Tree-Ring Talk

A review of the 2020 North American Monsoon season

After a relatively weak monsoon across the southwestern U.S. in 2019, expectations were high for an active 2020 monsoon season. Unfortunately, the opposite happened and June through September precipitation totals were record low for many stations across the region. The summer was also the hottest on record for many locations. This presentation will provide a basic background of the climatology of the North American Monsoon System with respect to shifts in circulation patterns, moisture sources, and patterns of precipitation.

Art and the Ecology of Time

Standard time is measured on atomic clocks, providing a technical basis for business and personal activities. Might trees be more meaningful timekeepers? Might a clock paced by their natural growth encourage us to nurture our environment and the relationships that matter most? Over the past several years, conceptual artist and experimental philosopher Jonathon Keats has been collaborating with the Long Now Foundation and the Nevada Museum of Art on a monumental clock calibrated by bristlecone pine trees.

dfoliatR empowers analyses of forest defoliator outbreak chronologies

Further extending the functional capacity of classic DPL programs, we developed “dfoliatR”, an R package based on the program OUTBREAK developed by Richard Holmes and Thomas Swetnam in the 1980s. dfoliatR uses dplR to access standardized tree-ring series from insect defoliator host species and chronologies from non-host species. It infers defoliation events with an indexing procedure that removes the climatic signal (represented in a non-host chronology) from individual host-tree series.

The Dendroarchaeology of Navajo Sites on Northern Black Mesa, Northeastern Arizona

From 1967 to 1986, scholars from, first, Prescott College and, subsequently, Southern Illinois University at Carbondale undertook one of the largest contract archaeological projects in Arizona.  The Black Mesa Archaeological Project (BMAP) was designed to mitigate the damage to the cultural resources of the Mesa caused by the construction of an open pit coal mine to provide fuel for the Navajo Generating Station near Page, Arizona.  Documentation of nearly 2,000 prehistoric (Ancestral Puebloan) and historic (Navajo) sites produced more than 8,000 archaeologic

This summer: what I did, what I didn't do, and what I wanted to do

The long-standing tradition of a round up of activities over the summer continues with a series of five-minute lightning talks by the following people:

  1. David Frank
  2. Margaret Evans
  3. Charlotte Pearson
  4. Paul Sheppard
  5. Peter Brewer
  6. David Meko
  7. Brandon Strange
  8. Ann Lynch
  9. Ramzi Touchan
     

Tree-ring data in collaborative forest management

Public land management agencies in the US have been shifting from top-down, command-and-control governance to models based on collaborative input from a variety of stakeholders. Stakeholder collaborative groups increasingly help define and prioritize land management policy and direction, assist in project implementation, and provide learning through adaptive monitoring efforts. Collaborative governance is increasingly seen as a means to build greater and more robust adaptive capacity of social, economic, and ecological systems, especially in the face of future impacts on ecosystems from climate change, increasingly severe wildfires and other disturbances, and human land use. In this talk, I outline how evidence of historical ranges of variability in fire and forest histories derived largely from dendroecological data sets have provided a crucial scientific foundation for collaborative governance in forests of the Front Range in Colorado. These efforts are directed primarily at reducing the ecological and social impacts of wildfires in montane forests where much of the wildland-urban interface is found, and that was historically characterized by frequent, low-intensity wildfires. I also provide examples from Mongolia and China of how models for collaborative governance based on dendroecological data are starting to be used within the context of current social, ecological, and economic realities.

Exploring wood anatomy, chemistry and climate through the world’s longest living organisms, North American Bristlecone Pine

Drought years cause wood density spikes in southwestern ponderosa pine

Expected vs observed carbon isotopic discrimination trends of woody plants

Large contribution from anthropogenic warming to an emerging North American megadrought

Over the past two decades much of western North America experienced persistent drought with little to no respite. Consequences were widespread, including declines in river flow and reservoir storage, over-extraction of ground water, explosion of forest-fire activity, and massive bark beetle outbreaks. Water-balance calculations make clear that 2000–2018 was easily the driest 19-year period in the past century. To what degree if at all is human-caused climate change responsible and what is the future trajectory of water supply in western North America?

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