Cercocarpus Montanus Research Articles

Condensed tannins and nutrient utilization by lambs and goats fed low-quality diets.

In the first of two experiments, four wether lambs (BW = 26.8 kg) and four wether Angora goats (BW = 31.7 kg) were used in two simultaneous 4 x 4 Latin squares to study the influence of condensed tannins (CT) on nutrient usage and concentrations of serum urea N, somatotropin (GH), and insulin (INS) when the animals were fed low-quality diets containing mountain mahogany (MM; Cercocarpus montanus) leaves. Diets were 8% CP and contained 25% or 50% MM (with hay or straw, respectively), either untreated or treated with polyethylene glycol (PEG; molecular weight 3,350) to reduce total reactive CT. Diets treated with PEG and 25% MM diets had less (P less than .05) CT than diets without PEG or those with 50% MM. Diets containing 50% MM resulted in greater N balance and lower serum urea N (P less than .01) than 25% MM diets. Concentrations of GH and INS were similar in animals fed the 25% and 50% MM diets. Reducing CT by adding PEG did not affect N balance or improve nutrient digestion by lambs or goats fed low-quality diets. In Exp. 2, four wether lambs (BW = 28.4 kg) were used in a 4 x 4 Latin square and fed the same diets as animals in Exp. 1 to study the influence of CT on ruminal fermentation and digesta kinetics. Dietary PEG treatment did not affect digesta kinetics except for a 30% increase in ruminal volume; 50% MM diets had faster particulate passage rates (P less than .05) than 25% MM diets. Ruminal ammonia N was greater (P less than .01) in lambs fed PEG-containing or 25% MM diets; however, rate of in situ NDF disappearance was not reduced by the lower ammonia N in the latter diets.

Preference of the mother affects selection and avoidance of foods by lambs differing in age

We studied the effects of mother's preference and lamb age on selection of Amelanchier alnifolia and Cercocarpus montanus by lambs. Thirty-six ewes and their lambs were divided into treatment and control groups. Mothers in the treatment group were conditioned to eat A. alnifolia, but avoid C. montanus, by pairing ingestion of C. montanus with lithium chloride (LiCl), a compound that causes gastrointestinal distress. Mothers in the control group were allowed to eat both foods with impunity. After ewes were conditioned, lambs were exposed daily for 5 days with their mothers to either A. alnifolia or C. montanus for 5 min followed by a 5 min exposure to the other food. Half of the lambs in the treatment and control groups were 6 weeks of age during exposure, while the other half were 12 weeks of age. Treatment lambs of both ages ate less C. montanus than control lambs during exposure. Lambs were weaned after exposure and tested 10 days later for preference. Preference indices ( PI) for C. montanus were calculated as the percentage of total bites contributed by C. montanus. Treatment lambs exposed at 6 weeks of age ate less C. montanus than A. alnifolia compared with control lambs during trials of 5 min day −1 for 7 days ( PI=0.07 vs. 0.44; P<0.05). Treatment lambs exposed at 12 weeks of age also ate less C. montanus than A. alnifolia compared with control lambs ( PI=0.26 vs. 0.45; P<0.05). Lambs that were 12 weeks of age during exposure, however, ate more C. montanus than lambs exposed at 6 weeks of age ( PI=0.26 vs. 0.07; P<0.05). Nine weeks after exposure, treatment lambs exposed at 6 weeks of age still showed lower preference for C. montanus than for A. alnifolia compared with control lambs ( PI=0.10 vs. 0.48; P<0.05). Treatment and control lambs that were 12 weeks of age during exposure, however, showed equal preference for C. montanus and A. alnifolia ( PI=0.42 vs. 0.42; P>0.05). We conclude that lambs 6 weeks of age were influenced more by their mothers dietary habits than were lambs 12 weeks of age.

