Green Canyon Environmental Research Area, Logan Utah Copyright (c) 2013 Utah State University All rights reserved. http://digitalcommons.usu.edu/grcanyon Recent documents in Green Canyon Environmental Research Area, Logan Utah en-us Sun, 27 Jan 2013 04:30:52 PST 3600 Tracking Variable Environments: There is More than One Kind of Memory http://digitalcommons.usu.edu/grcanyon/24 http://digitalcommons.usu.edu/grcanyon/24 Wed, 24 Feb 2010 14:20:18 PST Three kinds of memory help herbivores track changes in the environment. The first is the collective memory of the species with genetic instructions that have been shaped by the environment through millennia. This includes skin and gut defense systems. Auditory and visual stimuli and sensations of pain impinge upon the skin defense system that evolved in response to predation. The taste of food and the sensations of nausea and satiety are an integral part of the gut defense system that evolved in response to toxins and nutrients in plants. The second kind of memory in social mammals is represented by the mother, a source of transgenerational knowledge, who increases efficiency and reduces risk of learning about foods and environments. The third kind of memory is acquired by individual experience. Post-ingestive feedback from nutrients and toxins enables individuals to experience the consequences of food ingestion and to adjust food preference and selection commensurate with a food's utility. The three memories interact, each linking the past to the present, and collectively shape the present and future of every individual. Thus, the dynamics of foraging involves appreciating the uniqueness of individuals and subgroups of animals, each with their own genetic and behavioral history, and recognizing that foraging behaviors may not be stable, optimal, or even predictable in the conventional sense.

]]> Frederick D. Provenza Herbivore Response to Anti-Quality Factors in Forages http://digitalcommons.usu.edu/grcanyon/22 http://digitalcommons.usu.edu/grcanyon/22 Wed, 24 Feb 2010 14:20:17 PST Plants possess a wide variety of compounds and growth forms that are termed "anti-quality" factors because they reduce forage value and deter grazing. Anti-quality attributes can reduce a plant's digestible nutrients and energy or yield toxic effects. Herbivores possess several adaptive mechanisms to lessen the impacts of anti-quality factors. First, herbivores graze selectively to limit consumption of potentially harmful plant compounds. Grazing animals rely on a sophisticated system to detect plant nutritional value or toxicity by relating the flavor of a plant to its positive or negative digestive consequences. Diet selection skills are enhanced by adaptive intake patterns that limit the deleterious effects of plant allelochemicals; these include cautious sampling of sample ntt,v foods, consuming a varied diet, and eating plants in a cyclic, intermittent, or carefully regulated fashion. Second, grazing animals possess internal systems that detoxify or tolerate ingested phytotoxins. Animals may eject toxic plant material quickly after ingestion, secrete substances in the mouth or gut to render allelochemicals inert, rely on rumen microbes to detoxify allelochemicals, absorb phytochemicals from the gut and detoxified them in body tissues, or develop a tolerance to the toxic effects of plant allelochemicals. Understanding the behavioral and metabolic abilities of herbivores suggests several livestock management practices to help animals contend with plant anti-quality characteristics, These practices include offering animals proper early life experiences, selecting the appropriate livestock species and individuals, breeding animals with desired attributes, and offering nutritional or pharmaceutical products to aid in digestion and detoxification.

]]> K L. Launchbaugh et al. Food Aversion Conditioned in Anesthetized Sheep http://digitalcommons.usu.edu/grcanyon/23 http://digitalcommons.usu.edu/grcanyon/23 Wed, 24 Feb 2010 14:20:17 PST We discovered that a food aversion could be conditioned in anesthetized sheep. Sheep were allowed to eat a familiar food (alfalfa-grain pellets) for 30 min, and 90 min later they were given either an intraruminal (IR) injection of water (C), an IR injection of LiCl (L), anesthesia followed by an IR injection of water (A), or anesthesia followed by an IR injection of LiCl (A+L). Induction of anesthesia was by an intraveneous injection of pentobarbitone sodium, and maintenance of deep anesthesia was by halothane. Sheep were maintained in deep anesthesia for 2 h to ensure that the effects of LiCl on the acquisition of a food aversion, which occur within about 1 h, were completed before they awakened. When tested 5 days later, sheep that received LiCl (treatments L and A+L) consumed less alfalfa-grain pellets than sheep that did not receive LiCl (treatments C and A) (241 g vs. 306 g; p = 0.057). Intake of sheep that were anesthetized (treatments A and A+L) did not differ from that of sheep that were not anesthetized (treatments C and L) (295 g vs. 252 g; p = 0.183). Nor was there an interaction between LiCl and anesthesia (p = 0.423). Thus, we conclude that changes in preferences for foods caused by postingestive feedback occur automatically every time food is ingested (i.e., they are noncognitive), and the kind and amount of feedback is a function of the match between the food's chemical characteristics and its ability to meet the animal's current demands for nutrients.

