Evaluating the Effects of Traditional Harvest and Climate on Common Camas (Camassia quamash) in Weippe Prairie, Idaho

"Common camas (Camassia quamash) is a culturally important wetland plant, used as a staple food source by many indigenous peoples of western North America for thousands of years. Camas populations were once widespread, but conversion of wetland prairies to agriculture has led to declines in suitable habitat. Edible camas bulbs were traditionally harvested by digging the bulbs from soil, and it has been hypothesized that this process can result in an increase in the number of camas plants growing in harvested areas. Given that camas depends on seasonally wet prairies, climate and water balance are also likely drivers of camas population density fluctuations. To better understand the influences on camas populations, I conducted an experiment at the Weippe Prairie, Idaho historical site to evaluate the strength of treatment effects of simulated traditional harvest practices, including harvest, fire, and a combination of harvest and fire on three reproductive classes of common camas plants. I considered these impacts on native and non-native prairie grasses, litter, and bare ground as well. My experiment was conducted alongside of a longer-term camas population monitoring program. I used a 10-year set of camas density and flowering rate observations to analyze responses of camas to climatic and hydrological variables including average departure from 30-year means of precipitation, and minimum and maximum temperature, as well as water balance values including minimum soil moisture, actual evapotranspiration, and water deficit. I also evaluated the effects of elevation and topographic wetness index on camas densities within the study area. Study results indicate that both harvesting practices and climactic variation can have significant impacts on camas plant productivity and reproduction, and can maintain favorable growing conditions."