Recent expansion of erect shrubs in the Low Arctic: evidence from Eastern Nunavik

Abstract

In order to characterize shrub response near the treeline in Eastern Nunavik (Québec), a region under extensive warming since the 1990s, we compared two series (1964 and 2003) of vertical aerial photos from the vicinity of Kangiqsualujjuaq. Our study revealed a widespread increase in erect woody vegetation cover. During the 40 years spanning the two photo series, erect shrub and tree cover increased markedly on more than half of the land surface available for new colonization or infilling. Within the 7.2 km 2 analysed, areas with dense shrub and tree cover (>90%) increased from 34% to 44% whereas areas with low cover (<10%) shrank from 45% to 29%. This increase in cover of trees and shrubs occurred throughout the landscape regardless of altitude, slope angle and exposure, although to varying extents. The main shrub species involved in this increase was Betula glandulosa Michx. (dwarf birch), which was present in 98% and dominant in 85% of the 345 plots. In addition, numerous seedlings and saplings of Larix laricina (Du Roi) K Koch (eastern larch) were found above the treeline (25% of the plots), suggesting that the altitudinal treeline might shift upslope in the near future. Sites that remained devoid of erect woody vegetation in 2003 were either characterized by the absence of a suitable seedbed or by harsh local microclimatic conditions (wind exposure or excessive drainage). Our results indicate dramatic increases in shrub and tree cover at a Low Arctic site in Eastern Nunavik, contributing to a growing number of observations of woody vegetation change from various areas around the North.

Land Cover Change in the Lower Yenisei River Using Dense Stacking of Landsat Imagery in Google Earth Engine

“…At the 32-year scale, such changes are most likely due to the proliferation of relatively fast-growing shrubs in tundra and open forests. This finding is indirectly supported by numerous studies conducted throughout the circumpolar Arctic (e.g., [7,11,17,[54][55][56][57]). Specifically, within this study area a comparative analysis was done between high-resolution Gambit imagery from the 1960s and contemporary GeoEye-1 imagery over a 58 km 2 area in the vicinity of Dudinka (Figure 1).…”

Treelines—Approaches at Different Scales

“…Satellite images or other remote sensing techniques allow for the exploration of treelines even in almost unknown and often inaccessible areas, thus providing an unprecedented broad database for monitoring treelines and treeline shifts (e.g., [42,117,[151][152][153][154][155][156][157]). Spatial resolutions approximately at a 1-m scale are possible [13,158,159].…”

Land Cover Classification in SubArctic Regions Using Fully Polarimetric RADARSAT-2 Data

“…This process is characterized by an increase in shrub vegetation abundance [3,5,6], which generally expands at the detriment of lichens [7,8]. While the increase in vertical and radial growth of shrub vegetation was shown to correlate with rising summer air temperatures observed in northern environments [9,10], multiple other mechanisms are affecting the phenomenon.…”

“…The monitoring of shrub vegetation is therefore important for the understanding of the ongoing changes in northern environments. Current methods rely either on field sampling or aerial and satellite imagery in the visible and infrared spectrum to assess changes in shrub coverage or growth [6,8,[16][17][18][19][20]. However, these methods have certain limitations as the field sampling methods can be very costly and do not provide a high spatial coverage, while satellite imagery in the visible and infrared spectrum is affected by the presence of clouds, which can be persistent in northern regions [16,21].…”