Updated 2023, Aug 01

The limited spatial and temporal coverage of hydrological records often constrains the assessment of past and future hydrological conditions. Dendrohydrology can provide continuous, annually resolved hydrological reconstructions, as well as identify single, discrete hydrological events. Compared to other tree-ring proxies (e.g., ring width, ice-scars, isotopes...), the reactivity of vessel elements to changes in growing conditions offers a unique tool for reconstructing changes in hydrological dynamics and flooding when water availability is not a limiting factor for growth, as is the case in floodplains.

Flood rings have been mostly described in ring-porous tree species Fraxinus spp. and Quercus spp., which produce smaller than average and/or higher density of earlywood vessel in response to flooding. Flood-induced anatomical changes have also been described in diffuse-pourous trees species, with more complex responses than in ring-porous trees, including disruption of normal shape, density or position, and reduction in size of vessels. Understanding the variability of anatomical responses to flooding in tree rings of multiple species and assesssing their potential to develop paleoflood reconstructions is a precondition to the development of a large-scale mapping of paleoflood history derived from flood rings. 

Flood anatomical signature in tree rings of ring-porous trees

Flood anatomical signature in tree rings of diffuse-porous trees

Quantitative and semi-quantitative flood-ring chronologies derived from periodically flooded trees have proven to be a versatile tool in the reconstruction of paelofloods in North American natural and regulated rivers. Flood rings were experimentally induced below the water level and preliminary results from Lake Duparquet suggest that the height of disappearance of flood rings in black ash tree rings could therefore indicate the average height reached by the flood waters, allowing to map the spatial extent of historical flooding. The development of a large-scale network of flood rings would aid in reconstructing the history and variability of spring floods, and resolve their spatial footprint in watersheds where instrumental hydrological data are lacking. 

Recent development of high-resolution imaging techniques for tree rings, such as X-ray tomography and gigamacro pixel photography, offers an alternative to expensive and time-consuming microcellular sections. Coupled with automated quantitative wood anatomy, this paves the way for the refinement of measurements and the development of new proxies in dendrochronology. The study of flood rings can be extended to morphological parameters other than the vessel elements currently studied, such as cell wall or fiber thickness, and vessel groupings. Research for new proxies could allow (1) to study more effective indicators for reconstructing streamflow extremes (high and low) and (2) to better understand the morphological and physiological response of trees to flooding. 

Among the new applications of flood rings, such as reconstructing the maximum and average height of flood waters, or mapping the extent of a given historical flood, the study of isotopes in tree rings could, for example, allow to trace the origin of flood waters. In boreal environments, higher mean winter temperatures contribute, among other factors, to increased rain-on-snow and mid-winter thaw events that feed winter river flows. In addition, higher average temperatures in late spring are likely to shift the contribution of snow vs precipitation in spring flooding processes. Studying how the variability in isotope composition of flood ring relate to changes in precipitation patterns affecting spring floods could help mitigate flood risk in the context of climate change, particularly in boreal river basins that are not equipped with hydrometric sensors. 

Featured publications

Alexandre F. NOLIN, Jacques C. Tardif, France Conciatori, Yves Bergeron (2021). Flood-rings production modulated by river regulation in eastern boreal Canada. In Frontiers in Plant Science. https://doi.org/10.3389/fpls.2021.757280 (OpenAcess)

DATASET : https://doi.org/10.17632/6pgc25nk27.1 

Jacques C. Tardif, Susanne Kames, Alexandre F. NOLIN, Yves Bergeron (2021). Earlywood Vessels in Black Ash (Fraxinus nigra Marsh.) trees show contrasting sensitivity to hydroclimate variables according to flood exposure. In Frontiers in Plant Science. https://doi.org/10.3389%2Ffpls.2021.754596 (OpenAcess)

Jacques C. Tardif, Heather Dickson, France Conciatori, Alexandre F. NOLIN, Yves Bergeron (2021). Are periodic (intra-annual) tangential bands of vessels in diffuse-porous tree species the equivalent of flood rings in ring-porous speices ? Repoducibility and cause. In Dendrochronologia. https://doi.org/10.1016/j.dendro.2021.125889 

Alexandre F. NOLIN, Jacques C. Tardif, France Conciatori, Yves Bergeron (2021). Spatial coherency of the spring flood signal among major river basins of eastern boreal Canada inferred from flood rings. In Journal of Hydrology. https://doi.org/10.1016/j.jhydrol.2021.126084

DATASET : http://dx.doi.org/10.17632/94vjr69fb2.1 

Alexandre F. NOLIN, Jacques C. Tardif, France Conciatori, Susanne Kames, David M. Meko, Yves Bergeron (2021). Multi-century tree-ring anatomical evidence reveals increasing frequency and magnitude of spring discharge and floods in eastern boreal Canada. In Global and Planetary Change. https://doi.org/10.1016/j.gloplacha.2021.103444 

DATASET : https://doi.org/10.17632/d54gcxz9c5.2