PHYTOGEOGRAPHY AND FLORISTICS OF PINYON-JUNIPER WOODLANDS IN NORTHERN ARIZONA

This study assesses the floristic diversity and affinities of pinyon-juniper (PJ) woodlands ill northern Arizona at 2 different scales: regionally within the context of North American floristic patients and locally within the 2500-m elevation gradient of the San Francisco Volcanic Field (SFVF). An analysis based upon 245 North American floras indicates that the PJ woodlands of the SFVF share strong affinities with the adjacent Colorado Plateau and Apachian floristic elements but also show high floristic similarity to the Great Plains. Data suggest that mid-elevation woodlands of the Colorado Plateau share floristic affinities with the Great Plains that are its strong its or stronger than those shared with the Great Basin. A geostatistical analysis provides it spatially explicit depiction of these findings. A comparison of species occurrences between 6 adjacent biotic communities in northern Arizona reveals that the PJ woodlands host the most distinctive flora among local life zones. Despite what their simple woodland structure only suggest, PJ woodlands of, the SFVF host it moderately species-rich flora. This study suggests that the floras of PJ woodlands vary ill significant and important ways across the range of PJ woodlands in western North America.