Biocomplexity: Coupled Nutrient, Water, and Salt Cycles in Urban and Agricultural Ecosystems

Project Staff: 

Principal Investigator: Patrick L. Brezonik, Professor, Department of Civil Engineering

Additional Staff: Robert Sterner, Professor, Department of Ecology and Evolutionary Biology; David Mulla, Professor, Department of Soil, Water, and Climate; and Heinz Stefan, Professor, Department of Civil Engineering, University of Minnesota


National Science Foundation

Project Duration: 

September 2001 - August 2003


Humans dominate the world's nitrogen cycle: about half of the world's nitrogen fixation is mediated by human activities. On an areal basis, N fixation in cropland and urban areas is 100-200 times higher than in the rest of the world's surface. Much of this fixed N becomes pollution, with major impacts on drinking water supply, urban air quality, estuarine fisheries, recreational use of lakes and rivers, and forest health. Despite this, we have very limited knowledge of nitrogen cycling in human-dominated ecosystems, and there is a paucity of knowledge regarding the coupling of nitrogen with other biogeochemical cycles: C, P, water and salts.

The goal of this study is to develop an approach for studying coupled biogeochemical cycles in urban and agricultural ecosystems, with a primary focus on nitrogen. The project will include a series of focused workshops leading to the development of a conceptual plan for initiating this research and for integrating research into graduate education. Workshop topics will include:

  1. identification of knowledge gaps regarding key processes
  2. issues regarding temporal and spatial scales
  3. developing a modeling framework
  4. integration and education

Concurrently, data from both study areas will be synthesized to develop initial comparisons regarding nitrogen cycling and hydrology between the two regions.

Two study regions comprise the full-scale research program: the Central Arizona-Phoenix ecosystem and the Minnesota River-Twin Cities ecosystem. Both include major urban and agricultural components, but they vary with respect to climate and hydrology. Both regions have been the subject of intensive ecological studies, including most of the members of this research team. Over the past 3-4 years, the Central Arizona-Phoenix ecosystem has been studied through a NSF-supported Long-Term Ecological Research Project. The Minnesota River Basin has been the subject of an EPA/NSF "Water and Watersheds" study, as well as extensive state-sponsored research. The Twin Cities-Minnesota River area has also been the focus of a USGS NAWQA study. The extensive databases from these studies and the integration of these data into knowledge facilitate the initiation of this study.

This project will contribute substantially to our emerging conceptualization of farms and cities as "ecosystems." Understanding coupled biogeochemical cycles in human ecosystems could revolutionize our approach for managing pollution, ending an era of "end-of-pipe" strategies and beginning an era of holistic, integrated approaches that would make effective use of emerging information technologies to increase effectiveness and decrease the cost of pollution control.