THE ECOLOGICAL QUESTION

How have pine and hardwood stands in a temperate forest responded to 15 years of nitrogen additions?

ECOLOGICAL CONTENT

forest ecosystem, nitrogen (N) deposition, primary productivity, soil respiration, microbial community, replication

WHAT STUDENTS DO

Students work with data to ask and address questions about effects of chronic N additions to two forest types. Four Microsoft Excel files on net primary productivity, tree photosynthetic capacity, soil respiration, and soil microbial biomass allow students to consider effects of long-term N enrichment in northeast US forests. Students in a basic ecology class can use part of the data set; more advanced students, in a plant ecology class for example, can work up all the data.

SKILLS

Asking and addressing questions with data, critical thinking, graph preparation, data analysis and interpretation, and writing or oral presentation.

STUDENT-ACTIVE APPROACHES

Students examine data, ask their own questions, and then propose the most meaningful figures to get at these questions. A set of open-ended prompts are provided.

ASSESSABLE OUTCOMES

Simple statistics (means and standard errors), graphs from spreadsheet data, and written and oral communication of results and conclusions.

SOURCE

Bauer, G.A., F.A. Bazzaz, R. Minocha, S. Long, A. Magill, J. Aber, and G.M. Berntson. 2004. Effects of chronic nitrogen additions on tissue chemistry, photosynthetic capacity, and carbon sequestration potential of a red pine (Pinus resinosa Ait.) stand in the NE United States. Forest Ecology and Management 196:173-186.

Bowden, R.D., E. Davidson, K. Savage, C.Arabia, and P. Steudler. 2004. Chronic nitrogen additions reduce total soil respiration and microbial respiration in temperate forest soils at the Harvard Forest. 2004. Forest Ecology and Management 196:43-56.

Frey, S.D., M. Knorr, J. Parrent, and R.T. Simpson. 2004. Chronic nitrogen enrichment affects the structure and function of the soil microbial community in a forest ecosystem. Forest Ecology and Management 196:159-171.

Magill, A.H., J.D. Aber, W.S. Currie, K.J. Nadelhoffer, M.E. Martin, W.H. McDowell, J.M. Melillo, and P. Steudler. 2004. Ecosystem response to 15 years of chronic nitrogen additions at the Harvard Forest LTER, Massachusetts, USA. Forest Ecology and Management 196:7-28.

AUTHORS

Serita D. Frey

Department of Natural Resources, University of New Hampshire, Durham, NH, 03824, serita.frey@unh.edu

ACKNOWLEDGMENTS

This exercise is based on data published in a special issue of Forest Ecology and Management that provides a detailed report on results from the first 15 years of chronic N additions to pine and hardwood stands at the Harvard Forest in Petersham, MA, USA. I greatly acknowledge John Aber, Alison Magill, Richard Bowden, and Guntrum Bauer whose data and ideas contributed to this activity. Funding to develop this exercise was provided by the National Science Foundation (DEB-0224917).

CITATION

Frey, Serita D. April 2006, posting date.
Forest Ecosystem Responses to Chronic Nitrogen Additions, Teaching Issues and Experiments in Ecology, Vol. 4: Issues: Data Set #1 [online].
http://tiee.ecoed.net/vol/v4/issues/data_sets/nitrogen_additions/abstract.html