Harsh Desert Environment Research Articles

Effectiveness of an Eco-friendly Polymer Composite Sand-Fixing Agent on Sand Fixation

A novel and eco-friendly xanthan gum-g-poly(acrylic acid)/laterite (XG-g-PAA/laterite) organic-inorganic composite polymer used as chemical sand-fixing agent (CSFA) was successfully prepared by grafted copolymerization of natural XG, partially neutralized acrylic acid (NaA), and laterite in solution. FTIR spectra confirmed that NaA had been grafted onto XG chains, and the –OH groups of laterite participated in polymerization reaction. The influence of the content of CSFA on sand-fixing effect was investigated, and the results of the aging test indicated that the CSFA had remarkable water resistance, heat resistance, anti-freeze-thaw, and anti-ultraviolet aging performances, which could meet the requirement of application in the harsh desert environment. Moreover, it also showed excellent water-retaining and anti-evaporation properties.

Revisiting a Graduate Design Studio on Sacred Architecture: A Mosque Design in Yazd, Iran

Abstract This essay describes a graduate studio where students were asked to design a new mosque in the historic old town of Yazd, Iran. The project was formed under the broader theme ‘Sacred Architecture in International Historic and Sustainable Contexts’ and required the students to think critically about design within historic, cultural, environmental and tectonic contexts. The studio also responded to concerns expressed by the American National Architectural Accrediting Board (NAAB) about the limited international training and experience in architectural programmes. As such, the project addressed a particular design problem (a mosque design in Yazd, Iran) and responded to broader issues within the field of ­architectural pedagogy. Five examples of students’ projects demonstrate a variety of design concepts and architectural approaches to the design of the new mosque. All examples show attentiveness to faith requirements and sensitivity to the specific site restrictions, as well as to local climate conditions. The latter was emphasized by sustainable design proposals, which accommodate the harsh desert environment of Yazd. Reflections and recommendations follow the description of students’ projects and relate to the pedagogical issues in teaching global architectural history and contemporary practice.

Monitoring rarity: the critically endangered Saharan cheetah as a flagship species for a threatened ecosystem.

Deserts are particularly vulnerable to human impacts and have already suffered a substantial loss of biodiversity. In harsh and variable desert environments, large herbivores typically occur at low densities, and their large carnivore predators occur at even lower densities. The continued survival of large carnivores is key to healthy functioning desert ecosystems, and the ability to gather reliable information on these rare low density species, including presence, abundance and density, is critical to their monitoring and management. Here we test camera trap methodologies as a monitoring tool for an extremely rare wide-ranging large felid, the critically endangered Saharan cheetah (Acinonyx jubatus hecki). Two camera trapping surveys were carried out over 2–3 months across a 2,551km2 grid in the Ti-n-hağğen region in the Ahaggar Cultural Park, south central Algeria. A total of 32 records of Saharan cheetah were obtained. We show the behaviour and ecology of the Saharan cheetah is severely constrained by the harsh desert environment, leading them to be more nocturnal, be more wide-ranging, and occur at lower densities relative to cheetah in savannah environments. Density estimates ranged from 0.21–0.55/1,000km2, some of the lowest large carnivore densities ever recorded in Africa, and average home range size over 2–3 months was estimated at 1,583km2. We use our results to predict that, in order to detect presence of cheetah with p>0.95 a survey effort of at least 1,000 camera trap days is required. Our study identifies the Ahaggar Cultural Park as a key area for the conservation of the Saharan cheetah. The Saharan cheetah meets the requirements for a charismatic flagship species that can be used to “market” the Saharan landscape at a sufficiently large scale to help reverse the historical neglect of threatened Saharan ecosystems.

Landscape models of space use by desert bighorn sheep in the Sonoran Desert of southwestern Arizona

