, and microbial exoenzyme activity, and how these factors influence turnover of soil C and N. |
Plant-soil-microbe feedbacks
I examine the role that plants and their mycorrhizal symbionts play in mediating SOM decomposition, and how ecosystem recovery from acid rain may change this role. Particularly, I examine how possible forest compositional shifts toward more arbuscular mycorrhizal-associated trees wil alter C and N cycling. |
Nutrient processing in streams
Enhanced SOM turnover, like that observded in the watershed calcium enrichment experiment at Hubbard Brook, often leads to increased nutrient export from a watershed. I examine how the receiving aquatic ecosystems have responded to this increased nutrient loading, particularly with respect to increased loading of inorganic N . |