Vascular Flora of the Lower San Francisco Volcanic Field, Coconino County, Arizona Author(s): Kyle Christie Source: Madroño, 55(1):1-14. Published By: California Botanical Society DOI: http://dx.doi.org/10.3120/0024-9637(2008)55[1:VFOTLS]2.0.CO;2 URL: http://www.bioone.org/doi/ full/10.3120/0024-9637%282008%2955%5B1%3AVFOTLS%5D2.0.CO%3B2 BioOne (www.bioone.org) is a nonprofit, online aggregation of core research in the biological, ecological, and environmental sciences. BioOne provides a sustainable online platform for over 170 journals and books published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/page/ terms_of_use. Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder. BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. MADRON˜ O, Vol. 55, No. 1, pp. 1–14, 2008 VASCULAR FLORA OF THE LOWER SAN FRANCISCO VOLCANIC FIELD, COCONINO COUNTY, ARIZONA KYLE CHRISTIE Deaver Herbarium, Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011-5640 [email protected] ABSTRACT The San Francisco Volcanic Field lies near the southern edge of the Colorado Plateau in north- central Arizona, and is dominated by an extensive Pinyon-Juniper woodland. During 2004 and 2005, a floristic inventory vouchered 487 taxa from 74 families and 268 genera, including eight species endemic to Arizona. The Asteraceae, Poaceae, Fabaceae, Brassicaceae, and Scrophulariaceae comprised 51% of the total flora. Eriogonum, Muhlenbergia, Penstemon, Aristida, Astragalus,and Cryptantha were the best represented genera. Nonnative taxa accounted for ten percent of the total flora. Cryptantha minima and Suckleya suckleyana were vouchered as new records for Arizona. Key Words: Floristics, flora, Pinyon-Juniper woodlands, San Francisco Volcanic Field, volcanic endemism. Arizona displays the third highest diversity of distributions due to global climate change, vascular plants in the United States with over especially in semiarid environments and at 3,500 known taxa; however, it is also the fifth ecotones, are a definite possibility in upcoming most ‘‘at-risk’’ state with over 15% of its plant years (Allen and Breshears 1998). The ecophysio- species at risk of extinction due to rarity or graphic nature of the lower SFVF (it encompass- habitat loss (Stein 2002). While many floristic es a woodland community in a semi-arid climate, inventories document vascular plant diversity and has a widespread ecotonal component) lends around the state, no vascular plant inventory greater urgency to a floristic assessment of the exists for the lower San Francisco Volcanic Field area. The findings from this study will provide a (SFVF), an expansive Pinyon-Juniper woodland benchmark of local floristic diversity and serve as in north-central Arizona (Moore and Cole 2004). a basis for future comparisons. Inventories in adjacent areas have been primarily restricted to National Park Service units and Study Area scenic landscapes such as deep canyons or mountain peaks (e.g., McDougall & Haskell The SFVF lies near the southern edge of the 1960; Joyce 1976; Hazen 1978; Schilling 1980; Colorado Plateau physiographic province in Kierstead 1981; Gilbert and Licher 2005; Moir north-central Arizona; south-central Coconino 2006). Pinyon-Juniper woodlands have often County (Bailey et al. 1994; Bailey 1998). The been overlooked or ignored during the creation lower SFVF, and synonymously the study area, of inventories, and thus the relatively vast lower was defined as the contiguous Pinus edulis/ SFVF represents a significant gap in floristic Juniperus monosperma dominated portion of the knowledge. SFVF. It is elevationally bound by montane The SFVF lies at the convergence of several coniferous forests above and grasslands below biotic communities, in the middle of a large (Brown and Lowe 1980). Inclusions of other elevational gradient, and at the junction of vegetation on north-facing slopes, drainages, several known physiographic and floristic zones; canyons, or unusual microsites were also included and was therefore anticipated to have a high as part of the study area. diversity of vascular plants (Brown and Lowe The study area lies between 35u109470 and 1980; McLaughlin 1992). Cinder ecosystems 35u419300 latitude and between 2111u21930 and resulting from the recent Sunset Crater volcanic 2112u109120 longitude, and encompasses approx- eruption are also known to host several edaph- imately 1134 km2 (Fig. 1). Elevations range from ically-limited, rare, and endemic plants (AGFD 1700 to 2400 m; however, approximately 84% of 2005a, b, c). the study area falls between 1829 and 2134 m. The distributions of Pinyon-Juniper wood- Roughly 73% of the study area lies within the lands, and potentially the understory species Coconino and Kaibab National Forests, while associated with this community type, have varied the remainder occurs