The desert bighorn sheep (Ovis canadensis mexicana) is one of the few ungulates native to North America capable of surviving in harsh desert environments and xeric conditions. However, the effects of an increasingly arid climate on this species and its habitat are unknown. We sought to identify important predictors of desert bighorn sheep diurnal space use to provide new insight into management and conservation opportunities. We evaluated home range size and relative intensity of space use for 41 collared individuals monitored between 2007 and 2010 across a 14,217-km2 extent of Arizona's Sonoran Desert, including the Kofa National Wildlife Refuge and the United States Army Yuma Proving Ground. Using linear mixed models and an information-theoretic approach, we developed seasonal models of intensity of space use for the summer (Jun–Aug) and non-summer (Sep–May) seasons. Models included environmental variables representing escape terrain and distance from developed waters, and Normalized Difference Vegetation Index metrics that represented forage and preformed water resources. We found intensity of space use to be greater for females (than for males) in the summer season and smaller home range sizes for both sexes in the summer season. Escape terrain was the dominant predictor of intensity of space use in both seasons, but forage and preformed water resources were strong predictors only in the non-summer season. These results likely reflected a seasonal trade-off between escape terrain (i.e., predator avoidance) and limited forage and water resources, particularly for more risk-averse females. Effective conservation and management strategies for desert bighorn sheep should consider the availability of both quality forage and water resources in areas of escape terrain. Although more research is needed on species-specific vulnerabilities to climate change and drought, our approach to integrating vegetation indices into estimates of space use is highly transferable to analyses of other wide-ranging species occupying dynamic arid environments. © 2014 The Wildlife Society.

Desert Ants Locate Food by Combining High Sensitivity to Food Odors with Extensive Crosswind Runs

Desert ants feeding on dead arthropods forage for food items that are distributed unpredictably in space and time in the food-scarce terrain of the Saharan salt pans [1]. Scavengers of the genus Cataglyphis forage individually and do not lay pheromone trails [2]. They rely primarily on path integration [3] for navigation and, in addition, use visual [4] and olfactory cues [5-7]. While most studies have focused on the navigational mechanisms of ants targeting a familiar place like the nest or a learned feeding site, little is known about how ants locate food in their natural environment. Here we show that Cataglyphis fortis is highly sensitive to and attracted by food odors, especially the necromone linoleic acid, enabling them to locate tiny arthropods over several meters in distance. Furthermore, during the search for food, ants use extensive crosswind walks that increase the chances of localizing food plumes. By combining high sensitivity toward food odors with crosswind runs, the ants efficiently screen the desert for food and hence reduce the time spent foraging in their harsh desert environment.

The remarkable endemism of moths at White Sands National Monument in New Mexico, USA, with special emphasis on Gelechioidea (Lepidoptera)

The white sands formation, a snow-white gypsum dunes system, is the world's largest gypsum dune field. White Sands National Monument protects about 40% of the dunes; the dunes formation as it is known today was formed ca. 8,000 years BP. Prior to 8,000 years BP, the area covered by the dunes was a wet cool forest of the last glacial maximum in North America. The dunes were formed as a result of the hypsithermal, a warming and drying period which followed the most recent glacial maximum. The white sands formation is located in south central New Mexico in the Tularosa Basin of southwestern United States. A 10-year study of moths at the dunes was commissioned by the U. S. National Park Service in 2006. Almost immediately species new to science were detected. In the period of 6 years, 30 new species were discovered in the dunes. Several of the new species are white or very pale in color, and are endemic to the dunes. The focus of the 10 year project was modified to emphasize naming the undescribed species which helps the National Park Service catalog and manage the habitats. The data should encourage other researchers to explore the interactions of the animals with the plants and the harsh desert environment, to study DNA and evolution, and to study the rapid adaptation which seems to be occurring.

Degradation of seed mucilage by soil microflora promotes early seedling growth of a desert sand dune plant

In contrast to the extensive understanding of seed mucilage biosynthesis, much less is known about how mucilage is biodegraded and what role it plays in the soil where seeds germinate. We studied seed mucilage biodegradation by a natural microbial community. High-performance anion-exchange chromatography (HPAEC) was used to determine monosaccharide composition in achene mucilage of Artemisia sphaerocephala. Mucilage degradation by the soil microbial community from natural habitats was examined by monosaccharide utilization tests using Biolog plates, chemical assays and phospholipid fatty acid (PLFA) analysis. Glucose (29.4%), mannose (20.3%) and arabinose (19.5%) were found to be the main components of achene mucilage. The mucilage was biodegraded to CO(2) and soluble sugars, and an increase in soil microbial biomass was observed during biodegradation. Fluorescence microscopy showed the presence of mucilage (or its derivatives) in seedling tissues after growth with fluorescein isothiocyanate (FITC)-labelled mucilage. The biodegradation also promoted early seedling growth in barren sand dunes, which was associated with a large soil microbial community that supplies substances promoting seedling establishment. We conclude that biodegradation of seed mucilage can play an ecologically important role in the life cycles of plants especially in harsh desert environments to which A. sphaerocephala is well-adapted.

