Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. ‘e, United States ) Department of Agriculture Forest Service Intermountain Research Station Research Paper INT-473 April 1994 UAS ee, Cc vA Nutritive Quality and Mineral Content of Potential Desert Tortoise Food Plants E. Durant McArthur De a Stewart C. Sanderson St Ue) OMe Bruce L. Webb SCG tai ee Me Pe st seit Ss BS bre ea 0 a | fy Bd i ww Ss EI —< Bo oo) u? THE AUTHORS E. DURANT McARTHUR is Project Leader and re- search geneticist for the Shrubland Biology and Restora- tion Research Work Unit at the Intermountain Research Station’s Shrub Sciences Laboratory at Provo, UT. His degrees are from Dixie College, St. George, UT (A.S. in physical sciences, 1963) and the University of Utah (B.S. in molecular and genetic biology, 1965; and M.S., 1967, and Ph.D., 1970, in plant genetics). He was a postdoctoral research fellow in agricultural botany for the Agricultural Research Council of Great Britain at the University of Leeds during 1970 and 1971. He began his Forest Service research career at the Great Basin Experimental Range at Ephraim, UT, in 1972. He has been at the Shrub Sciences Laboratory in Provo, UT, since 1975 and has been Project Leader since 1983. He has held appointments as adjunct professor of botany and range science at Brigham Young University since 1976. STEWART C. SANDERSON is research geneticist for the Shrubland Biology and Restoration Research Work Unit at the Intermountain Research Station’s Shrub Sciences Laboratory at Provo, UT, and research associ- ate in the Department of Botany and Range Science, Brigham Young University, Provo, UT. His degrees are from Brigham Young University (B.S., 1967, and M.S., 1969, in botany) and the University of Texas at Austin (Ph.D. in botany, 1975). He was postdoctoral research fellow at the University of Durham, United Kingdom, dur- ing 1975 and 1976. He has held appointments at the Shrub Sciences Laboratory since 1981 and at Brigham Young University since 1976. BRUCE L. WEBB is director of the Soil and Plant Analy- sis Laboratory, Brigham Young University, Provo, UT, an appointment he has held since 1973. His degrees are from Brigham Young University (B.S., 1972, in agronomy with a chemistry minor and M.S., 1978, in agronomy with a statistics minor). He worked for the U.S. Department of Agriculture, Soil Conservation Ser- vice as a soil conservationist in Monticello, UT, from 1972 to 1973. RESEARCH SUMMARY Grasses, forbs, shrubs, and succulents (cacti) that desert tortoises (Gopherus agassizii) might eat were analyzed over the spring, summer, and fall seasons at two study areas in southwestern Utah (City Creek near St. George and Woodbury-Hardy on the Beaver Dam Slope) and at one site in northwestern Arizona (near Littlefield). Earlier researchers suggested that tortoises were healthier at City Creek than at the other areas, es- pecially Woodbury-Hardy. Plant materials were analyzed for moisture content, ni- trogen (total organic nitrogen; crude protein = 6.25 x total organic nitrogen), phosphorus, potassium, zinc, iron, manganese, copper, calcium, magnesium, sulfur, sodium, ADF (acid detergent fiber), TNC (total nonstructural car- bohydrates), and crude fat (ether extract) for a 3-year period (1989-91). Plants from the three areas had simi- lar values for most nutrients and minerals, but Littlefield plants had significantly (P < 0.05) higher values for po- tassium, copper, and fat. Some nutrition and mineral parameters were different for the six plant classes, an- nual and perennial grasses, annual and perennial forbs, shrubs, and succulents. In general, when differences existed, annual forbs were higher in mineral and nutrient content than other plant classes. Plants with high moisture content were high for other measured parameters. Various parameters were correlated; potassium and nitrogen were highly corre- lated with the other variables. Plant mineral values did not generally track soil mineral values. Values of miner- als and nutrients for both plants and soils fell in normal ranges for semiarid conditions; however, sodium was low for both soils and plants. Low sodium concentra- tions may contribute to health problems for desert tor- toises. The mineral and nutrient content of cow excre- ment does not appear to make it a quality food source for desert tortoises as has been recently suggested. ACKNOWLEDGMENTS This work was made possible, in part, by financial sup- port from the Cedar City and Arizona Strip Districts of the Department of the Interior, Bureau of Land Manage- ment (Interagency Agreement UT-910-IA9-787). Todd Esque and Lesley DeFalco provided the plant samples of appendix A. We thank Hal Avery, Scott Belfit, Timothy Duck, Todd Esque, Jerran Flinders, John Payne, Scott Walker, and Bruce Welch for assistance and counsel or review of earlier versions of the manuscript. Lesley DeFalco drew the desert tortoise on the cover. Intermountain Research Station 324 25th Street Ogden, UT 84401 CONTENTS Page Page NAtHOGUCH OM iccec-cete, chen corasescccstecs eas doce. ccc sccbisovessodsssoses 1 FRO OUOMCO Ssse soccer. o cacenecessateyesucaeuerearaces decavecess 14 Materials and Methods ...............cceceeeeesseeeeeeeseeeeeeeeeees 1 Appendixes PRO SUS ierectee pec cn cote cecccatet nce oecaht saz Sen tieestenessxbaes 3 A. Additional Plants Collected for Nutrient and DISCUSS OM ices: scassesseszcseteessdenecssasosassanaseacaracanattesensies 10 Mineral Content Sampling at City Creek and SHUG VIANCAS ccccecccscssosnscsvsscctsccetssstsaceseteesecettesrestees 10 BBICHQNIG ies saceassivessacsccscacereacsrdeneecyseectinthssusasienivess 16 Weather and! Water cc. .ccscssceces ses cos cectensscteteussectecs Ait B. Proportional Values of Potential Desert Plant Mineral and Nutrient Parameters ................ 12 Tortoise Food Plants by Season. ..............:00008 Vz The use of trade or firm names in this publication is for reader information and does not imply endorsement by the U.S. Department of Agriculture of any product or service. Nutritive Quality and Mineral Content of Potential Desert Tortoise Food Plants E. Durant McArthur Stewart C. Sanderson Bruce L. Webb INTRODUCTION The Mojave desert tortoise (Gopherus agassizii) population north and west of the Colorado River is protected under provisions of the Endangered Species Act (Federal Register 1990). Desert tortoise subpopula- tions in southwestern Utah and adjacent Arizona on the Beaver Dam Slope and north of St. George, UT, are at the northeastern limit of the species’ distribu- tion (fig. 1; Patterson 1982; Woodbury and Hardy 1948). The three study areas are City Creek, about 4 kilo- meters north of St. George; Woodbury-Hardy, on the Beaver Dam Slope about 3 kilometers north of the Arizona border; and Littlefield, about 3 kilometers City Creek study area St. George © Woodbury-Hardy study area Oui jefield study area ~|-------------;---------------------- Littlefield Figure 1—Location of plant collection study areas. northeast of Littlefield, AZ, also on the Beaver Dam Slope (fig. 1). The health of tortoises in these subpopu- lations apparently differs (Bostick 1990; Glenn and others 1990; Grover and DeFalco in press; Jarchow 1987). The City Creek subpopulation was deemed to be the healthiest, the Woodbury-Hardy subpopulation was deemed least healthy, and the Littlefield subpopula- tion was deemed intermediate, based on population density and structure, and carapace characteristics. The Woodbury-Hardy subpopulation has a high fre- quency of animals with bone deformations and thin- ning plastrons and carapaces (Jarchow 1987). This study was designed to evaluate the hypothesis that nutritive quality and mineral content of potential desert tortoise food plants differed at the three areas, possibly contributing to the apparent health differ- ences. A second hypothesis was that plant mineral content would be correlated with that of associated soil. Mineral nutrition has been shown to be impor- tant in desert tortoise ecophysiology (Nagy and Medica 1986). Information about the nutritive quality and mineral status of the plants should be useful for those concerned with the health and management of a wide range of herbivores. MATERIALS AND METHODS Eighteen plant species common to the three study areas form the core of this study (table 1). These spe- cies were chosen based on three criteria: (1) annual and perennial plants were included; (2) grasses, forbs, shrubs, and succulents (cacti) were included; and (3) there was evidence that they were, for the most part, desert tortoise food plants (Coombs 1974; Hansen and others 1976; Hohman and Ohmart 1980; Woodbury and Hardy 1948). A few additional species were sam- pled early or late in the study (for example, Abronia fragrans, Plantago patagonica, Schismus barbatus, and Sphaeralcea grossulariifolia) (table 1). Hansen and others (1976) and Nagy and Medica (1986) have listed desert tortoise food plants from other areas. After our study began, Esque and