Prescribed fires cause minimal damage to a threatened cactus (Tobusch fishhook cactus, Sclerocactus brevihamatus ssp. tobuschii, Texas, USA)

Abstract

The effects of fire on cacti depend on individual plant characteristics, fire intensity, and local conditions. Tobusch fishhook cactus (Sclerocactus brevihamatus ssp. tobuschii) is a small (<~7 cm diameter), globose cactus endemic to the Edwards Plateau of central Texas. This species grows in open sites with shallow, rocky soils, surrounded by oak-juniper woodlands and shrublands. Fire is thought to maintain the open character of the sites, but few studies have examined the effects of fire on this species. We investigated the effects of two prescribed fires on Tobusch fishhook cacti (n > 600) in long-term monitoring plots. The fires killed only one cactus and visibly damaged <28% of cacti, none of which died within the first two growing seasons. Visibly damaged cacti grew less than undamaged cacti in the first and/or second growing seasons, but fruit set was not reduced. Fire damage was best predicted by cactus diameter (>1 cm), cactus height (>1 cm), and proximity to bunchgrasses (<3 cm). Prescribed fire can be used to maintain Tobusch fishhook cactus habitat but should avoid flowering/fruiting seasons (~January through May) and years with above-average rainfall that create high fuel loads.