Tree rings are an important natural archive of past environments. Though these records have great value and potential, important details about rates and patterns of carbon storage in annual growth layers (tree rings) remain poorly understood. These gaps in knowledge concern the basic natural history of the tissue that forms wood. This research, led by scientists from the University of Arizona and Rocky Mountain Tree-Ring Research, Inc., aims to improve the scientific basis for the use of tree ring records by compiling data sets of when key tree growth processes start each year, the rate at which each proceeds and for how long, and how daily to seasonal variations in climate conditions relate to the timing, rate, and magnitude of each process. This will be the first such study in the Western US. The research team will collect data at four clusters of sites in Wyoming, Colorado and Arizona, all centered on existing flux tower facilities and including the major tree types used in dendroclimatology in this large region. They will then compare the tree growth data with air, stem and soil temperature, water availability, sapflow and other factors, as well as phenological events such as shoot extension and needle elongation. These data and comparisons are essential for improving forward models of tree ring growth control. The methods, based on and informed by sound process models of the climate control of tree ring formation, have the potential to improve robustness, extend generality, and better assess the biological validity of climate reconstructions based on tree rings. Such methods are also central to emerging Bayesian techniques of paleoclimate reconstruction, and to attempts to test reconstruction methodologies using synthetic proxy records.
The broader impacts of this research include improved understanding of past climates and improved understanding and prediction of responses of wood growth in western forests to recent or possible future climates. The latter is a significant practical concern, as much of the carbon in forests is stored in wood, and the results of this research will further inform projections of carbon allocation and storage in response to climate change. The project will involve undergraduate researchers in field and lab work and the publication of results. The PIs will engage in outreach both directly through public talks and media interviews as well as through the University of Arizona Extension Service.
