Funding is provided to develop replicated, multi-century tree-ring width and intra-to-inter annual oxygen isotopic proxy records of precipitation in North Queensland, Australia from plantation tree samples and long lived wild specimens of Callitris intratropica and Araucaria cunninghamii. The overarching scientific goal of the project is to develop a reliable archive of climate data from tropical tress for which classic annual growth bands are not formed. The region of study is strongly affected by El Nino-Southern Oscillation (ENSO) activity, as well as longer term droughts with great impact on agriculture and water resources.
The broader impacts involve strong international collaboration, supporting a graduate student and post-doctoral scholar, and bringing a different quantitative perspective to the analysis of paleoclimate data.
Research Accomplishments: Intellectual merit We developed reference materials and methods for making stable isotope measurements on wood quickly and cheaply, but with high precision and accuracy. A paper describing the approach is being prepared for submission to the peer-reviewed literature, and materials and methods are being shared with other stable isotope laboratories. In many regions of the tropics, tree rings are not reliably formed every year because of the absence of clearly-defined cold and warm seasons. The presence of clearly defined wet and dry seasons, however, allow us to use the stable isotopic composition of wood in tropical trees to establish the year in which the wood was formed. Variations above the seasonal cycle are related to variations in the amount of rainfall. In a pilot study for 1995-2010, we found statistically significant correlation between the oxygen isotopic composition of Kauri trees from northern Queensland and local rainfall. Since local rainfall varies during El Nino and La Nina events, the results suggest that isotopic data may be used to develop long-term (150+ year) rainfall reconstructions from the region and learn more about the long-term variations in El Nino frequency and strength. Ongoing work suggests that the same approach will be successful using samples from Hoop Pine, another long-lived conifer commonly found in the region. An open-access paper was published in PLOS One (www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0102336), and the data are publicly archived for further study (www.ncdc.noaa.gov/paleo/study/17267). See primary image (1) for a figure showing the key results. Training and Outreach: Broader impacts. Three high school students, 9 undergraduates and two graduate students received training and mentoring on research projects in the stable isotope laboratory. Presentations on research results were made at national and international workshops and conferences, 2009-2014, by the principal investigator, graduate students and collaborators. We presented and discussed results from this project at Maryland Days in 2010, 2011, 2012, 2013, and 2014. Maryland Day is an open house on the campus of the University of Maryland, College Park (www.marylandday.umd.edu) and annually attracts an estimated 65,000 attendees. See second image (2) for a picture of the principal investigator talking with two young scientists at Maryland Day 2014.
