Abstract
The analysis of wildfire impacts at the scale of less than a square kilometer can reveal important patterns of vegetation recovery and regrowth in freshwater Arctic and boreal regions. For this study, NASA Landsat burned area products since the year 2000, and a near 20-year record of vegetation green cover from the MODIS (Moderate Resolution Imaging Spectroradiometer) satellite sensor were combined to reconstruct the recovery rates and seasonal profiles of burned wetland ecosystems in Alaska. Region-wide breakpoint analysis results showed that significant structural change could be detected in the 250-m normalized difference vegetation index (NDVI) time series for the vast majority of wetland locations in the major Yukon river drainages of interior Alaska that had burned at high severity since the year 2001. Additional comparisons showed that wetland cover locations across Alaska that have burned at high severity subsequently recovered their green cover seasonal profiles to relatively stable pre-fire levels in less than 10 years. Negative changes in the MODIS NDVI, namely lower greenness in 2017 than pre-fire and incomplete greenness recovery, were more commonly detected in burned wetland areas after 2013. In the years prior to 2013, the NDVI change tended to be positive (higher greenness in 2017 than pre-fire) at burned wetland elevations lower than 400 m, whereas burned wetland locations at higher elevation showed relatively few positive greenness recovery changes by 2017.
Highlights
High-severity wildfires have been shown to have long-term impacts on freshwater ecosystems; as nutrients are mobilized, runoff and erosion can increase, and soil properties may be modified [1]
Based on yearly Monitoring Trends in Burn Severity (MTBS) RdNBR map collections, the names and locations of the largest contiguous wetland area that burned at high severity in Alaska were determined for each year since 2000
The region-wide BFAST analysis results from the present study indicated that significant structural change could be detected in the 250-m normalized difference vegetation index (NDVI) time series for the vast majority of wetland locations in the major Yukon river drainages of interior Alaska that had burned at high severity since the year 2001
Summary
High-severity wildfires have been shown to have long-term impacts on freshwater ecosystems; as nutrients are mobilized, runoff and erosion can increase, and soil properties may be modified [1]. While there is a growing literature for the effects of fire on upland vegetation types [2], the existing information on vegetation removal by burning remains limited for most freshwater plant communities globally To extend this knowledge base, satellite remote sensing can be used to effectively monitor changes in high-latitude (boreal and tundra) wetland vegetation cover and productivity, especially following disturbance events such as wildfires [3,4,5,6,7]. This result suggested that the wetland areas of Alaska can recover more completely and rapidly in greenness cover from recent wildfires than non-wetland land cover types; this supposition remains to be tested region-wide over longer time periods
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