A preliminary population study of alcove bog orchid (Platanthera zothecina) at Navajo National Monument, Arizona

Abstract

This study on Platanthera zothecina (alcove bog orchid) was initiated by the National Park Service after a recent threatened and endangered species survey at Navajo National Monument. It is listed as Category 2 (species of special concern) by the U.S. Fish and Wildlife Service, and Category 3 (likely to become endangered) by the Navajo Nation. Because P. zothecina is a fairly new taxon, and little is known about its ecology, this baseline study documents population size, number of basal leaves, flowering plant height, number of flowers, and fruit set rates for a 2-year period (1999 and 2000) at Betatakin Canyon. Population size dropped from 1,944 to 1,151 plants by the second year. Average number of basal leaves was three. Flowering plant height averaged 23 cm with the tallest measuring 60 cm. Number of flowers per spike averaged 5 with a high of 20. The flowering rate declined from 33 to 22 percent by the second year. Average number of seed capsules was four. Fruit set rate decreased from 81 to 61 percent in the plants that flowered. The proportion of the population to set fruit was down from 9 to 7 percent by the second year. Herbivory was quite high and appeared to affect fruit set rates and possibly long-term recruitment.

Parent Publication

• Southwestern rare and endangered plants: Proceedings of the Third Conference

Citation

Hudson, Laura E. 2001. A preliminary population study of alcove bog orchid (Platanthera zothecina) at Navajo National Monument, Arizona. In: Maschinski, Joyce; Holter, Louella, tech. eds. Southwestern rare and endangered plants: Proceedings of the Third Conference; 2000 September 25-28; Flagstaff, AZ. Proceedings RMRS-P-23. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 99-104.