others (1991) and Esque (1992) documented the primary food plants 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) + + + + + + es + Muhlenbergia porteri (bush muhly) + + + + + + + + + Schismus barbatus (Mediterranean grass?) - - + - - + = ee = Stipa hymenoides (Indian ricegrass) + + + + + + + - + Forbs Abronia fragrans (iragrant sand-verbena) + - - - 7 = = Es Baileya multiradiata (desert baileya) + + + + + + + + + Eriogonum inflatum + + + + + + + + + (bottlebush or bottlestopper) Eriodium cicutarium (storksbill?) + + + + + + + + + Plantago patagonica (wooly plantain) - - + - - + = = - Sphaeralcea ambigua (desert globemallow) * + + + + + + + + Sphaeralcea grossulariifolia - - - + = = - = a (gooseberryleaf globemallow) Shrubs Atriplex canescens (fourwing saltbush) + + + + + + + + + Ceratoides lanata (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) + + + + + + + + + 'A 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 realizing 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 Horowitz (1980) except for TNC determination, which followed the procedures of Tiedemann and others (1984). For the few samples with insufficient material for all analyses, fat and occasionally other parameters were not determined. Moisture content could not be determined in a few samples because of drying problems. Soil samples were also collected and analyzed. Six upland samples and six lowland samples collected from each of the three study areas were analyzed for pH, electrical conductivity (EC), sodium adsorption ratio (SAR), sand, silt, clay, calcium, magnesium, sodium, nitrogen, phosphorus, potassium, zinc, iron, and cop- per using the methods of Page (1982). The analyses for calcium, magnesium, and sodium were for the water-soluble forms used in the SAR analysis. Soils of the study areas have been classified as Winkel-Rock land, Pintura-Toquerville-Dune land, Cave, and Rock Outcrop-Rock land associations (Mortensen and others 1977). These are shallow, gravelly, fine sandy loams (Winkle-Rock and Cave), deep loamy fine sands and fine sands (Pintura-Toquerville-Dune), and shallow soils over bedrock (Rock Outcrop-Rock). The City Creek site includes Winkel-Rock, Pintura-Toquerville- Dune, and Rock Outcrop-Rock soil associations. The Woodbury-Hardy and Littlefield sites have Cave and Rock Outcrop-Rock soil associations (Mortensen and others 1977). The rocky soil associations in our study areas were sandy. Statistical analyses, including analysis of variance, Tukey means comparison tests, ¢ tests, and correlation coefficients, were performed using SAS (1985). Data are presented proportionally, in percent, for all param- eters except zinc, iron, manganese, and copper, which are given in parts per million (ppm). Differences were considered significant at the P < 0.05 level, but actual significance probability values are presented in some cases. All proportional data were arcsine transformed for analyses; they have been converted to real values for presentation here. In comparing cured (quiescent) and green (growing) samples, those with moisture con- tent of 0.23 or greater were considered “green” and those with moisture content less than 0.23 were con- sidered “cured”; 0.23 is the arcsine transfer value of 0.50. This was an arbitrary value that effectively sepa- rated green plant tissue (which fell above the value) and cured plant material (which fell below the value). Climatic data are from National Oceanic and Atmo- spheric Administration (NOAA 1988-91). Botanical nomenclature follows Welsh and others (1987) and Baird (1990). This study is part of a larger project designed to assay habitat and biological characteristics of desert tortoises at the northern extent of their distribution (Esque and others 1991; McArthur and Sanderson 1992a,b). RESULTS The appendixes list the species, times of collection, and seasonal means with significant differences for those species collected intensively for such comparisons. Table 2 lists mean values of all nutrients and min- erals by location. These values are in the normal range for semiarid sites for most parameters (Jones and Hanson 1985; Kincaid 1988; Miller and Ramsey 1988; Rains 1976). However, the level for sodium is abnormally low, the levels for sulfur and iron are low, and the level for phosphorus is in the low end of the Table 2—Nutrient and mineral values for each study area. Different letters in the same row indicate a significant difference in mean value City Creek Nutrient Units (n = 182) Moisture Percent! 38.08 A Nitrogen Percent 1.58 AB Phosphorus Percent 0.13 B Potassium Percent 1.29 A Zinc ppm 15.13 Iron ppm 283.41 A Manganese ppm 48.64 AB Copper ppm 6.00 A Calcium Percent 1.18 A Magnesium Percent 0.30 A Sulfur Percent 0.29 A Sodium Percent 0.010 A ADF2 Percent 36.34 A TNC$ Percent 7.32 A Fat* Percent 7.53 A Woodbury-Hardy Littlefield (n = 184) (n = 236) 41.50 AB 46.96 B 1.73 B 1.50 A 0.10 A 0.14 B 1.39 A 1.71 B 16.30 AB 18.56 B 289.34 A 371.12 A 39.54 A 49.14 B 5.79 A 6.76 B 1.43 AB 1.60 B 0.40 B 0.46 B 0.36 A 0.40 B 0.010 A 0.012 B 35.66 A 34.52 A 7.27 A 8.56 A 7.48 A 8.07 A ‘Based on fresh weight; all other values are based on dry weight. 2Acid detergent fiber. Total nonstructural carbohydrates. 4Sample numbers for fat were reduced to 153 (City Creek), 152 (Woodbury-Hardy), and 217 (Littlefield). normal range. Kincaid (1988) points out that sodium is often deficient in plants growing in semiarid envi- ronments. Plants in City Creek and Woodbury-Hardy are quite similar in mineral content and nutrients; they differ significantly only in phosphorus and mag- nesium content. Plants in City Creek were higher in phosphorus and those in Woodbury-Hardy were higher in magnesium. Plants in Littlefield had significantly higher values for potassium, copper, sodium, and fat than both the other areas. Plants in Littlefield had significantly higher values for several of the nutri- ents and minerals than those for either City Creek or Woodbury-Hardy but not for both: moisture content, zinc, calcium, magnesium, and sulfur were higher than for City Creek; nitrogen, phosphorus, and man- ganese were higher than for Woodbury-Hardy. When the plant nutrient and mineral contents of the three areas are considered together, they seem similar ex- cept for a trend of Littlefield to be high. Values in Littlefield are not significantly lower than any of the values in City Creek or Woodbury-Hardy and have the lowest mean value only for ADF, in which case the lowest value means the highest quality. The results in table 2 are strongly influenced by the contribution of perennial plants, which were more in- tensively sampled. Annual plant values are not signifi- cantly different among areas except for iron (Littlefield plants were significantly higher than Woodbury-Hardy, but not than City Creek, data not shown) and magne- sium (City Creek plants were significantly lower than both (Littlefield and Woodbury-Hardy, data not shown). For perennial plants the differences (table 3) were similar to those for all plants combined (table 2). Table 4 compares the data for all life forms of plants (annual grasses, perennial grasses, annual forbs, perennial forbs, shrubs, and succulents). An- nual grasses are low in water, calcium, and magne- sium content and high in nitrogen and copper with respect to the other plant life forms. Perennial grasses are low in nitrogen, phosphorus, potassium, manga- nese, copper, calcium, magnesium, sulfur, sodium, and fat and high in ADF. Annual forbs are not low in any nutrient or mineral but are high in nitrogen, phosphorus, potassium, iron, and copper. Perennial forbs are low in manganese and high in nitrogen, sul- fur, sodium, and fat. Shrubs are low in iron, manga- nese, and copper and high in nitrogen, potassium, sulfur, sodium, and fat. Succulents are low in nitro- gen, iron, copper, sulfur, sodium, and ADF and high in moisture content, potassium, manganese, calcium, and magnesium. These relative values (high, low, similar) are comparative values and should not be interpreted as high or low values outside the context of this study. When the mineral and nutrient contents are com- pared within plant life forms by season (table 5), the patterns are usually similar for all plant life forms. Moisture content decreases seasonally from spring to summer and fall except for succulents, which keep their moisture content relatively stable. Nitrogen, phosphorus, potassium, zinc, and fat also decline sea- sonally following the same general seasonal pattern as moisture content; some of these parameters decline more sharply than others, for example, phosphorus and potassium in perennial forbs, and fat in grasses and perennial forbs. Iron, manganese, copper, calcium, Table 3—Perennial plants: nutrient and mineral values at each study area. Different letters in the same row indicate a significant difference in mean value City Creek Nutrient Units (n = 158) Moisture Percent 40.81 A Nitrogen Percent 1.55 AB Phosphorus Percent 0.13 B Potassium Percent 1.29 A Zinc ppm 14.77 A Iron ppm 243.15 A Manganese ppm 47.51 A Copper ppm 5.77 AB Calcium Percent 1.18 A Magnesium Percent 0.31 A Sulfur Percent 0.30 A Sodium Percent 0.010 A ADF! Percent 36.34 A TNC2 Percent 7.37 A Fat? Percent 7.17 A ‘Acid detergent fiber. Total nonstructural carbohydrates. Woodbury-Hardy Littlefield (n = 167). (n = 202) 41.61 A 49.66 B 1.48 A 1.73 B 0.10 A 0.13 B 1.36 A 1.73,..B 15.84 AB 17.93 B 268.92 A 286.61 A 38.61 A 46.17 A 5.63 A 6.53 B 1.43 AB 1:55%-B 0.40 AB 0.49 B 0.35 AB 0.40 B 0.010 A 0.012 B 35.76 A 34.04 A 7.22 A 8.51 A 7.48 A 8.07 B 3Sample numbers for fat were 132 (City Creek), 137 (Woodbury-Hardy), and 184 (Littlefield). Table 4—Plant classes: nutrient and mineral values, with significant differences for study areas. Different letters in the same row indicate a significant difference in mean value Plant class' Annual Perennial Annual Perennial grasses grasses forbs forbs Shrubs Succulents Nutrient Units (n= 41) (n = 139) (n = 43) (n = 143) (n = 181) (n = 66) Moisture? Percent 20.83 A 27.97 AB 39.72 B 47.41 B 44.66 B W202" 'C Nitrogen Percent 1.61 B 1.22 A 1.84 B 1.82 B 1.95 B Aca OA Phosphorus Percent 0.12 ABC 0.09 A 0.19 D 0.15 CD 0.13 BC 0.11 AB Potassium Percent 1.19 B 0.75 A 1.52 BCD 1.62 BC 1.85 CD 2.10.