CAREER: The end of winter: How changing snow conditions affect soil redox and biogeochemistry

Dartmouth College, Hanover NH

Investigators

Abstract

Winter is changing faster than other seasons. Regions that once had regular snow cover during winter now experience warm spells and rain-on-snow events that can cause snow to melt. Without consistent snow cover, soils will no longer be insulated from freezing temperatures or protected from water during the winter. Most research has focused on soils during the summer season when plants are growing, so little is known about how changes in winter conditions will affect soil processes like decomposition, greenhouse gas emissions, and nutrient export. This research uses an experiment that will melt snow, along with observations along a snow-cover gradient in the New Hampshire mountains, to understand how changes in snow cover will affect soil processes. This project provides graduate and undergraduate education in winter ecology, experiments, and data analysis. This project also involves community members, including public school students, to help monitor snow and soil conditions in the New Hampshire mountains and to help the public learn more about the effects of changes in winter on their communities. The loss of a persistent snowpack is increasing soil climate variability as snowmelt periodically raises soil moisture levels and leaves the soil vulnerable to episodic freezing. Recent measurements in upland forest soils indicate this winter variability is causing redox fluctuations. Increased redox fluctuations will have profound effects on soil biogeochemistry with implications for greenhouse gases, such as increased N2O fluxes and reduced CH4 uptake, and may increase nutrient exports to aquatic systems. This research will 1) construct a novel in situ experiment that manipulates winter climate with three treatments: melting 50% of snowfall, melting 100% of snowfall, and a control, where snow is not manipulated; and 2) use a natural gradient of snow conditions as a space-for-future-time substitution. Within the experiment and across the gradient, soil environmental variables (temperature, moisture, frost depth, O2, and redox potential), and biogeochemical fluxes, including greenhouse gas production (CO2, N2O, CH4) and the leaching of carbon, nutrients, and metals through the soil profile, will be measured. This research will generate the knowledge needed to fill the unaddressed gap of how midwinter snowmelt affects soil biogeochemistry through changes to moisture, temperature, and redox and quantify how this loss of snow affects soil. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.