Global Nitrogen Seminar


1-unit Seminar for CCT CONICET Mendoza

Proposed for teaching component of sabbatical leave to Argentina

dendroenvironmental science


Dr. Paul Sheppard, email: sheppard @
Dr. Alejandro Casteller, email: casteller @
Dr. Julieta Aranibar, email: jaranibar @

General objectives of this course

Learn details of global nitrogen dynamics. Review natural versus anthropogenic sources of fixed nitrogen, forest ecosystem effects of increased environmental availability of fixed nitrogen, general techniques of assessing nitrogen in forests, and applications of dendrochemistry in environmental science of nitrogen.

Seminar meetings

We will meet for five days, about four hours per day. We will be spend time in lecture/discussion, where we will review relevant literature and learn concepts. We will cover methods of measuring nitrogen in the environment, including elemental analysis of wood and sediment samples. We will be in the lab, either together or individually, to actually do the many steps of sample preparation for measurement for nitrogen.

Obligations and Expectations


Office hours and readings

Flexible Schedule of Activities (subject to change)
1 Lecture: Global Nitrogen Cycling: Pools, Fluxes

Reading: Vitousek: 1995. Global Nitrogen.
Reading: ESA: 1998. Nitrogen: the Grand Challenge.

Lab: Prepare samples for measurement of nitrogen
2 Lecture: Importance of nitrogen for life on Earth

Reading: Nitrogen fixation in agriculture, forestry, ecology, and the environment: Nitrogen as a limiting factor in forests.
Reading: Nitrogen saturation in temperate forest ecosystems - Hypotheses revisited: Nitrogen oversaturation.

Lab: Prepare samples for measurement of nitrogen
3 Lecture: Dendrochemistry of nitrogen

Reading: Smith and Shortle: 1996. Tree biology and dendrochemistry.
Reading: Poulson et al.: 1995. N isotope variation in tree rings.
Reading: Sheppard and Thompson: 2000. Effect of extraction pretreatment on temporal variation of nitrogen in tree rings.
Reading: Sheppard and Topa: 2002. Physical-chemical pretreatment of wood for measuring tree-ring nitrogen.
Optional Reading: Heaton: 1990. 15N/14N ratios of NOx.

Lab: Submit samples for nitrogen measurement
4 Lecture: Chemical measurement of nitrogen in multiple sample types

Reading: EA basics.
Reading: Other measurement options.

Lab: Begin plotting measurement results
5 Lecture: Spatial analysis of nitrogen

Reading: Forest ecosystems and the changing patterns of nitrogen input and acid deposition today and in the future based on a scenario: Studies in North America.
Reading: Assessment of the relative importance of nitrogen deposition and climate change on the sequestration of carbon by forests in Europe: an overview: Studies in Europe.
Reading: More is less: agricultural impacts on the N cycle in Argentina: Studies in South America.

Lab: Plot out final results
Later Research paper due

Laboratory of Tree-Ring Research, University of Arizona
Tucson, Arizona 85721 USA
Office: (520) 621-6474, Fax: (520) 621-8229
Comments to Paul Sheppard: sheppard @