°—D Zinc ppm 17.17 B 12.89 A 24.10 C 18.41 BC 16.42 AB 19.23 BC Iron ppm 554.16 C 357.94 BC 1,050.23 D 319.50 B 215.60 A 148.09 A Manganese ppm 51.51 AB 37.34 A 68.40 B 40.10 A 36.56 A 101.57. .G Copper ppm 7.51 B 5.74 A 8.15 B 6.75 AB 5.83. A 5.52 A Calcium Percent 0.68 A 0.51 A 2.61 C 1:36: B 1.61 B 4.00 D Magnesium Percent 0.19 A 0.14 A 0.41 BC 0.38 B 0.47 C 1.20 D Sulfur Percent 0.26 AB 0.24 A 0.37 BCD 0.40 CD 0.44 D 0.25 AB Sodium Percent 0.009 AB 0.005 A 0.008 AB 0.016 C 0.013 BC 0.0105 A ADF? Percent 37.76 C 44.51 D 34.89 BC 36.64 C 31.45 B 23.87 A TNC4 Percent 9.33 A 6.40 A 9.61 A 8.09 A 8.12 A 6.89 A Fat Percent 7.85 AB 6.57 A 8.32 B 8.12 B 8.52 B 7.64 AB : Study areas® Units City Creek Woodbury-Hardy Littlefield Moisture Percent Perennial forbs 41.57 A 42.25 A 55.74 B Nitrogen Percent Shrubs 1.13 A 1.14 B 1.16 B Phosphorus Percent Shrubs 0.10 B 0.06 A 0.09 AB Zinc ppm Shrubs 9A 13 AB 18 B Manganese ppm Perennial forbs 48 B 33 A 41 AB Shrubs 37 AB 41 A 31 A Succulents 56 A 122 B 125..B Copper ppm Perennial grasses 4A 6 AB 7.8 Shrubs 6 AB 3 A 9B Magnesium Percent Perennial grasses 0.11 A 0.15 B 0.16 B Annual forbs 0.28 A 0.48 B 0.44 B Sulfur Percent Shrubs 0.34 A 0.43 AB 0.54 B ‘Sample numbers for the following analyses were reduced: annual grasses (moisture 39, fat 36), perennial grasses (fat 126), perennial forbs (fat 122), shrubs (moisture 179, fat 162), succulents (TNC and ADF 64, fat 46). Based on fresh weight; all other values are based on dry weight. 3Acid detergent fiber. ‘Total nonstructural carbohydrates. 5This portion of the table illustrates the 12 significant differences among sites out of 90 comparisons made. magnesium, sulfur, and sodium are essentially stable; The five perennial grasses included in our study however, iron increases in forbs and succulents, cal- differ in moisture content, potassium, iron, manga- cium increases in succulents, magnesium increases nese, calcium, magnesium, sulfur, sodium, and ADF in perennial forbs, and sodium decreases in perennial but not in nitrogen, phosphorus, zinc, copper, TNC, grasses. The TNC trends down seasonally in every and fat (table 6). Aristida purpurea is low in potas- case, but significantly so only for perennial forbs. The sium, calcium, magnesium, and sulfur and high in ADF increases seasonally, significantly so except for iron and ADF. Erioneuron pilosum is low in moisture annual forbs and succulents. content and potassium and high in iron, manganese, Table 5—Plant classes: nutrient and mineral values by season. Different letters in the same row within a plant class indicate a significant difference in mean value Nutrient Moisture Nitrogen Phosphorus Potassium Zinc Iron Manganese Copper Calcium Magnesium Sulfur Sodium ADF' TNC?2 Fat Moisture Nitrogen Phosphorus Potassium Zinc Iron Manganese Copper Calcium Magnesium Sulfur Sodium ADF! TNC2 Fat Moisture Nitrogen Phosphorus Potassium Zinc Iron Manganese Copper Calcium Magnesium Sulfur Sodium ADF! TNC2 Fat ‘Acid detergent fiber. Total nonstructural carbohydrates. Units Percent Percent Percent Percent ppm ppm ppm ppm Percent Percent Percent Percent Percent Percent Percent Percent Percent Percent Percent ppm ppm ppm ppm Percent Percent Percent Percent Percent Percent Percent Percent Percent Percent Percent ppm ppm ppm ppm Percent Percent Percent Percent Percent Percent Percent Annual grasses Spring Summer Fall (n= 17) (n = 8) (n = 12) 43.05 B 1.96 A 11.98 A 2.14 B 1.31 AB 1.146 A 0.22 B 0.09 A 0.04 A 1.93 B 0.80 AB 0.64 A 22.09 B 13.69 A 12.96 A 449.37 A 479.53 A 772.64 A 62.41 A 47.61 A 39.69 A 7.84 A 8.41 A 6.25 A 0.65 A 0.57 A 0.79 A 0.21 A 0.15: A 0.19 A 0.33 A 0.22 A 0.24 A 0.009 A 0.011 A 0.007 A 33.67 A 39.68 AB 42.38 B 12.16 A 7.76 A 6.82 A (n = 16) (n= 5) (n= 11) 9.37. B 6.46 AB 6.46 A Annual forbs Spring Summer Fall (n = 24) (n= 9) (n = 6) 48.99 A 27.19 A 23.72 A 2.07 A 1.47 A 1.53 A 0.23 B 0.15 AB 0.08 A 2.03 B 1.28 AB 0.88 A 27.04 A 21.16 A 20.25 A 728.82 A 1,721.26 B 1,631.27 A 72.25 A 67.24 A 60.84 A 7.74 A 9.61 A 7.84 A 2.32 A 3.50 A 2.55 A 0.39 A 0.49 A 0.40 A 0.42 A 0.42 A 0.27 A 0.009 A 0.010 A 0.047 A 33.37 A 33.24 A 43.66 A 10.82 A 7.11 A 8.96 A (n = 22) (n =9) (n = 6) 9.88 A 6.79 A 5.49 A Shrubs Spring Summer Fall (n = 72) (n = 56) (n= 51) 52.02 B 40.13 A 39.37 A 2.39 B 1.71 A 1.66 A 0.18 B 0.12 A 0.10 A 2.14 B 1.78 AB 1.54 A 20.25 C 1521.8 12.25 A 190.43 A 275.53 B 190.43 A 42.25 A 33.64 A 32.49 A 6.25 A 6.25 A 4.84 A 1.47 A 1.70 A 1.67 A 0.45 A 0.51 A 0.43 A 0.44 A 0.44 A 0.44 A 0.011 A 0.015A 0.014 A 28.59 A 33.81 B 32.99 B 8.65 A 7.17 A 8.44 A (n = 64) (n = 52) (n = 44) 8.99 A 8.08 A 8.38 A Perennial grasses Spring (n = 52) 36.85 1.50 w fo) o ‘ye ye) rPrrrrrwawaoawow Summer (n = 44) 24.23 1.03 w w foe) (oe) fo) BS PPrrrrrrrrrp?Pp Perennial forbs Summer (n = 42) 41.847 A 1.46 A w iva) w 2 i>>>OWS SY SDS YSD>Y Table 6—Perennial grass species: nutrient and mineral values with significant differences for study areas. Different letters in the same row indicate a significant difference in mean value Perennial grass species Aristida Erioneuron Hilaria Muhlenbergia Stipa purpurea pilosum rigida porteri hymenoides Nutrient Units (n= 28) (n = 29) (n= 29) (n = 22) (n = 22) Moisture! Percent 24.24 AB 17.55 A 35.76 B 33.91 B 31.06 AB Nitrogen Percent 1.12 A 1.25 A 1.18 A 1.23 A 1.25 A Phosphorus Percent 0.08 A 0.07 A 0.08 A 0.10 A 0.10 A Potassium Percent 0.41 A 0.49 A 0.97 B 0.87 B 119° B Zinc ppm 13.42 A 15.38 A 10.63 A 13.36 A 10.66 A lron ppm 305.65 B 1,194.52 C 274.34 AB 140.23 A 177.44 AB Manganese ppm 32.35 AB 53.53 C 40.16 B 27.55 A 35.04 AB Copper ppm 5.81 A 5.93 A 5.26 A 6.12 A 5.47 A Calcium Percent 0.35 A 0.76 C 0.50 B 0.43 AB 0.54 B Magnesium Percent 0.12 A 0.20 C 0.15 B 0.13 AB 0.13 AB Sulfur Percent 0.18 A 0.25 AB 0.26 AB 0.28 AB 0.34 B Sodium Percent 0.004 AB 0.006 B 0.008 C 0.004 AB 0.003 A ADF? Percent 46.08 C 46.73 C 42.58 AB 45.65 BC 41.31 A TNC? Percent 6.37 A 6.49 A 6.11 A 6.56 A 6.44 A (n = 26) (n = 24) (n = 28) (n = 22) (n= 21) Fat Percent 6.36 A 6.18 A 6.65 A 6.22 A 7.55 A Study area‘ Units City Creek Woodbury-Hardy Littlefield Zinc Percent Muhlenbergia porteri 11A 9A 20B Iron ppm Stipa hymenoides 117A 256 B 158 AB Manganese ppm Muhlenbergia porteri 21A 41B 20A Calcium Percent Stipa hymenoides 0.44 A 0.51 A 0.85 B Magnesium Percent Erioneuron pilosum 0.15A 0.28 B 0.20 AB Stipa hymenoides 0.09 A 0.14 AB 0.20 B Sulfur Percent Stipa hymenoides 0.26 A 0.32 A 0.64 B ‘Based on fresh weight; all other values are dry weight. Acid detergent fiber. Total nonstructural carbohydrates. ‘This portion of the table illustrates the 7 significant differences among sites out of 75 comparisons made. calcium, magnesium, sodium, and ADF. Hilaria rigida is high in moisture content, potassium, manganese, calcium, magnesium, and sodium. Muhlenbergia por- teri is low in iron and manganese and high in moisture content, potassium, and ADF. Stipa hymenoides is low in sodium and ADF and high in potassium, cal- cium, and sulfur. Cured plants were significantly different than green plants for all measured parameters except manganese and sodium (table 7). With the exception of iron and ADF the mean values were less for cured than for green plants. Cured plants differed by study area only in manganese, calcium, and magnesium with Littlefield being high in calcium, manganese, and magnesium; Woodbury-Hardy was low in manganese (table 8). Green plants showed more significant differences among the areas (table 8). Moisture content was low at City Creek, potassium and zinc were low at City Creek and high at Littlefield, iron was high at Littlefield, and calcium, magnesium, and sulfur were low at City Creek. When only annuals were considered, all param- eters except