During the 21st century, the boreal biome has warmed at rates 3-4 times the global average, impacting forests directly through changes in temperature and precipitation and indirectly through acceleration of disturbances including permafrost thaw and wildfire. Despite this, little is known about the ability of boreal trees to adapt in the face of such rapid environmental changes. Warming-induced growth rate increases are predicted for the boreal biome, but these would be largely dependent o...

As northern latitudes experience rapid winter warming, there is an urgent need to assess the effect of varying winter conditions on tree growth and forest carbon sequestration potential. We examined tree growth responses to variability in cold-season (November-April) frequency of freeze days (FFD) over 1951-2018 using tree-ring data from 35,217 trees and 57 species at 4,375 sites distributed across Canada. We found that annual radial growth responses to FFD varied by species, with some com...

Montane forests of Central Europe are experiencing faster changes in climate than the average trends. It is still unclear how these natural forests, and especially saplings, have responded to recent modifications in growth conditions. We took advantage of the REMOTE forests network to look at the changes in juvenile growth rates of Norway spruce and European beech, two economically important tree species in Europe. This network includes ring-widths series of more than 19,000 spruces and 14...

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...

Leaf water isotopic enrichment (ΔD[LW]) is the original source of climatic information stored in tree-ring δ¹⁸O and δD. Tree-ring δ¹⁸O temporal variability has been correlated to environmental variables such as temperature, precipitation, relative humidity (RH), and phenomena such as tropical cyclones and drought. Meanwhile, more development is needed to use tree-ring δD temporal variability as a paleoclimatic bioindicator. An increased understanding of the climatic signal of ΔD[LW] could ...

In the context of climate and environmental change, the boreal forest is subject to potential changes in structure and function. Stand-level physiological models can be used to predict these responses over time and to understand the interaction between tree ecophysiological processes and climate variability. We present here a project that aims to develop potential growth scenarios for Canadian boreal forest stands based on the characterization of their ecosystem fluxes using the MAIDEN mod...

In the tropical Andes several species of the genus Polylepis have been reported to be useful to record climate variability using tree-ring width, expanding the geographical distribution of proxy records into the tropical region. However, in the tropics classical dendrochronology based on ring-width patterns is often challenging, hampering the development of climate reconstructions. Alternative methods can confirm annual periodicity of tree rings, and help on extracting more reliable climat...

In temperature-limited ecosystems such as high-elevation forests, rising temperatures and increasing carbon dioxide can result in a greening effect, and changes in the phenology and tree growth rates of the forests. We assessed the long-term trend dynamics (greenness and land surface phenology) using the Normalized Difference Vegetation Index (NDVI) and compared them with data from an existing dendrochronological network that came from eight protected mountains in the Trans-Mexican Volcani...

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 ...

Treeline ecotones at high latitudes and high elevations are generally temperature-limited environments. However, there is evidence that temperature control on tree growth has recently decreased at treelines due to climate change, while water availability is increasingly reported as a seasonally important growth-limiting factor. Analyzing climate-growth responses at intra-annual (wood cell) level can help unravel these complex patterns, but long time series of wood formation data are often ...

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 ...

In mixed forests, diffuse-porous and ring-porous species represent two distinct functional groups undergoing similar environmental variations, but allegedly displaying different growth responses due to their anatomical features. We hypothesized that in sympatric species, functional groups-specific carbon allocation strategies result in different relationships between wood traits and canopy architecture, mirroring contrasting sensitivity to drought.We selected 2 diffuse-porous species (...

The boreal forest located in high northern latitudes stores about a third of the world’s carbon and covers almost a quarter of the Earth’s land surface. This region is experiencing one of the fastest temperatures increases on the planet. Yet it is unclear how global warming affects carbon sequestration and storage in this biome. Here, we explore how white spruce (Picea glauca [Moench] Voss) growing in North America responded to climate change during the 20th century using tree-ring width a...