Desert Mountain Research Articles

Social interaction between the coast and the highlands of Chile's arid north (20°S) during the mid‐Holocene: The case of Vicugna vicugna (Molina, 1782) and Hippocamelus antisensis (d'Orbigny, 1834)

AbstractThis article discusses the archaeological implications of the discovery of the highland species Hippocamelus antisensis (Cervidae) and Vicugna vicugna (Camelidae) in two coastal contexts in the Atacama Desert (20°S, Chile). H. antisensis is currently distributed throughout the Peruvian Andes, northern Chile, western Bolivia and northwestern Argentina, between 1800 and 5500 m above sea level. V. vicugna is distributed throughout northern Peru and northwestern Argentina, in environments that exceed 3200 m above sea level. The archaeological record of deer antlers on the Atacama coast has previously been documented at the Caleta Huelén‐42 site (21°S). In the case of V. vicugna, fibers have been recovered only at the coastal site of Camarones‐14 (19°S). A dating of 4180 ± 20 year BP obtained from V. vicugna bone and indirect dating of the antlers suggest an early social exchange between groups from coastal regions and those from the Atacama Desert Mountain range, as well as encourage to the potential record of remains/products of these animals in areas far from their natural habitats.

Precious and Base Metal Minerals in Black Sands of the Egyptian Mediterranean Coast: Mineralogical and Geochemical Attributes

This paper investigates the mineralogical and geochemical characteristics, as well as the possible sources, of gold, silver, platinum group elements (PGE), copper, and lead found in the beach sands along Egypt’s Mediterranean coast. Using scanning electron microscopy and electron probe micro-analysis, this study determines the morphology and micro-chemistry of separated grains to assess their economic potential and how various minerals respond to different transport distances. The analysis reveals that gold grains are of high purity (94.11 to 98.55 wt.%; average 96 wt.% Au) and are alloyed with Ag (1.28–2.32 wt.%) and Cu (0.16–3.15 wt.%). Two types of gold grains were identified, indicating differences in transport distances. Variations in morphology, surface features, inclusion types, rims, and chemistry of the native metals, including gold grains, suggest differences in composition, weathering degree, transport distance, deposit types, and host rocks. The average Ag concentration in gold grains (1.86 wt.%) suggests a link to mesothermal or supergene deposits. Most silver, copper, and lead grains are spherical, with some variations in shape. Silver grains have 71.66–95.34 wt.% Ag (avg. 82.67 wt.%). Copper grains have 92.54–98.42 wt.% Cu (avg. 94.22 wt.%). Lead grains contain 74.22–84.45 wt.% Pb (avg. 79.26 wt.%). The identified platinum group minerals (PGM) belong to the Pt–Fe alloys and sperrylite, both of which are PPGE-bearing minerals. These metals likely originate from the weathering of upstream Nile tributaries surrounded by igneous and metamorphic rocks from Ethiopian and Central African regions, with a minor contribution from the Egyptian Eastern Desert Mountains.

The Geomechanics of the Dangkhar Landslide, Himachal Pradesh, India

The Dangkhar Landslide is an extremely large landslide located in the Spiti Valley of Himachal Pradesh, India. The landslide is situated in a remote high mountain desert within the Tethys Himalaya at elevations between 3400 m and 5600 m. It is amongst the five largest continental landslides on earth, covering an area of approximately 54 km2 and having an estimated volume of 15–20 km3. Geomechanical evaluations based on the block theory indicate that the Dangkhar Landslide formed as a result of unfavorable combinations of structural geological features and complex surface morphology. A massive kinematically removable block is created by a regional synclinal flexure that is crosscut and kinematically liberated by bounding side valleys. Three-dimensional block kinematics are necessary to permit the release of the giant block and its sliding along the synclinal flexure. Pseudostatic slope stability sensitivity analyses incorporating estimates of site seismicity and shear strength parameters suggest that earthquake shaking could have triggered instability if the static factor of safety was less than or in the range of about 1.5–1.9. Considering the glacial history of the region, ice debuttressing represents an additional potential triggering mechanism.