Food aversion learning in sheep: persistence of conditioned taste aversions to palatable shrubs (Cercocarpus montanus and Amelanchier alnifolia)

We studied the persistence of conditioned taste aversions in sheep and whether or not sheep averted to one shrub species would avoid another shrub species. Three-month-old lambs were averted to the shrub Cercocarpus montanus by pairing its ingestion with lithium chloride (LiCl), a nonlethal gastrointestinal poison. When lambs were yearlings, they were offered C. montanus plants growing in 8-liter pots. During the persistence trial, averted sheep took fewer (P less than .05) bites of C. montanus than controls did (19 vs 64 bites/sheep, respectively). Following the persistence trial, sheep that had been previously averted to C. montanus and consumed C. montanus received LiCl. Complete aversion to C. montanus was re-established in previously averted sheep with a single dose of LiCl. When sheep previously averted to C. montanus were offered potted Amelanchier alnifolia shrubs, averted sheep consumed 21 bites of A. alnifolia but controls consumed 58 bites (P less than .05). This result suggests that previously averted sheep were either more food neophobic than controls or generalized their aversion from C. montanus to A. alnifolia. As with C. montanus, a single dose of LiCl completely averted sheep to A. alnifolia. When sheep grazed a pasture containing C. montanus and A. alnifolia averted sheep took fewer (P less than .05) bites of the two shrubs than controls did (.2% vs 18%). Sheep showed no signs of extinguishing the aversion to either shrub during the grazing season (May-Sept.). Aversive conditioning may be useful to manipulate diet selection of free-ranging livestock.

The establishment and persistence of food preferences in lambs exposed to selected foods.

Our study determined whether lambs' food preferences developed as a result of exposure to specific foods early in life and whether the presence of the mother affected the development of dietary preferences. In the first experiment, lambs were fed wheat (W) and mountain mahogany (MM) (Cercocarpus montanus) from 50 to 110 d of age. After exposure to W and MM, lambs preferred (P less than .05) W when offered with barley (B) but did not prefer (P greater than .05) MM when offered with serviceberry (SB) (Amelanchier alnifolia), probably because lambs were reluctant to eat mountain mahogany during exposure. Persistence was determined by dividing lambs exposed to W or MM into four groups: 1) continued exposure to W (MM); 2) exposure to B (SB); 3) no further exposure; and 4) exposure to W + B (MM +SB). Preferences for wheat persisted (P less than .05) regardless of the second exposure. In the second experiment, lambs were exposed to W (MM) either alone or with their mothers. Persistence was determined after 21 d of exposure to B (SB). Lambs preferred (P less than .05) W and MM whether they were exposed alone or with their mothers. However, preferences persisted longer in lambs exposed with their mothers. Finally, lambs exposed to either SB or MM with their mothers were later allowed to choose between SB or MM. Lambs strongly preferred (P less than .05) the shrub to which they were exposed early in life.

Effect of age of exposure on consumption of a shrub by sheep.

We investigated the influence of age of exposure to a specific forage on its consumption by young sheep both during and after that exposure. Prior exposure to the shrub Cercocarpus montanus enhanced subsequent consumption (P less than or equal to .05) of that shrub by lambs and yearlings during two experiments in consecutive years. Effects of prior exposure persisted as long as 9 mo without intervening exposure. Age of exposure influenced consumption in lambs both during the period of exposure (P less than or equal to .0001) and during feeding trials following exposure (P less than or equal to .07) in Exp. 1. Lambs exposed at 1 to 5 wk of age, when they are nonruminant and normally are dependent on the dam, browsed less of the time while at the shrub (P less than or equal to .02) and consumed less of the shrub (P less than .02) at a slower rate (P less than or equal to .03) than did lambs exposed at older ages. Lambs exposed at 4 to 8 wk of age, a period corresponding to the transition from nonruminant to ruminant digestion, consumed more shrub following exposure than did lambs exposed at younger or older ages (P less than equal to .05, unprotected least significant differences test). In Exp. 2, which compared naive yearlings with the experienced yearlings exposed as lambs in Exp. 1 the previous year, age of exposure did not influence consumption by yearling sheep following exposure; however, the number of months that had elapsed from the period of exposure varied from 0 to 13 among experimental groups and may have confounded results. Learning of forages appeared poor among nonruminant lambs; data were inconclusive concerning the efficiency of learning of lambs in the transition to ruminant digestion.

