Dissertation Research: Winter soil respiration in southeast Wyoming

University Of Wyoming, Laramie WY

Investigators

Abstract

In seasonally snow covered regions, the metabolism of living roots and microorganisms in the soil over the winter may be an important part of the total annual transfer of carbon dioxide from ecosystems on land into the atmosphere. This project will measure wintertime soil respiration in southeast Wyoming and determine the factors that control it. Measurement plots have been established across a range of ecosystems from short grass prairies to subalpine forests that experience a wide range of winter weather conditions. The highest elevation site, at about 10,000 feet, is a subalpine forest that has snow cover for more than eight months at depths up to ten feet. The lowest elevation site, at 5400 feet, has only four months of snow that is shallow and patchy. This results in contrasting midwinter soil environments. At the high elevation site, snow provides a deep insulating layer that effectively insulates the soil from extremely cold air temperatures and prevents soil freezing. In contrast, soils at the lowest elevation site are often directly exposed to the air and often freeze in midwinter. This has the counterintuitive result that soils in the coldest, snowiest ecosystems at the highest elevations are actually the warmest in midwinter. The organisms responsible for soil respiration, mainly bacteria, fungi and plant roots, rely on the presence of liquid water to be biologically active. Therefore, it is expected that the highest elevation sites will have higher rates of soil respiration during the winter than the lowest elevation sites. Measurements will be made of soil respiration at the different study sites in ways that will enable the relative amounts coming from microbes and roots to be determined. Laboratory experiments will be done to determine the controls over respiration at cold temperatures. Over a year the flux of carbon dioxide from the land into the atmosphere is many times greater than the amount released by the burning of fossil fuels. Over the earth, most of the released carbon is taken back up by plants. But small shifts in the relative rates of release and uptake can have a large impact on atmospheric concentrations of carbon dioxide. Current computer models generally contain overly simple descriptions of soil processes and how they may respond to climate change, particularly at cold temperatures. Therefore, it is important to learn about the interacting biological and physical factors that control these processes. In addition to addressing the socially relevant issue of global climate change, this project will help educate and train a new generation of scientists through the employment of an undergraduate research assistant.