Blow flies (Diptera: Calliphoridae) of the Baja California Peninsula.

The blow fly fauna of the Baja California peninsula, Mexico has been sparsely documented. This study incorporates and lists recent and historical records of blow flies from collecting trips throughout the peninsula, visits to major southern California museums for historical collection records, and a literature search. Seven genera and 16 species are reported from the two peninsular Mexican States, Baja California, and Baja California Sur. Three species are recorded that are not included in the 2020 Catalog of Mexican Calliphoridae by Jaume-Schinkel, & Ibanez-Bernal (2020), they are: Calliphora livida, Calliphora terraenovae, and Calliphora vomitoria. One blow fly species, Cochliomyia hominivorax (the primary Screw-Worm Fly) is not included here but is found in museum collections. Once present in Baja, it is considered eradicated from continental North America as far south as the Panama Canal by the U.S. Department of Agriculture (USDA) however, it is occasionally reintroduced (Skoda et al. 2018) and is still present in some Caribbean islands. It is noteworthy that all calliphorid species from this mountainous desert peninsula are also found in the State of California, USA which supports 11 genera and 47 species in this family (Whitworth 2006) primarily because of its more varied climate and terrain. The Baja peninsula can be considered a southern extension of the State of California, with reduced species representation due to reduced climate and terrain variation, so no separate identification keys are necessary. Forensic entomologists and taxonomists can use the blow fly keys for North America by Whitworth, 2006, and 2017 for this region. The latest key by Jones, Whitworth, and Marshall (2019) is revolutionary and much welcome in taxonomy in that it is an online computer-aided key that has actual macro-photos of species identification characters and is intended to be used with a computer screen next to your microscope for identifications in place of printed material.

An Analysis of the Main Nutrient Components of the Fruits of Different Macadamia (Macadamia integrifolia) Cultivars in Rocky Desertification Areas and a Comprehensive Evaluation of the Mineral Element Contents

This study aims to understand the main nutrient composition and comprehensively evaluate the differences in the mineral element contents of fruits of different macadamia cultivars, as well as screen good cultivars that are suitable for use in rocky desert mountains. Nine macadamia nut cultivars were selected as test materials in rocky desert mountain orchards. The contents of crude fat, crude protein, and total soluble sugar in kernels and N, P, K, Ca, Mg, Fe, Mn, Cu, Zn, and B in peels and kernels were determined, respectively. Then, the kernels’ mineral element contents were comprehensively evaluated based on principal component analysis. The results showed that the kernels were rich in crude fat, protein, and soluble sugar, with the crude fat content reaching 75% or greater, and the variation among cultivars was small. However, the variation in soluble sugar content was extensive. The content of mineral elements varied in different cultivars and parts of the fruit, with the average macronutrient content being K > N > Ca > P > Mg in the pericarp and N > K > P > Mg > Ca in the kernel, and the content of micronutrients in the pericarp and the kernel being Mn > Fe > Zn > Cu > B. By principal component analysis, the 10 mineral nutrient indexes were calculated as four principal components, with a cumulative contribution rate of 88.051%. Using the affiliation function value method and the calculation of the comprehensive evaluation value, the nine cultivars could be classified into three categories. The cultivar with the highest comprehensive evaluation value of the mineral element content was O.C. The one with the lowest value was H2, which indicated that O.C is a suitable variety for popularization in rocky desert mountainous areas. Stepwise regression analysis concluded that P, K, Fe, Mn, and Cu were the indicators significantly influencing the mineral element content of macadamia nuts and fruits in rocky desert mountains.

