VEGETATION AND INVERTEBRATE SPECIES DIVERSITY AND RICHNESS AT SPRINGS ECOSYSTEMS OF THE SOUTHWESTERN U.S

Over the past 10 years, over 230 springs ecosystems in the Southwestern U.S. have had comprehensive inventories conducted on them. The inventories included site descriptions, environmental and climate conditions, vegetation and invertebrate surveys, wildlife observations, water-quality analyses, geomorphology descriptions, and water-quantity measurements. Spring discharge was usually less than 1.0 liter/second or immeasurable at most of the springs. Almost all of the springs discharged from sedimentary rocks and sandstone was the rock type of most of the springs. Most of the spring waters are of a Calcium-sodium/Bicarbonate-chloride-sulfate type, although some of the springs had a much different type of water. At 75 springs on National Park Service units, there were a total of 633 plant taxa on 157 geomorphic surfaces adding more than 150 plant specimens to the various park herbaria, including more than two dozen previously undetected species in cooperating parks. Average total plant species richness at the springs inventoried was 44.1 (1 sd = 24.58) species/site, a value that is relatively high for southwestern landscapes. Average springs area surveyed was 0.147 ha but highly variable (1 sd = 0.221). The largest springs had the most plant species; however, species richness also varied by geomorphic setting (sloping bedrock surfaces and backwalls had fewer species than channel terraces and colluvial slopes), and by elevation. That total springs diversity varies non-linearly with elevation, with greatest species diversity at intermediate elevations (1500-2500 m). We detected and identified more than 8,000 invertebrates at least to the level of taxonomic order, including many new records of aquatic and terrestrial species for the cooperating parks. Invertebrate diversity is strongly related to plant diversity (p<0.001).