The Effects of Woody Plant Management on Habitat Conditions, Plant Demography, and Transplantation Success of the Endangered Orchid Spiranthes parksii Correll

Abstract

Spiranthes parksii Correll is a federally endangered species endemic to 13 counties of the Post Oak Savanna in Central Texas. Approximately 700 S. parksii are located on the Brazos Valley Solid Waste Management Agency’s (BVSWMA) Twin Oaks landfill property in Grimes County, Texas. The opportunity to study S. parksii was created through the mitigation requirements set forth by the United States Fish and Wildlife Service (USFWS) on the property.

Studies were designed to assess the effect of woody plant management on the target species with the overall goal of enhancing the establishment, growth, and reproductive success of S. parksii. Evergreen midstory shrub removal and woody patch clearing to produce varying sized open grassland and woody patches to increase edge effect were studied to determine their influence on habitat for S. parksii. S. parksii were transplanted from at risk areas to permanently protected areas to evaluate potential effective procedures for transplanting of the species.

Seasonal variability in S. parksii and Spiranthes spp. numbers were common across all studies, however, flower production in the fall was positively correlated with the summed January through March precipitation. In general, the removal of encroached woody plants resulted in a positive orchid response, though poor herbicide efficacy may limit this treatment effect in the long-term. Transplantation of S. parksii into areas which received woody plant management resulted in at least a 50% survival rate 3 years post-transplant.