]]> Frederick D. Provenza et al. Food Preferences in Lambs After Exposure to Flavors in Solid Foods http://digitalcommons.usu.edu/grcanyon/21 http://digitalcommons.usu.edu/grcanyon/21 Wed, 24 Feb 2010 14:20:16 PST The aim of this study was to determine whether experience with onion- or garlic-flavored food early in life affected subsequent intake of foods with those flavors. From 30 to 110 days of age, lambs were exposed to either an onion- or a garlic-flavored ration of ground alfalfa and rolled barley. Lambs were tested using both two-choice and single-choice tests. The two-choice tests were between: (1) onion- and garlic-flavored rations; (2) onion-flavored and unflavored rations; (3) garlic-flavored and unflavored rations. In the single-choice tests, acceptance of food was tested with each flavor at the concentration (2%) received during exposure and with 5, 10, 15, 20 and 25% of each flavor. When offered a choice between onion- and garlic-flavored food, lambs exposed to garlic ate more (P < 0.05) garlic-flavored food, while lambs exposed to onion ate more (P < 0.05) onion-flavored food. When offered a choice between flavored and unflavored foods, lambs ate more unflavored than flavored foods; however, lambs exposed to onion ate relatively more (P < 0.05) onion-flavored food than did lambs exposed to garlic in these tests. Exposure to garlic did not increase (P > 0.05) intake of garlic-flavored food when offered with unflavored food. In the single-choice tests, early experience with flavors did not (P > 0.05) increase intake of flavors at the 2% concentration. Lambs exposed to onion, however, ingested more (P < 0.05) onion-flavored food at higher concentrations than did lambs exposed to garlic. Lambs exposed to garlic did not (P > 0.05) ingest more food with higher concentrations of garlic than did lambs exposed to onion. Despite differences between groups of lambs shortly after exposure to flavors (1988), there were no differences in intake of flavored foods 9 months later (1989).

]]> Dale L. Nolte et al. A Seasonal Comparison of Metabolic and Water Loss Rates of Three Species of Grasshoppers http://digitalcommons.usu.edu/grcanyon/19 http://digitalcommons.usu.edu/grcanyon/19 Wed, 24 Feb 2010 13:59:38 PST 1. 1. Seasonal differences in metabolic and water loss rates were examined in three related species of grasshoppers collected from shrub-steppe communities in Utah: Arphia conspersa, A. pseudonietana and

2. 2 cohorts of Trimerotropis pallidipennis. 2. No significant differences (P = 0.05) in metabolic rates were observed between seasons (early vs late), between genera (Arphia vs Trimerotropis) nor among species.

3. 3. Early season (spring) grasshoppers had a higher (but non-significant) mean water loss rate (±X ± SD in mg.g−1-hr−1) (4.81 ± 1.53) than late season (summer) grasshoppers (4.43 ± 1.43).

4. 4. Among species, early season A. conspersa had a significantly higher water loss rate (5.22 ± 1.76) under similar conditions than late season A. pseudonietana (3.67 ± 1.22), but early season T. pallidipennis had a significantly lower water loss rate (4.40 ± 1.17) than the late season generation (5.32 ± 1.12).

5. 5. Because of variables that were not or could not be controlled, the relationship between these physiological traits and season was difficult to address.