Partial Analysis of Olfactory Receptor Subgenome in the Arabian Camel

Abstract Many animals have evolved mechanisms to withstand the harsh desert environment, characterized by extreme high temperatures and scarce water supplies. The Arabian Camel, and the Arabian Oryx are valued economically and culturally. These animals can survive for several days without food or water. As the Arabian peninsula undergoes rapid and vast industrial changes, it is increasingly important to understand the biological aspects of these animals. From the unicellular microbes to the sophisticated multi-cellular animals, sensing the chemical composition of the surrounding environment is essential for survival. The vertebrate chemosensory receptors genes, which are members of the seven transmembrane -helical G-protein coupled receptors (GPCRs), are encoded by six different multigene families. Four of these genes encode receptor proteins for sensing odors. The olfactory (odorant) receptors (ORs) are predominately expressed in the sensory neurons of the main olfactory epithelium, and can sense either water-soluble (class I) or volatile (class II) molecules. Furthermore, certain OR genes are expressed in non-olfactory tissues, such as brain, kidney, testis, and placenta. Being adapted to very harsh conditions with elevated temperature, scarce water supply and limited vegetation, we hypothesize that desert animals have evolved the ability to detect water either from volatiles liberated by water in the environment or through the blooming of short-lived vegetation, via their olfactory systems. To explore this possibility we have undertaken the study of the Camel OR genes. We identified approximately one hundred candidate OR genes, all of which are ortholgos to OR genes in other mammals and most closely related to those of the Equus caballus. Preliminary analysis revealed an enrichment in OR gene family 2/13, found in the highest proportion in aquatic animals, as compared to other mammals. This finding provides the intriguing suggestion that desert animals have evolved specific OR genes to adapt to the desert ecosystem. We are currently working to identify the complete OR gene repertoire in the Camel, and to identify and characterize the OR subgenome in other desert animals such as the Arabian Oryx.

Vertical Distribution of Microbial Community Functionality under the Canopies of Zygophyllum dumosum and Hammada scoparia in the Negev Desert, Israel

Patchy desert shrubs magnify the horizontal heterogeneities of carbon source and nutrient availability in an arid ecosystem, significantly affecting the abundance and activity of the soil microbial community. Since each shrub species develops special ecophysiological adaptations to the extreme harsh desert environments, previous studies elucidated that the effects of perennial shrubs on microbial diversity are unequal. The aim of the present study, conducted in the Negev Desert, Israel, was to illustrate the vertical changes of soil microbial community functionality in the root zone of perennial shrubs. Soil samples were collected from the 0-50 cm depth at 10-cm intervals under the canopy of Zygophyllum dumosum, Hammada scoparia, and from the open spaces between them, in the wet and dry seasons. Soil moisture and organic matter exhibited a significant (P<0.001) plant and depth dependence. The mean basal respiration rates and microbial biomass in soils collected beneath perennial shrubs were relatively higher than the control during the wet season, however, a contrasting trend was observed at some soil depths during the dry season. Relatively high abundance and activity of aromatic and carboxylic acid utilizers were observed in the vicinity of perennial shrubs, and the values recorded during the dry season were generally higher than the corresponding values during the wet season. In addition, a "mirror effect" in vertical changes of the community-level physiological profile was observed between Z. dumosum and H. scoparia. This study demonstrated the stratification of the functional aspects in soils under the canopy of perennial shrubs, thus indicating that the scattered distribution of vegetation not only causes horizontal heterogeneities of the microbial community in an arid system, but also that the ecophysiological adaptations developed by xerophytes regulate the abundance and saprotrophic functionality of microorganisms in the root zone.

