The prairie turnip paradox: Contributions of population dynamics, ethnobotany, and community ecology to understanding Pediomelum esculentum root harvest on the Great Plains

Pediomelum esculentum (Pursh) Rydberg (Fabaceae), an edible plant native to North American prairies, has a long history of wild harvest. Wild-harvested plants are increasingly of conservation concern, yet demographic data needed to assess the sustainability of harvest are unavailable for most species. Methods used by harvesters and responses to harvest are rarely incorporated into demographic studies. Several of the species' traits, including wide-ranging disperse populations, longevity, and cryptic life stages, make it difficult to accurately monitor population dynamics. However, because the species shares these traits with many wild-harvested species of conservation concern, P. esculentum makes a good test case for combining ethnobotanical information with ecological models.; Populations monitored in the absence of harvest are largely stable, with considerable variation in projected growth rates. Challenging life history traits, including the possibility of an entire season spent dormant, and small numbers of hard-to-find individuals in some life stages, add to uncertainty about the accuracy of population projections. Despite this uncertainty, matrix models provide more information about wild-harvested plants that could be of use to conservation practitioners than simpler census techniques could.; Harvest increases adult plant mortality, but P. esculentum harvesters paradoxically report that harvest helps populations. Experimental mimicry of traditional harvest led to a pronounced increase in seedling recruitment. Incorporating the observed increase in recruitment into models of harvest led to a nearly three-fold increase in the sustainable yield of roots harvested from the generalized population. This mode of compensation, in which the act of harvest, rather than the removal of competitors, leads to increased recruitment is newly named (harvest induced compensatory recruitment), but likely applies to many other species.; The disturbances caused by harvest of P. esculentum and Echinacea angustifolia roots lead to changes in prairie plant composition. Forb species diversity increases in harvested plots and grass cover dominance decreases. These subtle changes in plant community composition persist for over a year, even following a homogenizing mowing disturbance. This suggests that as traditional harvesters dug millions of roots from across the prairie, they were creating conditions that favored the category of plant they were harvesting.