Variables that Influence the Endangered Pima Pineapple Cactus (Coryphantha scheeri var. robustispina) Mortality after Transplanting

Coryphantha scheeri var. robustispina (Schott) L. Benson, the Pima pineapple cactus, herein referred to as C. scheeri, was declared an endangered species in 1993 and only occurs in a limited range in Arizona, USA and northern Sonora, Mexico between 2,300'-4,500' asl. Development within the range of C. scheeri threatens individuals, but transplanting to conserve them while allowing for development has been considered to be ineffective for conservation due to low post-transplant survival rates in past studies. The construction of a natural gas pipeline provided the opportunity to conduct a transplant experiment on 82 individual C. scheeri transplanted in July and August 2014. The plants were randomized into one of four transplant methods: bare-root with supplemental water, bare-root without supplemental water, soil-and-plant moved with supplemental water, and soil-and-plant moved without supplemental water. Higher than average precipitation occurred during the 2014 monsoon season including after transplanting. A subset of the transplanted C. scheeri (n=17) were transplanted back onto the pipeline after pipeline construction was completed. Survival rates were monitored through December 2016 and compared to undisturbed C. scheeri near the pipeline ROW and those on other sites. For the plants transplanted once, no significant effect of moving the plants with soil compared to no soil (X2 = 2.9, p = 0.09), no significant effect of adding water at the time of transplant compared to not adding water (X2 = 1.2, p = 0.26), and no significant interaction among treatments (X2 = 0.06, p = 0.81) was observed. For plants transplanted twice, a significant effect of moving the plants with the soil compared to no soil (X2 = 5.0, p = 0.02) was found, while due to the random selection of plants to be transplanted twice there was too little data to adequately test other comparisons. There was no significant difference in mortality between the transplanted once (27% mortality) and the transplanted twice (31% mortality) treatments (p = 0.78), but there was a significant difference between transplanted and non-transplanted plants (2% mortality in non-transplanted plants; p < 0.05). Soil series did not appear correlated with mortality. Plants in good condition (scored 4 or 5 on scale of 0-5) at the time of transplanting had low mortality rates (16%) while plants scored 3 or lower had high mortality rates (60%) but deaths did not occur immediately after transplanting: 5 died after 8 or 9 months, 4 after 13-16 months, and 9 after 23 or 24 months. The majority of the deaths occurred after numerous months of declining in condition but six plants died suddenly. Good condition plants were more likely to flower than those in poor condition. Transplanting appears to conserve some of the C. scheeri population which would have otherwise been lost to development