Photosynthetic and cytological recovery on remoistening Syntrichia caninervis Mitt., a desiccation-tolerant moss from Northwestern China

Syntrichia caninervis Mitt. is the dominant species in the moss crusts of the Gurbantunggut Desert, Northwestern China. We experimented with this species under controlled environmental conditions. Modulated chlorophyll (Chl) fluorescence was used to test the speed of recovery as evidenced by the time course of photosynthetic activity following remoistening. Transmission electron microscopy was used to explore the cytological characteristics of the leaf cells. Minimum and maximum fluorescence (F0 and FM) and photosynthetic yield (FV/FM) of photosystem II (PSII) recovered quickly when shoots were remoistened in the dark. This was especially the case of FV/FM; within the first minute of remoistening this reached 90% or more of the value attained after 30 min. These physiological changes were closely paralleled by cytological changes that indicated no damage to membranes or organelles. Correlation analysis showed that Chl fluorescence decreased both above and below a narrow moisture optimum. Our results underline the capability of S. caninervis to photosynthesize after remoistening. Utilizing precipitation events such as dew, fog, rain, and melting snow allows S. caninervis to survive and grow in a harsh desert environment.

Influence of livestock on the regeneration of fodder trees along ephemeral rivers of Namibia

Faidherbia albida and Acacia erioloba (Mimosoideae) are important fodder trees for livestock and wildlife along the westward flowing ephemeral rivers of the Namib Desert. Together with other, mainly woody vegetation, F. albida and A. erioloba line these rivers and present a linear oasis in a resource poor environment. For centuries nomadic to semi-nomadic inhabitants seasonally utilised the resources of these ephemeral rivers to survive in the otherwise harsh desert environment. In the past decades, more permanent settlements were established along these rivers, with small stock subsistence farmers making a living from the available resources. Livestock (mainly goats) usually moves freely around, feeding on the available vegetation.This study investigated the influence of free moving animals on the regeneration and recruitment of F. albida and A. erioloba along the Kuiseb ephemeral river. It was found that a large numbers of recently emerged seedlings were removed soon after germination. In addition, tree densities of adult versus juvenile individuals differed in areas with large numbers of livestock. The overall height increase and health of juvenile plants were influenced negatively by browsing livestock. In general, browsing pressure differed spatially and was higher close to the main water channel.

All Astir

All Astir Our New World’s worldly wit so shrewd Lacks the Semitic reverent mood, Unworldly—hardly may confer Fitness for just interpreter Of Palestine. Clarel 1.1.92–6 M elville’s title, Clarel: A Poem and a Pilgrimage, aptly describes the concerns of the Melville Society’s seventh international conference, which took place in Jerusalem June 17–21, 2009. Members and scholars of all stripes journeyed to discuss a poem (and much more). But the gathering was also a pilgrimage for those who came to see the world Melville observed so cogently in 1857 and pondered for decades thereafter. As we discovered, a brief sojourn “hardly may confer” the wisdom needed for understanding Melville’s Palestine or the contested lands of today. For some, North American “worldly wit” failed in the face of intractable political crises, a harsh desert environment of breathtaking beauty, and a city whose “thronged streets astir” challenged conventional assumptions. Co-chairs Basem Ra’ad, Hilton Obenzinger, and Timothy Marr nevertheless created a congenial space for discussion at the École Biblique, organized countless festive meals, and led splendid tours through ancient and modern sites in and around Jerusalem and in Jordan. We will offer a full report on this superb conference, with photographs and samplings of keynotes, panels, and excursions, in Leviathan 12.1, our issue of Spring 2010. For anyone who cannot wait that long and would like to see evidence of the joyful confluence of Melville scholars, young and seasoned, in what Melville called the Holy Land, we draw your attention to this link: http://www.youtube.com/view play list?p=3858ED79E9C67595. When members of the conference visited Jericho on the date of Walter Bezanson’s ninetyseventh birthday, someone got the bright idea of conveying affectionate greetings to the person without whose work the study of Clarel and the conference itself are unimaginable. Even the video clips cannot convey, however, the depth of gratitude for Walter’s groundbreaking scholarship expressed in paper after paper presented at the gatherings in Jerusalem. In other Melville-related news, the American Literature Association met in Boston in May, and we are pleased to present abstracts and summaries from not one but two events: the Melville Society panel chaired by Maurice Lee (Boston University), called “Melville and the End(s) of Philosophy”; and a C 2009 The Authors Journal compilation C 2009 The Melville Society and Wiley Periodicals, Inc. 116 L E V I A T H A N A J O U R N A L O F M E L V I L L E S T U D I E S A L L A S T I R roundtable discussion chaired by Joseph Fruscione (Georgetown University, George Washington University), titled “‘Past, Present, and Future Seemed One’: Approaches to Teaching Melville.” The Melville Society Cultural Project met in New Bedford, MA for the Melville Birthday Lecture on July 30. This year’s speaker was D. Graham Burnett (Princeton University), whose talk addressed issues explored in his recent book, Trying Leviathan: The Nineteenth-Century New York Court Case That Put the Whale on Trial and Challenged the Order of Nature. We will present a fuller report on the lecture, the Melville Society Archive Fellowship, and new developments at the New Bedford Whaling Museum in our next issue. The MLA convention meets in Philadelphia this year from December 27–30. The Melville Society panel, chaired by Peter Norberg (St. Joseph’s University), features “Herman Melville: A Writer and His Books.” The papers include Dennis Berthold (Texas A & M University) speaking on “‘Mute Marbles’: Roman Aesthetics in the Poetry”; Shelley Jarenski (University of Michigan, Dearborn) on “‘Secret[s] published in a portrait ’: Melville’s Disruptive Visual Aesthetics in Pierre”; Ida Rothschild (Boston University) on “Melville’s ‘Mousetrap’: Using Shakespeare to Unmask Manifest Destiny in Moby-Dick”: and Brian Yothers (University of Texas at El Paso) on “‘Crack’d Archangel’: Thomas Browne’s Religio Medici, the Bible, and Religious Difference in Melville Fiction and Poetry.” For details about the Melville Society business meeting and dinner, please write Mary K. Bercaw Edwards (maryk.bercawedwards@mysticseaport.org) or Joseph Fruscione (jf284@georgetown.edu). For links to these individuals and MLA...