Influence of Native Shrubs on Nutritional Status of Goats: Nitrogen Retention

In vivo digestibility trials were conducted to evaluate the influence of shrubs containing low and high levels of soluble phenolic/tannins on digestibility and nitrogen retention by Angora goats. Each of 6 shrubs and alfalfa hay (Medicago sativa L.) were fed to goats at 30% (dry matter basis) of the diet in a barley straw-prairie hay mixture. The mixture was regulated so that all diets contained about 8% crude protein. High soluble phenolic shrubs used included big sagebrush (A rtemisia tridentata Nutt. ssp. tridentata), gray oak (Quercus grisea Liebm.), true mountain mahogany (Cercocarpus montanus Raf.), and one-seed juniper (Juniperus monosperma [Engelm.] Sarg). Low-soluble phenolic species included common winterfat (Ceratoides lanata [Pursh.], J.T. Howell), fourwing saltbush (A triplex canescens [Pursh.], Nutt.), and alfalfa. Nitrogen digestibilities of winterfat, gray oak, mountain mahogany and one-seed juniper diets were less (P .05) compared with the alfalfa control. Retained nitrogen (g/d) differed (P<.05) only among alfalfa, juniper, and mountain mahogany diets. Goats fed juniper had greater (P<0.05) retained nitrogen than the alfalfa control. Shrubs high in soluble phenolics, with the exception of big sagebrush, had elevated fecal nitrogen losses, but reduced urinary nitrogen losses compared with the alfalfa control. Forage organic matter intake (% body weight) and nitrogen intake (g/d) were correlated more highly with nitrogen retention than dietary crude protein (%) or digestible protein (%). Present data indicate that protein found in palatable native shrubs is assimilated with similar efficiency to that in alfalfa hay if these shrubs are consumed at

Habitat Selection and Activity Patterns of Female Mule Deer in the Front Range, Colorado

Twenty-two adult, female mule deer (Odocoileus hemionus hemionus) were radio-collared with activity sensors and monitored with ground triangulation from mid-November through March, for 3 years (1982-1985) in the foothills west of Fort Collins, Colorado, to test 4 general hypotheses about habitat selection and activity: (1) The proportion of time deer spend feeding and resting varies with time of day. (2) Deer alter their activity patterns in response to environmental influences. (3) Selection of specific vegetation types for feeding and resting varies with time of day. (4) Ecotones are preferred habitats. Deer were monitored during 6-hr sampling periods: sunrise, daytime, sunset, and night. Deer fed most during sunset, night, and sunrise periods and least during the day. Feeding occupied similar proportions of an average deer's time during sunset, night, and sunrise periods. They preferred the grassland type for feeding and resting at night and the mountain mahogany (Cercocarpus montanus) type for both activities during all other periods. Preference deer showed for the ponderosa pine (Pinusponderosa) type for feeding activity was inversely related to canopy cover. Deer rested most during daytime and night periods. During periods of daylight, deer using the grassland type showed preference for ecotones with certain types offering escape cover. No such preference was observed at night. Deer fed less and rested more when snow depth exceeded 36 cm. No significant differences (P>0.05) in the proportion of time deer devoted to feeding were found in the following comparisons: clear versus cloudy full-moon nights (-50 vs. + 50% cloud cover), full-moon versus new-moon, low versus high wind speeds (0-32 vs. 32-56 km/hr), and warm versus cold temperatures (+18 to -15 vs. -15 to -23? C). No significant relationships were found for the same comparisons in proportion of time devoted to resting.

The Interaction of Pinon Pine and Gambel Oak in Plant Succession near Dolores, Colorado