iron, manganese, sodium, TNC, and fat were significantly different (table 9). Green and cured plants in the common annual grass, Bromus rubens, differed in respect to nitrogen, phosphorus, potassium, zinc, magnesium, sulfur, and ADF (table 10). Table 7—Green versus cured samples: nutrient and mineral values for all plant collections Green Cured Nutrient Units (n = 481') (n= 121) Significance Moisture Percent 53.90 6.00 <0.0001 Nitrogen Percent 1.80 1.01 <0.0001 Phosphorus Percent 0.14 0.05 <0.0001 Potassium Percent 1.70 0.66 <0.0001 Zinc ppm 18.31 11.46 <0.0001 lron ppm 257.68 622.52 <0.0001 Manganese ppm 45.82 46.44 0.8723 Copper ppm 6.39 5.59 0.0095 Calcium Percent 1.52 0.98 <0.0001 Magnesium Percent 0.44 0.24 <0.0001 Sulfur Percent 0.38 0.23 <0.0001 Sodium Percent 0.015 0.008 0.0523 ADF? Percent 33.00 44.20 <0.0001 TNCS Percent 8.07 6.35 ‘0.0075 Fat Percent 8.11 6.75 0.0003 ‘Except moisture and sulfur, for which green and cured were 482 and 121, respectively; ADF and TNC (479 and 121); and fat (419 and 103). Acid detergent fiber. Total nonstructural carbohydrates. Table 8—Green versus cured samples: nutrient and mineral values for each study area. Different letters in the same row within a treatment group (green or cured) indicate a significant difference Green Cured Woodbury- Woodbury- Differences City Creek Hardy Littlefield City Creek Hardy Littlefield between green Nutrient Units (n = 142) (n=137) (nm=202) (n = 40) (n = 47) (n= 34) and cured! Moisture Percent 50.36 A 55.85 B 55.95 B 498 A 7.48 A 5.24 A id Nitrogen Percent 1.73 A 1.73 A 1.84 A 1.02 A 0.96 A 1.12 A ig Phosphorus Percent 0.16 A 0.14 A 0.14 A 0.06 A 0.04 A 0.06 A . Potassium Percent 1.50 A 1.73 AB 1.86 B 0.64 A 0.52 A 0.81 A F Zinc ppm 16.33 A 18.66 AB 19.52 B 11.24 A 10.33 A 13.39 A . Iron ppm 224.87 A 213.51 A 315.84 B 545.84 A 575.98 A 791.38 A if Manganese ppm 49.76 A 39.56 A 47.54 A 44.78 AB 39.48 A 59.19 B NS Copper ppm 6.20 A 5.94 A 6.85 A 5.32 A 5.38 A 6.23 A 3 Calcium Percent 1.27 A 1.66 B 1.65 B 0.84 A 0.84 A 1.36 B . Magnesium Percent 0.35 A 0.46 B 0.49 B 0.18 A 0.23 AB 0.28 B : Sulfur Percent 0.31 A 0.41 B 0.43 B 0.22 A 0.23 A 0.23 A e Sodium Percent 0.010 A 0.009 A 0.012 A 0.007 A 0.009 A 0.009 A NS ADF2 Percent 34.23 A 32.35 A 33.10 A 45.67 A 45.57 A 43.08 A i TNC? Percent 7.69 A 7.96 A 8.45 A 7.01 A 6.31 A 5.98 A ig Fat Percent 7.64 A 7.64 A 8.73 A 6.31 A 6.31 A 7.48 A . ™ = P< 0.05, NS = not significant. Acid detergent fiber. Total nonstructural carbohydrates. Table 9—Green versus cured samples: nutrient and mineral values for all annual plants Green Nutrient Units (n = 45) Moisture Percent 62.24 Nitrogen Percent 2.35 Phosphorus Percent 0.24 Potassium Percent 2.12 Zinc ppm 25.64 Iron ppm 775.39 Manganese ppm 64.25 Copper ppm 8.44 Calcium Percent 1.78 Magnesium Percent 0.37 Sulfur Percent 0.46 Sodium Percent 0.008 ADF' Percent 32.07 TNC?2 Percent 10.38 Fat Percent 8.90 ‘Acid detergent fiber. Total nonstructural carbohydrates. Cured (n= 31) Significance 1.10 <0.0001 1.00 <0.0001 0.08 <0.0001 0.64 <0.0001 14.23 <0.0001 809.21 0.843 53.81 0.143 6.99 0.032 1.16 0.029 0.18 <0.0001 0.18 <0.0001 0.008 0.479 42.59 <0.0001 8.23 0.167 6.81 0.057 Table 10—Bromus rubens: nutrient and mineral values for green versus cured samples Green Nutrient Units (n = 12) Moisture Percent 59.70 Nitrogen Percent 2.63 Phosphorus Percent 0.26 Potassium Percent 2.35 Zinc ppm 24.69 Iron ppm 365.67 Manganese ppm 47.95 Copper ppm 8.68 Calcium Percent 0.74 Magnesium Percent 0.26 Sulfur Percent 0.49 Sodium Percent 0.010 ADF! Percent 31.88 TNC2 Percent 10.38 Fat Percent 9.13 ‘Acid detergent fiber. Total nonstructural carbohydrates. Figure 2 illustrates the correlation many of the measured parameters had with one another. The most tightly correlated parameters included potas- sium (13 significant correlations out of 14 possible), nitrogen and ADF (11 each), zinc and manganese (9 each), and phosphorus, copper, and fat (8 each). The least tightly correlated parameters included moisture content (2), TNC (3), and calcium and so- dium (5 each). The average number of significant correlations for each parameter was 7.53. Cured (n= 15) Significance 24.14 <0.0001 1.00 <0.0001 0.06 <0.0001 0.69 <0.0001 13.72 0.001 646.41 0.085 47.64 0.974 6.42 0.065 0.64 0.406 0.15 0.025 0.16 0.014 0.010 0.941 42.98 <0.0001 6.17 0.201 6.66 0.057 Analysis of soil characteristics detected no significant differences between upper and lower collection sites at the three study areas. When the different study areas were compared (table 11), significant differences among the areas were pH (lower at City Creek), so- dium (higher at City Creek, lower at Woodbury-Hardy), SAR (higher at City Creek), and nitrogen (lower at Littlefield). The SAR was very low at all study areas and therefore would not affect pH values to any great extent; ordinarily, it would be inconsistent to have the H,O0 N P Fe Moisture content i Nitrogen Phosphorus Potassium Zinc Iron Manganese Copper Calcium Magnesium Sulfur Sodium ADF (acid detergent fiber) TNC (total nonstructural carbohydrates) Fat (ether extract fraction) ee N =] Mn Cu Ca Mg * * * * * * * *& * * * * * ® * * * Figure 2—Significant correlations (P < 0.05) among minerals and nutrients in plant samples (n = 602 except for comparisons with fat where n= 522). “Indicates significant correlations. highest SAR and lowest pH on the same sites in com- parisons like ours. Table 12 compares the soil and plant values for elements in the soil and plants at the three study areas. DISCUSSION Study areas, weather and water, and plant mineral and nutrient content are all important when consid- ering the data collected. Each of these topics is dis- cussed separately. Study Areas Plants of the same species growing on the different areas generally had similar values for City Creek and Woodbury-Hardy; plants at Littlefield often had slightly higher values. In 12 of the 14 cases in which one area had significantly higher values than an- other, Littlefield had the higher value (table 2). In the other two cases Littlefield shared the significantly higher values with another area: City Creek in the case of phosphorus, and magnesium in the case of Table 11—Mean values of soil parameters for each study area. Different letters in the same row indicate a significant difference in mean value Soil parameter Units City Creek Calcium ppm 1219 A Magnesium ppm 193 A Sodium ppm 4.64 C Nitrogen ppm 453.0 B Phosphorus ppm 11.1 8A Potassium ppm 104.5 A Zinc ppm 0.527 A Copper ppm 0.663 A pH 6.8 A EC! ds/L 0.695 A SAR? 0.112 B Sand Percent 76.9 A Silt Percent 118 A Clay Percent 11.3 A 'Electroconductivity. 2Sodium adsorption ratio. 10 Woodbury-Hardy Littlefield 132.2 A 150.7 A 142 A 172 A 2.24 A 3.31 B 475.0 B 183.0 A 10.9 A 47 A 1296 A 102.9 A 0.520 A 0.333 A 0.500 A 0.453 A 75 B 75, 8B 0.465 A 0.523 A 0.052 A 0.073 A 65.7 A 78.2 A 24.7 A 14.1 A 96 A 76 A Table 12—Comparison of plant and soil values for various parameters for each study area City Creek Soil parameter Units Soil Plant Calcium ppm 122 11,800 Magnesium ppm 19 3,100 Sodium ppm 4.6 100 Nitrogen ppm 453 15,500 Phosphorus ppm Adel 1,300 Potassium ppm 104 12,900 Zinc ppm 0.527 15 Copper ppm 0.663 6 pH 6.8 _— EC' ds/L 0.695 — SAR? 0.112 — 'Electroconductivity. ?Sodium adsorption ratio. Woodbury-Hardy. The slightly elevated values for Littlefield may relate to slightly better weather con- ditions (see next section) during the period of study. Soil mineral content is not higher at Littlefield (table 12). In fact, soil characteristics measured in our study are quite similar among the areas; when City Creek is compared to the other areas, it is high in sodium and SAR but low in pH; City Creek and Woodbury-Hardy are high in nitrogen. Our 3-year study could not support the hypothesis that nutrient and mineral content were more favorable for the ap- parently healthier desert tortoise subpopulation at City Creek. Weather and Water The higher nutrient and mineral values for Littlefield may well be associated with a higher moisture content (table 2). Moisture input at our study sites is sporadic, in common with the Mojave environment in general (McArthur and Sanderson 1992a). No data are avail- able to document that the Littlefield area received more moisture than the others; however, more sampling was associated with arroyos there and at Woodbury-Hardy than at City Creek. Sporadic storms could have favored Littlefield over the other areas. Both Woodbury-Hardy and Littlefield are on the Beaver Dam Slope. Figure 3 shows that, during the study period, the Lytle Ranch climatic station on Beaver Dam Wash had a more fa- vorable moisture regime than did the St. George cli- matic station near City Creek. Plants with higher moisture content were also higher in nutritive quality and mineral content on a dry- weight basis when all plants were considered (table 7), when annuals were considered (table 9), and when just Bromus rubens was considered (table 10). Quality 11 Woodbury-Hardy Littlefield Soil Plant Soil Plant 132 14,300 151 15,500 14 4,000 17 4,900 2.2 100 3.3 120 475 14,800 183 17,300 10.9 1,000 4.7 1,300 130 13,600 103 17,300 0.520 16 0.333 18 0.500 6 0.453 7 75 —_ 7.5 — 0.465 = 0.523 = 0.052 = 0.073 = i October: March Precipitation BB April-September ” o ® E -_ 8 23 4 Normal St. George 1988-91 26 Temperature 24 ° 22 as] & 20 2 oa 8 18 om 16 ; 14 St. George 4 Normal ; Lytle Ranch 1988-91 Figure 3—Average values of precipita- tion and maximum daily temperature for St. George and the seasonal aver- age values for those parameters for St. George and Lytle Ranch during the study period. Number 1 = October- March 1988-89, 2 = April-September 1989, 3 = October-March 1989-90, 4 = April-September 1990, 5 = October- March 1990-91, 6 = April-September 1991. Data for Lytle Ranch were not collected for period 1. 