Isotope Dendrochronology

GEOS/WSM 595E, Section 4

Fall 2004

1-3 credits

TIME: Organizational Meeting 8/27, 1-2 pm Room 20 Tree-Ring Annex (Math East)

Class period Fridays 1-3 pm, 9/10, 9/17, 9/24, 10/01, 10/8, 10/15, 10/22

LOCATION: Room 20 Tree-Ring Annex (Math East)

INSTRUCTOR: Steven W. Leavitt, Professor, Lab. of Tree-Ring Research

Office: 218 W. Stadium (621-6468); sleavitt@ltrr.arizona.edu

Office Hours: by appointment

Purpose: To introduce fundamental concepts, terminology and parameters pertinent to isotopes and isotope fractionation. To examine (1) historical applications of isotopes in tree rings with respect to atmospheric chemistry, climatology and ecology, (2) mechanistic models of tree-ring isotopes, (3) exciting new findings and future directions in isotope dendrochronology.

Organization & Grading: There will be assigned readings to be discussed in class and practice homework sets to help develop skills and understanding. Each student will be responsible for presenting and leading discussion on two related articles in one of the class meetings. Every student is responsible for reading articles before each class.

Students taking 2 credits will undertake a study on an isotope dendrochronology topic of the student's choice, the culmination of which is a term paper (about 10 pages of text, plus references and figures/tables due on or before the last day of semester classes) or presentation in our final class meeting. Students taking the course for 3 credit hours must develop and conduct a significant lab-based component of their project in addition to their literature study. Students taking 2 or 3 credits should present and discuss their proposed research topic with the instructor early in the semester.

For 1 credit, grades will be based on general class participation [25%] and their performance in presentation of their chosen articles [75%]. For 2-3 credits, grades will be based on general class participation [25%] and their performance in presentation of their chosen articles [25%], and their term paper or term presentation [50%].

An optional final exam will be available for students wishing to improve their course grade.

Attendance is mandatory and 1/5^th of general class participation grade will be deducted for each unexcused absence.

Week 0 (8/27) Organizational Meeting (Organizational Information)

Bibliography of Isotope Dendrochronology

Week 1 (9/10) Isotope and tree rings

Elements, nuclides, isotopes, isotope effects, isotope fractionation (kinetic and

equilibrium), δ notation, isotope standards, mass spectrometry, isotopic preparation

Study Questions 1

McCarroll, D. and Loader, N.J., 2004. Stable isotopes in tree rings. Quaternary Science Reviews 23: 771-801.

Slides/notes

Week 2 (9/17) Modelling isotopes in tree rings

meteoric water line, H & O isotopes in precipitation, H & O

isotopes in plant-soil systems, carbon isotope models, isotopic variability in tree rings

Study Questions 2

Francey, R.J. and Farquhar, G.D., 1982. An explanation of ¹³C/¹²C variations in tree rings. Nature 297: 28-31.

Roden, J.S., Lin, G. and Ehleringer, J.R. 1999. A mechanistic model for interpretation of hydrogen and oxygen isotope ratios in tree ring cellulose. Geochimica et Cosmochimica Acta 64: 21-35.

Week 3 (9/24) Isotope preparation and methods (Kevin Jones)

Study Questions 3

Borella, S., Leuenberger, M, Saurer, M. and Siegwolf, R. 1998. Reducing uncertainties in d¹³C analysis of tree rings: pooling, milling, and cellulose extraction. J. of Geophysical Research 103: 19,519-19,526.

Borella, S., Leuenberger, M, Saurer, M. 1999. Analysis of d18O in tree rings: Wood-cellulose comparison and method dependent sensitivity. J. of Geophysical Research 104: 19267-19273.

Hoper, S.T., McCormac, F.G., Hogg, A.G., Higham, T.F.G. and Head, M.J., 1998. Evaluation of wood pretreatments on oak and cedar. Radiocarbon 40: 45-50.

Week 4 (10/1) Stable-carbon isotopes and water-use efficiency (April Chiriboga)

Waterhouse, J.S., Switsur, V.R., Barker, A.C., Carter, A.H.C., Hemming, D.L., Loader, N.J. and Robertson, I., 2004. Northern European trees show a progressive diminishing response to increasing atmospheric carbon dioxide concentrations. Quaternary Science Reviews 23: 771-801.

Feng, X. 1999. Trends in intrinsic water-use efficiency of natural trees for the past 100-200 years: A response to atmospheric CO₂ concentration. Geochimica et Cosmochimica Acta 63: 1891-1903.

Week 5 (10/8) Isotopes in Hydrology (Scott St. George)

Waterhouse, J.S., Barker, A.C. and Carter, A.H.C., 2000. Stable carbon isotopes in Scots pine tree rings preserve a record of flow of the river Ob. Geophys. Res. Lett. 27: 3539-3532.

Potts, D.L. and Williams, D.G., 2004. Response of tree ring holocellulose d¹³C to moisture availability in Populus fremontii at perennial and intermittent stream reaches. Western North American Naturalist 64: 27-37.

Dawson, T.E. and Ehleringer, J.R. 1991. Streamside trees that do not use stream water. Nature 350: 335-337.

Week 6 (10/15) Nitrogen Isotopes in Tree Rings (Sammy Moses)

Poulson, S.R., Chamberlain, P.,C. and Friedland, A.J. 1995. Nitrogen isotope variation of tree rings as a potential indicator of environmental change. Chemical Geology (Isotope Geoscience Section) 125: 307-315.

Saurer, M., Cherubini, P., Ammann, M., De Cinti, B. and Siegwolf, R., 2004. First detection of nitrogen from NO_x in tree rings: A ¹⁵N/¹⁴N study near a motorway. Atmospheric Environment 38: 2779-2787.

Tracing source or strength of source of precipitation (Erica Bigio)

Feng, X., Cui, H., Tang, K. and Conkey, L.E., 1999. Tree-ring D as an indicator of Asian Monsoon Intensity. Quaternary Research 51: 262-266.

Week 7 (10/22) Kevin Jones presentation of term project (opportunity for other class members to present an article; or unfinished business)