Three Decades of Oasis Transition and Its Driving Factors in Turpan–Hami Basin in Xinjiang, China: A Complex Network Approach

As a predominant ecosystem-providing area and distinctive landscape in arid regions, an oasis plays an important role in maintaining land stability, human production, and daily activities. Studying the dynamics of oasis and its driving factors is vital to supporting arid regions’ sustainable development. As a typical mountain–desert–oasis landscape, the Turpan–Hami (Tuha) Basin, located in Xinjiang, China, includes complex interactions among different land types. For this study, we revealed the spatio-temporal patterns and transition processes of the oasis using a complex network method between 1990 and 2020 in the Tuha Basin. In the oasis transition network, the degree value, betweenness centrality, and average path length were calculated to express the transition relationship, key oasis type, and oasis structural stability, respectively. Six factors related to climate change and human actives were selected to investigate the driving forces behind oasis transitions, including the average temperature and precipitation in the growing season, the total power of agricultural machinery (TAMP), the production of raw coal (PRC), the total output value of the plantation industry (TPI), and the population (Pop). Our results show that the oasis area of the Tuha Basin, including the natural oasis and artificial oasis, all grew from 1990 to 2020, with the natural oasis expanding more than the artificial oasis. The transitions between oasis types became more frequent as the area of oasis land types increased throughout the study period. Grassland acted as the most important oasis type in the network, with the highest betweenness centrality, but its importance declined due to the increasing complexity of the oasis transition network from 1990 to 2020. The transitions between oasis types became simpler, and the oasis structural stability decreased. Through driving force analysis, the oasis changes showed a positive correlation with the temperature (p-value < 0.05, r = 0.88), and urbanization and industrialization factors prompted transitions to built-up areas and cropland from grassland and shrubland. In summary, our results suggest that to create a harmonious symbiotic relationship between the natural environment in dryland and human activities, preventing grassland degradation and excessive reclamation of land cover is an available way. Meanwhile, the protection of shrubland and water resources is also important. This study provided reference and theory support for promoting the sustainable development of oases.

Functional diversity and carbon storage of plant community elevation patterns and carbon accumulation mechanisms in desert shrubland of Yanqi Hola Mountain, China

Exploring the distribution characteristics of plant community functional diversity, functional traits and plant and soil carbon stocks along elevation and the effects of functional diversity and functional traits on carbon stocks is of great significance for revealing the distribution characteristics of plant community functional diversity and carbon stocks in the desert area and understanding the carbon accumulation mechanism. In this study, we took the leaf functional traits of plant community species and the carbon stocks of plants and soils of sample plots in the pre-Hola Mountain desert area as the research objects and explored their altitudinal distribution characteristics and their interrelationships. The results showed that (1) the plant carbon storage capacity of the shrub - herb association was the strongest, and the soil carbon storage capacity of the herb association was the strongest. (2) Functional richness and plant carbon storage capacity tended to increase and then decrease with elevation, while functional evenness and leaf phosphorus content tended to decrease and then increase with elevation. Functional dispersion, leaf water content, chlorophyll content, leaf carbon, nitrogen content, and soil carbon stock all showed a gradual increase with elevation, and the total carbon stock gradually increased with elevation in the middle and low elevation areas (1200–1800 m), and showed a wave-like change in the high elevation areas (1800–2400 m). (3) The accumulation of soil carbon stocks in the study area is mainly dominated by the “mass ratio hypothesis”, while the accumulation of plant carbon stocks is mainly dominated by the “ecological niche complementarity hypothesis”, and plant and soil carbon stocks are mainly affected by the specific leaf area and the content of carbon, nitrogen, and phosphorus in leaves.

Salinity matters the most: How environmental factors shape the diversity and structure of cyanobacterial mat communities in high altitude arid ecosystems.