123456 Lytle Ranch 1988-91 123 45 6 differences of plants among the study areas were more pronounced when only green plants were considered (table 8). Our data confirm that moisture content is important to plant nutrient and mineral content (Black 1968). Moisture content was highest in the spring for all plant life forms except succulents (table 5), significantly so for annual and perennial grasses, perennial forbs, and shrubs. On an individual species basis, spring moisture content was significantly higher for 10 of the 20 species of appendix B (omitting from consideration the special flower, fruit, and leaf collections). For in- dividual species and for plant life forms, spring was also the season of highest content for several other nu- trients and minerals. For the plant life forms shrubs and succulents, nitrogen, phosphorus, potassium, and zinc were all highest and ADF was lowest in spring (table 5). For individual species (appendix B), spring values were significantly higher than at least one of the other seasons for potassium (10 of 20 species, ex- cluding the special parts collections), nitrogen and phosphorus (9 species), zinc (5 species), sodium (2 spe- cies), and manganese, sulfur, and TNC (1 species). In general, values for all measured parameters de- crease from a spring high through summer and fall (increasing ADF represents declining quality). There are, however, exceptions for individual species (appen- dix B). For Bromus rubens, new plants in the fall cause moisture content to rebound. For Krameria parvifolia, calcium, magnesium, and sodium are high in the fall. Desert tortoise activity is controlled by moisture and heat so these animals are generally ac- tive in foraging and drinking in the spring and fall when food and habitat conditions are best for them (Nagy and Medica 1986; Woodbury and Hardy 1948). They seek shelter underground and become inactive during winter cold and summer heat and drought. Plant Mineral and Nutrient Parameters Our discussion is limited to the growing season when desert tortoises may be feeding on the plants we stud- ied. We recognize that these plants have other eco- system values, such as providing food and habitat for other animals. For discussion of winter values of vari- ous plant classes and some individual species, please see Tueller (1979) and Welch (1989) and the references they cite. The values obtained in this study seem to be within the normal range for plants growing in semi- arid sites (Krausman and others 1990; Seegmiller and others 1990). As figure 2 illustrates, the elements sampled often covary. Potassium, for example, is sig- nificantly correlated with the content of all 10 other elements, manganese with all but sodium and sulfur, nitrogen with all but calcium and magnesium, and copper with all but calcium, sodium, and sulfur. 12 The very low sodium values for both the soils and plants of our study deserve comment. The soil values for sodium are for water soluble sodium only; even so, the values are low. The sandy nature of our study sites (table 11) no doubt contributed to these low val- ues. The plant sodium values are low but not unprec- edented for semiarid sites (Jones and Hanson 1985; Kincaid 1988). The various mineral and nutrient values were often significantly different among plant classes (table 4). During the sampling seasons of our study it would seem that forage from a mixture of plant life forms would be desirable for foraging animals. Water con- tent is highest in succulents (cacti), also high in peren- nial and annual forbs and shrubs, and low in annual and perennial grasses. Grasses dry out through the summer and fall. Annual forbs tend to disappear after the spring season unless new cohorts are stimulated by precipitation. Nitrogen (protein) is higher in shrubs, annual and perennial forbs, and annual grasses than it is in perennial grasses and succulents. Phosphorus, zinc, and iron are highest in annual forbs; values are high in perennial forbs as well and in shrubs (phos- phorus), succulents (zinc), and annual grasses (iron). Potassium is highest in succulents; values are also high in perennial forbs and shrubs. Manganese and calcium are highest in succulents and annual forbs. Copper is highest in annual forbs and annual grasses. Magnesium is highest in succulents and shrubs. Sul- fur is highest in shrubs but is also high in perennial and annual forbs. Sodium is highest in perennial forbs. The ADF is lowest in succulents and highest in peren- nial grasses. Fat is highest in shrubs and perennial forbs. Some plants in our study deserve special comment. The introduced annuals, Bromus rubens, Schismus barbatus, and Erodium cicutarium, are by far the most common and readily available herbaceous plants in the study areas (Baird 1990; Esque and others 1991; McArthur and Sanderson 1992a). These plants are also common desert tortoise foods in the study areas under present conditions (Esque and others 1991; Woodbury and Hardy 1948). Schismus barbatus is exceptionally high in TNC (13.64 percent) and E. cicu- tarium is high in nitrogen (2.03 percent N = 12.69 percent protein), potassium (1.76 percent), and TNC (8.96 percent) (appendix B). Other species with notably high values for mineral and nutrient parameters in- clude Plantago patagonica (calcium and TNC), Baileya multiradiata (calcium), Eriogonum inflatum (potas- sium), Atriplex canescens (nitrogen, potassium, calcium, and low ADF), Ceratoides lanata (nitrogen and potas- sium), Hymenoclea salsola (nitrogen, fat and low ADF), Eriogonum fasciculatum and Krameria parvi- folia (TNC), and Opuntia basilaris and O. erinacea (water content, potassium, and calcium) (appendix B). Table 13—The species with the highest and lowest mean values for 13 minerals and nutrients (from appendix B) Exceptional value (high or low) from special plant parts (Eriogonum inflatum, leaves) (Eriogonum inflatum, leaves) (Sphaeralcea ambigua, flowers) (Sphaeralcea ambigua, flowers) (Opuntia erinacea, fruits) (Opuntia erinacea, fruits) Nutrient High value Low value Percent Percent Percent Moisture 74.18 (Opuntia erinacea) 17.55 (Erioneuron pilosum) — Nitrogen 2.63 (Atriplex canescens) 1.12 (Aristida purpurea) 2.93 Protein 16.44 (Atriplex canescens) 7.12 (Aristida purpurea) 18.31 Phosphorus 0.20 (Erodium cicutarium) 0.07 (Erioneuron pilosum) 0.30 Potassium 4.19 (Atriplex canescens) 0.42 (Aristida purpurea) Zinc 23.28 (Erodium cicutarium) 9.91 (Ephedra nevadensis) 25.32 Iron 1,561.62 (Plantago patagonica) 116.02 (Ephedra nevadensis) 98.08 Manganese 95.46 (Opuntia basilaris) 19.02 (Eriogonum fasciculatum) 133.44 Sulfur 0.98 (Atriplex canescens) 0.17 (Eriogonum fasciculatum) — Sodium 0.043 (Krameria parvifolia) 0.003 (Hymenoclea salsola and Stipa hymenoides) — ADF! 46.73 (Erioneuron pilosumand 17.87 (Atriplex canescens) Plantago patagonica) = TNC? 15.26 (Eriogonum fasciculatum) 5.11 (Ceratoides lanata) — Fat 18.23 (Hymenoclea salsola) 5.24 (Plantago patagonica) — ‘Acid detergent fiber. Total nonstructural carbohydrates. Table 13 shows the species with the highest and low- est mean values for 13 minerals and nutrients. Fat and protein (total organic nitrogen) had a sig- nificant (P < 0.05) positive correlation; protein and ADF, and TNC and ADF were negatively correlated. There were no significant correlations between pro- tein and TNC or fat and ADF (fig. 2; appendix B). For four species we sampled different plant parts (appendix B). The regular samples for Eriogonum inflatum consisted of leaves and small twigs; separate collections were made for flowers and flowering stems, for large flowering stalks, and for small inflorescences and flowers. Leaves and twigs were higher in many measured parameters than the large flowering stalks. Those parameters include moisture content, nitrogen, phosphorus, potassium, iron, manganese, calcium, magnesium, and TNC; ADF was lower. Flowers and flowering stems were lower than the large flowering stalks in potassium, calcium, and (especially during the spring) sodium. We sampled Sphaeralcea ambigua flowers and flow- ering stems, as well as leaves and twigs. Flowers and flowering stems were higher in