Sessions in which Daniel Griffin participates
Tuesday 28 June, 2022
Ultra high resolution imaging is becoming standard across the sciences and must be a priority for dendrochronology. Large format scanners fail to resolve micro rings and the anatomical structures of increasing scientific interest. Meanwhile, current software limitations include cost, user experience, data management flexibility, and capacity for handling large file sizes. We argue for a new paradigm and present a technology framework that integrates gigapixel macro photography, a cloud-hos...
Sessions in which Daniel Griffin attends
Monday 27 June, 2022
Free, in person and onlineWe will hold a practical, skills-based workshop introducing openDendro -- an open-source framework of the base analytic software tools used in dendrochronology in both the R and Python programming languages. openDendro is a new unified set of tree-ring analysis tools in open-source environments that provides the necessary baseline for dendro...
Tuesday 28 June, 2022
Africa is faced with a number of challenges including climate change and ecological disturbance due to various anthropogenic activities. These problems adversely affect the forests and also ecosystem services. My appreciation for the forests motivated me to pursure my undergraduate studies in Forestry. I first applied dendrochronology during my PhD research which focused on understanding the climate change vulnerability of the Zambezi teak forests in Zambia. However, lack of research facil...
Maritime forests are extremely important for coastal protection as they buffer storm surge and wind, conserve nutrients, and store groundwater. They grow several 100 meters behind primary beach dunes or along intertidal marsh-forest ecotones and within range of salt spray, near shoreline estuaries, where they support large amounts of biodiversity and migratory birds. Trees in these forests typically handle small concentrations of salt spray, strong winds, and slight flooding, but prolonged...
Climate change poses an existential threat to trees, given our understanding of the importance of climate in shaping their geographic distributions. Climate envelope models are commonly used to predict how species will respond to climate change. These models give rise to the leading edge-trailing edge paradigm for range change: populations at the cool edge of a species’ distribution are expected to benefit from warming, whereas populations at the warm edge are expected to decline. We chall...
Evidence of volcanic cooling and its human impacts has been described for various regions of the globe over the past several centuries to millennia, derived from paleoclimatic and historical data. Due to its remote location, detailed accounts of such impacts over Northwestern North America (NWNA) are still quite limited. Here we use a newly expanded tree-ring density network (derived from blue intensity as well as maximum latewood density parameters) to assess the climatic and human impact...
The spatial scale of climate fluctuations, or effective spatial degrees of freedom (ESDOF), depends on the timescale and the forcing: while local scale variability between far away locations may be independent on short timescales, they may become coherent over sufficiently long timescales, or if they are driven by a common forcing. While ESDOF have been estimated from instrumental data over the historical period and climate model simulations, it remains difficult to perform such analysis o...
"Emerging in the early 20th century, the scientific study of tree-rings has a rich but under-cultivated history. This project reviews the historiography (or the history of historical writing) of dendrochronology. From the pioneering work of A.E. Douglass and others to the establishment of institutions dedicated to advancing dendrochronology by the 1950s, the field has secured its place as an ensemble of techniques to interpret tree rings, with applications in archeology, climatology, ecolo...
Tree-ring research has given generations of scientists a long memory of what is acceptable for a tree to be included for data analysis. The established criteria, however, were set through purposeful goals to maximize the response for climatic reconstructions. Ecology is different. Tree-rings are increasingly being used to study a wide swath of ecology, including the carbon cycle or the response of ecosystems to global changes. A fundamental aspect of ecology is to understand the range of r...
Complex topography can facilitate climatic and hydrologic microenvironments that buffer plants against climate change and extreme drought. However, the extent to which topographic position mediates tree growth response to climate is still poorly understood. Dendrochronology, the use of precisely dated tree rings to study environmental processes and history, has been critical for assessing tree growth response to climate variability across topographical gradients. We developed new tree-ring...