]]> Lynn J. Forlow et al. Spider Community Organization : Seasonal Variation and the Role of Vegetation Architecture http://digitalcommons.usu.edu/grcanyon/20 http://digitalcommons.usu.edu/grcanyon/20 Wed, 24 Feb 2010 13:59:38 PST The relationship between vegetation architecture and spider community attributes were examined in a big sage community. Spiders were separated into guilds using similarities of species' hunting behavior. Shrub architecture was experimentally manipulated in the field by either clippings 50% of the shrub's foliage to decrease foliage density or tying together a shrub's branches to increase foliage density. Shrub perturbations resulted in changes in the number of spider species, spider guilds and guild importance values. The number on spider species and guilds in the tied shrubs were significantly higher than those in the clipped or control shrubs sampled. Spider species diversity and the number of species and guilds were positively correlated with indicators of shrub volume and shrub foliage diversity. This suggests that structurally more complex tier shrubs can support a higher number of spider species and species diversity. Temporal patterns of the number of spider species, and species diversity showed midsummer peaks in both 1974 and 1975. Evenness remained relatively constant through both seasons. The data suggest that architectural properties of habitat may be an important determinant of the distribution and species diversity of predatory invertebrates.

]]> Cynthia L. Hatley et al. The Effects of Ultraviolet-B Radiation on Plant Competition in Terrestrial Ecosystems http://digitalcommons.usu.edu/grcanyon/18 http://digitalcommons.usu.edu/grcanyon/18 Wed, 24 Feb 2010 13:59:37 PST Evidence regarding the interaction of ultraviolet-B radiation and plant competition in terrestrial ecosystems is examined. The competitive interactions of some species pairs were affected even by ambient solar UV-B radiation when compared to control pairs grown without UV-B. Also, the total shoot biomass of these species pairs was depressed under ambient UV-B. Relatively large increases in UV-B radiation altered the competitive interactions of some species pairs grown in pots under field conditions, but did not affect the total shoot biomass production of those pairs. Recent field experiments have examined the competitive interactions of wheat and wild oat under a simulated increased UV-B regime resulting from a 16% ozone layer reduction when weighted with the generalized plant action spectrum. This increase in UV-B altered the competitive interactions of these two species without affecting the total shoot biomass production for the species pair. The manner in which increased UV-B affected the relative competitive abilities of the two species was highly dependent upon the environmental conditions during the early life stages of the plants. The implications of these results for both agricultural and natural plant communities are discusses.

]]> Warren G. Gold et al. Food Preferences in Lambs After Exposure to Flavors in Milk http://digitalcommons.usu.edu/grcanyon/16 http://digitalcommons.usu.edu/grcanyon/16 Wed, 24 Feb 2010 13:59:36 PST This study determined whether experience with onion- or garlic-flavored milk affected intake of foods with those flavors. Orphaned lambs were exposed from 2 to 3 days of age for 50 days to either onion- or garlic-flavored milk at a 0.1% concentration. Lambs were then offered a choice of (1) onion- and garlic-flavored food; (2) onion-flavored and unflavored food; (3) garlic-flavored and unflavored food. Intake of foods offered in single choice tests with each flavor at concentrations of 2, 4, 6, 8, 10, 12, 14, and 16% was also measured. Although all lambs ingested more onion-flavored food than garlic-flavored food, they ate relatively more (P < 0.05) food with the flavor to which they were exposed in milk than did lambs exposed to the alternate flavor in milk. Lambs exposed to onion-flavored milk also ingested more (P < 0.05) onion-flavored food, when it was offered with unflavored food, than did lambs exposed to garlic-flavored milk. Experiences with flavors in milk did not affect (P > 0.05) intake of garlic-flavored food when offered with unflavored food. Regardless of which flavor they were exposed to in milk, intake of onion- and garlic-flavored food offered alone was similar (P > 0.05) at all flavor concentrations.

