Table 1 — Species that were analyzed for nutrients and minerals by study area^ 



City Creek Woodbury-Hardy Littlefield 

 Species 1989 1990 1991 1989 1990 1991 1989 1990 1991 



Grasses 



Aristida purpurea (purple threeawn) + + + + + + + + + 



Bromus rubens (red brome^) + + + + + + + + + 



Erioneuron pilosum (hairy tridens) + + + + + + + + + 



Hilaria rigida (big galleta) + + + + + + + + + 



Muhlenbergia porteri (bush muhly) + + + + + + + + + 



Schismus barbatus (Mediterranean grass^) - -+ - -+ - - + 



Stipa hymenoides (Indian ricegrass) + + + + + + + _ + 



Forbs 



Abronia fragrans (fragrant sand-verbena) + -- ___ ___ 



Baileya multiradiata (desert baileya) + + + + + + + + + 



Eriogonum inflatum + + + + + + .+ + + 

 (bottlebush or bottlestopper) 



Eriodium cicutarium (storksbilP) + + + + + + + + + 



Plantago patagonica (wooly plantain) - - + - - + - - + 



Sphaeralcea ambigua (desert globemallow) + + + + + + + + + 



Sphaeralcea grossulariifolia - - - + - _ . _ _ _ 

 (gooseberryleaf globemallow) 



Shrubs 



Atriplex canescens (fourwing saltbush) + + + + + + + + + 



Cerato/c/es /ana/a (winterfat) + + + + + + + + + 



Ephedra nevadensis + + + + + + + + + 



(Nevada ephedra or mormon tea) 



Eriogonum fasciculatum (Mojave buckwheat) + + + + + + _ __ 



Hymenoclea salsola (burrobrush) + + + + + + + + + 



Krameria parvifolia (range ratany) + + - + + + + + + 



Succulents 



Opuntia basilaris (beavertail pricklypear) + + + + + + 



Opuntia erinacea (grizzlybear pricklypear) + + + + + + + + + 



plus sign (+) indicates that a sample was taken, a minus sign (-) indicates no sample. The core species are those sampled every year. 

 ^Introduced species. 



in the Beaver Dam Slope and St. George areas, includ- 

 ing most of the species that we sampled. Plants were 

 collected for analysis in the spring (April, May), sum- 

 mer (June), and fall (October) from 1989 to 1991. The 

 plants in table 1 were all collected in 2-day periods, 

 stored in sealed plastic bags in ice chests for up to 

 36 hours, weighed, ovendried for 5 to 10 days (depend- 

 ing on their succulence) at 40 to 60 °C, reweighed, and 

 ground to powder in a Wiley Mill using a 1-millimeter 

 screen. Additional plant samples (appendix A) collected 

 during April 1990 were treated in the same manner; 

 these samples were largely the same species as those 

 of table 1, but included a few additional species. 



In general, we collected leaves and associated small 

 twigs as a single collection; in some cases we collected 

 fruits, flowers, and stems separately (appendix B). 

 Leaves and small twigs are the plant parts most likely 

 to be foraged by desert tortoises. Some current-season 

 cow dung was collected, stored, and analyzed in the 

 same manner as the plant material in light of the 



recent claim by Bostick (1990) that desert tortoises 

 evolved and flourished as dung feeders. 



The nutritive quality and mineral data for plant sam- 

 ples include moisture content, nitrogen (total organic 

 nitrogen; crude protein = 6.25 x total organic nitrogen), 

 phosphorus, potassium, zinc, iron, manganese, copper, 

 calcium, magnesium, sulfur, sodium, acid detergent 

 fiber (ADF), total nonstructural carbohydrates (TNC), 

 and crude fat (ether extract). We use the terms nutri- 

 tive quality and mineral content reahzing the sampled 

 minerals are nutrients for most animals (Robbins 

 1983). However, the nutritive requirements for desert 

 tortoises are poorly known (Grover and DeFalco in 

 press). Except for moisture content, which was based 

 on total fresh weight, data were collected on a dry 

 weight basis. All analyses, except for moisture con- 

 tent, were performed in the Brigham Young Univer- 

 sity Plant and Soil Analysis Laboratory. The methods 

 used are found in Horov^dtz (1980) except for TNC 

 determination, which followed the procedures of 



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