Tracking MODIS NDVI time series to estimate fuel accumulation

Patterns of post-fire recovery in southern California chaparral shrublands are important for understanding fuel available for future fires. Satellite remote sensing provides an opportunity to examine these patterns over large spatial extents and at high temporal resolution. The relatively limited temporal range of satellite remote sensing products has previously constrained studies of post-fire recovery to chronosequence approaches, in which space is substituted for time, but the lengthening satellite data record is easing this limitation. In this study, we tracked vegetation recovery using a pixel-explicit approach from 2000 to 2013 using normalized difference vegetation index (NDVI) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. We attempted to control for inter-annual precipitation variation and examined the influence of shrub cover on MODIS NDVI during the post-fire recovery process. We find strong variation in recovery trajectories associated with site differences, which would have been lost in a chronosequence approach. Shrub cover plays a larger role in explaining annual NDVI variation during the early stages of post-fire recovery, and is a less important factor in more mature stands.