Tree-Ring Talk

“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.

Assimilation of tree ring and forest inventory data to forecast future growth responses of Pinus ponderosa

Forest responses to future climate changes are highly uncertain, but critical for forecasting and managing for forest carbon dynamics. To improve ecological forecasts of forest responses, we harness the strengths of two large ecological datasets: tree-ring time series data that provide annually resolved growth responses, and repeated measurements of tree size measurements from spatially extensive forest inventory (FIA) data.

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.

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