This study assessed the long-term effect of prescribed burning on three prevalent cacti (often invasive on grassland overgrazed by livestock): brown-spine pricklypearOpuntia phaeacantha, walkingstick cholla O.imbricata and tasajillo O.leptocaulis (and several less common cacti) growing in semi-arid Southern Mixed Prairie at sites in three counties in western Texas (southwest USA).
The three study locations (and dominant plants) were:
1) Beckham Ranch (Callahan County) - sites dominated by little bluestem Schizachyrium scoparium,
buffalograss Buchloe ductyloides, sideoats grama Bouteloua curtipendula and Texas wintergrass Stipa leucotricha;
2) Dalby Ranch (Garza County) - an area dominated by tobosagrass Hilaria mutica, alkali sacaton Sporobolus airoides, walkingstick cholla and honey mesquite Prosopis glandulosa;
3) Renderbrook-Spade Ranch (Mitchell County) - sites on a tobosagrass-mesquite community.
Brown-spine pricklypear were marked (with metal stakes) on prescribed spring burn sites on the Beckham Ranch in 1971, and Renderbrook-Spade and Dalby Ranches in 1972 and 1974. Additional
pricklypear plants were marked on a wildfire that occurred on Dalby Ranch in July 1970. Walkingstick cholla were marked on two prescribed fire sites on Dalby Ranch in spring 1973. Tasajillo were marked on Renderbrook-Spade Ranch in 1973 and 1974. Smaller numbers of four less common cacti were also monitored.
Mortality (absence of living tissue) was recorded in July and December each year until December 1976.
Mortality was based on observations of 600 brown-spine pricklypear, 200 walkingstick cholla, 175 tasajillo, 79 devil’s pincushion Echinocactus texensis, 66 Mammillaria gummifera (not native to the state),18 lace cactus Echinocereus reichenbachii and10 star cactusCoryphantha (Escobaria)vivipara
About 20% of brown-spine pricklypear were killed by fire within the first year. Most plants were damaged but resprouted after burning. However mortality increased over time (averaging 70% by the end of the fourth year after burning). Insect and rodent damage in conjunction with that caused by burns caused most deaths.
Walkingstick cholla and tasajillo were more directly affected by fire. First-year mortality was 40 and 65%, respectively, and fourth year mortality 57 and 80%.
Mortalities of the other species were:
devil’s pincushion - 17% year 1, 19% year 4;
Mammillaria - 33% year 1, 74% year 4;
lace cactus - 17% year 1, 94% year 3;
star cactus - 100% year 1
Overall, fire was effective in controlling these cacti species.