Tree-Ring Talk

High-resolution field reconstructions of Mediterranean hydroclimate during the last millennium

The Mediterranean region is projected to experience severe drying trends and more extreme hydroclimate events as a consequence of anthropogenic climate change over the next century.   In some places, this signal may have already emerged from natural variability.  Here we provide content for recent and future changes using new high-resolution spatial reconstructions of multiple hydroclimate fields from a tree-ring network that spans the last millennium.

Back To The Future With Tree-Ring Standardization: Maybe Schulman Did It The Right Way

This talk reflects over 45 years of research and contemplation by me on the tree-ring standardization problem. There is no optimal solution to this problem because the statistical properties of the raw ring-width data we typically process are very complicated and their expressions of radial growth over time are totally unobserved. It has recently become apparent to me that we spend too much time letting the computer do the standardization for us without taking time to look at the data.

Connecting tributary erosion to downstream floodplain forest establishment in a large river network

Sediment eroded from the headwaters of a large basin strongly influences channels and ecosystems far downstream, but the connection is difficult to trace. Disturbance dependent riparian trees are thought to rely upon floods for creation of the sand bars necessary for establishment, but pulses of sediment should also promote formation of this habitat.

Living with the star: Carbon-14 excursions in tree rings as the evidence for extreme solar activity

The annual 14C data in tree rings is an outstanding proxy for uncovering extreme solar energetic particle events (SEP, also called SPE -solar particle event) in the past. Signatures of extreme SEP events have been reported in 774/775CE, 992/993 CE, and ~660 BCE.

Tree-rings to biomass trajectories: uncertainty and fading records

Tree-rings provide evidence of past aboveground carbon storage that can be used to inform and constrain ecosystem model predictions. However, formal state data assimilation requires the characterization of the uncertainty associated with the data being assimilated. In addition, aboveground biomass reconstructions from living trees typically suffer from the fading record problem- that trees that once contributed to the aboveground biomass pool may have died.

Is understanding the past enough to predict the future? Global tree-ring data show complex impacts of climate change.

A deep-rooted concept in the dendrosciences is to infer climate or ecosystem variability from statistical relationships established between tree-ring and instrumental data. By extent, these relationships can then be extrapolated into past or future time frames, for example, to anticipate the impacts of anthropogenic climate change on forest ecosystems. Problematically, evidence is mounting that matters are not so simple and that the uncertainties associated with temporal and spatial scaling of tree-ring data are substantial.

Stable isotopes of tree rings reveal seasonal-to-decadal patterns during the emergence of a megadrought in the Southwestern US

Recent evidence has revealed the emergence of a megadrought in southwestern North America since 2000. In this occasion I will talk about how we examined tree-ring growth and stable isotope ratios in Pinus ponderosa at its driest niche edge to investigate whether trees growing near their aridity limit were sensitive to the megadrought climatic conditions during or before the establishment of the current megadrought.

Multicentennial perspectives on extreme climate and natural disasters in the northeastern Pacific

Over the past decade, the northeastern Pacific has witnessed repeated and severe heatwaves that have profoundly impacted the functioning and productivity of marine and adjacent terrestrial ecosystems. However, there remains considerable and long-standing uncertainly regarding NE Pacific climate variability prior to 1900 CE and the extent to which recent extremes are atypical in a longer-term context.

RingdateR: A statistical and graphical tool for crossdating

Crossdating is the defining technique of dendrochronology, ensuring that all measurements in a dataset are annually resolved and absolutely dated. This level of accuracy allows for the development of high-resolution environmental reconstructions of climate, disturbance, and productivity not only in trees, but also in other ring-forming organisms including fish, corals, and bivalves. However, crossdating is a laborious process and can be a significant bottleneck in the development of new chronologies, especially when attempting to find matches among undated, dead-collected material.

How Mountain Topography Shaped Fire Use in the Southern Canadian Rocky Mountains

The Kootenai people of southern Canada historically traversed the Rocky Mountains, often several times annually, to hunt bison on the eastern front ranges. Some routes across this complex landscape were more energetically efficient than others, producing a tendency for archaeological and historical sites to be located along least-cost paths as strongly predicted by this project’s geographical computer models. Bison wallows also occurred across low travel cost areas from the eastern front well into the Rocky Mountain interior.

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