-Pinus edulis (piiion pine) and Quercus gambelii (Gambel oak) near Dolores, Colorado, coexist in successional sequence leading to woodland regeneration. The germination of seeds and the establishment of seedlings of Pinus edulis are enhanced under an oak canopy. In a mature pifion woodland, oak exists as scattered understory, and pifion individuals of less than 10-cm diameters constitute 45% of the population. In contrast, 75% of the pifiones have diameters less than 10 cm in a stand which is invading an oak-dominated habitat. Near Dolores, Colorado, the oak stand is viewed as successional, leading to a pinion woodland. The vegetation of the Dolores River Valley, northwest of Dolores, Montezuma Co., Colorado, consists of Pinus ponderosa and Pseudotsuga menziesii at higher elevations of 2,548 m, and a lower pifion-juniper (Pinus edulis, Juniperus osteosperma, J. scopulorum) zone which extends to the river bottom at 2,184 m. Shriubland communities, often on east-facing slopes, consist of Amelanchier utahensis, Quercus gambelii, and Cercocarpus montanus. Considerable overlap exists in the oak and pifion-juniper vegetation types. The present-day vegetation in and around the Dolores River Valley was mapped during the summer of 1979 in an effort to determine the successional seres leading to potential climax vegetation. Comparison of presentday vegetation with 1973 aerial photographic coverage made it possible to detect the interrelationships between Gambel oak and pifion-juniper in this successional sequence. Four studies were designed to elucidate the role of oak in germination, establishment, and early growth of pinion. Stands of oak in the Dolores River valley are dense when young, but the individual trees become relatively spindly at approximately 75 to 100 years of age, permitting increased light penetration into the stand. Litter accumulation alters the seed bed, increasing its moisture retention capacity, and decomposition of oak leaves allows the release of volatile secondary plant compounds. These habitat changes could provide a suitable environment for piiion germination and establishment. It has been reported (Meagher, 1943) that shading of pinion seeds promotes early germination, and that pinion saplings become shade intolerant beyond the seedling stage (Tueller and Clark, 1975). The hypothesis that oaks facilitate germination of seeds and establishment and early growth of pinion individuals was tested in the Dolores River Valley. MATERIALS AND METHODs.-Germination of Pinon Seeds.-Pinus edulis seeds were allowed to imbibe in distilled water for 24 h. Fifty seeds were placed in germination cages under each of the following conditions: (1) under a mature pifion; (2) under a stand of mature oaks; (3) under sagebrush (Artemisia tridentata); (4) in the open, no plant cover; (5) in the open, no cover, and no germination cage. Germination cages were 1 by 1 m, 0.5 m tall, made of 4 wire mesh, and were designed to exclude large seed-predators. Seeds were planted in early June 1979 in approximately THE SOUTHWESTERN NATURALIST 27(2): 143-147 MAY 21, 1982 This content downloaded from 207.46.13.193 on Thu, 08 Sep 2016 04:30:03 UTC All use subject to http://about.jstor.org/terms 144 The Southwestern Naturalist vol. 27, no. 2 2 cm of litter and soil, in rows of 12 and 13 seeds. All plots were within 100 m of each other to control soil and climatic differences as much as possible. Soils consisted of gladel stony fine sandy loam. The latter condition served as the control group. The number of seeds germinated were recorded at 5 weeks and continued daily until snow cover prevented access to the germination cages at the end of October. After 60 days, four ungerminated seeds per treatment were removed and viability was tested. Viability was determined by a positive pink reaction in the megagametophytic tissue and embryo when soaked in 1% tetrazolium chloride, indicating the presence of deh-

