The Peak Fire of June 1988, originated in Mexico, but spread into the United States, and affected most of Coronado National Memorial. The Oak - Mexican Pinyon Pine - Juniper Woodland Association was most affected, as about 2,600 acres (1050 ha) of the 3,700 acres (1500 ha) that burned were in this habitat. Most of this biotic community was burned to a moderate degree, except for some severely burned areas in the western portion of the Memorial. Fire tolerant species like Emory and Arizona white oaks are able to survive intense fire as do succulents. by August 1989, many of the trees had resprouted either from the roots or from undamaged areas of the trunk. Plants incapable of or only sometimes resprouting, however – notably alligator juniper and Mexican pinyon pine – have been largely eliminated by the intense fires in woodland communities. There has been a noticeable increase in species diversity of the herbaceous understory plants in woodland communities following the fire. The species composition of the woodland understory was significantly changed after the fire, probably due to the influx of nutrients and/or appropriate conditions for germination of numerous herbaceous species that were either rare or absent before the fire.
The Grama Grass - Mixed Grass - Mixed Shrub Association was relatively unaffected by the fire because little fuel was present to sustain a high temperature fire. Rabbit brush and hedgehog cactus have been eliminated or reduced in density on grasslands as a result of the Peak Fire. Honey mesquite and other woody species may be increasing within the grassland communities of the memorial. Aperiodic fire is an important mechanism in maintaining dominance of grasses in these communities.
The riparian habitats of the memorial, although not directly affected by the Peak Fire, have been modified by physical processes associated with it. Transport of sediments downslope from burned areas, mediated by heavy summer rains following the fire, resulted in initial scouring and subsequent filling of the ephemeral channel of Montezuma Canyon. Dominant woody riparian plant species were not directly affected; however, their habitat has definitely been modified by the fire.
