EFFECTS OF CATTLE DISTURBANCE ON CHANGE IN POPULATION DENSITIES AND FLOWERING OF WRIGHT FISHHOOK CACTUS (SCLEROCACTUS WRIGHTIAE LD BENSON)

摘要

In 1979, the United States Fish and Wildlife Service listed the Wright fishhook cactus (Sclerocactus wrightiae L.D. Benson) as endangered. Since that time, the potential impacts associated with cattle grazing have been a central focus of land management policies and debate. To better understand and monitor the impacts of cattle disturbance on Wright fishhook cactus population trends, the Bureau of Land Management established 30 macroplots (25 x 50 m). These macroplots were placed in multiple grazing allotments and located in areas representing different levels of disturbance (high, moderate, and low). Our objective was to evaluate the effects of cattle soil disturbance on change in population densities (individuals/macroplot), flowering plant frequency (%), and flowering density (number of reproductive structures/macroplot) of Wright fishhook cactus across 7 years (2011-2017). Our analysis suggests that decreased flowering frequency (%) is significantly associated with high cattle disturbance. However, we observed no significant association between level of disturbance and flower density or change in population density. These results indicate that soil disturbance by cattle may not be significantly impacting Wright fishhook cactus populations or contributing to their range-wide population decline.