Dendroclimatic reconstructions play a key role in contextualizing recent climate change by improving our understanding of past climate variability. The climatically-sensitive blue intensity (BI) parameter is gaining prominence as a more accessible alternative to X-ray densitometry. Yet accurately representing low-frequency trends and high-frequency extremes using scanner-based BI remains a challenge due to color biases and resolution limitations. As part of the REPLICATE project, methodolo...
In this work we show the application of dendrochronology as an educational resource for schoolchildren and as a mean to disseminate science to society. Tree rings are popularly known in Chile due to the massive use of wood for construction, handicrafts and firewood. The visible tree rings generate a distinct, tangible and familiar curiosity in many people. “Tree-Rings as a Natural Encyclopedia of Environmental Archives” is an exhibition built as an educational project for schoolchildren, w...
Climate extremes are driven by a combination of thermodynamical and dynamical factors. In Europe, the primary dynamical driver of summer climate extremes is the position of the jet stream over the Europe-North Atlantic (EU) region. To study long-term variability in the position of the EU jet, as well as its potential impact on past climate extremes and human systems, we have reconstructed EU jet variability over the past 800+ years (1200-2005 CE). To accomplish this, we have combined five ...
It is generally assumed that tree-rings, and their vessel diameters, are wider in warmer and wetter years. To maintain constant conductance per unit leaf area as trees grow taller, stem vessels should widen from tip to base. But wider vessels are more susceptible to embolism, so taller plants are progressively becoming more vulnerable to drought or cold as they grow. The traditional theory of vessel hydraulic adaptation postulates that vessel diameter is affected by climate, with cold envi...
Historical accounts in the Brazilian Digital Library provide independent support for most of the tree-ring reconstructed wet season rainfall extremes in the eastern Amazon during the late-18th and 19th centuries. Newspapers, government reports, and other documents describe crop failure, livestock mortality, water shortages, and ship groundings on the Amazon River during many of the tree-ring reconstructed drought extremes. Heavy rains and flooding are described during some of the wet extre...
Half of the tributaries of the Amazon River originate in the tropical Andes; however, it is difficult to assess hydroclimatic conditions due to the scarcity of long, high-quality instrumental records. Data from the Global Precipitation Climatology Project (GPCP) provides a complete record since 1979 and offers a good representation of rainfall over the tropical Andes. Longer records are needed to improve our understanding of rainfall variability and summer monsoon behavior at various scale...
Regional teleconnections permit cross-continental modeling of hydroclimate throughout the world. Tree-rings are a good hydroclimatic proxy used to reconstruct drought and streamflow in regions that respond to common global forcings. We used a multi-species dataset of 32 tree-ring width chronologies from Chile and Uruguay as a climate proxy to infer annual streamflow (Q) variability in the Negro River basin, a grassland-dominated watershed of lowland Southeastern South America. A positive l...
The Colorado river supplies water to forty million people. The river system in crisis due to; an ongoing twenty year drought, a historical overallocation of river flows and an increasing demand for water due to an increasing population. One historical cause of the crisis was the assumption one hundred years ago by the signatories of the Colorado River Compact that the natural flows of the Colorado River do not vary significantly on timescales longer than a decade. Since then, one hundred a...
Climate models for North Patagonia in Argentina project dryer conditions, due to a decrease in mean precipitation combined with an increase in mean temperatures. The temperate mixed Nothofagus forest, which exists along a steep precipitation gradient, could be directly impacted. For this study, we evaluated the influence of mean climate on the growth of the significant deciduous species: N. nervosa and N. obliqua. For the first time in Argentina, dendroclimatological analyses were done on ...
Annually resolved subfossil kauri (Agathis australis) trees, recovered from bogs in northern New Zealand, provide unique insights into past climate events over multi-millennial timescales. Their tree-rings faithfully capture annually resolved information about climate and carbon dynamics occurring during their lifespan. Preserved material has contributed tree-ring chronologies spanning much of the Holocene and extending into the late Pleistocene (i.e. the last 50,000 years). A recently dis...