nitrogen, phosphorus, potassium, zinc, iron, copper, and calcium than were leaves and twigs. We sampled flowers and fruits of Ceratoides lanata as well as leaves. The two kinds of samples differed little, but potassium was up slightly for the samples of flowers and fruit; water content, cal- cium, and TNC were down slightly. We sampled fruits as well as the pads of Opuntia basilaris. The fruits were lower than the pads in respect to moisture con- tent, calcium, and magnesium, but were higher in nitrogen, phosphorus, potassium, and fat. These samples of separate plant parts suggest some differences, usually not dramatic, for the measured parameters. Our regular samples were of leaves and closely attached stems—the material most likely to be foraged. One spring during the course of our col- lections we saw a large desert tortoise with its beak stained purple from the Krameria flowers it had eaten. Tortoises, like other herbivores, can be selective in eat- ing plant parts. On another occasion, we noted a tor- toise in a patch of Erodium. This tortoise voraciously consumed several whole Erodium plants. Esque and others (1991) have meticulously documented feeding preferences and habits of tortoises at City Creek and Littlefield. They found that tortoises fed mostly (up to 80 percent) on the plentiful ephemerals, Bromus, Erodium, and Schismus, but that they also consumed a wide array of grasses, forbs, and shrubs. Perhaps desert tortoises fare well on exotic plants as does the Townsend’s ground squirrel (Sperophilus townsendii) in southwestern Idaho (Yensen and Quinney 1992). Woodbury and Hardy (1948) and Hansen and others (1976) suggested that the desert tortoise’s preferred foods were perennial grasses, especially Muhlenbergia porteri. Our analyses do not show a nutritional advan- tage for perennial grasses; rather annual grasses, an- nual forbs, and shrubs appear better when nitrogen, phosphorus, and TNC are considered (table 4). Suc- culents have favorable moisture content, potassium, calcium, magnesium, and ADF. Perennial grasses do have the advantage of consistent production. Among the perennial grasses we studied, nutrient and min- eral values were quite similar. However, high values for the following parameters are of note: moisture con- tent (Hilaria rigida and Muhlenbergia porteri), potas- sium (Stipa hymenoides, Hilaria rigida, and Muhlen- bergia porteri), iron (Erioneuron pilosum and Aristida purpurea), manganese, magnesium, and sodium (Erioneuron pilosum and Hilaria rigida), calcium (Stipa hymenoides and Hilaria rigida), and sulfur (Stipa hymenoides) (table 6). Low values of ADF were found in Stipa hymenoides and Hilaria rigida. Harper and Pendleton (1993) recently presented data indicating that cryptobiotic crusts enhance the nutri- ent and mineral status of plants in desert habitats. They suggested that the associated animals, includ- ing desert tortoises, may benefit from the cryptobiotic crust nutrient input. We did not examine this aspect but did note that cryptogams are present at our study sites (McArthur and Sanderson 1992a). Bostick (1990) suggested that desert tortoises evolved as dung eaters, presenting anecdotal evidence that cow excrement was a useful food for tortoises. Our data included only current-year cow excrement (n = 11 from 2 years, three seasons, and two Beaver Dam Slope sites). Cow excrement ranked 21st, last, for several important parameters when compared to the 20 spe- cies in appendix B. These were for moisture content (14.00 percent, cow excrement dries out quickly), po- tassium (0.28 percent), TNC (5.15 percent), and fat (3.87 percent). Cow excrement ranked first in ADF (51.48 percent), a negative food quality characteristic. Cow excrement ranked 12th for nitrogen (1.53 per- cent = 9.56 percent protein), ahead of perennial grasses and cacti, but behind most other species. Cow excre- ment generally retained or concentrated high levels of minerals: phosphorus (first, 0.23 percent), zinc (first, 30 ppm), iron (first, 3,400 ppm), manganese (first, 150 ppm), copper (first, 10 ppm), calcium (third, 3.37 percent), sodium (third, 0.037 percent), magnesium (fourth, 0.59 percent), and sulfur (fifth, 0.45 percent). On the whole, our data do not demonstrate that cow ex- crement is a quality food source. We question Bostick’s (1990) thesis that desert tortoises evolved as dung eaters. It is, however, beyond question that tortoises ingest a diverse array of items, including insects, soil, bones, feathers, and excrement (Esque and others 1991; Hansen and others 1976). 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APPENDIX A: ADDITIONAL PLANTS COLLECTED FOR NUTRIENT AND MINERAL CONTENT SAMPLING AT CITY CREEK AND LITTLEFIELD Scientific name Abronia fragrans Androstephium breviflorum Aristida purpurea Atriplex canescens Baileya multiradiata Bromus rubens Ceratoides lanata Cryptantha micrantha Ephedra nevadensis Erodium cicutarium Eriogonum fasciculata Eriogonum inflatum Erioneuron pilosum Hilaria rigida 16 Scientific name Hymenoclea salsola Muhlenbergia porteri Oenothera pallida Opuntia basilaris Opuntia erinacea Oryzopsis hymenoides Plantago patagonica Rafinesquia neomexicana Schismus barbatus Sphaeralcea ambigua Stephanomeria exigua Stipa hymenoides Streptanthella longirostris APPENDIX B: PROPORTIONAL VALUES OF POTENTIAL DESERT TORTOISE FOOD PLANTS BY SEASON Significant differences among seasons indicated by different letters on a line. The abbreviations ADF and TNC stand for acid detergent fiber and total nonstructural carbohydrates. Nutrient Moisture Nitrogen Phosphorus Potassium Zinc Iron Manganese Copper Calcium Magnesium Sulfur Sodium ADF TNC Fat Moisture Nitrogen Phosphorus Potassium Zinc Iron Manganese Copper Calcium Magnesium Sulfur Sodium ADF TNC Fat Moisture Nitrogen Phosphorus Potassium Zinc Iron Manganese Copper Calcium Magnesium Spring eal 0.39069 B 0.01989 A 0.00221 B 0.01964 A 0.00002 A 0.00041 A 0.00005 A 0.00001 A 0.00620 A 0.00205 A 0.00314 A 0.00010 A 0.34652 A 0.11015A n=11 0.09294 A n=5 0.52749 B 0.02538 C 0.00207 B 0.01852 C 0.00002 B 0.00056 A 0.00008 B 0.00001 B 0.00736 A 0.00229 A 0.00358 B 0.00006 A 0.31333 A 0.15114 A 0.09552 A n=10 0.27857 A 0.01467 B 0.00125 B 0.00572 B 0.00002 A 0.00024 A 0.00003 A 0.00001 A 0.00299 A 0.00102 A Summer Annual grasses Bromus rubens n=6 0.01761 A 0.01299 A 0.00097 AB 0.00817 A 0.00002 A 0.00042 A 0.00004 A 0.00001 A 0.00567 A 0.00141 A 0.00234 A 0.00009 A 0.39744 A 0.06789 A n=3 0.05968 A Schismus barbatus n=2 0.02627 A 0.01356 B 0.00044 A 0.00767 B 0.00001 A 0.00070 A 0.00005 AB 0.00001 C 0.00584 A 0.00164 A 0.00182 AB 0.00017 B 0.39470 AB 0.11059 A 0.07223 A Perennial grasses Aristida purpurea n=9 0.25130 A 0.01009 A 0.00082 AB 0.00378 AB 0.00001 A 0.00029 A 0.00003 A 0.00001 A 0.00354 A 0.00098 A i? Fall Average n=9 0.18841 AB 0.21267 0.01405 A 0.01627 0.00058 A 0.00129 0.00905 A 0.01303 0.00002 A 0.00002 0.00074 A 0.00051 0.00004 A 0.00005 0.00001 A 0.00001 0.00837 A 0.00676 0.00206 A 0.00190 0.00292 A 0.00288 0.00008 A 0.00009 0.41324 A 0.37979 0.05166 A 0.07927 n=8 0.06764 A 0.07862 n=3 0.00446 A 0.19637 0.00551 A 0.01569 0.00002 A 0.00080 0.00115 A 0.00919 0.00001 A 0.00001 0.00089 A 0.00068 0.00004 A 0.00006 0.00000 A 0.00001 0.00663 A 0.00682 0.00132 A 0.00185 0.00116 A 0.00237 0.00005 A 0.00007 0.45576 B 0.37127 0.13050 A 0.13641 0.05669 A 0.07616 n=9 0.19614 A 0.24242 0.00896 A 0.01124 0.00045 A 0.00080 0.00299 A 0.00414 0.00001 A 0.00001 0.00040 A 0.00031 0.00004 A 0.00003 0.00001 A 0.00001 0.00398 A 0.00347 0.00100 A 0.00116 (con.) APPENDIX B (Con.) Nutrient Sulfur Sodium ADF TNC Fat Moisture Nitrogen Phosphorus Potassium Zinc Iron Manganese Copper Calcium Magnesium Sulfur Sodium ADF TNC Fat Moisture Nitrogen Phosphorus Potassium Zinc Iron Manganese Copper Calcium Magnesium Sulfur Sodium ADF TNC Fat Moisture Nitrogen Phosphorus Potassium Zinc Spring n=10 0.00173 A 0.00006 B 0.43697 A 0.07264 A n=9 0.08626 A n=11 0.24905 A 0.01365 A 0.00077 A 0.00628 A 0.00002 A 0.00107 A 0.00005 A 0.00001 A 0.00701 A 0.00187 A 0.00212 A 0.00006 A 0.45536 A 0.07611 A n=9 0.07348 A n=11 0.46304 B 0.01542 B 0.00111 A 0.01249 A 0.00002 B 0.00024 A 0.00004 A 0.00001 A 0.00528 A 0.00156 A 0.00260 A 0.00011 A 0.39704 A 0.07063 A n=10 0.07547 A n=10 0.46174 B 0.01462 A 0.00122 A 0.01294 B 0.00002 A Summer Perennial grasses Aristida purpurea n=9 0.00166 A 0.00004 A 0.47651 A 0.06002 A n=9 0.05997 A Erioneuron pilosum n=9 0.11971 A 0.01084 A 0.00080 A 0.00362 A 0.00002 A 0.00134 A 0.00005 A 0.00001 A 0.00762 A 0.00200 A 0.00277 A 0.00007 A 0.48650 A 0.06049 A n=9 0.06063 A Hilaria rigida n=9 0.31938 AB 0.00905 A 0.00083 A 0.00885 A 0.00001 AB 0.00033 A 0.00003 A 0.00001 A 0.00459 A 0.00133 A 0.00255 A 0.00008 AB 0.44452 B 0.05278 A n=9 0.06319 A Muhlenbergia porteri n=9 0.29384 AB 0.01149 A 0.00092 A 0.00639 A 0.00001 A 18 Fall n=9 0.00219 A 0.00003 A 0.47162 A 0.05790 A n=8 0.04560 A n=9 0.15244 A 0.01280 A 0.00063 A 0.00477 A 0.00002 A 0.00121 A 0.00006 A 0.00001 A 0.00837 A 0.00229 A 0.00279 A 