SGER: Measuring and Interpreting Nitrogen in Tree Rings

University Of Arizona, Tucson AZ

Investigators

Abstract

Abstract 00-87007 Sheppard SGER: Measuring and interpreting nitrogen in tree rings Presently, scientists cannot unequivocally interpret nitrogen concentrations in tree rings. The ability to do this would greatly improve understanding of N cycling, including the effects of recent large anthropogenic increases in N deposition. One difficulty in interpreting N concentration in tree rings is that N is notoriously mobile across plant tissues, rendering questionable its simple interpretability in tree rings as indicators of environmental availability at the time of ring formation. Another difficulty that has confounded simple interpretations of tree-ring N concentration is that its response to changes in N availability and uptake is still uncertain. This exploratory research has two objectives: to refine techniques for accurately measuring N in tree rings and accounting for possible translocation of N across rings, and to calibrate the response of N concentration in tree rings to known changes in N availability.