]]> Dale L. Nolte et al. The Voluntary Forage Intake of Heifers Grazing a Diminishing Supply of Crested Wheatgrass http://digitalcommons.usu.edu/grcanyon/17 http://digitalcommons.usu.edu/grcanyon/17 Wed, 24 Feb 2010 13:59:36 PST Intake estimates for Angus heifers grazing a declining quantity of available creasted wheatgrass forage were obtained during the summer grazing seasons of 1978 and 1979. The study was conducted on rangelands in Central Utah that are characteristic of the Eastern Great Basin. Organic matter intake (OMI) was measured by total collection procedures during five periods each year following forage maturation. Available forage was reduced prior to each succeeding intake measurement within each year by grazing animals. In the first year, OMI averaged 1.2% of body weight as available forage decreased from 920 to 140 kg/ha. In the second year, OMI averaged 1.3% of body weight as available forage decreased form 880 to 280 kg/ha. Intake differences between periods within years were not significant. In vitro organic matter digestibility ranged from 33 to 40% in the first year and 34 to 43% in the second year.

]]> Kris M. Havstad et al. Photosynthetic Characteristics of Crested Wheatgrass and Bluebunch Wheatgrass http://digitalcommons.usu.edu/grcanyon/15 http://digitalcommons.usu.edu/grcanyon/15 Wed, 24 Feb 2010 13:59:35 PST Light and temperature dependencies for net photosynthesis and stomatal conductance were generally very similar between foliage on crested wheatgrass plants and that on bluebunch wheatgrass plants. The similarity of these gas exchange characteristics between the 2 bunchgrass species was true for foliage on unclipped plants as well as on partially defoliated plants. However, light and temperature dependencies for senescing leaf blades that were exserted in late-spring were significantly different for unclipped plants of these 2 species. Photosynthetic rates and stomatal conductance of senescent late-season blades on bluebunch wheatgrass plants were greater than those on creasted wheatgrass plants at light intensities greater than 0.8 mmol photons m-2 s-1 and at all foliage temperatures between 18 degrees C and 41 degrees C. These greater photosynthetic rates and stomatal conductance do not mean that bluebunch wheatgreass tillers gained substantially more carbon or lost substantially more water than created wheatgreass tillers. If both the photosynthetic area composition of tillers and the environmental conditions of the northern Utah study site were considered, carbon gain and water loss for individual bluebunch wheatgreass tillers would be very similar to those for individual created wheatgreasa tillers despite the significantly different responses to light and temperature during mid-summer.

]]> Robert S. Nowak et al. Sheep Fed Grain Prefer Foods and Solutions That Attenuate Acidosis http://digitalcommons.usu.edu/grcanyon/14 http://digitalcommons.usu.edu/grcanyon/14 Wed, 24 Feb 2010 13:59:34 PST We conducted experiments to determine whether lambs fed grain prefer foods and solutions containing sodium bicarbonate (NaHCO3) and lasalocid, compounds capable of attenuating acidosis. In Exp. 1, we determined whether lambs fed barley preferred flavored rabbit pellets (RP) containing NaHCO3 and lasalocid. Lambs in two groups (n = 10/group) were fed increasing amounts of barley on d 1 to 12 (300 to 1,100 g) and again on d 23 to 34 (300 to 1,350 g). After ingesting barley on d 1 to 12, lambs were fed ground RP containing lasalocid and NaHCO3 (i.e., medicated) and flavored with either 2% onion (group 1) or 2% oregano (group 2). During d 23 to 34, lambs were fed unmedicated RP containing NaCl and flavored with either 2% oregano (group 1) or 2% onion (group 2). During preference tests on d 35 to 40, lambs fed grain preferred RP with NaHCO3 to RP with NaCl (151 vs. 96 g; P < .01). In the Exp. 2, we determined whether wheat ingestion affected consumption of aqueous solutions containing NaHCO3. In trial 1, 28 lambs were assigned to four treatments: 1) low-wheat + 2% NaHCO3, 2) high-wheat + 2% NaHCO3, 3) low-wheat + water, and 4) high-wheat + water. For 12 d from 0800 to 0830, lambs in treatments 1 and 3 were fed 300 g of wheat and lambs in treatments 2 and 4 were fed up to 1,300 g of wheat; fluids (NaHCO3 and water) were then offered from 0930 to 1230 daily. Lambs drank more NaHCO3 on the high-than on the low-wheat diet (1,332 vs 890 g; P = .03); water consumption was similar for lambs on the high-and low-wheat diets (1,675 vs 1,700 g; P > .10). In trial 2, lambs in treatments 3 and 4 were offered a solution containing 1.4% NaCl. For 13 d from 0800 to 0830, lambs in treatments 1 and 3 were fed 500 g of wheat and lambs in treatments 2 and 4 were fed up to 1,700 g of wheat. Lambs had access to fluids from 0800 to 1200 daily. Lambs drank nearly twice as much NaHCO3 solution on the high-than on the low-wheat diet (1,066 vs 572 g), whereas they drank only 1.4 times more NaCl solution on the high-than on the low-wheat diet (888 vs. 634 g; P < .001). Fewer lambs showed signs of acidosis in treatment 2 than in treatment 4 in trials 1 (2 vs 9) and 2 (7 vs 17). Collectively, these results are consistent with the hypothesis that lambs fed grain prefer substances that attenuate acidosis.