0.00005 A 0.46294 A 0.05659 A n=6 0.04762 A n=11 0.27338 A 0.01059 AB 0.00045 A 0.00736 A 0.00001 A 0.00026 A 0.00004 A 0.00000 A 0.00512 A 0.00173 A 0.00265 A 0.00006 A 0.44243 B 0.05888 A n=9 0.06044 A n=9 0.25626 A 0.01153 A 0.00074 A 0.00714 A 0.00001 A Average 0.00185 0.00004 0.46084 0.06368 0.06363 0.17553 0.01249 0.00073 0.00492 0.00002 0.00120 0.00005 0.00001 0.00347 0.00203 0.00252 0.00006 0.46733 0.06495 0.06183 0.35760 0.01179 0.00080 0.00965 0.00001 0.00028 0.00004 0.00001 0.00500 0.00154 0.00260 0.00008 0.42578 0.06106 0.06654 0.33912 0.01231 0.00096 0.00874 0.00001 (con.) APPENDIX B (Con.) Nutrient Iron Manganese Copper Calcium Magnesium Sulfur Sodium ADF TNC Fat Moisture Nitrogen Phosphorus Potassium Zinc Iron Manganese Copper Calcium Magnesium Sulfur Sodium ADF TNC Fat Moisture Nitrogen Phosphorus Potassium Zinc Iron Manganese Copper Calcium Magnesium Spring n=10 0.00011 A 0.00003 A 0.00001 A 0.00401 AB 0.00122 A 0.00220 A 0.00004 A 0.45148 A 0.06880 A n=8 0.06436 A n=8 0.38962 A 0.01640 A 0.00138 A 0.01637 A 0.00002 A 0.00014 A 0.00004 A 0.00001 A 0.00539 A 0.00158 A 0.00336 A 0.00003 A 0.37562 A 0.08128 A n=8 0.07706 A n=13 0.58371 A 0.02269 A 0.00237 A 0.02062 A 0.00002 A 0.00094 A 0.00007 A 0.00001 A 0.02666 A 0.00432 A 0.00450 A 0.00008 AB 0.28830 A 0.10476 A n=12 0.07916 A Summer Perennial grasses Muhlenbergia porteri n=9 0.00018 A 0.00002 A 0.00001 A 0.00370 A 0.00118 A 0.00276 A 0.00005 A 0.47851 A 0.06251 A n=9 0.06145 A Stipa hymenoides n=7 0.31640 A 0.00969 A 0.00088 A 0.01074 A 0.00001 A 0.00018 A 0.00003 A 0.00000 A 0.00475 A 0.00117 A 0.00355 A 0.00003 A 0.43360 A 0.05056 A n=7 0.08177 A Annual forbs Erodium cicutarium n=8 0.33477 A 0.01559 A 0.00170 A 0.01402 A 0.00002 A 0.00159 A 0.00007 A 0.00001 A 0.03705 A 0.00518 A 0.00396 A 0.00009 B 0.31417 A 0.06799 A n=8 0.07068 A 19 Fall n=9 0.00014 A 0.00003 A 0.00001 A 0.00539 B 0.00150 A 0.00367 A 0.00003 A 0.44015 A 0.06535 A n=7 0.06054 A n=7 0.22116 A 0.01141 A 0.00061 A 0.00872 A 0.00001 A 0.00023 A 0.00003 A 0.00000 A 0.00593 A 0.00108 A 0.00329 A 0.00002 A 0.43618 A 0.06078 A n=6 0.06664 A n=4 0.45267 A 0.02296 A 0.00143 A 0.01520 A 0.00003 A 0.00154 A 0.00007 A 0.00001 A 0.03290 A 0.00526 A 0.00358 A 0.00005 A 0.39998 A 0.08795 A n=4 0.05467 A Average 0.00014 0.00003 0.00001 0.00432 0.00130 0.00283 0.00004 0.45646 0.06564 0.06217 0.31046 0.01251 0.00095 0.01192 0.00001 0.00018 0.00003 0.00001 0.00535 0.00128 0.00341 0.00003 0.41314 0.06441 0.07552 0.48231 0.02031 0.00199 0.01751 0.00002 0.00122 0.00007 0.00001 0.03080 0.00474 0.00417 0.00008 0.31389 0.08960 0.07197 (con.) APPENDIX B (Con.) Nutrient Spring Summer Fall Average Annual forbs Plantago patagonica n=4 n=1 n=2 Moisture 0.69995 B 0.00000 A 0.00251 A 0.30097 Nitrogen 0.01814 B 0.00850 AB 0.00464 A 0.01201 Phosphorus 0.00211 B 0.00060 AB 0.00013 A 0.32041 Potassium 0.01887 C 0.00500 B 0.00120 A 0.00971 Zinc 0.00002 B 0.00001 A 0.00001 A 0.00001 Iron 0.00105 A 0.00298 A 0.00184 A 0.00149 Manganese 0.00006 A 0.00006 A 0.00005 A 0.00006 Copper 0.00001 A 0.00001 A 0.00001 A 0.00001 Calcium 0.01686 A 0.02091 A 0.01351 A 0.01640 Magnesium 0.00336 A 0.00310 A 0.00195 A 0.00288 Sulfur 0.00736 A 0.00620 A 0.00132 A 0.00499 Sodium 0.00017 A 0.00017 A 0.00005 A 0.00013 ADF 0.44094 A 0.48630 AB 0.51060 B 0.46723 TNC 0.10797 A 0.09859 A 0.09283 A 0.10220 Fat 0.05211 A 0.04699 A 0.05558 A 0.05233 Perennial forbs Baileya multiradiata n=11 n=9 n=9 Moisture 0.68555 B 0.46483 AB 0.32246 A 0.50490 Nitrogen 0.01903 A 0.01365 A 0.01251 A 0.01520 Phosphorus 0.00195 B 0.00111 AB 0.00095 A 0.00135 Potassium 0.01895 B 0.01238 AB 0.00857 A 0.01335 Zinc 0.00002 A 0.00002 A 0.00002 A 0.00002 Iron 0.00056 A 0.00063 A 0.00150 B 0.00083 Manganese 0.00003 AB 0.00002 A 0.00004 B 0.00003 Copper 0.00001 A 0.00001 A 0.00001 A 0.00001 Calcium 0.01898 A 0.01947 A 0.02359 A 0.02051 Magnesium 0.00303 A 0.00249 A 0.00358 A 0.00302 Sulfur 0.00405 A 0.00356 A 0.00329 A 0.00366 Sodium 0.00006 A 0.00006 A 0.00004 A 0.00005 ADF 0.34538 A 0.40980 A 0.42825 A 0.39079 TNC 0.10244 A 0.07410 A 0.05926 A 0.07932 n=10 n=6 n=6 Fat 0.12232 A 0.10741 A 0.08565 A 0.10778 Smaller inflorescence branches, leaves, and flowers Eriogonum inflatum n=11 n=9 n=9 Moisture 0.61185 B 0.44104 B 0.19820 A 0.42420 Nitrogen 0.02473 B 0.01678 A 0.01258 A 0.01814 Phosphorus 0.00216 B 0.00131 B 0.00053 A 0.00130 Potassium 0.01803 B 0.01096 A 0.00779 A 0.01229 Zinc 0.00002 B 0.00002 AB 0.00001 A 0.00002 Iron 0.00010 A 0.00017 AB 0.00021 B 0.00015 Manganese 0.00003 A 0.00005 AB 0.00007 B 0.00005 Copper 0.00001 A 0.00001 A 0.00000 A 0.00001 Calcium 0.00413 A 0.00758 B 0.01314 C 0.00757 Magnesium 0.00292 A 0.00412 B 0.00558 C 0.00405 Sulfur 0.00265 A 0.00348 A 0.00229 A 0.00277 Sodium 0.00015 A 0.00029 B 0.00027 B 0.00022 ADF 0.30428 A 0.38504 B 0.43330 B 0.36856 TNC 0.12735 B 0.09847 AB 0.06644 A 0.09800 n=9 n=9 n=7 Fat 0.07468 A 0.07992 A 0.07043 A 0.07531 (con.) 20 APPENDIX B (Con.) Nutrient Moisture Nitrogen Phosphorus Potassium Zinc Iron Manganese Copper Calcium Magnesium Sulfur Sodium ADF TNC Fat Moisture Nitrogen Phosphorus Potassium Zinc Iron Manganese Copper Calcium Magnesium Sulfur Sodium ADF TNC Fat Moisture Nitrogen Phosphorus Potassium Zinc Iron Manganese Copper Calcium Magnesium Sulfur Sodium ADF TNC Fat Spring n=14 0.56660 B 0.02266 B 0.00155 B 0.02799 B 0.00002 A 0.00016 A 0.00005 A 0.00001 A 0.01005 A 0.00520 A 0.00261 A 0.00050 A 0.29402 A 0.10599 B 0.07473 A n=1 0.81002 B 0.03111 A 0.00110 A 0.04589 B 0.00001 A 0.00035 A 0.00008 B 0.00001 A 0.01920 A 0.00750 A 0.00510 A 0.00092 A 0.33326 B 0.09452 A 0.04518 A n=11 0.55161 A 0.02368 B 0.00173 A 0.02094 B 0.00002 A 0.00024 A 0.00004 A 0.00001 A 0.01936 A 0.00383 A 0.00783 A 0.00007 A 0.31018 A 0.07862 A n=10 0.09018 A Summer Main fruiting stalk Eriogonum inflatum n=9 0.45865 AB 0.01260 A 0.00178 B 0.01398 A 0.00002 A 0.00012 A 0.00003 A 0.00001 A 0.00709 A 0.00327 A 0.00254 A 0.00033 A 0.44511 B 0.07531 B 0.07374 A Leaves Eriogonum inflatum n=0 Sphaeralcea ambigua n=9 0.47222 A 0.01283 A 0.00121 A 0.01663 AB 0.00002 A 0.00036 A 0.00004 A 0.00001 A 0.01911 A 0.00282 A 0.00563 A 0.00010 A 0.38339 A 0.06704 A n=9 0.07685 A 21 Fall n=8 0.24749 A 0.01019 A 0.00040 A 0.00991 A 0.00001 A 0.00026 A 0.00004 A 0.00000 A 0.01164 A 0.00473 A 0.00212 A 0.00038 A 0.54325 B 0.05641 A 0.06030 A n=4 0.64096 A 0.02876 A 0.00175 A 0.02189 A 0.00002 A 0.00056 A 0.00005 A 0.00001 A 0.01426 A 0.00473 A 0.00323 A 0.00023 A 0.20957 A 0.14419 B 0.05808 A n=9 0.41009 A 0.01862 AB 0.00109 A 0.01223 A 0.00001 A 0.00027 A 0.00003 A 0.00001 A 0.01738 A 0.00413 A 0.00658 A 0.00008 A 0.37775 A 0.04900 A n=7 0.07161 A Average 0.44989 0.01604 0.00124 0.01838 0.00002 0.00017 0.00004 0.00001 0.00991 0.00448 0.00246 0.00041 0.35626 0.08739 0.07058 0.67735 0.02923 0.00161 0.02602 0.00002 0.00051 0.00006 0.00001 0.01520 0.00523 0.00357 0.00033 0.23280 0.13354 0.05540 0.48291 0.01846 0.00135 0.01670 0.00002 0.00029 0.00004 0.00001 0.01865 0.00358 0.00673 0.00008 0.35348 0.06525 0.08008 (con.) APPENDIX B (Con.) Nutrient Spring Summer Fall Average Flowers Sphaeralcea ambigua n=11 n=9 Moisture 0.67595 B 3.14321 A — 0.45785 Nitrogen 0.02963 B 0.01947 A — 0.02548 Phosphorus 0.00385 B 0.00201 A — 0.00308 Potassium 0.02335 B 0.01801 A —_— 0.02122 Zinc 0.00003 B 0.00002 A —_— 0.00003 Iron 0.00014 A 0.00070 B — 0.00031 Manganese 0.00003 A 0.00003 A _— 0.00003 Copper 0.00001 A 0.00001 A — 0.00001 Calcium 0.01192 A 0.01772 B — 0.01402 Magnesium 0.00297 A 0.00322 A — 0.00307 Sulfur 0.00656 A 0.00663 A — 0.00660 Sodium 0.00008 A 0.00020 B — 0.00012 ADF 0.31705 A 0.37591 A — 0.33940 TNC 0.07079 A 0.05734 A — 0.06545 n=7 n=4 Fat 0.08243 A 0.07621 A — 0.08002 Shrubs Atriplex canescens n=11 n=9 n=9 Moisture 0.55410 A 0.52399 A 0.51110A 0.53148 Nitrogen 0.02812 A 0.02662 A 0.02359 A 0.02621 Phosphorus 0.00192 B 0.00104 A 0.00099 A 0.00132 Potassium 0.04498 A 0.04329 A 0.03683 A 0.04184 Zinc 0.00003 B 0.00002 A 0.00002 A 0.00002 Iron 0.00017 A 0.00023 A 0.00014 A 0.00018 Manganese 0.00005 A 0.00005 A 0.00005 A 0.00005 Copper 0.00001 A 0.00001 A 0.00001 A 0.00001 Calcium 0.01852 A 0.02494 A 0.02174A 0.02142 Magnesium 0.01037 A 0.01751 A 0.01183 A 0.01287 Sulfur 0.00810 A 0.01168 B 0.01011 AB 0.00977 Sodium 0.00017 A 0.00018 A 0.00016 A 0.00017 ADF 0.17424 A 0.16821 A 0.19455 A 0.17850 TNC 0.06251 A 0.05545 A 0.06092 A 0.05978 n=11 n=9 n=7 Fat 0.06900 A 0.06304 A 0.08431 A 0.07073 Leaves and twigs Ceratoides lanata n= 11 n=9 n=9 Moisture 0.49380 B 0.26257 A 0.29758 A 0.46683 Nitrogen 0.02691 B 0.01642 A 0.01822 A 0.02071 Phosphorus 0.00150 B 0.00076 A 0.00091 A 0.00106 Potassium 0.02770 B 0.01619 A 0.01483 A 0.01972 Zinc 0.00002 A 0.00001 A 0.00001 A 0.00002 Iron 0.00033 A 0.00065 A 0.00036 A 0.00043 Manganese 0.00010 B 0.00007 AB 0.00006 A 0.00008 Copper 0.00001 A 0.00001 A 0.00001 A 0.00001 Calcium 0.01589 A 0.01574 A 0.01402 A 0.01530 Magnesium 0.00590 A 0.00454 A 0.00417 A 0.00491 Sulfur 0.00423 A 0.00381 A 0.00311 A 0.00374 (con.) 22 APPENDIX B (Con.) Nutrient Sodium ADF TNC