Get reliable science

A history of overgrazing and fire suppression along with prolonged drought events has resulted in elevated soil erosion and decreased forage productivity throughout Texas rangelands. This study is examining how prickly pear (Opuntia) cactus responds to seasonal disturbances (e.g. prescribed fire and grazing) following periods of drought. Prickly pear is a native succulent that has significantly increased in cover during the past century to the point of being considered a problematic pest-like species. This experiment is being conducted at the Texas A&M AgriLife Research Station, in Sonora, Texas, on a site with significant Opuntia cactus encroachment. In early June 2010, a total of 48 cactus mottes were selected and randomly assigned an experimental treatment combination that included prescribed fire (dormant season fire, growing season fire, or no fire/control) and a drought treatment (rain-out shelter or ambient conditions/control). This experimental design provided eight replicates of each treatment combination. The mottes assigned a drought treatment were placed under a rainout shelter structure covered by a clear polycarbonate plastic that intercepts precipitation from reaching the motte. Monitoring and data collection of the treatment sites shows a decrease in herbaceous species under the shelters, however it is still early for us to determine if these combined drought and prescribed fire treatments have resulted in prickly pear mortality. In the mottes where rainfall is suppressed, I expect that the growth of the cactus mottes will be temporarily limited; in addition this environmental stress could result in an increased susceptibility to other disturbances (e.g. herbivory, fire).