Response of Chihuahuan Desert Mountain Shrub Vegetation to Burning

The effects of fire on vegetation in the desert mountain shrub community were studied on 3 to 7-year-old burned sites near the northern limits of the Chihuahurn Desert. Coverage and frequency of redberry juniper (Juniipcruspinchotii) and frequency of whitebail acacia (Acacia texends) were lower, while frequencies of catclaw mimosa (Mimosa biunc~em) and skeleton goldeneye (Viguiera stenoloba) were higher on burned sites when_compared with unburned paired piants. Lechuguiiia (Agave lecheguil&, sotoi (DasytYrion leiophylbun), and sacahuista (Nor and Texas Tech University. It is a contribution of College of Agricultural Sciences, Publication No. T-9-235. Texas Tech University. Manuscript received March 28, 1980. huan Desert. Bunting and Wright (1977) reported theeffectsof fire on desert mountain shrub vegetation 2 years after burning in the Texas Big Bend country. Kittams (1973) noted that in burned desert mountain shrub communities, catclaw mimosa (Mimosa biuncifera). skunkbush (Rhus aromatica), silver dalea (Dalea argyraea), skeleton goldeneye (Viguiera stenoloba). mountain mahogany (Cercocarpus montanus), scrub oaks (Quercus spp.), redberry juniper (Juniperus pinchotii) and alligator juniper (J. deppeana) usually recovered through some form of vegetative sprouting. He observed that lechuguilla (Agave lecheguilla), datil (Yucca baccata), and mature soto (Dasylirion leiophyllum) were usually killed by fire. ,Bunting and Wright (1977) found that fire reduced shrub cover and total grass cover 43% and 72% respectively in a desert mountain shrub community 2 years after burning. Coverage of forbs and half shrubs increased 650%. The fire significantly reduced the density or cover of sideoats grama (Bouteloua curtipendula), blue three-awn (Aristida glauca), sotol, and lechuguilla, whereas coverage contributed by skeleton goldeneye tripled through vigorous sprouting and seedling establishment on the burned area (Bunting and Wright 1977). Information pertaining to other species common to the Chihuahuan Desert is available from studies conducted elsewhere. Mortality rates for cholla (Opuntia imbricata) and pricklypear (0. phaeacantha) two growing seasons after a prescribed burn on the Texas High Plains averaged 45% and 68%, respectively (Heirman and Wright 1973). Pricklypear mortality was 3270 the first year following a prescribed burn (Cable 1967) and 28% the second growing season after an experimental tire (Reynolds and Bohning 1956), in two separate studies conducted in the Arizona Sonoran Desert. Survival of ocotillo (Fouquieria splendens) following a 62 JOURNAL OF RANGE MANAGEMENT 35(l). January 1999 wildfire in the Sonoran Desert was 33Ycfor heavily damaged plants and 50% for plants only scorched (White 1969). Regeneration occurred primarily through basal sprouting. Algerita (Berberis trifoliolata) sprouted vigorously following a wildfire in south central New Mexico (Dwyer and Pieper 1967). The objective of this study was to document longer term effects of fire on vegetation in the mountain shrub community of the Chihuahuan Desert by examining 3 to ‘I-year-old burned areas.

Ecology of Small Mammals on Two Isolated Buttes in Canyonlands National Park, Utah

Ecology of Small Mammals on Two Isolated Buttes in Canyonlands National Park, Utah

Diets of Domestic Sheep and Other Large Herbivores in Southcentral Colorado

Diets of Domestic Sheep and Other Large Herbivores in Southcentral Colorado

Response of Wavyleaf Oak to Nitrogen Fertilization

This study was conducted to determine the response of wavyleaf oak to nitrogen fertilization, at rates of 0, 112, and 224 kg of elemental nitrogen per ha. Over the three years of the study, twigs were longer on fertilized areas than on unfertilized areas. Nitrogen at 112 kg/ha was generally as effective as 224 kg/ha in stimulating twig growth. Slope position did not have an effect on all sites. Where slope position was significant, plants on the upper and middle slopes responded better to fertilization than did plants growing on lower slopes. Site appeared to influence twig growth more than slope. Differences in twig growth among sites were attributed to differences in soil depth and density of vegetation. Twig length was significantly different among years due to uneven distribution of rainfall. As wildlife populations are restricted to less favorable areas, it is increasingly important to develop new and better methods of habitat manipulation. One important area involves improvement of quality and quantity of food, as demonstrated in several studies of mule deer (Odocoileus hemionus) and white-tail deer (0. virginianus). Deer densities can be controlled by quantity and nutritive quality of available forage (Hagen 1953, Swank 1956). Many deer diseases are due to inadequate nutrition (Lang 1957, Taylor and Hahn 1947), and fertility levels in deer generally correspond with the quality of their range (Cheatum and Severinghaus 1950, Julander et al. 1961). Recently, fertilization has gained importance in improvement of wildlife ranges. Williams (1969) stated that soil fertilization may be valuable in correcting nutritional deficiencies occurring within a wild population, providing the deficiencies are properly diagnosed and fertilizers are administered accordingly. Fertilization can significantly increase production of range plants (Schultz et al. 1958) and substantially increase carrying capacity of the range (Ward and Bowersox 1970). Fertilization can cause major compositional changes in vegetation (Basile 1970, Gibbens and Pieper 1962, Schultz et al. 1958), improve the palatability of certain species (Brown and Mandery 1962, Gibbens and Pieper 1962, Schultz et al. 1958), and improve the quality of forage (Rogler and Lorenz 1957, Ward and Bowersox 1970, Wood 1966). On the Fort Stanton Cooperative Experimental Range, Anderson et al. (1974) fertilized mountain mahogany (Cercocarpus montanus) and wavyleaf oak (Quercus undulata) with urea at the rate of 101 kg nitrogen (N)/ha. The mounAuthors are professor, Department of Fishery and Wildlife Sciences, New Mexico State University, Las Cruces 88003; research scientist USDA, Rangelands Weed and Brush Control, Tucson, Arizona 85719; and professor, Department of Experimental Statistics New Mexico State University, Las Cruces, New Mexico 88003. This study was supported by the New Mexico Agricultural Experiment Station and McIntire-Stennis funds. Nipak, Inc., Dallas, Texas donated the fertilizer for this project. This Journal Article 681, Agricultural Experiment Station, New Mexico State University, Las Cruces, New Mexico 88003. Manuscript received August 7, 1978. tain mahogany showed a growth response to the fertilizer, and the percent crude protein in leaves of wavyleaf oak increased. Mule deer use was greater on fertilized plots than on control plots. Since oak constitutes a major portion of mule deer diets in the Southwest (Anderson et al. 1965, Boeker et al. 1972, Lamb 1971, Smith 1959), this study was initiated to determine growth response of wavyleaf oak to different rates of fertilization in a pinyon-juniper woodland.