]]> Timothy S. Phy et al. Seasonal Timing of Root Growth in Favorable Microsites http://digitalcommons.usu.edu/grcanyon/13 http://digitalcommons.usu.edu/grcanyon/13 Wed, 24 Feb 2010 13:19:07 PST The heterogeneous nature of soil is well known. Over short distances, a soil may vary considerably in nutrient and water availability, physical impedance, toxic ion concentration, and other factors that affect plant growth and function. Proliferation of roots in small volumes of soil with favorable chemical and physical characteristics has been shown (Fitter and Hay 1981, St. John et al. 1983, Wang et al. 1986). Such responses are generally considered to be mechanisms by which plants more efficiently exploit the soil environment (e.g., St. John et al. 1983). In this field study, we compare rates and spatial patterns of root growth in favorable microsites by two Agropyron species and a common shrub codominant Artemisia tridentata ssp. vaseyana (Rydb.) Beetle. These two Agropyron tussock grasses differ strikingly in their ability to compete with A. tridentata (Eissenstat and Caldwell 1988). The grass of greater competitive ability, Agropyron desertorum (Fisch. ex Link) Schult., was introduced from Eurasia and has been widely planted in the Great Basin steppe of North America. Agropyron spicatum (Pursh) Scribn. and Smith and A. tridentata are native. (A recent revision of the perennial North American Triticeae [Barkworth and Dewey 1985] recommends that the name Agropyron spicatum be changed to Pseudoroegneria spicata [Pursh] A. Love subsp. spicata.)

]]> David M. Eissenstat et al. Tannin Allocation in Blackbrush (Coleogyne ramosissima) http://digitalcommons.usu.edu/grcanyon/12 http://digitalcommons.usu.edu/grcanyon/12 Wed, 24 Feb 2010 13:12:03 PST Blackbrush (Coleogyne ramosissima) is a spinescent shrub occurring in nearly monospecific stands in the southwestern United States. Winter browsing by domestic goats stimulates spring twig production by blackbrush plants. Current season's twigs produced by older branches growing on the outer edges of the plant canopy (terminal branches) contained 2.37 times more tannins than did older twigs. Within blackbrush plants, current season's twigs on terminal branches contained 1.34 times more tannins than did current season's twigs on sprouts and younger branches (basal branches). When analysed separately, current season's terminal twigs contained 1.47 times more tannins than did leaves, while current season's basal twigs contained 1.10 times more tannins than did leaves. Phytochemicals, mainly phenolics, in blackbrush reduce its risk of being over-utilized by domestic herbivores, and the occurrence and distribution of tannins in blackbrush lend support to hypotheses dealing with secondary compounds as plant defenses.

]]> F D. Provenza et al. Green Canyon Recreation Management Plant http://digitalcommons.usu.edu/grcanyon/11 http://digitalcommons.usu.edu/grcanyon/11 Wed, 24 Feb 2010 13:12:02 PST The purpose of this plan is to look at the way Green Canyon is currently being managed and make recommendations for management based on our findings. Prior to this document, a Landscape Assessment was conducted on Green Canyon. This plan incorporates that assessment but focuses on the recreation management of the canyon. We will discuss history, current management, social conditions, purpose and need, as well as methods we used to go about gathering information. The focus is to identify key issues and concerns within the canyon. Management recommendations will be made based on the issues and concerns identified.