Microbial mats are complex communities of benthic microorganisms that occur at the soil-water interphase in lakes' shores, streams, and ponds. In the cold, mountainous desert of Eastern Pamir (Tajikistan), where scarce water bodies are influenced by extreme environmental conditions, photosynthetic cyanobacteria form diverse mats. The mats are characterized by different morphology and thickness. Their habitats exhibit a wide range of conditions; from oligosaline to hypersaline, oligotrophic to hypertrophic, and from cold ponds to hot springs. The aim of the present study was to reveal the taxonomic composition and structure of these mats and to examine which environmental factors influence them. Fifty-one mats were collected from small water bodies around Bulunkul, Karakul, and Rangkul Lakes in 2015 and 2017. The physical and chemical properties of the water were measured in situ, while the concentration of nutrients was analyzed ex-situ. To reveal the taxonomic composition of the mats, the hypervariable V3-V4 region of the 16S rRNA gene was examined using NGS technology. The results of bioinformatic analyses were compared with microscopic observations. They showed that Cyanobacteria was the dominant phylum, constituting on average 35% of bacterial ASVs, followed by Proteobacteria (28%), Bacteroidota (11%), and Firmicutes (9%). Synechococcales, Oscillatoriales, and Nostocales orders prevailed in Oxyphotobacteria, with a low contribution of Chroococcales, Gloeobacterales, and Chroococcidiopsidales. Occasionally the non-photosynthetic Vampirivibrionia (Melainabacteria) and Sericytochromatia from sister clades to Oxyphotobacteria were noted in the samples. Moreover, there was a high percentage of unidentified cyanobacterial sequences, as well as the recently described Hillbrichtia pamiria gen. et sp. nov., present in one of the samples. Salinity, followed by Na and K concentrations, correlated positively with the composition and structure of Oxyphotobacteria on different taxonomic levels and the abundance of all bacterial ASVs. The study suggests that the investigated communities possibly host more novel and endemic species. Among the environmental factors, salinity influenced the Oxyphotobacteria communities the most. Overall, the microenvironmental factors, i.e. the conditions in each of the reservoirs seemed to have a larger impact on the diversity of microbial mats in Pamir than the "subregional" factors, related to altitude, mean annual air temperature and distance between these subregions.

Ice Stupas. Ein Projekt zum Wassermanagement im Gebirgsraum

The essay goes into the prototype project called ‘Ice Stupa’. The project was realised in Ladakh (India), a territory in the Indian part of the Himalayas. Specifically, the project is located in the Indus Valley at an altitude of 3500 metres above sea level. Its location under the monsoon rains, behind the first great Himalayan Mountain range, makes the valley a natural high mountain desert. It is, therefore, scorched with little rainfall. The sun shines for about 360 days. The remaining glaciers provide water for living beings and agriculture. Due to the cold at these altitudes, the glaciers only begin to melt in May and only release sufficient water for cultivated land downstream. However, sowing and the start of growth should occur much earlier because plants grow much more slowly at this altitude. The result is an often poor harvest, which further impacts the already difficult living conditions of the Ladakhi people. The ‘Ice Stupa’ project represents an exciting water management solution when the virtuous management of natural resources is a crucial issue. The Ice Stupa system concretises the interaction between architecture and the environment. The essay also presents some projects realised in the Swiss Grisons.

Black bear density and habitat use variation at the Sierra Nevada‐Great Basin Desert transition

AbstractIn the first 2 decades of the twenty‐first century, American black bear (Ursus americanus) populations rebounded with range expansions into areas where the species was previously extirpated. While there are a number of factors that limit range expansion, habitat quality and availability are among the most important. Such factors may be particularly important in western Nevada, USA, at the transition zone of the Sierra Nevada and the Great Basin Desert. We deployed a multi‐faceted data collection system including motion‐sensitive cameras, noninvasive hair sampling and genotyping, and global positioning system (GPS) tracking. We analyzed data using spatial capture‐recapture to estimate population density and dynamic occupancy models to estimate habitat use. Black bear habitat use and density were substantially higher in the Sierra Nevada than the Great Basin Desert and had strong positive relationships with the presence of conifer land cover in the transition zone. The average black bear density was >4 times higher in the mixed‐conifer forests of the Sierra Nevada (12.4 bears/100 km2) than in desert mountain ranges with piñon (Pinus monophylla)‐juniper (Juniperus spp.) woodland (2.7 bears/100 km2). The low‐elevation shrub and grassland portions of the study area had even lower estimated black bear density (0.6 bears/100 km2) and probability of use (0.03, 95% CI = 0.00–0.09). Across these spatially variable configurations in black bear density, we estimated the population size to be 418 individuals (95% CI = 239–740). Declining density towards the range edge, coupled with a relatively stable range of black bears in Nevada observed since 2000, suggests that further species range expansion into the western Great Basin may be limited by habitat quality and availability.

