Tree-Ring Talk

Miracle March, August flooding, and October atmospheric rivers: Seasonal wet extremes & the tree-ring record

Moisture-sensitive trees provide exceptional long-term records of streamflow, snowpack, and rain within the context of our changing climate. The delivery of a large portion of annual moisture in a short period of time can present a challenge to our interpretation of these records. This is particularly true in arid and semi-arid regions, where late-spring snowpack, summer convective storms, or autumn atmospheric rivers can provide a high percentage of annual water in a season that might not be aligned with tree growth.

Using tree-ring chronologies to calibrate a forest gap model in Denali National Park

Merging robust statistical methods with complex simulation models is a frontier for improving ecological inference and forecasting. However, bringing these tools together is not always straightforward particularly with tree-ring data. Matching tree-ring data with model output, determining starting conditions, and addressing high dimensionality are some of the complexities that arise when attempting to incorporate tree-ring data with mechanistic models directly using sophisticated statistical methods. To illustrate these complexities and pragmatic paths forward, we

Tree rings and the Truckee River: paralleling the past and the present

The Truckee River Basin, located on the Nevada-California border, is an area of extreme hydrologic variability, being subject to both prolonged multi-decadal droughts and devastating floods; however, due to its brief instrumental record, understanding the full range of this variability is limited. To address concerns over the potential severity of the current post-2000 drought, I created a new streamflow reconstruction of the Truckee River.

A spatial field reconstruction of North American summer air temperatures derived from a tree-ring blue intensity network 

Spatially-resolved climate field reconstructions are opportune for analyzing spatial anomaly patterns and characterizing regional-scale trends resultant from climate change. To date, few fine-scale (<5o by 5o) spatially-resolved paleo-temperature datasets exist in the Northern Hemisphere, especially those with representation of locations below 40oN.

A multimillennial snow water equivalent reconstruction from giant sequoia tree rings

The first dendroclimatic reconstruction of May 1 Snow Water Equivalent (SWE) was developed from a Sequoiadendron giganteum regional tree-ring chronology network of 23 sites in central California for the period 90-2012 CE. The reconstruction is based on a significant relationship between May 1 SWE and tree-ring growth and shows climate variability from inter-annual to inter-centennial time scales. A regression-based reconstruction equation explains up to 55% of the variance of SWE for 1940-2012.

Forests, climate, and tree rings: forecasting the future state of complex systems

At this stage in the Anthropocene, answering questions about the future state of ecological systems has become critical – the future growth of trees exposed to changing climate, tree species’ future geographic distributions, and the future role of forests in the global carbon cycle – yet ecological systems are complex. Summarizing four lines of research, I will illustrate how the use of tree-ring and forest inventory data can help address questions about and improve prediction of forest and climate system dynamics.

What I did this summer

Our traditional "what I did this summer" lightning talks by students and faculty of LTRR; you are welcome to take 1-5 minutes to say a few words and share one or more slides related to work or fun.

Progress report on reanalysis of the Hawley-Bell collection: Tree-ring chronology building and 14C dating at the religious and political centers of pre-contact eastern North America

During the twelfth century A.D. Indigenous societies across the Mississippi River Basin transformed: populations aggregated into towns around dramatic monumental constructions that represented the seat of polities, communities adopted foreign styles, and more centralized leadership roles emerged. While the general outline of Mississippian history is known, exactly how people came to abandon old cultural practices in favor of the Mississippian pattern is not understood, nor are the historical details of individual mound centers.

The Missouri River: A Story of Two Basins

The Missouri River is unusual because of its two main source regions, one in the high headwaters and one close to the mouth of the river.  In this talk, I report the results of research which explored the hydroclimatology of the basin to better understand the climatic controls on the two parts of the basin, the contribution of the snowmelt-driven streamflow to total Missouri River flow, and the nature of droughts in the instrumental record.  I will also discuss the first comprehensive set of streamflow reconstructions for the upper Missouri River, and the Turn-of-the-21st Century

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