COMPARISON OF SOIL PROPERTIES CONTAINING THE WHITE FRINGED PRAIRIE ORCHID (PLATANTHERA PRAECLARA) IN NORTHWEST MISSOURI PRAIRIES AND ADJACENT AGRICULTURAL FIELDS

The goal of this project was to identify soil chemical properties that are correlated with microhabitats where the white fringed prairie orchid (Platanthera praeclara) resides. This plant is an endangered species within Missouri and is federally threatened within the US. Helton, Little Tarkio, and Tarkio Prairies are relatively undisturbed, state-managed remnants and are the only known locations of this species within the state. Soil cores were collected at systematic grid locations within these prairies and within 3 m of stable orchid populations (≥ 10 year-old plants). Additionally, soil in adjacent agricultural fields were sampled for comparison as physically disturbed, high chemical input locations. Soil cores were taken from the top 10 cm of the A-horizon as well as 10 cm beneath this layer (n = 80 samples total). We quantified soil chemistry using a LaMotte agricultural soil kit. Statistical analysis was accomplished by using a multivariate analysis of variance (MANOVA) with predictor variables as site (Helton, Little Tarkio, Tarkio Prairies), and vegetation type (orchid location, non-orchid grid within prairie, adjacent agricultural field). Response variables were the 10 quantified chemicals, and these were Mn, Mg, Fe, Al, K, Cu, Ca, NH³, pH, and humus. We found no significant differences among sites for soil chemistry with the exception of Mg (p = 0.01). This may indicate that sites containing glacial till within this area are quite homogenous. Soil attributes among areas with differing vegetation types were not significant with the exception of Ca, pH, and humus (p < 0.05), and these areas had significantly higher soil chemical values in the orchid and agricultural areas versus the non-orchid prairie locations. These results indicate that the white fringed prairie orchid may have substrate-specific requirements for Ca, pH, and humus but may be a generalist for the other tested nutrients.