Department of Environmental Sciences
Esther Lévesque (Regular member)
Vincent Maire (Regular member)
IntroductionWarmer temperatures due to global warming cause a modification of the plant communities of the tundra, by increasing the abundance and cover of species of erect shrubs such as the dwarf birch transform the vegetation zone where the prostrate berry shrubs dominate. Berries are particularly important for Inuit communities and wildlife. The temporal dynamics of the shrub can be studied with satellite imagery and the use of the Normalized Difference Vegetation Index (NDVI), but it is less obvious to determine the changes specifically associated with berry shrubs such as some ericaceous plants. These prostrate shrubs produce a high concentration of anthocyanins in their leaves which could be used to detect their presence with a new index sensitive to anthocyanins: the NARI index (Normalized Anthocyanin Reflectance Index). This tool has successfully distinguished between ericaceous shrubs and grasses in the French Alps. ObjectivesTo test this promising index in a new environment we must first demonstrate the abundance of pigments in the plants of the plant communities of interest and assess their variation over time, to eventually assess whether there is a relationship between the concentration of pigments in the leaf and the NARI index captured by drone at a height of 35m.The first objective of this research project is to study the temporal variability of anthocyanins and chlorophylls in the leaves of berry shrubs and associated vegetation. The second objective will be to use hyperspectral images taken from the leaves in order to quantify the NARI, NDVI and PRI (photochemical Reflectance Index) indices and compare them with the pigments present in the leaves. Study sitesFour sites are under consideration. Two in Mauricie, Quebec, the first of which is in a wild blueberry production site and the second is on the campus of the University of Quebec in Trois-Rivières (UQTR). The other two are near two Inuit communities in Nunavik, Kuujjuaq and Kangiqsualujjuaq. Regular sampling throughout the period of leaf growth was completed of small-fruited ericaceous species and the dominant species of the surrounding vegetation. The choice of sites makes it possible to have plots of different communities along a mixed gradient of plants of the Ericaceae family in two different climatic regions of Quebec. Material and methodsThe leaves harvested from the various sites will be processed at the UQTR plant ecology laboratory for pigment extraction and spectrophotometric analyses. The interspecific and temporal variations of the pigments will be compared to determine whether the fluctuations are related to species, families of plants, physiological traits or even geographic regions. Expected resultsIn general, Ericaceae species should have a higher concentration of anthocyanins in young leaves at the start of the season and in senescent leaves while the concentration of chlorophyll should decrease at the end of the season. In other common tundra shrub families (Salicaceae, Betulaceae), the concentration of anthocyanins should also increase at the end of the season and the pattern of change will or will not differentiate them from Ericaceous plants. Finally, for other non-ericaceous plants such as conifers and graminoids, a very low concentration of anthocyanins in the leaves is expected throughout the season. Peak anthocyanin concentrations should correspond to a high NARI index while peak chlorophyll concentrations should correspond to high NDVI index.
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