]]> Jesse Evans et al. Using Eggs Containing an Irritating Odor to Teach Mammalian Predators to Stop Depredating Eggs http://digitalcommons.usu.edu/grcanyon/10 http://digitalcommons.usu.edu/grcanyon/10 Mon, 08 Feb 2010 12:21:28 PST Mammalian predation on eggs has reduced many avian populations below historic levels. Nonlethal approaches to resolve predation problems are preferred by society, but often are ineffective or too expensive. We examined whether mammalian predators could be taught to stop opening all eggs (treated and untreated) after the predators were preconditioned by being allowed to open eggs containing an irritating odor. We tested this using 29 captive coyotes (Canis latrans) and pulegone, a Volatile chemical that is irritating to coyotes. The first experiment consisted of a 1-day pretreatment when each coyote was given an untreated egg, a 5-day treatment period when each coyote was given daily an egg injected with pulegone, and a 1-day post-treatment period when each coyote was given an untreated egg. This was followed by a 4-day choice test during which each coyote was given 3 eggs daily: one untreated, one coated with pulegone, and one injected with putegone and then sealed in polyurethane. All coyotes ate untreated eggs during the pretreatment period and also ate the first pulegone-treated egg presented to them. After that, coyotes gradually stopped opening and consuming eggs injected with pulegone. During the post-treatment period, coyotes resumed eating untreated eggs, indicating that they had developed an aversion to putegone but not to eggs. During choice tests, coyotes discriminated against pulegone-injected eggs and pulegone-scented eggs. This suggested that it might be possible to deceive predators into avoiding untreated eggs by spraying nests with pulegone. We tested this by creating a simulated nesting colony consisting of 16 nests in a field, each containing one egg. Following a treatment period when all eggs were injected with pulegone, Lye conducted a choice test in which 8 nests contained untreated eggs, 4 nests contained eggs sprayed with pulegone, and 4 nests were spayed with pulegone but contained untreated eggs. Coyotes consumed fewer eggs from pulegone-scented nests than from unscented nests. These experiments indicate that it may be possible to deflect predation in an avian nesting colony away from specific nests by exposing local predators to pulegone-injected eggs prior to the nesting season and then spraying pulegone on the ground near those nests that we wish to protect. Such an ability would be useful in multi-species colonies when we want to protect a particular species from predation. However, pulegone is toxic to egg embryos, so care must be taken not to allow it to contact the eggs.

]]> Suzanne E. Hoover et al. Role of Toxins in Intake of Varied Diets by Sheep http://digitalcommons.usu.edu/grcanyon/8 http://digitalcommons.usu.edu/grcanyon/8 Mon, 08 Feb 2010 11:43:32 PST Herbivores foraging on toxic plants may consume a variety of foods that contain different toxins to increase food intake and to avoid toxicosis. We studied whether lambs offered two foods, each containing a different toxin, could ingest more food than lambs offered one food with a single toxin. Thirty-two lambs were allotted to four groups that received: (1) a ration with toxin A, (2) a ration with toxin B, (3) two rations, one with toxin A and the other with toxin B, and (4) a ration with no toxins. Toxin pairs used in the study were(1) amygdalin and lithium chloride (LiCl), (2) LiCl and LiCl, (3) sparteine and saponin, (4) oxalate and nitrate, and (5) tannin and saponin. For an hour each morning, lambs were offered their ration(s) and intakes were measured. Lambs were maintained on an alfalfa pellet or grass hay diet. Each trial lasted either five or six days. Whether or not lambs ate more when offered foods with different toxins depended on the kind and amount of toxin in the food. Lambs offered rations with amygdalin and LiCl or oxalate and nitrate consumed more food than lambs offered a ration with only one of these toxins. Lambs offered rations with sparteine and saponin or tannin and saponin did not eat more food than lambs offered a ration with either saponin or sparteine or tannin alone. Nor did lambs eat more when offered two rations both containing LiCl. In all trials, lambs offered toxins showed no signs of toxicosis, and they ate less food than lambs offered rations without toxins. Our results indicate that in some cases ruminants can increase intake of toxic foods by consuming foods containing different toxins. However, currently the only way to determine how specific toxins may interact in the body to influence intake would be to conduct feeding trials using plants or ground diets that contain toxins.

