MRI: Acquisition of Instrumentation for Measurement of Trace Gas Fluxes in the Arizona Highlands

Prescott College, Prescott AZ

Investigators

Abstract

A grant has been awarded to Dr. Jack Herring and Dr. Tim Crews at Prescott College. The sophisticated research instrumentation provided by this grant will allow measurement of the exchange of variety of trace gases between the atmosphere and the land surface. The primary goal of the research is to better understand the cycling of nitrogen in the highlands of central Arizona. A secondary goal is to study the relationship between the cycling of nitrogen and carbon in these ecosystems. Additionally, the instruments will play a central role in training students at Prescott College in these analytical techniques. Initially, the instrumentation will be installed in chaparral, an important plant community in the southwestern U.S. for which there is little information on the dynamics of nitrogen cycling. Chaparral is interesting because it has among the highest, if not the highest, density of nitrogen-fixing woody plants in the United States. Due to the potentially high inputs of nitrogen via biological fixation, and an annual precipitation regime that favors extreme drying and wetting events, it is suspected that the interior chaparral ecosystem may support at least periodically high to very high rates of nitrogen oxide emissions. Specifically, this equipment will be used to make continuous, long-term measurements of exchanges of NO2, NO + NO2 (NOx), and N2O using a laser-based technique. The instrument tower will also be equipped with a special device for measuring vertical winds and a device for measuring CO2 and H2O concentrations. In addition to these measurements of gas exchange, supporting short-term chamber studies of N2O emissions by gas chromatography and chamber measurements of NO emissions will be conducted. These chamber studies will be conducted both in chaparral and in other ecosystems that are characterized by human alteration of the N cycle; these include fire-treated ponderosa woodlands, arid agricultural land and livestock-grazed arid grasslands. The results will guide the use of the instrumentation when the chaparral study is completed. As scientists from many disciplines work toward a better understanding of the processes underlying global change, it becomes increasingly clear that the knowledge of the interactions between living organisms and the atmosphere needs to be improved. The linkage between nitrogen cycling and global change is both direct (due to the greenhouse effect of N2O emissions) and indirect (due to the effects of nitrogen availability on the net absorption or release of key greenhouse gases CO2 and CH4). A good understanding of these ecosystem dynamics is key to understanding the potential for the biosphere to absorb the CO2 currently being released by fossil fuel combustion as well as to understanding how ecosystems will respond to the many environmental changes they are now being exposed to. Such information is vital to policymakers who are currently wrestling with issues such as that of global climate change. The answers to these questions will only come from extensive networks of such instrumentation; this will necessitate the training of large numbers of scientists in the specialized techniques involved in these measurements.