Fire and floods in the Valles Caldera National Preserve, New Mexico: The 2011 Las Conchas Fire impacts on montane species diversity and food webs

Background/Question/Methods

The Las Conchas Fire in northern New Mexico during June-August, 2011, burned over 63,000 ha of forest and grassland in the Jemez Mountains, and became the largest wildfire ever recorded in New Mexico history.  At the top of the burned watersheds, the fire covered over 12,000 ha (34%) of the 36,000-ha Valles Caldera National Preserve.  While large-scale uncharacteristic wildfires are increasing in North America, few areas that burn in these fires have pre-existing, detailed ecological monitoring sites that can be used to evaluate fire impacts on ecosystem structure and functioning.  The Valles Caldera is an exception, where existing long-term monitoring programs for climate, hydrology, water quality, vegetation and wildlife/fisheries provide extensive data on pre-fire ecosystem variables.  Instruments deployed for weather stations, stream discharge flumes and gauges, and water quality monitors (Sondes) recorded events continuously throughout and following the fire, and because only a third of the Preserve burned, vegetation and wildlife monitoring sites recorded fire impacts in both burned and unburned areas.  Additional post-fire monitoring sites for vegetation, fish and wildlife (including terrestrial and aquatic invertebrates) were established immediately after the fire.  Thus, the purpose of this study is to provide detailed post-fire ecological information to managers for developing effective and efficient restoration programs.

Results/Conclusions

Post-fire monitoring for terrestrial vegetation, terrestrial and aquatic invertebrates, fisheries, and the Jemez Mountains elk herd, revealed highly variable patterns across taxa of survival, recovery and recolonization in the first year after the fire.  Streams subjected to flash floods exhibited high ammonia and turbidity spikes, depressed dissolved oxygen, and elevated pH values, contributing to the near-annihilation of brown and rainbow trout – but aquatic invertebrates and native non-game fish species were only slightly affected.  No fire-induced mortalities of adult elk or calves were recorded.  With the onset of the monsoon rains, herbaceous vegetation diversity, species richness and cover recovered quickly in the first post-fire growing season.  Terrestrial arthropod community and food-web structure was temporarily affected, but recovery was proceeding quickly through the autumn, especially in grassland habitats.  The Preserve’s long-term monitoring program has been expanded to provide managers with detailed information on post-fire recovery rates of these important ecosystem components.