]]> Elizabeth A. Burritt et al. Lambs Form Preferences for Nonnutritive Flavors Paired with Glucose http://digitalcommons.usu.edu/grcanyon/9 http://digitalcommons.usu.edu/grcanyon/9 Mon, 08 Feb 2010 11:43:32 PST We studied lambs' preferences for nonnutritive flavors that were paired with a glucose solution. On the 1st d of the experiment, lambs were offered a saccharin solution flavored with either orange or grape. The following day lambs received a glucose solution containing either orange or grape flavor. Lambs that had received grape and saccharin on d 1 received orange and glucose on d 2, and the reverse was true for the remaining lambs. Conditioning lasted 10 d; odd days were like the first and even days like the second. After conditioning, when lambs were offered a choice between orange- or grape-flavored water without sweeteners, lambs chose the flavor that had been paired with glucose. We also tested the initial hedonic response of naive lambs to the flavor of glucose and saccharin solutions. Lambs exhibited no initial preference. Our results indicate that lambs preferred the flavor that was paired with glucose (calories). Furthermore, results of this study suggest that ruminants may not innately recognize specific chemical constituents in foods or select diets based on initial hedonic value. Rather, learning plays a key role in the formation of dietary preference.

]]> Elizabeth A. Burritt et al. Stratospheric Ozone Reduction, Solar UV-B Radiation and Terrestrial Ecosystems http://digitalcommons.usu.edu/grcanyon/7 http://digitalcommons.usu.edu/grcanyon/7 Mon, 08 Feb 2010 11:43:31 PST Stratospheric ozone reduction is occurring and will continue to increase in magnitude into the next century. Yet, the consequences for terrestrial ecosystems of the increased solar W-B (280-320 nm) radiation resulting from total column ozone reduction are not understood. Based on studies of higher plant response to UV-B, several possible consequences for ecosystems include decreased primary production, altered plant species composition, and altered secondary chemistry with implications for herbivory, litter decomposition and biogeochemical cycles. However, like the assessment of increased atmospheric CO2, extrapolation from studies with isolated plants to ecosystem function is very tenuous at best. Very few UV-B studies have dealt with multispecies systems. Most of the UV-B research in the past two decades (since the first suggestions of ozone reduction) has been conducted as short-term experiments in growth chambers and greenhouses where the unnatural spectral balance of radiation can lead to unrealistic conclusions. Technical difficulties in suitable measurement and manipulation of UV-B radiation also complicate the conduct of reliable experiments. This essay surveys and categorizes some 300 papers from the past 20 years on this subject, draws general conclusions from the research and offers some recommendations with respect to ecosystem consequences.

]]> Martyn M. Caldwell et al. Hydraulic Lift and Soil Nutrient Heterogeneity http://digitalcommons.usu.edu/grcanyon/5 http://digitalcommons.usu.edu/grcanyon/5 Mon, 08 Feb 2010 11:43:30 PST Water released at night from roots into upper portions of the soil profile in the process of hydraulic lift may contribute to reducing spatial soil nutrient heterogeneity. A manipulative field experiment was conducted in a semiarid shrub stand to determine if circumvention of hydraulic lift, by nighttime illumination of the shrub canopy, would result in greater soil nutrient heterogeneity than if the hydraulic lift process was allowed to operate. Nutrient-enriched patches were superimposed on the existing soil heterogeneity and after 40 days, the patches and interspaces were sampled for ions of different mobility and for root mass. There was no indication under these conditions that hydraulic lift was contributing to smoothing spatial nutrient heterogeneity.

]]> Martyn M. Caldwell et al. Internal Filters : Prospects for UV-Acclimation in Higher Plants http://digitalcommons.usu.edu/grcanyon/6 http://digitalcommons.usu.edu/grcanyon/6 Mon, 08 Feb 2010 11:43:30 PST Wavelength-selective absorption of solar radiation within plant leaves allows penetration of visible radiation to the chloroplats, while removing much of the damaging ultraviolet-B radiation. Flavonoids are important in this wavelength-selective absorption. Induction of flavonoid synthesis by solar radiation, and specifically by UV-B radiation, is discussed as this relates to the potential acclimation of plants to enhanced solar UV-B radiation that would result from stratospheric ozone reduction.

]]> Martyn M. Caldwell et al.