Түркістан облысында агрометеорологиялық жағдайлардың ерекшеліктері

Анализированы тенденции изменения агрометеорологических показателей в Туркестанской области за период с 1991 по 2022 год. Наблюдается тенденция роста суммы температуры воздуха за вегетационный период, тенденция снижения суммы осадков за вегетационный период, тенденция снижения значений коэффициента увлажнения К и индекса засухи ГТК. Такие условия предполагают рост теплообеспеченности вегетационного периода, рост количества жарких дней, снижение влагообеспеченности и усиление засушливости вегетационного периода. Годы с благоприятными погодными условиями имеют повторяемость 30 % в горной полупустынной зоне. Годы с удовлетворительными погодными условиями имеют повторяемость 20% в горной полупустынной зоне и 10 % в горной пустынной зоне. Годы с неблагоприятными погодными условиями имеют повторяемость 100 % в пустынной зоне, 90 % в горной пустынной зоне и 50 % в горной полупустынной зоне.

Snow Cover and Snowline Variation in Relation to Land Surface Temperature in Spiti Valley, Himachal Pradesh, India

Spiti Valley, a cold desert mountain is located in the Trans Himalaya region where snow cover is a dominant type of land cover. Characterized, as a rain shadow area where precipitation occurs in the form of snowfall and almost negligible rainfall. Thus, snowmelt water is a single source of freshwater which is used in agricultural and household activities by mountain dwellers. The main objective of the study is to determine the effects of Land Surface Temperature (LST) on snow cover and snow line position in Spiti Valley. This study is based on geospatial techniques in which Landsat imagery was the main source of data for snow cover, snow line position, and Land Surface Temperature (LST) analysis. It includes Operational Land Imager/Thermal Infrared Sensor (OLI / TIRS) and Thematic Mapper (TM) scenes of the twelve months for the reference years 1990 and 2015. Snow cover was extracted from January to December; using Normalised Difference Snow Index (NDSI). According to NDSI result, the average snow cover was 4, 68,998.50 ha (61.68%) in 1990 and 3, 69,676.4 ha (48.71%) in 2015. Approximately 98,422.08 ha (0.51%) of snow cover was converted into a non-snow cover area at an average rate of 3,937 ha/year. Analysis of the position of the snow line indicates that it moved upward 445.11 meters in Spiti Valley during the study period. In 1990, the snow line was visible at the height of 5,159.37 meters at the end of the summer, but reached at 5,604.48 meters height in 2015, marking the loss of snow accumulation in the lower heights.

Natural Hydrogen: A New Source of Carbon-Free and Renewable Energy That Can Compete With Hydrocarbons

Natural Hydrogen: A New Source of Carbon-Free and Renewable Energy That Can Compete With Hydrocarbons

Assessing the Safety of Settlements from Flood Risk

The fact that Egypt falls within the arid and semi-arid areas, makes it always vulnerable to sudden storms, which have increased significantly during the past ten years. Climate change is one of the factors that cause the increasing of the sudden storms frequency, intensity and expansion to cover new areas. During three days, from November 11 to 13, 2021, a severe storm hit the city of Aswan and its suburbs, leaving behind extensive property damage and loss of life. Where heavy rains, fell in a short time, on the Eastern Desert Mountains led to torrential rains (flash flood) that flowed to the plains through the paths of the valleys, causing severe damage to several villages, which are located in the hydrologically active valleys (Al-Heita, Al-Kimab, Umm Buirat and Abu Al-Rish Qebli). In this paper, the November 2021 storm will be analyzed using Global Precipitation Measurement (GPM) data, with temporal and special resolution of 30 minutes and 0.1^o respectively. The data will give a distribution of the storm for each 1 hour during the storm for three days. The amount of water and its velocity will also be simulated using the (HEC-HMS) hydrological model. In addition, the (HEC-RAC) model is used in order to simulate the distribution and expansion of the flood during the storm time step. The results provide an actual simulation of what happened during the 2021 storm. In addition, this model is applied again with the highest values to produce the worst scenario. The final part of this paper highlights the value of this model as a supportive tool for urban planning to achieve sustainability. So, both results of the simulation and the worst scenario were compared to the development plan of the study area. Then, the suitable planning recommendations were accordingly suggested for the areas at risk to ensure sustainable future development.