Diameter-Age Relationships of Two Species of Mountain Mahogany

Diameter-age relationships of two species of mountain mahogany (true mountain mahogany and curlleaf mountainmahogany) were investigated. Data were taken from populations of true mountain mahogany in the Laramie Basin of Wyoming (Brooks 1962) and the Uintah Basin of Utah. Data for curlleaf mountain mahogany were obtained from populations in the Whitehorse mountains of Oregon, the Trout Creek mountains of Nevada (Dealy 1975) and from several areas in north-central Utah. Equations were developed for age prediction from stem diameters. Age prediction was most accurate within local population boundaries and less so when used to predict ages across population boundaries. Aspect was shown to be an important factor in influencing age prediction in curlleaf mountain mahogany. Variations in the growth rings of trees and shrubs have been used for years as dating techniques (Douglas 1935; Glock 1937) and to gain information about climatic differences of the past (Schulman 1956; Fritts 1971; Stockton and Meko 1975; Harper 1979). Ring-width variations have also been used to assess differences in the environments of selected habitats (Ferguson and Humphrey 1959; Fritts 1962; Stockton and Fritts 1973; Fritts 1974). Although trees have been the major object of such studies (Glock 1955; Authors are associate professor of botany and range science, Department of Botany and Range Science, Brigham Young University, Provo, Utah 84602; research scientist, Shrub Sciences Laboratory, U.S. Forest Service, Provo, Utah 84601; and range conservationist, Bureau of Land, Richfield, Utah 84701. Manuscript received March 30, 1979. JOURNAL OF RANGE MANAGEMENT 33(5), September 1980 Argeter and Glock 1965) papers dealing with shrubs can also be found (Ferguson 1958; Ferguson 1959; Ferguson and Humphrey 1959). The shrub studies have generally dealt with variations of moisture in the habitat or as aids to archaeological interpretation. Studies dealing with diameter-age relationships of shrubs and their values in the development of age-prediction models, interpretations of environmental factor differences, site-quality estimates, and measurements of successional trends are generally lessknown. The objectives of this study were: to assess the stem diameter-age relationships in true mountain mahogany (Cercocarpus montanus) and curlleaf mountain mahogany (Cercocarpus Zedifolius), to develop age prediction models from stem diameters, to assess the accurateness of the models within and between populations, and to evaluate the effects of aspect on the growth patterns of the shrubs and thus the predictive value of the models.

