Abstract
Satellite remote sensing is a popular approach for identifying vegetation change in northern environments; however, disentangling ecological processes causing variability in spectral indices remains a challenge. Here, we aim to determine how shrub characteristics differ between low and rapidly greening areas near Nain, Nunatsiavut, Canada. Using a cross-scale approach, we combined remotely sensed spectral greening trends (Normalized Difference Vegetation Index; Landsat Collection 1, 1985–2018) with shrub dynamics derived from ring-widths of green alder (Alnus alnobetula (Ehrh.) K. Koch) and dwarf birch (Betula glandulosa Michx.). Differentiation of spectral greening classes appears to be driven by the distribution of shrub species. Alder were taller, grew faster, had more recent stem initiation than dwarf birch, and were dominant in rapid greening subplots. In low greening subplots, alder were co-dominant with dwarf birch, whose dominant stems initiated more gradually, were shorter, and had lower rates of vertical growth. The radial growth of both shrub species was favoured by warm winter temperatures and precipitation, whereas rapid greening alder was also favoured by warm summer temperatures. Further shrub growth will likely be enhanced under continued climate warming if moisture does not become limiting. This research demonstrates the importance of species identity in determining rates of spectral greening in northern environments.
Highlights
There is widespread evidence that recent climate change has altered the distribution, composition, and phenology of Arctic and subarctic vegetation (e.g., Elmendorf et al 2012; Bjorkman et al 2018)
These results suggest that greater radial shrub growth was linked to warm and snowy winter conditions, and rapid greening alder growth was associated with warm summer temperatures
We combined Landsat imagery with dendrochronological techniques to gain insight into the in situ dynamics underlying rates of spectral greening at a field site located near the coastal community of Nain in Nunatsiavut, Labrador
Summary
There is widespread evidence that recent climate change has altered the distribution, composition, and phenology of Arctic and subarctic vegetation (e.g., Elmendorf et al 2012; Bjorkman et al 2018). Shrubification can impede travel across tundra landscapes and can change the distribution and availability of culturally significant plants (e.g., berry plants; Cuerrier et al 2015; Anderson et al 2018; Siegwart Collier 2020) and wildlife (Andruko et al 2020). Investigations of the ecological processes that cause spatial variability in shrubification are important for predicting where future changes may occur in Arctic and subarctic environments
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