|Groffman, Peter - INST ECOSYSTEM STUDIES|
|Verchot, Louis - INTL CTR RES AGRO FORESTR|
|Potter, Christopher - NASA AMES RESEARCH CTR|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: July 16, 2004
Publication Date: March 15, 2006
Citation: Groffman, P.M., Venterea, R.T., Verchot, L.V., Potter, C.S. 2006. In: Wu, J., Jones, H., Li, H., Loucks, O., editors. Scaling and Uncertainty Analysis in Ecology: Methods and Applications. Landscape and regional scale studies of nitrogen gas fluxes. Springer, Dordrecht, The Netherlands. p. 191-203. Interpretive Summary: A central challenge confronting many areas of research within the earth and environmental sciences is extrapolating measurements made at spatial and temporal scales corresponding to the measurement methodologies to larger scales that have more relevance with respect to the environmental impact of the measured variables. The ever-increasing use of nitrogen fertilizers and the combustion of fossil fuels world-wide have caused an accelerated rate of release of nitric oxide (NO) and nitrous oxide (N2O) gases from soils. Measurements of NO and N2O release rates from soils are commonly done using methods that capture information on spatial scales of square centimeters to hectares, and time scales of minutes to hours, while the impact of NO and N2O on atmospheric processes is most important at much larger scales. This chapter describes a case study of how experimental design and modeling can assist in partly addressing these scaling challenges, while also describing some limitations that remain relatively intractable in the absence of measurement methodologies that are applicable over the larger scales of interest.
Technical Abstract: This chapter presents a case study of scaling one particular biogeochemical process: soil-to-atmosphere fluxes of nitrogen (N) gases. These fluxes present great conceptual and practical scaling challenges because they are mediated by microorganisms at the scale of microns and seconds but have relevance at relatively large spatial (meters to kilometers and larger) and temporal (years, decades) scales. The case study is based on a US Environmental Protection Agency funded research project investigating the "effects of N deposition on gaseous N loss from temperate forest ecosystems." This project takes advantage of an N deposition gradient in the northeastern US that runs from West Virginia (high deposition) north and east to Maine (low deposition). In this paper we address three scaling challenges, 1) the need to account for landscape scale variability in regional scale studies, 2) the use of models as tools to account for the episodic nature of gas fluxes and 3) validation of landscape and regional scale flux estimates. We first discuss "motivations for scaling," introduce the topics of N gas fluxes and deposition, briefly describe our regional project and then show how we have addressed the three scaling challenges listed above.