Response of Curlleaf Mountain Mahogany to Pruning Treatments in Northern Utah

Production of curlknf mountain mahogany (Cercocarpus Iedifoliur) within browsing height of big game on winter ranges was increased 500-900% when 90-99% of the canopy was pruned from mature trees. However, since ndventitioussproutingdidnot occur, numerous live twigs must he present in the browsing zone before treatment for any practical benefit to accrue. Pruning at less than 90% canopy removal and girdling showed positive but smaller vegetative responses, while 100% canopy removal and application of pruning paint to wound surfaces in an attempt to eliminate sap flow had no effect on forage production available to big game. Improvement of the forage resource on big game winter range is one method to compensate partially for past and present reductions in habitat caused by human encroachment. Improvement can be via range restoration through reductions of competing low-value vegetation and reseeding, or improvement of existing, on-site conditions through intensified management. Methods found to increase the forage yield of desirable range plants become potential management tools (Plummer et al. 1968). Curlleaf mountain mahogany (Cercocarpus ledifolius) occurs throughout most of the Intermountain Area as part of the mountain brush zone. It is usually associated with true mountain mahogany (Cercocarpus montanus) at lower elevations and often grades into Douglas-fir (Pseudotsuga menziesii). When foliage is within the browsing reach of deer and elk, intensive utilization reduces available forage by shifting the competitive growth advantage to the upper unused portions. It has been shown to be high in nutritive value (Smith 1952; Bissell and Strong 1955), palatability (Smith 1950; Hoskins and Dalke 1955), digestibility (Smith 1957a), and dietary importance (Mitchell 1951; Smith and Hubbard 1954). Unfortunately, in many mature stands, most of the production is unavailable except through occasional snow or wind breakage of limbs. Thus a practical means of reducing canopy height while retaining productivity of these low trees could be highly beneficial to big game. Revegetation with curlleaf mountain mahogany is generally impractical because oflow seed viability(Younget al. 1978), poor seedling survival (Holmgren 1954) eve” with hand-planted nursery stock (Brown and Martinson 1959), and slow growth (Plummer et al. 1957). Likewise, bulldozing of mature trees has been unsuccessful due to high mortality (Dealy 197 I). Pruning has been found to stimulate vegetative growth in many shrubby species (Ferguson and Basil 1966; Plummer 1974), with variable success for curlleaf mountain mahogany (Smith 1957b; Phillips 1970); Thompson 1970). I” s”mmary, a successful methodology has not yet been defined, “or has the magnitude of change m available production been determined under various intensities and methods of treatment. These were the objectives of this study.

Vesicular-Arbuscular Mycorrhizae Associated with Actinomycete-Nodulated Shrubs, Cercocarpus montanus Raf. and Purshia tridentata (Pursh) DC.

Roots and rhizosphere soil of representative plants of Cercocarpus montanus Raf. and Purshia tridentata (Pursh) DC. were collected from several locations in New Mexico and the Laramie and Medicine Bow Mountains of southeastern Wyoming and examined for vesicular-arbuscular (VA) mycorrhizal symbionts. Spores of VA mycorrhizal fungi were isolated from rhizosphere soil and identified. Field plants were found heavily infected with VA mycorrhizal fungi. The isolated mycorrhizal symbionts were identified as species of Glomus. Microscopic examination of roots suggested Gigaspora and Acaulospora species were also present. All species identified at the generic level have not been previously described.

Effects of Water Stress and Temperature on Germination of True Mountainmahogany

Highlight: The effects of five levels of available water and four constant temperature regimes upon the germination of two eco typic collections of true mountainmahogany (Cercocarpus montanus Raf.) were investigated. Results indicate that moisture stress significantly decreases both the rate and final amount of germination in this species. The amount of moisture stress required to cause these decreases was found to be dependent upon both the seed source and the temperature. Temperature was found to be more important in determining the rate than the amount of germination.

Effects of Fire and Mechanical Treatment on Cercocarpus montanus and Ribes cereum

Effects of Fire and Mechanical Treatment on Cercocarpus montanus and Ribes cereum

Shrub Age Structures on a Mule Deer Winter Range in Colorado

Age—determination techniques for selected shrub species utilized by deer were tested on known—age specimens and refined. Intact plants and descriptive data were collected on circular milacre plots in random locations in selected stands. Prepared specimens of Purshia tridentata and Artemisia tridentata were readily aged by crossdating xylem growth layers. Cercocarpus montanus proved difficult and supplemental ring counts were used, reducing accuracy of the age determinations. Ribes cereum samples were unsuitable for the techniques employed. Ages in years were estimated for 3,231 plants, and age structures were graphed by 5—year classes. The "die—away" curve is used as a hypothetical norm for self—replacing populations in the interpretation of age structures. Shrub age structures may reflect current and past reproductive success and, hence, successional status. Irregularities may be related to fires, climate, rodent seed—caching, reproductive cycling, and use by animals.

