Geology and Soils in Deserts of the Southwestern United States - Design with the Desert: Conservation and Sustainable Development - page 53

Soil temperature controls the activity of soil organisms and also the respiration rates
of plant roots. Soils in urban systems are typically warmer than those of nonurbanized
systems because of decreased surface shading, decreased albedo (or reflectance), and
increased compaction. Higher temperatures may lead to faster organic matter decomposi-
tion and to stressed plants.
Urban soils often contain considerable amounts of manmade materials such as con-
struction debris (e.g., bricks, pipe cement, metals) that, while not immediately hazardous,
may reduce water-holding capacity and interfere with root penetration and water move-
ment within the soil profile. Contaminants that may be present include pesticide residues,
hydrocarbons, and other materials (see Chapter 5).
These differences from naturally developed soils make urban soils a unique manage-
ment challenge for urban planners and soil scientists alike. Most soil data in the United
States are based on soils of natural systems or agricultural soils, and the applicability of
much of the data to all soils in urban areas may be questionable.*
2.11 Accessing Geological and Soils Information
The primary source of information for geological surface and subsurface maps and
profiles, hydrologic information, geological hazard assessments, and mineral resource
information for the United States—including the desert regions—is the U.S. Geological
Survey (USGS). † State agencies are another important source of geological information
for the desert regions of the continental United States. ‡ The USDA Natural Resources
Conservation Service (NRCS) is the primary source of information for soils data in the
United States. The NRCS publishes soil surveys for counties or parts of counties. These
soil surveys contain a great deal of useful soils information including location maps of
different soil types, soil classifications, and interpretation for different uses. The most
current soil survey information is available through the Web Soil Survey online map-
ping and data query tool, which provides interactive access to the U.S. General Soil Map
(STATSGO2) and Soil Survey Geographic (SSURGO) databases. Soil data can also be
downloaded in digital formats suitable for use in Geographic Information System (GIS)
software environments through the Web Soil Survey interface. The NRCS also provides
information on soil-related hazards such as shrink-swell potential, which can cause
severe damage to house foundations. §
* As a starting point for information about urban soils, the reader is referred to Craul. 22
† The majority of data available from the USGS can be accessed at http://www.usgs.gov (accessed August 21,
2012).
‡ All of these state geological surveys provide some data access through their websites: Arizona Geological
Survey—http://www.azgs.az.gov/ (accessed August 21, 2012); California Geological Survey—http://www.
conservation.ca.gov/cgs/Pages/Index.aspx (accessed August 21, 2012); Idaho Geological Survey—http://www.
idahogeology.org/ (accessed August 21, 2012); New Mexico Bureau of Geology and Mineral Resources—http://
geoinfo.nmt.edu/ (accessed August 21, 2012); Nevada Bureau of Mines and Geology—http://www.nbmg.unr.
edu/ (accessed August 21, 2012); Oregon Department of Geology and Mineral Industries— http://oregongeology.
com/sub/default (accessed August 21, 2012); Texas Bureau of Economic Geology—http://www.beg.utexas.edu/
(accessed August 21, 2012); Utah Geological Survey—http://geology.utah.gov/ (accessed August 21, 2012).
§ NRCS data is available online at http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm (accessed August 21,
2012).