Data release for it matters when you measure it: using snow-cover Normalised Difference Vegetation Index (NDVI) to isolate post-fire conifer regeneration
Dates
Publication Date
2019-03-08
Start Date
1984-03-01
End Date
2017-12-31
Citation
Vanderhoof, M.K., and Hawbaker, T.J., 2019, Data release for it matters when you measure it: using snow-cover Normalised Difference Vegetation Index (NDVI) to isolate post-fire conifer regeneration: U.S. Geological Survey data release, https://doi.org/10.5066/P9UOBL50.
Summary
Landsat Normalised Difference Vegetation Index (NDVI) is commonly used to monitor post-fire green-up; however, most studies do not distinguish new growth of conifer from deciduous or herbaceous species, despite potential consequences for local climate, carbon and wildlife. We found that dual season (growing and snow cover) NDVI improved our ability to distinguish conifer tree presence and density. We then examined the post-fire pattern (1984–2017) in Landsat NDVI for fires that occurred a minimum of 20 years ago (1986–1997). Points were classified into four categories depending on whether NDVI, 20 years post-fire, had returned to pre-fire values in only the growing season, only under snow cover, in both seasons or neither. We found [...]
Summary
Landsat Normalised Difference Vegetation Index (NDVI) is commonly used to monitor post-fire green-up; however, most studies do not distinguish new growth of conifer from deciduous or herbaceous species, despite potential consequences for local climate, carbon and wildlife. We found that dual season (growing and snow cover) NDVI improved our ability to distinguish conifer tree presence and density. We then examined the post-fire pattern (1984–2017) in Landsat NDVI for fires that occurred a minimum of 20 years ago (1986–1997). Points were classified into four categories depending on whether NDVI, 20 years post-fire, had returned to pre-fire values in only the growing season, only under snow cover, in both seasons or neither. We found that each category of points showed distinct patterns of NDVI change that could be used to characterise the average pre-fire and post-fire vegetation condition Of the points analysed, 43% showed a between-season disagreement if NDVI had returned to pre-fire values, suggesting that using dual-season NDVI can modify our interpretations of post-fire conditions. We also found an improved correlation between 5- and 20-year NDVI change under snow cover, potentially attributable to snow masking fast-growing herbaceous vegetation. This study suggests that snow-cover Landsat imagery can enhance characterisations of forest recovery following fire.
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Related External Resources
Type: Related Primary Publication
Vanderhoof, M.K., and Hawbaker, T.J., 2018, It matters when you measure it: using snow-cover Normalised Difference Vegetation Index (NDVI) to isolate post-fire conifer regeneration: International Journal of Wildland Fire, v. 27, no. 12, p. 815-830, https://doi.org/10.1071/WF18075.
The purpose of the analysis was to improve our ability to distinguish post-fire successional trajectories, in particular, distinguish conifer from deciduous species by pairing growing season with snow-cover Landsat greenness indices. The "cover_density_points" were used to characterize the dual-season spectral reflectance values for different conifer forest density and different vegetation cover types. These points were identifed from commercial high-resolution imagery.