Mule Deer Numbers and Shrub Yield: Utilization on Winter Range

Counts of mule deer (Odocoileus hemionus) fecal groups on 960, 100-ft2 circular plots located on three north-central Colorado winter range study areas of about 500 acres each, were related to mean forage yields in pounds (ovendry) per acre and mean utilization per plot (percentage weight) of true mountain mahogany (Cercocarpus montanus), antelope bitterbrush (Purshia tridentata), and big sagebrush (Artemisia tridentata) sampled on those plots from 1962 to 196S. Scatter diagrams and regression analysis revealed no significant ( P > O.OS ) correlations between the indices of deer numbers and mean yield or utilization of true mountain mahogany and antelope bitterbrush. Mean yield and mean utilization were significantly (P<0.05) correlated (r=-0.90) for true mountain mahogany but not for antelope bitterbrush (r =-0.S4). Inadequate sample sizes precluded similar analysis of big sagebrush. Neff (1968) has reviewed the technique of counting fecal groups as commonly used to assess population levels and distribution of big game. Counts of fecal groups on sample plots have also been used to approximate the weights of air-dry browse consumed by deer on winter range (McCain 1948, Leopold et al. 1951:110, Richens 1967: 654) as well as total forage produced (Giles and Snyder 1970:40). McCain and Taylor (1956:440) suggested that the percentage consumption of key browse species may be used to estimate trends in deer numbers. Julander et al. (1963:108) stated thatResearch on the relation of pellet group density to forage utilization is needed to determine whether pellet group counts might measure range use more accurately than utilization estimates alone. The objective of the present paper is to report on the relationship of counts of mule deer fecal groups to yields and utilization of three major shrub species on winter ranges. \Ve thank the many individuals who pro1A contribution from Colorado Federal Aid Project NV-105-R. 2 Present address: U. S. Forest Service, Intermountain Forest and Range Experiment Station, Boise7 Idaho. vided field or office assistance, particularly T. E. Hakonson, W. E. Jones, Jr., O. D. Markham, L. Nelson, Jr., K. A. Porter, and D. F. Stearns. J. Kovner and M. Morris, Biometricians, U. S. Forest Service, advised on the procedures used to estimate and analyze browse yield and utilization. STUDY AREAS AND POPULAT10N Three study areas, about 500 surface acres each, were selected to characterize the vegetation of winter range at different elevations within the Cache la Poudre River drainage, Roosevelt National Forest, northcentral Colorado. Soils are derived from schist, schist-gneiss, and granitic rocks (Lovering and Goddard 1950). Steep to precipitous slopes, with massive granitic outcrops are characteristic of each area. As described by Costello ( 1954), the mountain shrub community ( designated as shrub habitat in this report) comprised about 60 percent of each area, whereas the ponderosa pine-Douglas fir ( Pinus ponderosa-Pseudotsuga menziesii ) and ponderosa pine communities ( designated as coniferous habitat) comprised about 23 (Study Area 1), 38 (Study Area 2), and 28 (Study Area 3) percent of each area. Minor communities

Histological studies of ectomycorrhizae and root nodules from Cercocarpus montanus and Cercocarpus paucidentatus

The ectomycorrhizae of Cercocarpus montanus Raf. and Cercocarpus paucidentatus Britt. displayed morphologies ranging from single swollen short lateral roots on long roots to terminal pyramidal clusters. Most short roots appeared to be mycorrhizal, although C. paucidentatus was only infected under growth chamber conditions. Histological sections revealed a conspicuous fungal mantle, averaging 30 μ in thickness, and a Hartig's net.The root nodules appeared as swellings on lateral roots, and later formed compact coralloid orange-colored masses several centimeters in diameter. Histological analyses indicated that both species of Cercocarpus harbored a similar endophyte. Three developmental stages were noted in cortical tissue, including (a) hyphal masses in apical nodule cells; (b) hyphae terminating in 3 × 4 μ club-shaped vesicular swellings; and (c) older structureless hyphal masses in cells of mature nodule branches. The older hyphal masses did not appear to be absorbed by the host plant. The endophyte possessed branching filaments 0.5 μ in diameter and was considered to be an actinomycete.