on essentially undeveloped historically with changing climate variables (Be- private (16%) and State (11%) land. Approxi- tancourt et al. 1990). Shifts in vegetation mately 70 widely-spaced cinder cones dot the 2 MADRON˜ O [Vol. 55 FIG. 1. Location of the lower San Francisco Volcano Field (lower SFVF). otherwise flat plateau of the lower SFVF. The continuously for the past three million yrs study area lacks major river systems, bodies of (Moore et al. 1976). Paleomagnetic data, Potas- water or streams, and perennial water is essen- sium-Argon dating, and thorough field mapping, tially absent. Biotic communities are solely suggest that substrates of the SFVF range from restricted to Great Basin Conifer Woodlands less than one-thousand yrs old at the eastern edge with several small inclusions of Petran Montane of the volcanic field to over six-million yrs old at Conifer Forests and Desert Grasslands at anom- the southwestern edge of the volcanic field, only alous sites (Brown and Lowe 1980). The SFVF 100 km away (Tanaka et al. 1986; Moore and sits near the junction of the Colorado Plateau and Wolfe 1987; Wolfe et al. 1987) Apachian floristic areas (McLaughlin 1989). Due to its volcanic history, igneous rocks and The lower SFVF has a semi-arid climate and their associated soils are the dominant substrates receives approximately 38 cm of precipitation of the SFVF. Basaltic rocks, cinders, and lava annually; however, precipitation can vary dra- from the Holocene to Middle Pliocene cover matically, often ranging between 25 and 65 cm about 80% of the of the study area. Quaternary from year to year (Bailey et al. 1994; Bailey 1998; alluviums (3.5%), Holocene to Middle Pliocene WRCC 2005). Precipitation is bi-modal, as very rhyolites and andesites (3%), Pleistocene alluvi- dry late springs and early summers punctuate ums (2%), and Permian sandstone and limestone winter and monsoonal moisture. Approximately (11%) comprise the additional surficial geology 50% of the annual precipitation comes from (Richard et al. 2000). summer monsoons. The winter of 2004–2005 received 200% of the historical precipitation METHODS average, while the spring of 2005 was 140% wetter than normal. Summer rains of 2005 Vascular plants were collected for 55 d (ca. brought 75% of the historical precipitation 400 hr) between March and October of 2004 and average (WRCC 2005). 2005. An effort was made to collect every taxon, The SFVF was created by at least seven major as well as to collect from the entire geographic eruptive events, and is one of the major basaltic and habitat range of the study area. Special effort volcanic fields of the Colorado Plateau (Cooley was made to target areas and habitats that 1962; Tanaka et al. 1986). It includes over 600 harbored greater diversity or locally unusual Pliocene, Pleistocene, and Holocene volcanic taxa. Voucher collections included plant descrip- vents, volcanoes, and cinder cones, and their tions, habitat descriptions, locality descriptions, associated sheet deposits and lava flows (Tanaka and lists of associated species. UTM coordinates et al. 1986). Local basaltic volcanism began and elevations were taken from a Garmin eTrex roughly six millions yrs ago and has occurred Legend GPS unit (Garmin International; Olathe, 2008] CHRISTIE: VASCULAR FLORA OF THE LOWER SFVF 3 TABLE 1. TAXONOMIC COMPOSITION OF THE LOWER SAN FRANCISCO VOLCANIC FIELD. Divisions and Classes Families Genera Species Infraspecific taxa Total Taxa Polypodiophyta 2 3 3 0 3 Pinophyta 6 Pinopsida 2 2 5 0 5 Gnetopsida 1 1 1 0 1 Magnoliophyta 478 Magnoliopsida 57 212 372 6 378 Liliopsida 12 50 98 2 100 Totals 74 268 479 8 487 KS). Voucher specimens were pressed, dried, dix A.) This absence may suggest that these mounted, and deposited in the Deaver Herbari- species are locally uncommon; as approximately um (ASC) at Northern Arizona University one-third reach the extent of their ranges near the following typical protocols (Weber 1976). Spec- SFVF, and another one-third lack much suitable imens were identified primarily using the Inter- habitat in the SFVF. On average it has been mountain Flora (Cronquist et al. 1972+), the Flora 25 yrs since one of these species was collected of North America (Flora of North America from the SFVF, perhaps because these species Editorial Committee 1993+), treatments from simply no longer occur or have decreased in the Manual of Vascular Plants of Arizona as abundance locally. Fourteen additional common published in the Journal of the Arizona-Nevada taxa were encountered in the field but were not Academy of Science (Vascular Plants of Arizona collected due to documentation by extant her- Editorial Committee 1992+), and Seed Plants of barium collections. These taxa are indicated with Northern Arizona (McDougall 1973). All nomen- a pound sign (#) in Appendix A.