Date of this Version
The Prairie Naturalist· 42(1/2): June 2010, pp 45-49
QuantifYing impacts of livestock grazing and prairie management strategies on the threatened western prairie' fringed orchid (Platanthera praeclara) is difficult due to the erratic appearance of the orchid above-ground. We monitored above-ground survival of orchids from flowering to mature seed capsule production, comparing plant height, flower numbers, and seed capsule numbers from 2002-2004 in rotationally grazed pastures and non-grazed sites. Orchid survival differed significantly between grazed and non-grazed pastures, with the proportion of plants surviving from flower to capsule production consistently lower in grazed pastures. Mean orchid survival in grazed and non-grazed areas was 40% and 87%, respectively. The proportion., of surviving plants producing capsules greater than 3 mm in diameter was significantly greater in non-grazed pastures. Flower and bud production did not differ between grazed and non-grazed areas, tlnd plant height was significantly greater in non-grazed) areas. High levels of above-ground plant mortality may reduce orchid tuber winter survival and robustness of above-ground; growth the following growing season. Creation of protected orchid nursery areas within grazed pastures is suggested to reduce high mortality of above-ground orchid plants.