Tree-Ring Talk

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.

“Blue Rings" in paleoclimate reconstruction and beyond

'Blue Rings' are an anatomical anomaly found in conifers characterized by incomplete cell wall lignification, visible in safranin-Astrablue stained anatomical thin sections (Piermattei et al. 2015). This talk will guide you through a journey from the accidental discovery of 'Blue Rings', to the most recent application of their detection and enumeration in dendrochronology, forest ecology, and palaeoclimatology. The significance of the first millennium-long 'Blue Ring' chronology in detecting post-cooling volcanic eruptions will be discussed.

Dendrochronology in Motion: Visualizing Cottonwood Tree Growth across Space and Time

Cottonwood (Populus deltoides subsp. Monilifera) tree rings have been shown to faithfully record river discharge through time (Meko et al. 2015). What is less understood, however, is 1) how a tree's position on the floodplain influences its growth and its relationship to climate, and 2) how this influence changes through time. Taking advantage of the existing tree ring, hydrologic, and remote sensing datasets, we can watch the growth and development of a centuries-old riparian forest in a 10-minute video.

A hotter-drought fingerprint on Earth’s forest mortality sites – warming accelerates risks, especially for historical forests

Earth’s forests face grave challenges in the Anthropocene, including hotter droughts increasingly associated with widespread forest die-off. But despite the vital importance of forests to global ecosystem services, their fates in a warming world remain highly uncertain.

When the signal is the noise: Does aggregation impede prediction of forest response to climate?

Forest management aimed at promoting climate change resilience hinges on accurately quantifying the relationship between tree growth and climate. Aggregation is commonly used to upscale individual tree response (e.g., ring-width time series) to broader scales of inference, prediction, and decision-making. This approach assumes non-climatic drivers of tree growth vary randomly across a population such that their effects cancel out with replication and climate emerges as a strong predictor of aggregate tree growth.

Continental-scale tree ring-based projection of Douglas-fir growth - Testing the limits of space-for-time substitution

Nature-based solutions to the climate crisis increasingly focus on forests. In this research, we address the question “how much CO2 will trees remove from the atmosphere in the future?”, by projecting the future absolute growth of trees under future climate conditions. We confront the problem of extrapolation – i.e., that we must predict the response of trees to climate that is increasingly different from historical conditions.

The North American tree-ring fire-scar network

Fire activity is increasing across much of North America, driven by climate change and human land use. Instrumental records of fire are too short to quantify patterns and drivers of fire regimes to accurately model future fire.  Tree-ring fire scars are sub-annually resolved and span centuries to millennia.  We present the newly compiled North American tree-ring fire-scar network (n = 2,548 sites). It spans biomes from northern Alaska to southern Mexico and from California to northeastern Canada, including 104 different tree species.

The tracks of my floods: tree-ring memoirs of an Arctic river

The shortness of gaged river flows limits our understanding of the variability of the river component of heat and fresh water inflow to the Arctic Ocean. This talk describes a tree-ring approach to addressing the uncertainty of Arctic river flows using a combination of non-riparian and riparian  trees growing in the floodplain of the lower Ob River, in western Siberia. The talk focuses specifically on the tree-ring signal for inter-annual variability of flooding, which happens on a massive spatial scale each year along the Ob with spring ice break.

Revisiting the response of the Asian monsoon system to volcanic eruptions over the last millennium

Volcanic eruptions are the most important natural climate forcing over the last millennium.  Reductions in top of the atmosphere incoming shortwave radiation and the concomitant declines in global temperatures are expected to cause a weaker hydrological cycle, a reduction in precipitable water, and a drier monsoon.  The putative response of the ENSO system to volcanic eruptions should likewise result in drought of south and southeast Asia, enhancing this effect.

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