The invasion and spread of the Emerald ash borer (EAB) in northeastern America has endangered black ash (Fraxinus nigra Marsh.), the most northerly distributed of ash trees in North America. Projected climate change is likely to shift its optimal distribution range northward while accelerating the spread of EAB to the north, and modifying the hydrological dynamics at which the riparian black ash forests are currently flooded in spring which conditioned their seedling recruitment and stand age structure through spring flood water level, duration and timing. This tree could thus be among the most affected by climate change in eastern boreal Canada. Black ash trees occupied unique wetland ecosystems, are deeply embedded in the Canadian Aboriginal culture, and contain valuable paleoclimatic information to reconstruct historical water levels since their tree-ring anatomy record stresses associated with spring flooding (flood rings). Locating them effectively in the landscape and understanding their ecological processes and climate - growth interactions in relation to changing hydroclimatic conditions are prerequisites for their conservation.

The volume of research on black ash has increased in response to the  Emerald ash borer (EAB) outbreak, but its integration into climate change research remains limited, particularly in regions seeking post-epidemic alternatives. At the same time, indigenous communities in eastern North America, who depend on black ash for cultural and economic purposes, have observed an unexplained decline in wood quality, unrelated to EAB. This decline in wood quality for traditional uses may be linked to climate change, and requires investigation of the relationship between climate and ash growth. Despite the challenges posed by ongoing EAB losses, the study aims to establish these relationships for long as viable numbers of black ash are available. The objectives are to consolidate as many tree-ring chronologies as possible across the range of black ash in North America (map below), identify the climatic determinants of its growth, generate future climate projections and discuss implications for future black ash forest dynamics, conservation management and native traditions.

This project set the framefork for our BLACK ASH RESEARCH COLLECTIVE (17 scientists from Canada & USA) 

Project coordinated by Dr. Amy Whotherspoon and Sylva21 at Université Laval, Québec, Canada.

Preliminary map of tree-ring data sites collected by the black ash research collective that are being used to assess the climate-growth relationship across the range of black ash.

The updated sylvics of north America project (USNAP) has provided a good opportunity for the black ash research group to assess and synthesize current knowledge on the dynamics and ecology of black ash forests throughout their geographic range. The aim will also be to identify knowledge gaps and guide the direction of future research efforts.

Understanding how seasonal water levels shape the diversity and regeneration of black ash forests, and predicting how hydrological changes (increase of decrease of seasonnal water levels and spring flooding) might affect their survival are essential for conservation. Riparian forests of Lake Duparquet are home of the oldest living black ash (Fraxinus nigra Marsh.) trees in its northern distribution limit and protected by the Exceptional Forest Ecosystems of Québec (EFE). Previous studies indicate that the riparian forest fringe of Lake Duparquet migrated inland in response to the increase in lake levels after the end of the Little Ice Age  (~1850). This project will characterize current and potential black ash habitat and ecological dynamics on the shores of Lake Duparquet to improve our conservation and mitigation strategies for future fluctuations in spring flooding regimes in eastern boreal Canada.

This project is part of Lou Delayance M.Sc. Thesis : Environmental conditions associated with black ash habitat in the floodplain of Lake Duparquet

Studying the forest dynamics and current composition of black ash forests throughout their geographical range could help assess their regeneration potential in a scenario of black ash decline in North America, and particularily in the northernmost forests. This project investigates the influence of global change and emerald ash borer on black ash stand composition along a south-north gradient in western Québec. The objectives are to consider scenarios of progressive replacement of black ash by other tree species co-occuring in the canopy, and to project the distribution of black ash forests under various climate change and EAB dispersal scenarios.

This project is part of Corentin Juanole Ph.D. Thesis : Influence of climate change on black ash stands in Québec

In eastern boreal Canada, the limited mapping and exclusion of black ash from forest inventories as a non-commercial species is a constraint to its conservation, as well as to using  its valuable paleoclimatic and hydrologic information. This project aim to assess the potential of using a multi-spectral remote sensing approach (Sentinel 2) to estimate the location of black ash trees at its northern distribution range, and taking advantage of synchronizing the timing of satellite imagery with the timing of black ash phenology.

Featured publications

Alexandre F. NOLIN, Ingrid B. Cea Roa, Lou J. Delayance, Yves Bergeron, Jacques C. Tardif, Osvaldo Valeria (in prep). Identifying riparian black ash (Fraxinus nigra Marsh.) forests from remote sensing - A case study from Lake Duparquet, eastern boreal Canada. In Canadian Journal of Remote Sensing.