Seasonal effect of three desert halophytes on soil microbial functional diversity

The objective of this study was to evaluate the effect of some plant ecophysiological adaptations on soil microbial functional diversity in a Negev Desert ecosystem. Soil samples from the upper 0–10 cm layer were collected at the study site under three species of halophyte shrubs, Zygophyllum dumosum, Hammada scoparia, and Reaumuria negevensis. These halophytes represent the most typical cover of the Negev Desert and each of them develops complex strategies that enable greater adaptation and hence, survival. The microhabitat of the shrubs showed differences in trends and magnitude of organic matter content, electrical conductivity, total soluble nitrogen, microbial functional diversity, and C compound utilization. The trends are assumed to be driven by various mechanisms of shrub adaptation in order to be able to survive the harsh desert environment. This study provides evidence that ecophysiological strategies developed by halophytes force microbial communities (from the point of view of activity, composition, and substrate utilization) to adapt to a beneficial plant-microorganism relationship.

COST-EFFECTIVE AND RELIABLE DESIGN OF A SOLAR THERMAL POWER PLANT

A design study was conducted to evaluate the cost-effectiveness of solar thermal power generation in a 50 kWe power plant that could be used in a remote location. The system combines a solar collector-thermal storage system utilizing a heat transfer fluid and a simple Rankine cycle power generator utilizing R123 refrigerant. Evacuated tube solar collectors heat mineral oil and supply it to a thermal storage tank. A mineral oil to refrigerant heat exchanger generates superheated refrigerant vapor, which drives a radial turbogenerator. Supplemental natural gas firing maintains a constant thermal storage temperature irregardless of solar conditions enabling the system to produce a constant 50 kWe output. A simulation was carried out to predict the performance of the system in the hottest summer day and the coldest winter day for southern California solar conditions. A rigorous economic analysis was conducted. The system offers advantages over advanced solar thermal power plants by implementing simple fixed evacuated tube collectors, which are less prone to damage in harsh desert environment. Also, backed up by fossil fuel power generation, it is possible to obtain continued operation even during low insolation sky conditions and at night, a feature that stand-alone PV systems do not offer.

Characterization of Some Post-Consumer Thermoplastic Food Packaging Reclaimed from Remote Desert Areas in Saudi Arabia

Discarded plastic food packaging articles taken from the Thomamah desert area near Riyadh in Saudi Arabia were characterized rheologically and thermally. These articles are made of polystyrene (PS), high-density polyethylene (HDPE), and polyethyleneterephthalate (PET). The aim was to assess the degradation of these plastic articles caused by prolonged exposure to a harsh desert environment such as sunlight radiation. The reduction in molecular weight of the degraded plastics relative to that of the virgin plastics was estimated from the zero-shear viscosity-molecular weight relationship η0 = k (Mw)a. The degradation was more pronounced with PS (THO6C) and PET2 (THO1BS) where the reduction in their molecular weight was estimated to be ∼ 23%. There was a lack of sharp transition from glassy to rubbery state at the Tg of the degraded PS (THO6C) in comparison with the behavior of virgin PS. In addition, the degree of crystallinity of degraded PET1 (THO1BW) and degraded HDPE (THO2BW) was less than that of the virgin PET1 and virgin HDPE.

