What factors determine the northernmost limit of singleleaf pinyon?
The northern limits of singleleaf pinyon appear to correspond to the strength of cold Pacific fronts resulting in rapid cycling of warming periods interrupted by cold periods during late winter and early spring (Nowak et al. 1994a; West et al. 1978a). These warm periods encourage pinyon to break dormancy early, making them susceptible to frost damage.
The northernmost limit of singleleaf pinyon is several miles north of the City of Rocks National Reserve near Castle Peak in southeastern Idaho. This boundary coincides with the northern most edges of the Basin and Range Ecoregion (also mapped as the Great Salt Lake Major Land Resource Area)(Photo: singleleaf pinyon at City of Rocks National Reserve by Rick Miller, Oregon State University)