"Maximum latewood density (MXD) is the most sensitive proxy for reconstructing temperature variations over past centuries to millennia. However, the development of long MXD chronologies has lagged far behind that of ring width chronologies, especially in North America. Among a handful of millennial MXD records across the northern hemisphere, only a few are from North American sites.In this study, we fill this data gap by developing a millennial MXD data network from an unprecedented...

MAIDENiso is a numerical process-based model that allows researchers to simulate the growth of a virtual tree. Using daily meteorological data, the model simulates the physical and physiological processes taking place in the tree and its environment, to produce daily and yearly outputs comparable to dendrological observations. The model has been adapted and used successfully in boreal regions in North America. In an inverse mode, tree-ring obs...

Free, in person and onlineThe stable isotopic compositions of carbon and oxygen (d13C and d18O) measured in tree rings are valuable proxies for reconstructing paleoclimate and are increasingly used as paleophysiological proxies. Applying these proxies in ecophysiology and paleoclimate can be challenging as they rely on complex process-based models and poorly constrained input data. In recent years, h...

Although numerous proxy-based climate reconstructions have been developed and despite the prevalence of relatively long instrumental records throughout Europe, reliable information about past climate is still lacking in some regions, particularly eastern parts of the continent. This issue is linked to limitations in data quality and large uncertainties in existing records. The REPLICATE project aims to fill this spatial paleoclimatic and data quality gap by applying a tree-ring multi-param...

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...

Mexico has a forest cover of 660,400 km2, representing 34% of its territory. Due to deforestation and land-use change, Mexico has lost 32,200 km2 over the last 25 years, representing 1.9% of its territory. Mexican forests are now additionally threatened by climate change. Currently, there is no assessment of the impact of current and future climatic changes on forest productivity to develop mitigation and adaptation plans in the forestry sector. Most growth studies in Mexico focus on clima...

Few spring paleoclimate records are available for boreal Canada and given the warming of spring temperatures in recent decades and its impact on snowmelt and hydrological processes, the search for spring climate proxies is receiving increasing attention. Tree-ring anatomical features and intra-annual widths were used to reconstruct regional mean March-April-May temperature from 1770 to 2016 in eastern boreal Canada. Nested principal component regressions calibrated on 116 years of gridded ...

Our understanding of climate change impacts on boreal forest net primary productivity (NPP) largely rely on terrestrial biosphere models (TBMs). TBMs characterize forest NPP through predictions of plant carbon fluxes and allocation from climatic data, physiological parameters and process logic. TBMs’ outcomes may be highly variable, a major source of uncertainty being the formulation of ecophysiological processes and their parameterization. In our study, we compared patterns of growth resp...

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...

The Pliocene is often identified as an example of a past warmer world. Studies of sub-fossil wood from fossil forest localities in the Canadian Arctic have allowed us to explore the amplified effects of global climate change in the Arctic during the Pliocene and to provide important information on how arctic ecosystems respond to these changes. Here we report new annually resolved climate records developed from Meighen and Prince Patrick Islands, which span a time period from 6.2 Ma to 2.7...

Ring-width (RW) and Blue Intensity (BI) parameters (earlywood - EWB, inverted latewood – LWBinv, and delta - DB) were measured from samples of Araucaria araucana from six sites in northern Patagonia, Argentina. The distance between the most southerly and northerly sites is ca. 130 kms. Despite a much weaker between-tree signal for the BI parameters than RW, principal component analysis identifies a much stronger regional between-site signal for the BI parameters. Split period correlation r...

"Little is known about the impact of volcanoes on trees from the Southern Hemisphere. In this study, we investigated whether volcanic signals could be identified in ring widths from eight dendrochronological species from New Zealand, using superposed epoch analysis. We found that most species are good recorders of volcanic dimming and that the magnitude and persistence of the post-event response can be broadly linked to plant life history traits - whether the species responds as a 'stress ...

The current climate warming is unique in terms of its ubiquity and synchrony on a global scale. Over the last millennium, pre-industrial periods with warmer and colder temperatures occurred at different times in different locations around the globe (Neukom et al., 2019). Long-term temperature reconstructions in the Southern Hemisphere remain sparse and not always consistent among them (Lara et al., 2020). Therefore, to understand the temporal and spatial patterns of global-scale temperatur...

Over the past 10 years, X-ray Computed Tomography (CT) has been increasingly applied to dendrochronological research. This technique provides 3D images of the internal structure of objects, allowing non-invasive access to tree rings in cultural heritage objects that are often inaccessible from the outside. Here, we will present the state-of-the-art of tomographic X-ray imaging for the application to dendrochronology. We will give a comprehensive overview of how X-ray computed tomography is...

The Miombo woodlands of interior Africa are fire adapted ecosystems with a relatively open canopy dominated by Brachystegia spp., Julbernardia spp., and Isoberlina spp. These ecosystems are threatened due to deforestation, habitat fragmentation, and impacts from climate change, and in Zambia, they are further threatened by the rapidly growing mining industry which contributes to air pollution, contamination of soils and water, and land degradation. In this study, we used modified variable ...

The assessment of pre-instrumental climate variability during the Common Era (CE) has been a key element of IPCC reports and was recently emphasized by showing a single temperature reconstruction as the first figure in the 2021 Summary for Policymakers (SPM). This reconstruction is derived from dozens of proxy records including tree-rings, corals, ice cores and sediments, and displays the course of global temperatures over the past 2000 years. Show casing a single study for paleoclimate co...

The use of multiple data from tree-rings, including isotopic ratios and xylogenesis monitoring, can enhance our interpretations on tree functioning and on tree-environment relations. Here, we explored whether understanding of carbon deposition to tree-rings could be improved using: (1) monitoring of wood cell formation during the growing season, (2) intra-annual data of d13C in tree-ring cellulose and (3) ecophysiological modelling. We collected wood micro-cores to monitor wood cell format...

Neogene fossil beds in the Canadian Arctic Archipelago (CAA) provide a window into past greenhouse intervals and insights on what a future, warmer Arctic may look like. In this study, we use the hydrogen isotopes of lignin-methoxy groups (δ2HLM) from sub-fossil wood from six CAA sites (73-80°N) as a proxy for the δ2H of precipitation-derived plant water and paleotemperatures; five study sites cover Pliocene timeslices (~5.3-2.6 Ma) and the other site captures the middle Miocene (~15 Ma). F...

A gap of millennial tree-ring data suitable for dendroclimatology has long been evident in the North American boreal forest. In my talk, I will describe the adaptive approach we have developed to build and improve a data network for millennial dendroclimatology in the eastern Canadian taiga. Recurrence of stand replacing wildfires is the most important constrain to the elaboration of long tree ring chronologies, which can only be developed away from regions ...

Intra-annual density fluctuation (IADF) is a structural modification of the tree ring in response to fluctuations in the weather. To reveal the timings and physiological mechanisms behind IADF formation, we monitored cambial activity and wood formation in Chinese pine (Pinus tabuliformis) during 2017-2019 at three sites in semi-arid China. We compared the dynamics of xylem formation under a drought event, testing the hypothesis that drought affects the process of cell enlargement and thus ...