Effects of fire severity and pre-fire stand treatment on plant community recovery after a large wildfire

The Rodeo-Chediski fire burned approximately 189,650 ha in east-central Arizona from June 18 to July 7, 2002, 113,700 ha of it on White Mountain Apache tribal land. In 2004 and 2005, we measured plant canopy cover and richness in areas of high and low burn severity in each of two treatments: (1) cutting and prescribed burning, or (2) untreated, in the 11 years prior to the wildfire. Total understory plant canopy cover was significantly higher in areas of high severity (p = .0002 in 2004 and p = .0001 in 2005). Overall, there was high richness of exotic species but cover was surprisingly low at <3% across all years, severities, and treatments. There were no significant differences in exotic species cover between high and low severity or between treated and untreated areas. Areas of high severity burn were seeded after the fire with several native grasses, native forbs, and common wheat (Triticum aestivum L.). Wheat had a strong presence in the plant community in 2004, but was uncommon by 2005. Indicator Species Analysis showed the indicators of high severity were seeded or early successional species. In contrast, indicators of low severity included several perennial bunchgrasses. While our results show that wheat declined quickly and exotic plants were uncommon, any longer-term impacts of the fire on the plant community can only be addressed by continued monitoring of these sites.