Biophysical and spectral responses to various burn treatments in the northern mixed-grass prairie

Abstract

Over the past century, environmental managers have worked to suppress fire throughout various biomes. Today, burning is generally considered beneficial to many ecosystems, though the precise effects are not entirely understood. This research aims to further our understanding of the biophysical effects of fire in C3 dominated mixed-grass prairies and to find an effective remote sensing approach for differentiating between burn treatments in late spring. Biophysical properties including vegetation cover, biomass, soil properties, canopy height, Leaf Area Index (LAI), and individual wavebands of the SPOT-5 sensor as well as two vegetation indices (Normalized Difference Vegetation Index and Normalized Burn Ratio Index) derived from SPOT-5 images were compared among unburned sites and sites with various burning treatments in Grasslands National Park, Canada. Results showed that significantly higher soil temperature and lower LAI were found in burned sites. Dead material biomass, total biomass, and percentage of standing dead cover were significantly lower in burned and grazed sites. The percentage of bare ground cover was the only biophysical variable to show significant changes in all burning treatments. Burned and unburned sites could not be distinguished based on assessing the changes of individual wavebands of the SPOT-5 sensor and the two vegetation indices. Models based on linear combinations of spectral indices were developed for biophysical properties that show significant changes in burned sites. The agreement between model simulated biophysical properties and field measured values suggest the feasibility of remote sensing to assess or monitor post-fire effects in mixed grasslands.