The relation between active layer depth and a spectral vegetation index in arctic tundra landscapes of the North Slope of Alaska

Models of regional CO2 exchange processes in arctic tundra environments using landscape characteristics may need to incorporate spatial and temporal variations in the depth to the permafrost layer because it influences soil drainage, aeration, decomposition, and nutrient availability. However this depth, or the depth of the active layer (DAL), will have to be estimated indirectly since it is not practical to make a large number of ground measurements on a regular basis. Previous research has demonstrated that spatial variations in DAL are strongly related to aboveground vegetation production in sub-arctic tundra. Since aboveground vegetation production in Alaskan arctic tundra has been related to the Normalized Difference Vegetation Index (NDVI), it was hypothesized that spatial variations in NDVI would follow variations in DAL in these environments. Studies were conducted on the North Slope of Alaska during the summers of 1994 and 1995 to determine the feasibility of estimating DAL at multiple spatial scales using the NDVI. Experiments were performed at sites with distinctly different topographic relief using hand-held and satellite spectral radiometric data and ground measurements of DAL. Overall, our results suggest that there is no relation between NDVI and DAL in areas with little variation in relief. However, in areas where topography strongly controls the flow and redistribution of water, NDVI did account for approximately 40 per cent of the variability in DAL.