Abstract
Changes in vegetation productivity based on normalized difference vegetation index (NDVI) have been reported from Arctic regions. Most studies use very coarse spatial resolution remote sensing data that cannot isolate landscape level factors. For example, on Yamal Peninsula in West Siberia enhanced willow growth has been linked to widespread landslide activity, but the effect of landslides on regional NDVI dynamics is unknown. Here we apply a novel satellite-based NDVI analysis to investigate the vegetation regeneration patterns of active-layer detachments following a major landslide event in 1989. We analyzed time series data of Landsat and very high-resolution (VHR) imagery from QuickBird-2 and WorldView-2 and 3 characterizing a study area of ca. 35 km2. Landsat revealed that natural regeneration of low Arctic tundra progressed rapidly during the first two decades after the landslide event. However, during the past decade, the difference between landslide shear surfaces and surrounding areas remained relatively unchanged despite the advance of vegetation succession. Time series also revealed that NDVI generally declined since 2013 within the study area. The VHR imagery allowed detection of NDVI change ‘hot-spots’ that included temporary degradation of vegetation cover, as well as new and expanding thaw slumps, which were too small to be detected from Landsat satellite data. Our study demonstrates that landslides can have pronounced and long-lasting impacts on tundra vegetation. Thermokarst landslides and associated impacts on vegetation will likely become increasingly common in NW Siberia and other Arctic regions with continued warming.
Highlights
Rapid change in Arctic vegetation productivity since the 1980’s—generally referred to as ‘Arctic greening’—has been linked to climate warming and to changes in sea ice extent (Bhatt et al 2010, Dutrieux et al 2012, Myers-Smith et al 2020, Berner et al 2020)
Landslide delineation and impacts assessed with landsat Approximately 65 new landslides appeared within our study area in 1989, which triggered a pronounced decline in tundra greenness (NDVI)
Landsat mean summer normalized difference vegetation index (NDVI) time series for the 500 sample sites shows the decrease in NDVI within landslide polygons after 1989 and regeneration of vegetation during the following decades
Summary
Rapid change in Arctic vegetation productivity since the 1980’s—generally referred to as ‘Arctic greening’—has been linked to climate warming and to changes in sea ice extent (Bhatt et al 2010, Dutrieux et al 2012, Myers-Smith et al 2020, Berner et al 2020). The strongest responses observed have been increases in shrub cover and height, especially within the Low Arctic tundra zone, where vegetation is highly sensitive to air and soil temperature during the growing season (Epstein et al 2004, Macias-Fauria et al 2012). Most remote sensing assessments of Arctic ‘greening’ or ‘browning’ have been based on changes in the normalized difference vegetation index (NDVI) derived from satellite sensors such as the Advanced Very-High Resolution Radiometer (AVHRR, 1981— present) (Walker et al 2009, Bhatt et al 2010, Forbes et al 2010) or the Moderate Resolution Imaging Spectroradiometer (MODIS, 2000—present) (Dutrieux et al 2012, Miles and Esau 2016). Bhatt et al (2010) found that GIMMSg NDVI was relatively stable on Yamal from 1982 to 2008, which they connected to the lack of positive trend in summer warmth index (sum of positive monthly mean temperatures) and/or to widespread reindeer herding
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