Exploring Symbolic Meaning in Landscaping Choices within a Desert City

Metropolitan Phoenix, Arizona, in the Sonoran Desert, provides an excellent opportunity to understand residents’ preferences for desert-adapted xeric landscaping. While much is known about the relationships between sociodemographics and broad environmental values on xeric landscaping choices, the influence of other variables remains unexplored, especially interactions with and attachments to the desert. We therefore examined the influences of recreational visits to local desert mountain parks and symbolic meanings associated with the native desert on household xeric landscaping preferences. Within a larger study, select questions captured socio-demographics, visitation to desert parks and open spaces, place identity, and xeric landscape preferences. Using Ordinary Least Squares (OLS) regression, we confirmed that homeownership and a shorter residency predicted preference for xeric landscapes. Hispanics were less likely to prefer xeric landscaping. Interestingly, the novel factor of identity with the desert significantly and positively predicted xeric landscaping preference while visitation to desert parks and open spaces did not. Findings provide several important management implications. First, Phoenix has an opportunity to foster connections with the surrounding environment through its extensive desert mountain parks. Increasing connections between residents and the parks may help shift personal preferences to xeric yard types. Park managers might also work to further stress how household decisions can affect the desert environment. Second, park visitation alone may not suffice to create connections with the desert environment. Instead, park managers should focus on creating opportunities for visitors to recognize the unique, living aspects of the parks and build personal relationships with the ecosystem. Interpretation encouraging emotional connections to the desert environment may aid in fostering an identity with the desert. In addition, messaging and signage campaigns that link people to the parks may prove a novel way of combatting lawn water usage within desert cities. Given their opportunities to foster place identity, urban parks may be important influencers in promoting native plant landscaping. In conclusion, connecting people to their surrounding environments can influence preferences for similar landscape types at the household level.

A serosurvey for spotted fever group Rickettsia and Coxiella burnetii antibodies in rural dogs and foxes, Chile

Antibodies against Spotted Fever Group (SFG) Rickettsia and Coxiella burnetii, investigated through indirect antibody immunofluorescence tests, were detected in serum samples from 3.1% and 0% of 358 rural dogs, respectively, and in none of 32 wild foxes tested. SFG Rickettsia seropositive dogs were only detected in the Mountain Desert (8%) and the Steppe-Mediterranean (9%) regions. Exposure in the Mountain Desert, where no ticks and fleas were found on any dog, could correspond to a new SFG Rickettsia sp. recently described in soft ticks or to a related agent. Our survey confirms low endemicity in the country of C. burnetii, as observed in recent serosurveys in humans.

Climate Witness: Oral Environmental History and Community-Based Research—A Case Study from Trans-Himalayan India

ABSTRACT On August 5, 2010, a violent cloudburst dumped fourteen inches of rain on Ladakh, a mountain desert region in the far north of India accustomed to getting just three inches of rain in a year. Five years later, flooding recurred on a wider scale, destroying buildings, roads, fields, and orchards all over Ladakh and provoking a wide-ranging discussion among locals about the causes of climate catastrophe. In this essay, we attend to those local voices and allow the people of Ladakh to speak for themselves about the causes and consequences of climate change as well as the best forms of climate change adaptation in the trans-Himalayan region. We offer a two-year progress report on our ongoing oral history fieldwork in this unique and ecologically sensitive high desert region. At the same time, we offer some reflections on the discipline of oral history itself and the promise it offers in conjunction with community engagement to the study of climate change. The surprising fact remains that despite much recent and inspiring work at the compelling intersection of oral and environmental history, few oral historians have taken on directly the subject of climate change, and those who have tend to dwell on the specific experience of the American West. Here we join those few oral and environmental historians who are approaching climate change by way of global community engagement. Only by way of such engagement, we argue—only by following the best practices of what has come to be known as community-based participatory research, can oral history fulfill its public mission as we understand it and contribute decisively to the humanistic study of the Anthropocene.

