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View repeat photography of the stations
By Robert Fulton, California State University Desert Studies Center
Latitude: 35° 13.479'
Longitude: 116° 04.125'
Elevation: 925 ft (282 m)
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The results of the line-intercept transects are summarized in Table 1.
1branches and trunks of deceased specimens still anchored in soil |
Vegetation at this site is dominated in both aspect and coverage by the two perennial evergreen shrubs Atriplex polycarpa, and A. canescens canescens. Together, these saltbushes represent about 60% of the living vegetation cover present during sampling, but only about 6% of the total plot area. Using frequency data and field observations as a simple measure of dispersion, these two species trend towards hyperdispersion (patchy distribution) on this plot. However, observation of the surrounding Saltbush Scrub community indicates that areas of more normal dispersion (random distribution) are present as well. Selection of this site for its relatively barren aspect may mean it is not representative of the community as a whole. All of the remaining ground covered by plant material results from the persisting woody remnants of deceased Atriplex shrubs, and the dried remnants of an introduced annual grass, S. barbatus. The frequency of deceased Atriplex shrubs indicate a more normal (random) dispersion may have been present within the plot in the past, but that ecological dynamics have produced localized hyperdispersion now. All Atriplex encountered, living or not, were found on coppice-like mounds ranging from approximately 1.5 - 4.5 m high by 1.0 - 5.5 m across. Living Atriplex specimens ranged from about 0.5 - 1.4 m tall.
The annual grass S. barbatus grows in response to summer precipitation, and did not germinate in this area in 1999, but did germinate widely in this basin during the summer of 1998 (personal observation). Judging from the condition of the grass during sampling, it was the 1998 crop being counted. This grass had a preference for slight depressions (where water may collect), or on the coppice mounds anchored by Atriplex. In this latter habit, it sometimes formed an understory beneath Atriplex, with the result that the sum of all coverage in Table 1 is 101.35%. This overage of 1.35% represents that understory, leaving 0.25% of the plot covered by this grass in open areas. S. barbatus was included in the sampling as an indicator of possible increased coverage by annual plants during wet years, but this dead material likely underestimates that potential due to withering and possible herbivory. No other signs of annual plants were noted at the site, and it is unknown what potential exists for additional plant cover by other ephemerals in wet years; however, the soil conditions and personal experience would indicate it is relatively low.
No animal species were directly observed during the site visit, with the exception of two common ravens (Corvus corax) overhead. The species present, as indicated by indirect means, are given in Table 2.
1primarily on coppice mounds |
The low diversity of vegetation and relative lack of cover at the site likely results in a reduced animal diversity relative to the adjacent Creosote Bush Scrub. Birds resident to the desert should be transient in this habitat, as would be many migrants, but no species are likely to nest here. Predators such as red-tailed hawk (Buteo jamaicensis calurus) or the greater roadrunner (Geococcyx californianus) are likely to be opportunistic feeders here, as are scavengers like the turkey vulture (Cathartes aura teter) or common raven (Corvus corax). Other vertebrates which may occur here are listed below, many of whom would be casual migrants from the Creosote Bush Scrub community to the east.
coyote (Canus latrans)
deer mouse (Peromyscus spp.)
white-tailed antelope squirrel (Ammospermophilus leucurus)
desert iguana (Dipsosaurus dorsalis dorsalis)
zebra-tailed lizard (Callisaurus draconoides)
side-blotched lizard (Uta stansuriana stejnegeri)
desert horned lizard (Phrynosoma platyrhinos calidiarum)
western whiptail (Cnemidophorus tigris tigris)
coachwhip snake (Uvlasticophis flagellum piceus)
gopher snake (Pituaphis melanleucus deserticola)
Mojave rattlesnake (Crotalus scutulalus scutulatus)
Invertebrates in this habitat are likely to include many species, probably dominated by ground beetles (Tenebrionidae), weevils (Curculionidae), gall forming wasps on Atriplex (Hymenoptera), grasshoppers (Orthoptera), flies (Diptera), and ground spiders (Lycosidae). The lack of harvester ant nests near the site is remarkable, as these ants usually represent a significant portion of the animal biomass in many desert habitats. Their absence here may be due to soil conditions, and/or competition for seeds (their primary food) from rodents.
U.S. Department of the Interior | U.S. Geological Survey
URL: http://esp.cr.usgs.gov/info/sw/clim-met/sodalake.html
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Page Last Modified: Thu 11-May-2006 14:11:51 MDT
