Spiranthes parksii, Navasota Ladies’ Tresses, is a federally endangered plant species endemic to Texas post oak savannah. Although primarily threatened by land development, S. parksii also suffers degradation due to woody plant encroachment closing the savannah canopy. We designed an experimental study to investigate the effects of shrub removal on S. parksii establishment and abundance. Twenty-one 20x20m plots were randomly assigned one of three treatments. In addition to undisturbed control plots, evergreen shrub species were removed using two different removal methods (cut with herbicide application and cut only) in January 2008 prior to peak rosette production. Pre-treatment demographic data were collected in spring and fall 2007 for S. parksii and related Spiranthes species (S. cernua and S. lacera).
Results/Conclusions The total number of Spiranthes plants increased from 2007 to 2008 in all treatments, but initial data indicate a greater increase in the shrub removal plots (38.3% increase in cut and 44.9% in cut/herbicide treatments versus 22.0% increase in control plots). Populations of S. parksii are known to be extremely variable with yearly fluctuations from a few dozen to several hundred individuals. Nevertheless, the immediate rosette response to shrub removal we observed is encouraging and requires further investigation to elucidate the mechanisms responsible for promoting S. parksii abundances. Shrub removal in association with other management practices appears to be a potentially effective conservation and mitigation strategy for S. parksii.