The most frequent fire regimes in the world exist in environments that balance maximum fuel production and maximum fire occurrence potential. Often these environments exist at low elevations, correspond to subtropical climates, and have long growing seasons that push the limits of reliable annual ring formation. Historical fire regimes in ecosystems with these conditions are poorly studied. We investigated fire scarring in such conditions in southwestern Georgia, USA and successfully const...
Wednesday 29 June, 2022
Fluctuations in water resources is one of the main factors modulating ecosystem dynamics, human population changes and culture in semiarid regions. One of the largest high-altitude semiarid regions of South America is the Altiplano in the Central Andes. With an elevation of 4.000 m this region has been the environment for the settlement of many communities who have inhabited the region for thousands of years. Tree-ring research has been developed in this region allowing the reconstruction ...
Fire-dependent red pine (Pinus resinosa Ait.) vegetation communities in the central Appalac...
The Tiger Creek Preserve in central Florida has one of the highest concentrations of threatened and endangered plants and animals in the United States. Historically it was probably a longleaf pine savanna, but fire exclusion in recent decades has almost certainly led to increased basal area by mid-story oaks (mainly Quercus geminata and Q. laevis). Determining the date of establishment of these trees, as well as the early fire history of the site, would provide evidence to supp...
Beaver Island, Michigan was occupied by a religious sect led by James J. Strang from 1848-1856. Strang was crowned king of the group, but assassinated by disgruntled followers in 1856, whereupon local fishermen drove the “Strangites” off the island and reportedly took over or destroyed their buildings. Some of the structures from the Strangite period have known construction dates, while details for others are uncertain. We identified the species and cutting dates for logs in eight structur...
We reconstructed wildfire history from fire-scars to detect the influences of climatic variability and land-use change on wildfire dynamics in the lodgepole pine (Pinus contorta var. latifolia Engelm.) forests of Jasper National Park in the Canadian Rocky Mountains. New original analyses were performed on 170 cross-section samples collected in the 1970s from 52 sites around Jasper, Alberta. The updated fire record reveals that fire occurrence was highly variable: site-lev...
Despite their potential benefits, streamflow reconstructions from tree-rings have not been widely used in water systems analysis because the flow is generally constructed at annual resolution, which may be too coarse for analysis of drought/flood vulnerability and decision making. In semi-arid regions of Chile there are very good relationships between these daily and annual flow, which is explained because within these regions, few hydrological events within a year explain most of the annu...
Western Ukraine are largely forested, especially Transcarpatia with more than 50% of the land covered by forests. Despite this fact, Transcarpathian Ukraine belongs to the last European regions without a long and well replicated oak TRW chronology. The first step in compiling a new tree-ring width (TRW) chronology is to start with living trees; therefore, a new recent oak TRW chronology was assembled.In this study, totally 336 oak samples from 16 oak forest stands and 1 sawmill from th...
Spatially-resolved climate field reconstructions are ideal for analyzing spatial anomaly patterns and characterizing regional-scale trends resultant from climate change. To date, few fine-scale, spatially-resolved paleotemperature datasets exist in the Northern Hemisphere. Here, we present a 2.5x2.5o temperature field reconstruction of warm season (April-August) mean surface air temperatures, developed from a network of 130 tree-ring chronologies. In the reconstruction’s current form, stat...
The classic definition of the so-called “divergence problem” is a decoupling of temperature sensitive tree-ring chronologies from the instrumental record – expressed either as a loss or weakening in the inter-annual signal, or a divergence in trend in the recent period. Western Canada is one such area where divergence is ostensibly prevalent. However, recent observations using ring-width (RW) and latewood blue intensity (LWB) parameters challenge our views on divergence in this region: tre...
Thursday 30 June, 2022
How old are tropical trees? This fundamental question has long driven the curiosity of laymen and scientists. But only recently, a great number of studies conducted by many brave dendrochronologists resulted in a significant tree-ring-based knowledge that allows us to start accurately estimating tree ages across the globe. As science goes, not only knowing the longevity of tropical trees is essential to understanding forest dynamics and its role in biogeochemical cycles, but one must also ...