Indicators of burn severity at extended temporal scales: a decade of ecosystem response in mixed-conifer forests of western Montana

Abstract

Abstract. We collected field and remotely sensed data spanning 10 years after three 2003 Montana wildfires to monitor ecological change across multiple temporal and spatial scales. Multiple endmember spectral mixture analysis was used to create post-fire maps of: char, soil, green (GV) and non-photosynthetic ( Initial estimates of char and NPV from the HS images were significantly correlated with their ground-measured counterparts (r ¼ 0.60 (P ¼ 0.03) and 0.68 (P ¼ 0.01) respectively), whereas HS GV and Landsat GV were correlated with canopy GV (r ¼ 0.75 and 0.70 (P ¼ 0.003) respectively). HS imagery had stronger direct correlations with all classes of fine-scale ground data than Landsat and also had stronger predictive correlations with 10-year canopy data (r ¼ 0.65 (P ¼ 0.02) to 0.84 (P ¼ 0.0003)). There was less than 5% understorey GV cover on the sites initially, but by 2013, it had increased to nearly 60% regardless of initial condition. The data suggest it took twice as long for understorey GV and NPV to replace char and soil as primary ground cover components on the highburn-severity sites compared with other sites.

Does burn severity affect plant community diversity and composition in mixed conifer forests of the United States Intermountain West one decade post fire?

“…Edwards et al (2015) did not find significant differences in understory green cover between burn severity classes in sub-boreal conifer forest in British Columbia, Canada, five to six years after an experimental burn. A remote sensing study by Lewis et al (2017), on some of the same Montana fires as in this study, suggested that, 10 years post fire, green cover had increased to approximately 60% regardless of initial condition, but that this took about twice as long on high burn severity sites. Remote sensing studies have also shown that Net Primary Productivity (NPP) in North American boreal forests has returned to pre-fire levels nine years following fire (Hicke et al 2003).…”

The Cooney Ridge Fire Experiment: An Early Operation to Relate Pre-, Active, and Post-Fire Field and Remotely Sensed Measurements

“…Other researchers have found significant correlations between field-measured ground cover and MESMA predicted fractional cover [5,65]. These broad fractional cover classes (their presence or absence as well as their condition) can indicate first-order fire effects on vegetation and soil [66].…”

“…These broad fractional cover classes (their presence or absence as well as their condition) can indicate first-order fire effects on vegetation and soil [66]. They can also be monitored as second-order fire effects, such as vegetation recovery over time [5,67]. Residual litter, newly deposited needlecast and downed woody debris provide protection to soils from wind-and water-driven erosion [68].…”

“…The spectroradiometer collects spectra in 2050 channels with 1 nm bandwidths spanning 350-2500 nm. Reference endmember bundles of green needle, dead needle, charred wood, ash, and mineral soil spectra ( Figures 3 and 4) were used to unmix all of the hyperspectral image swaths collected over the Cooney Ridge wildfire [5], and the experimental burnout area was subsequently subset from the MESMA image outputs for this study. …”

“…Fire behavior also has significant influences on second-order fire effects (e.g., vegetation recovery and succession, erosion, and hydrology) [4], with the effects of a high severity wildfire lasting a decade or longer in forested ecosystems [5].…”