Fat Moisture Nitrogen Phosphorus Potassium Zinc Iron Manganese Copper Calcium Magnesium Sulfur Sodium ADF TNC Fat Moisture Nitrogen Phosphorus Potassium Zinc Iron Manganese Copper Calcium Magnesium Sulfur Sodium ADF TNC Fat Moisture Nitrogen Phosphorus Potassium Zinc Spring n= 11 0.00013 B 0.31148 A 0.05554 A n=9 0.09764 A n=8 0.51390 B 0.02819 B 0.00195 B 0.02504 B 0.00002 B 0.00026 B 0.00008 A 0.00001 A 0.01124 A 0.00418 A 0.00379 A 0.00009 A 0.32564 A 0.04473 A n=5 9.09006 A n=11 0.62370 B 0.02669 B 0.00225 A 0.02504 B 0.00002 A 0.00015 A 0.00002 A 0.00001 A 0.01503 A 0.00393 A 0.00499 A 0.00004 B 0.27027 A 0.09393 A n=11 0.14964 A n=11 0.40931 A 0.01691 A 0.00089 A 0.00529 A 0.00001 A Summer Leaves and twigs Ceratoides lanata n=9 0.00012 B 0.39734 B 0.04498 A n=7 0.06804 A Flowers Ceratoides lanata n=5 0.15079 A 0.01544 A 0.00082 A 0.01983 A 0.00001 A 0.00065 A 0.00007 A 0.00001 A 0.01809 B 0.00522 A 0.00509 A 0.00014 B 0.35626 B 0.02389 A n=4 0.06834 A Hymenoclea salsola n=9 0.54484 AB 0.01607 A 0.00203 A 0.01709 A 0.00003 A 0.00013 A 0.00002 A 0.00001 A 0.01515 A 0.00386 A 0.00399 A 0.00003 AB 0.33571 B 0.07787 A n=8 0.18990 AB Ephedra nevadensis n=9 0.40194 A 0.01569 A 0.00102 A 0.00661 A 0.00001 A 23 Fall n=9 0.00006 A 0.41817 B 0.05175 A n=8 0.06589 A n=9 0.49660 A 0.01663 A 0.00146 A 0.01627 A 0.00002 A 0.00012 A 0.00002 A 0.00001 A 0.01459 A 0.00344 A 0.00551 A 0.00002 A 0.29795 AB 0.07883 A n=7 0.21455 B n=9 0.36346 A 0.01367 A 0.00066 A 0.00651 A 0.00001 A Average 0.00010 0.37059 0.05100 0.07781 0.36173 0.02284 0.00144 0.02296 0.00002 0.00039 0.00008 0.00001 0.01367 0.00456 0.00427 0.00011 0.33732 0.03597 0.08008 0.56016 0.01997 0.00193 0.01967 0.00002 0.00013 0.00002 0.00001 0.01493 0.00379 0.00482 0.00003 0.29914 0.08409 0.17866 0.39274 0.01549 0.00085 0.00607 0.00001 (con.) APPENDIX B (Con.) Nutrient Spring Summer Fall Average Flowers Ephedra nevadensis n=11 n=9 n=9 Iron 0.00009 A 0.00015 B 0.00011 AB 0.00011 Manganese 0.00003 A 0.00002 A 0.00003 A 0.00003 Copper 0.00000 A 0.00000 A 0.00000 A 0.00000 Calcium 0.02513 A 0.02485 A 0.02148 A 0.02389 Magnesium 0.00403 A 0.00314 A 0.00316 A 0.00347 Sulfur 0.00414 A 0.00297 A 0.00282 A 0.00334 Sodium 0.00011 A 0.00011 A 0.00017 A 0.00013 ADF 0.38952 A 0.40518 B 0.43588 B 0.40872 TNC 0.08682 A 0.08553 A 0.08248 A 0.08509 n=10 n=9 n=9 Fat 0.07537 A 0.07068 A 0.05609 A 0.06295 Eriogonum fasciculatum n=7 n=6 n=6 Moisture 0.51870 B 0.31947 A 0.27633 A 0.37659 Nitrogen 0.01564 B 0.01227 AB 0.01057 A 0.01289 Phosphorus 0.00131 A 0.00088 A 0.00071 A 0.00097 Potassium 0.01305 B 0.00957 A 0.00676 A 0.00979 Zinc 0.00002 B 0.00002 B 0.00001 A 0.00001 Iron 0.00015 A 0.00025 B 0.00020 AB 0.00019 Manganese 0.00002 A 0.00001 A 0.00002 A 0.00002 Copper 0.00000 A 0.00000 A 0.00000 A 0.00000 Calcium 0.01158 A 0.01190 A 0.01310 A 0.01216 Magnesium 0.00243 A 0.00264 A 0.00261 A 0.00255 Sulfur 0.00164 A 0.00170 A 0.00183 A 0.00171 Sodium 0.00010 A 0.00008 A 0.00007 A 0.00008 ADF 0.26690 A 0.37340 A 0.36972 A 0.33203 TNC 0.17318 A 0.14363 A 0.13738 A 0.15222 n=6 n=6 n=5 Fat 0.07140 A 0.06198 A 0.06183 A 0.06520 Krameria parvifolia n=8 n=9 n=9 Moisture 0.51590 A 0.49670 A 0.38786 A 0.46463 Nitrogen 0.02359 B 0.01599 A 0.01604 A 0.01819 Phosphorus 0.00253 B 0.00170 AB 0.00106 A 0.00168 Potassium 0.01838 A 0.01942 A 0.01604 A 0.01790 Zinc 0.00002 B 0.00001 AB 0.00001 A 0.00001 Iron 0.00022 A 0.00022 A 0.00027 A 0.00023 Manganese 0.00002 A 0.00002 A 0.00002 A 0.00002 Copper 0.00001 A 0.00001 A 0.00000 A 0.00001 Calcium 0.00868 A 0.01101 AB 0.01481 B 0.01147 Magnesium 0.00248 A 0.00268 A 0.00358 B 0.00291 Sulfur 0.00404 A 0.00344 A 0.00414 A 0.00386 Sodium 0.00017 A 0.00050 B 0.00059 B 0.00041 ADF 0.29184 A 0.37059 A 0.29357 A 0.31919 TNC 0.11260 A 0.09300 A 0.12608 A 0.11008 n=7 n=9 n=8 Fat 0.06779 A 0.06198 A 0.06130 A 0.06343 (con.) APPENDIX B (Con.) Nutrient Moisture Nitrogen Phosphorus Potassium Zinc Iron Manganese Copper Calcium Magnesium Sulfur Sodium ADF TNC Fat Moisture Nitrogen Phosphorus Potassium Zinc Iron Manganese Copper Calcium Magnesium Sulfur Sodium ADF TNC Fat Spring n=8 0.58961 A n=7 0.01151 A 0.00097 A 0.02111 A 0.00002 A 0.00019 A 0.00014 A 0.00000 A 0.04473 A 0.01326 A n=8 0.00478 A n=7 0.00005 A n=7 0.18771 A n=6 0.13388 A n=5 0.08068 A n=13 0.72938 A 0.01188 A 0.00117 A 0.02006 A 0.00003 A 0.00011 A 0.00009 A 0.00000 A 0.03630 A 0.01051 A 0.00217 A 0.00005 A 0.26389 A 0.10238 A n=8 0.07145 A Summer Succulents Pads Opuntia basilaris n=6 0.83134 A n=6 0.00774 A 0.00070 A 0.01825 A 0.00001 A 0.00025 A 0.00007 A 0.00001 A 0.06078 A 0.01452 A n=6 0.00282 A n=6 0.00006 A n=5 0.15222 A n=5 0.08739 A n=5 0.05417 A Pads Opuntia erinacea n=9 0.74896 A 0.00887 A 0.00081 A 0.01604 A 0.00002 A 0.00011 A 0.00009 A 0.00000 A 0.03664 A 0.01372 A 0.00196 A 0.00007 A 0.26389 A 0.05264 A n=6 0.07192 A 25 Fall n=6 0.82554 A n=6 0.00923 A 0.00049 A 0.02091 A 0.00001 A 0.00035 A 0.00007 A 0.00001 A 0.06915 A 0.01753 A n=6 0.00230 A n=6 0.00005 A n=6 0.25906 A n=6 0.06505 A n=6 0.08276 A n=9 0.75234 A 0.00828 A 0.00082 A 0.01491 A 0.00001 A 0.00013 A 0.00009 A 0.00001 A 0.04325 A 0.01240 A 0.00226 A 0.00005 A 0.23052 A 0.05766 A n=6 0.07285 A Average 0.74068 0.00953 0.00072 0.02011 0.00002 0.00026 0.00009 0.00001 0.05706 0.01496 0.00336 0.00006 0.19996 0.09393 0.08221 0.74182 0.00989 0.00095 0.01732 0.00002 0.00012 0.00009 0.00001 0.03835 0.01196 0.00213 0.00005 0.25408 0.07332 0.07202 (con.) APPENDIX B (Con.) Nutrient Moisture Nitrogen Phosphorus Potassium Zinc Iron Manganese Copper Calcium Magnesium Sulfur Sodium ADF TNC! Fat Spring n=7 0.83655 B 0.01931 B 0.00253 B 0.03366 B 0.00002 A 0.00008 A 0.00013 A 0.00001 A 0.02224 A 0.00786 A 0.00247 A 0.00003 A 0.23866 A 0.07048 n=5 0.08160 A Summer Succulents Fruits Opuntia erinacea n=3 0.23475 A 0.00811 A 0.00126 AB 0.02169 A 0.00001 A 0.00008 A 0.00013 A 0.00000 A 0.02836 A 0.00781 A 0.00231 A 0.00003 A 0.30116 A n=2 0.10214 A 'Technical problems with the summer and fall data led to their omission. 26 Fall n=1 0.12239 A 0.00631 A 0.00030 A 0.01450 A 0.00001 A 0.00027 A 0.00016 A 0.00001 A 0.03132 A 0.00829 A 0.00220 A 0.00008 A 0.26442 A n=1 0.11842 A Average 0.61866 0.01445 0.00187 0.02819 0.00002 0.00009 0.00013 0.00001 0.02463 0.00788 0.00240 0.00004 0.25784 0.07048 0.11071 *U.S. GOVERNMENT PRINTING OFFICE 1994-0-573-029/81032 McArthur, E. Durant; Sanderson, Stewart C.; Webb, Bruce L. 1994. Nutritive quality and mineral content of potential desert tortoise food plants. Res. Pap. INT-473. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 26 p. Minerals and nutrients for desert tortoise food plants from the northeastern Mojave Desert are generally in the normal range for semiarid environments, except that sodium values are low for plants and soil. Annual forbs are often higher in nutritive quality than other plant classes. KEYWORDS: Gopherus agassizii, animal nutrition, mineral nutrition, nutrient content, grasses, forbs, shrubs Federal Recycling Program ie Printed on Recycled Paper INTERMOUNTAIN RESEARCH STATION The Intermountain Research Station provides scientific knowledge and technology to im- prove management, protection, and use of the forests and rangelands of the Intermountain West. Research is designed to meet the needs of National Forest managers, Federal and State agencies, industry, academic institutions, public and private organizations, and individu- als. Results of research are made available through publications, symposia, workshops, training sessions, and personal contacts. The Intermountain Research Station territory includes Montana, Idaho, Utah, Nevada, and western Wyoming. Eighty-five percent of the lands in the Station area, about 231 million acres, are classified as forest or rangeland. They include grasslands, deserts, shrublands, alpine areas, and forests. They provide fiber for forest industries, minerals and fossil fuels for energy and industrial development, water for domestic and industrial consumption, forage for livestock and wildlife, and recreation opportunities for millions of visitors. Several Station units conduct research in additional western States, or have missions that are national or international in scope. Station laboratories are located in: Boise, Idaho Bozeman, Montana (in cooperation with Montana State University) Logan, Utah (in cooperation with Utah State University) Missoula, Montana (in cooperation with the University of Montana) Moscow, Idaho (in cooperation with the University of Idaho) Ogden, Utah Provo, Utah (in cooperation with Brigham Young University) Reno, Nevada (in cooperation with the University of Nevada) The policy of the United States Department of Agriculture Forest Service prohibits discrimination on the basis of race, color, national origin, age, religion, sex, or disability, familial status, or political affiliation. Persons believing they have been discriminated against in any Forest Service related activity should write to: Chief, Forest Service, USDA, P.O. Box 96090, Washington, DC 20090-6090.