Soil Microbial Population in the Vicinity of the Bean Caper ( Zygophyllum dumosum) Root Zone in a Desert System

The aim of the current study was to gain a better understanding of the changes in soil microbial biomass and basal respiration dynamics in the vicinity of the bean caper ( Zygophyllum dumosum) perennial desert shrub and the inter-shrub sites. Microbial biomasses as well as basal respiration were found to be significantly greater in the soil samples taken beneath the Z. dumosum shrubs than from the inter-shrub sampling sites, with no differences between the two sampling layers (0-10 and 10-20 cm) throughout the study period. However, seasonal changes were observed due to autumn dew formation, which significantly affected microbial biomass and basal respiration in the upper-layer inter-shrub locations. The calculated metabolic coeffcient ( qCO 2) revealed significant differences between the two sampling sites as well as between the two soil layers, elucidating the abiotic effect between the sites throughout the study period. The substrate availability index was found to significantly demonstrate the differences between the two sites, elucidating the significant contribution of Z. dumosum in food source availability and in moderating harsh abiotic components. The importance of basal microbial parameters and the derived indices as tools demonstrated the importance and need for basic knowledge in understanding plant-soil interactions determined by an unpredictable and harsh desert environment.

Research &amp; Conservation Report

In the first study of its kind, TD Drezner at the University of Wisconsin has quantified and statistically analyzed the spatial relationships between saguaros and the plants that serve to protect them as they grow, a.k.a. nurse plants. Thirty populations of C. gigantea in the northern Sonoran Desert were examined and catalogued based on their proximity to each other and to nurse plants of three types: leguminous trees; small, densely canopied Ambrosia shrubs; and the larger, less dense L. tridentata. The study found that all young saguaros favor being as close to the base of plants as possible, but they tend to prefer trees and shrubs with denser canopies. The author concludes that “microclimate differences are the most likely factor shaping cacti-nurse association in the harsh desert environment.” Drezner tD. Plant facilitation in extreme environments: the nonrandom distribution of saguaro cacti (Carnegiea gigantea) under their nurse associates and the relationship to nurse architecture. Journal of Arid Environments, in press.

Desert Patriarchy: Mormon and Men-nonite Communities in the Chihuahua Valley

Desert Patriarchy: Mormon and Mennonite Communities in the Chihuahua Valley. By Janet Bennion. (Tucson: University of Arizona Press, 2004. Pp xvii + 207, preface, acknowledgments, photographs, maps, chart, notes, bibliography, index, $45.00 cloth) In the promisingly titled Desert Patriarchy, Janet Bennion, descendant of Utah Mormon setders and self-described rat, explores the intersection of gender dynamics and religious fundamentalism in three contemporary separatist religious communities in Mexico. Two are settlements of Utahns of differing Mormon belief - Colonia Juarez (founded in the late nineteendi century) and Colonia LeBaron (founded in the early twentieth) - while the third, Capulin, is Old Colony Mennonite community formed by conservative Mennonites who came from Manitoba in the early twentieth century. The author's thesis, that a harsh desert environment plays a central role in supporting religious patriarchy, particularly the subjugation of women, proves elusive. Her field research is directed toward exposing patriarchy in the two Mormon communities, the Old Colony Mennonites serving mainly for comparison. Overall, the reviewers find that while Bennion's writing style is easy to follow and the information interesting, Desert Patriarchy presents so many factual and methodological problems that it is unlikely to further our knowledge. It is difficult to fathom how ethnographer could expect to conduct significant and sensitive field research on three different groups in one summer, yet this our author did, in 1999, assisted by three undergraduate anthropology students. Through interviews and participant observation with a limited number of individuals, Bennion forges idiosyncratic that is written, as Bennion notes, using the self-reflexive ?,' to help the reader understand the components of the communities studied and the factors involved in their adaptation to desert (xiii). She presents herself as both anthropologist and outsider. As she puts it, am posing here as the interpreter of the culture, offering my own vision of what I saw based on my experiences with the natives (xii) while claiming a heavy reliance on the natives' voices, through narrative (xi) . It is not clear to the reader what the communities and individuals Bennion studied were told about her public interpretation of their lives and motives. Her descriptive commentary may be intended to give voice to her field consultants, but it seems overwhelmingly to reflect her own impressions. Some quite complex cultural situations and dynamics are too sweepingly summed up. Critical insights into communities are often left hanging, with litde to substantiate them, and at times they almost appear to communicate a lack of respect for the people being studied. While Bennion claims to be insider in the Mormon faith, she makes too many doctrinal and cultural mistakes to be considered insider by active members of the Church of Jesus Christ of Latter-day Saints (Mormon). A temple is not used, as she claims, for Sunday worship (118); a widower marrying again does not call his wife his handmaid (115); marrying into certain families does not provide an instant place in the kingdom in this life or the next (112). The church views the Saints in Colonia Juarez as it does Latter-clay Saints elsewhere in the world - not as fanatical or lhe most devoted and valiant (120). As to Colonia LeBaron, the author devotes much time to its religious doctrine, but fails to say that the people who live there are not members of the Church of Jesus Christ of Latter-day Saints. …

