Tree-Ring Talk

Asian Monsoon Variability over the Past Millennium Reconstructed from Long Tree-Ring Records: the Monsoon Asia Drought Atlas, version 2 (MADAv2)

The Monsoon Asia Drought Atlas, version 2 (MADAv2), is a substantially updated and improved year-to-year reconstruction of summer drought and wetness on a 1.0° grid over Monsoon Asia. It has been developed using the same basic methodology as that used in producing the previous version (MADAv1) published in 2010 and is now based on an improved target field of self-calibrating Palmer Drought Severity Indices (scPDSI) and a significantly larger network of 453 tree-ring chronologies compared to the previous effort.

Alex Arizpe thesis defense (public talk)

Despite increasing aridity, climate change promotes growth of North American grasslands

A grassland productivity model, based on temperature-moisture interactions and informed by observations made across a range of North American grassland ecosystems, was used to predict the response to climate change based on CMIP-5 climate projections over the next century. I will present the results of the model analyses which indicate a future shift of grassland growth towards both earlier spring emergence and delayed senescence in autumn, which together compensate for drought-induced reductions in summer productivity in most North American grassland regions.

A new laboratory of dendrochronology in Valparaíso, Chile: Expanding the tree-ring applications in South America

The breadth of geographic conditions, climatic variations, and dynamics of the landscape of Chile makes Chile a natural laboratory for the use of dendrochronology in several of its applications. In this talk, we will share some of the experiences that are taking place in the new Laboratory of Dendrochronology and Environmental Studies in the city of Valparaíso to study the dynamics of the environment in Chile.

Tipping point analysis of geophysical data

We apply the tipping point toolbox [1-8] to study transitions and bifurcations in various geophysical datasets. We study early warning and detection signals of the records using methodology that combines degenerate fingerprinting and potential analysis techniques for anticipation, detection and forecast of tipping points in a dynamical system. Degenerate fingerprinting indicator is a dynamically derived lag-1 autocorrelation, ACF (or, alternatively, short-range scaling exponent of Detrended Fluctuation Analysis, DFA [1]), which shows short-term memory in a series.

Probing the Error Term in Streamflow Reconstruction

Water balance models were first applied indirectly by tree-ring researchers in reconstructions of Palmer Drought Severity Index in the mid-1970s. Recent years have seen more direct and explicit use of water-balance models. This talk explores how a simple monthly water-balance model can be applied to diagnose possible causes of large errors in reconstructions of streamflow.

Drought in the rainforest? A shifting perspective on water scarcity in coastal British Columbia from tree-ring records

Summer streamflow droughts on British Columbia's rainforest coast have worsened dramatically over the last two decades, impacting human and ecological water supply. This region's unique hydroclimatology means that the "wettest part of Canada" is often the most water-scarce during summer, when demand is highest. The perception of being water-rich consistently undermines water conservation efforts in this densely populated area.

An exploratory study in wood anatomy, crossdating, climate-growth relationships, life history, and above-ground productivity

Velvet mesquite (Prosopis velutina Woot.) is a common tree in semi-arid, southwestern U.S. savanna ecosystems. While there are studies that examine some of the physiological and ecological aspects of this tree (response to fire, net ecosystem exchange, encroachment into grasslands, yearly growth through dendrometer bands, etc…), the wood anatomical features of a growth ring, suitability for dendrochronological research, life history, and above-ground productivity through time are knowledge gaps that can be filled.

Dendro Potential Along the John Muir Trail

I hiked the John Muir Trail this summer, noting lots of potential sites and projects for dendrochronology.

A process-based approach to understanding ecosystem-scale variation in n-alkane δD

Normal alkanes (n-alkanes) are long-chain fatty acids that are synthesized by terrestrial plants and then accumulate in soils and sediments. Since the hydrogen in the n-alkanes is derived from the hydrogen in plants’ water sources, the stable hydrogen isotopic composition (δD) of the n-alkanes includes information about the δD of environmental water.

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