Snag and woody debris dynamics following severe wildfires in northern Arizona ponderosa pine forests

Following severe wildfires in southwestern ponderosa pine forests, dead trees remain on the landscape and eventually fall, but relatively little is known about the quantity and quality of post-wildfire coarse woody debris (CWD). To describe post-fire conditions, we measured snags, CWD, and fine woody debris and forest floor depth on seven fires in a chronosequence from 3 to 27 years old in northern Arizona. Snags declined in density with increasing time since fire and generally followed expected patterns of decay, except that few snags stood long enough to reach a clean-bark state. The mean biomass of the surface CWD ranged from as low of 3.3 Mg ha−1 to a high of 41.3 Mg ha−1. Total CWD biomass in the surface fuel load remained roughly comparable from 8–9-year-old fires to a 27-year-old fire but the state of the CWD changed from sound to rotten. The change to a rotten condition suggests an increase in ignitability of the post-fire fuel load, but fine fuels that could support high fireline intensity were relatively low. The number of “jackstraws,” points where intersecting downed logs could create a hot spot if reburned, was slightly higher in the oldest fire. Few fire-created snags remained by the 27th year post-fire. Management options to reduce fuels after severe wildfire, such as salvage logging, prescribed burning, or passive management, should be addressed in a broad ecological context.