PARENT SESSION
Symposium #10: Every Last Drop: Ecology, Conservation, and Restoration of North American Springs Ecosystems.
Organized by: LE Stevens and VJ Meretsky
Tuesday, August 6. 8:00 AM to 11:30 AM. Turquoise Ballroom, TCC.
Southwestern springs vegetation: biogeography, human impacts, and restoration.
Meretsky, Vicky*,1, Spence, John2, Stevens, Lawrence3, 1 School of Public and Environmental Affairs, Bloomington, IN2 Glen Canyon National Recreation Area, Page, AZ3 Consulting Ecologist, Flagstaff, AZ
ABSTRACT- The vegetation of springs ecosystems in the American Southwest reflects interactions between regional climate history, geomorphology, microsite factors, water quality, and human impacts. We examined the plant species composition at >200 springs in Utah and Arizona, bridging the 2000 m high southern margin of the Colorado Plateau and extending into low elevation Sonoran Desert. Climate in this region varies strongly across elevation, and elevation is a surrogate for latitude. The array of springs examined included low gradient settings to hanging gardens (vertical cliff springs). We recorded water quality, aspect, spring type, and human impacts, and describe the elevational distribution of springs vegetation across the study region. Local microsite conditions modify composition, with north-facing slopes supporting more boreal species, and south-facing sites supporting more desert taxa. We identified several patterns of rarity among the springs flora, including restricted endemics (<1% of the species), widely distributed endemics (<10%), and widespread habitat specialists. Springs plant diversity is strongly negatively related to elevation. The rarity of local endemics is attributable to the high density of springs in this region (0.0163/km2 in Arizona, 0.0119/km2 in Utah), and landscape connectivity, conditions which do not obtain for springs in other regions (e.g., the Great Plains). Human activities have strongly reduced or eliminated springs wetland plant diversity at >90% of the springs in much of the region, making springs high priority targets for inventory, protection and restoration. Global warming may strongly affect springs vegetation because of restricted gene flow in these often isolated ecosystems.
KEY WORDS: springs, American Southwest, biogeography, refugia