Ph.D. 2006, University of Pennsylvania
B.S. 2002, University of Pennsylvania
My research employs the quantitative methods of stable isotope geochemistry to answer questions concerning environmental reconstruction and environmental health. I have applied these methods to the remains of multi-million-year-old floodplain forests that grew in the Canadian Arctic and Siberia, as well as to carbon, nutrient, and heavy-metal budgets in modern ecosystems. I am currently pursuing how beef stable isotope ratios are influenced by the diet of cattle, as well as how vegetables grown organically differ chemically from conventional produce.
Johnson, A.H. and S.L. Richter. Changes in organic matter, copper and zinc in organic horizons of mid-Atlantic region forest soils: 1978-2004. Soil Science Society of America Journal (in press).
Johnson, A.H., A. Moyer, J. Bedison, S. Richter, S. Willig, and M. Boyer. Seven decades of calcium depletion in organic horizons of Adirondack forest soils. Soil Science Society of America Journal (in press).
Helliker, B.R. and S.L. Richter. 2008. Subtropical to boreal convergence of tree-leaf temperatures. Nature 454: 511-514.
Richter, S.L., A.H. Johnson, M.M. Dranoff and K.D. Taylor. 2008. Continental-Scale Patterns in Modern Wood Cellulose d18O: Implications for Interpreting Paleo-Wood Cellulose d18O. Geochimica et Cosmochimica Acta72(12): 2735-2743.
Richter, S.L., A.H. Johnson, M.M. Dranoff, B.A. LePage, and C.J. Williams. 2008. Oxygen Isotope Ratios in Fossil Wood Cellulose: Isotopic Composition of Eocene- to Holocene- Aged Cellulose. Geochimica et Cosmochimica Acta 72(12): 2744-2753.
Williams, C., E. Mendell, J. Murphy, W. Court, A. Johnson, and S. Richter. 2008. Paleoenvironmental Reconstruction of a Middle Miocene Forest from the Western Canadian Arctic. Palaeogeography, Palaeoclimatology, Palaeoecology 261: 160-176.
Johnson, A.H., A. Moyer, J. Bedison, S. Richter, S. Willig, and M. Boyer. Seven Decades of Calcium Depletion in Organic Horizons of Adirondack Forest Soils. Soil Science Society of America Journal (in press).
Bedison, J.E., A.H. Johnson, S.A. Willig, S.L. Richter, and A. Moyer. 2007. Two Decades of Change in Vegetation in Adirondack Spruce-Fir, Northern Hardwood and Pine-Dominated Forests. Bull. Torrey Botanical Society 134(2): 238-252.
Richter, S.L. and B.A. LePage. 2005. A high-resolution palynological analysis, Axel Heiberg Island, Canadian High Arctic, Chapter 3 in: The Geobiology and Ecology of Metasequoia, LePage, B.A., C.J. Williams and H. Yang, eds. Springer, The Netherlands. pp. 137-158.
ENV/GEO 114 - Earth, Environment and Humanity
ENV/GEO 172 - Changing Climate, Changing Weather
ENV/GEO 274 - Footprints of Crime and Climate