Plant facilitation in extreme environments: The non-random distribution of saguaro cacti ( Carnegiea gigantea) under their nurse associates and the relationship to nurse architecture

This study samples 247 saguaros ( Carnegiea gigantea) and their nurses in 30 populations in the northern Sonoran Desert to determine whether saguaros are randomly distributed beneath their nurses’ canopies. Saguaro–nurse association patterns are compared across three nurse groups distinguished by canopy architecture characteristics (leguminous trees, small dense Ambrosia spp. shrubs, and the larger, open-canopied shrub Larrea tridentata). For all three nurse types, saguaros are significantly clustered near the center of their nurse's base. Clustering varies with nurse architecture, as saguaros are most tightly clumped under the most open-canopied species ( L. tridentata), as more than 80% of saguaros were under the innermost 10% of L. tridentata's subcanopy area. Saguaros showed the least basal clustering about tree nurses, though not significantly less than Ambrosia spp. nurses. More saguaros establish under Ambrosia relative to its cover in sampled populations, while saguaros were underrepresented under L. tridentata. All analyses suggest that L. tridentata is an inferior nurse for saguaros. Different canopy architecture influences the extent of ground available to a nursed species to benefit from, for establishment and survival. While herbivory, rodents or other factors may play a role in these patterns, ultimately microclimate differences are the most likely factor shaping cacti–nurse associations in the harsh desert environment.

Effects of dehydration on plasma osmolality, thirst-related behavior, and plasma and brain angiotensin concentrations in Couch's spadefoot toad, Scaphiopus couchii.

Under dehydrating conditions, many terrestrial vertebrates species exhibit increases in plasma osmolality and their drinking behavior. Under some circumstances, this behavioral change is accompanied by changes in plasma and central angiotensin concentrations, and it has been proposed that these changes in angiotensin levels induce the thirst-related behaviors. In response to dehydration, the spadefoot toad, Scaphiopus couchii, exhibits thirst-related behavior in the form of cutaneous drinking. This behavior has been termed water absorption response (WR) behavior. Spadefoot toads live in harsh desert environments and are subject annually to dehydrating conditions that may induce thirst-related behavior. We tested the hypothesis that an increase in WR behavior is associated with both an increase in plasma osmolality and an increase in plasma and brain angiotensin concentrations. First, we determined the degree of dehydration that was necessary to initiate WR behavior. Animals dehydrated to 85% of their standard bladder-empty weight via deprivation of water exhibited WR behavior more frequently than control toads left in home containers with water available. Next, using the same dehydration methods, we determined the plasma osmolality and sodium concentrations of dehydrated toads. Toads dehydrated to 85% standard weight also had a significant increase in plasma osmolality, but exhibited no overall change in plasma sodium concentrations, indicating that while an overall increase in plasma osmolality appears to be associated with WR behavior in S. couchii, changes in sodium concentrations alone are not sufficient to induce the behavior. Finally, plasma and brain angiotensin concentrations were measured in control toads and toads dehydrated to 85% standard weight. Plasma and brain angiotensin concentrations did not increase in dehydrated toads, indicating that dehydration-induced WR behavior that is associated with changes in plasma osmolality may not be induced by changes in endogenous angiotensin concentrations in S. couchii.