Burn Severity of Areas Reburned by Wildfires in the Gila National Forest, New Mexico, USA

摘要

We describe satellite-inferred burn severity patterns of areas that were burned and then reburned by wildland fire from 1984 to 2004 within the Gila Aldo Leopold Wilderness Complex, New Mexico, USA. Thirteen fires have burned 27 000 hectares across multiple vegetation types at intervals between fires ranging from 3 yr to 14 yr. Burn severity of reburned areas showed sensitivity to the severity of the initial fire. The severity of reburned areas also varied by vegetation type and time elapsed between fires. Initial fires that burned at low severity tended to reburn at low severity, while reburned areas where initial fire was severe showed higher probability of reburning at high severity. Our analysis also suggests that there may be thresholds in the severity of an initial burn above which the severity of the subsequent fire is likely to increase. Because the spectral index used primarily reflects changes in vegetation relative to pre-burn conditions, a large relative change in post-fire vegetation (e.g., shrubs and small trees), as inferred from remotely sensed spectral data, is likely at sites that previously burned at high severity. Field data are needed to fully assess the reburn severity issue, in order to demonstrate that severe reburns may be a relatively new phenomenon occurring outside the historical norm, with potential long-term ecological significance.