The Navasota Ladies’ Tress (Spiranthes parksii, referred to as NLT henceforth) is a federally listed endangered species which is endemic to the Brazos Valley.  In order to develop conservation principles, the environmental factors responsible for promoting and inhibiting successful NLT seed maturation, dispersal, and establishment must be determined.  Assessing the effects of fire and herbivore grazing is important to the development of conservation principles as these disturbances historically occurred in the post oak savannah ecosystems where NLTs are located.  We have selected 32 (1.5m x 1.5m) plots in areas of known high NLT density and will initiate four experimental treatments manipulating fire and herbivory.  We will burn and fence eight plots, burn eight unfenced plots, fence eight unburned plots, and leave eight plots unburned and unfenced as controls to determine the effects of fire, herbivory and their interaction on NLTs.  We will use fire treatments in the period between basal rosette senescence and flowering stalk emergence, using a burn box to control for variation in fire intensity and flame residence time. A thermocouple will be used to measure time-temperature relationships inside the burn box.  Within each plot we will measure and analyze NLT demographic characteristics, such as leaf area and number, flower stalk height, number of flowers, and longevity of each of these structures.  We will also record herbivore damage.  We will use ANOVA to determine whether basal rosette or flowering stalk emergence is increased and whether demographic or population characteristics are affected by the treatments.   

Results/Conclusions

Prior experiments performed in conjunction with this study examined the effects of understory brush clearing and nutrient addition combined with biomass removal.  These studies have illustrated the importance of decreased competition and increased light availability for NLT establishment.  We predict that controlled burning will similarly enhance light and nutrient availability while reducing woody and herbaceous plant competition.  We predict that excluding herbivore grazing will promote NLT establishment given observed high rates of herbivory of rosettes and flowering stalks.  The data obtained from this suite of experiments will establish a baseline of information regarding optimal conditions for NLT establishment and maturation and will provide scientifically sound principles upon which to base management recommendations for conserving existing NLT populations and increasing total numbers of NLTs.