Предварительный хорологический анализ флоры сосудистых растений горно-тундрового пояса и пояса гольцовых пустынь Хибинских гор (Мурманская область)

Percentage of bio-geographic elements of vascular plants was analysed in Mountain Tundra (MT) and the cold Arctic Mountain (goltzovy) desert (AMD) belts in Khibiny Mountains. Flora of MT (191 species) is richer than flora of AMD (62 species) more than three times. Arctic group of species in MT comprises 42 %, hypoarctic (26 %) and boreal together with polyzonal (32 %). In flora of AMD prevails arctic group of species (63 %), hypoarctic group is on the second place (23 %) and boreal (14 %). The ratio of latitudinal bio-geographical groups in MT corresponds to the hypoarctic type of flora, and in AMD — to the arctic type, that confirms the differentiation of treeless belts in Khibiny Mountains. Groups of species with circumpolar distribution prevail in the species lists of both treeless belts (45 % in MT and 55 % in AMD). Other longitudinal groups in MT include species with east-American-European (10 %), east-American-European-Asiatic (10 %), Euro-Siberian (Euro-Asiatic) (15 %), and European (10 %) distribution. In AMD species with amphi-Atlantic distribution comprise 25 %, species with Euro-Siberian (Euro-Asiatic) and European distribution have less share (8 and 3 %)

Spatial pattern and association of shrub species in gravel hilly and rocky low mountain desert dominated by relict Helianthemum songaricum in China

Helianthemum songaricum is a tertiary relict plant and an endemic species found in the central of Asia. It is the only species of the Cistaceae family found in China and categorized as a rare and endangered one. However, little is known about how this strong xerophytic cushion plant maintains community structure and what are underlying mechanisms. Therefore, the present study investigated the structure and dynamics of H. songaricum desert in the west Ordos of Inner Mongolia Plateau in China by analyzing the intra- and interspecific spatial associations and distribution patterns of the major woody species in two H. songaricum communities with significantly different soil conditions. By using point pattern analysis based on the univariate and bivariate transformations of Ripley’s L function, we revealed that both facilitation and competition acted in the H. songaricum desert, but facilitation occurred more frequently in a more water-stressed rocky habitat than less water-stressed gravel habitat, while the opposite was observed for competition. The whole population of H. songaricum and the individuals of different size classes were distributed randomly and regularly at most of the spatial scales in the gravel habitat, while tended to distribute clearly clumped in the rocky habitat. These differences in spatial distribution patterns of H. songaricum in the two habitats could be related to the differences in the neighborhood effects of intraspecific individuals and other woody species on H. songaricum. The lower number of H. songaricum juveniles and intra- and interspecific competition detected to the juveniles in both H. songaricum communities indicated limited regeneration of H. songaricum population. These findings have important implications for H. songaricum population protection.

Tracking the desert's edge with a Pleistocene relict

In addition to the Sky Islands of the southwestern U.S. and northwestern Mexico, a series of 900–1200 m desert peaks surrounded by arid lowlands support temperate affiliated species at their summits. The presence of disjunct long-lived plant taxa on under-explored desert mountains, especially Isla Tiburón at 29° latitude in the Gulf of California, suggests a more southerly extent of Ice Age woodlands than previously understood. The phylogeography of the desert edge species Canotia holacantha (Celastraceae) was investigated to test the hypothesis that insular desert peak populations represent remnants of Pleistocene woodlands rather than recent dispersal events. Sequences of four chloroplast DNA regions totaling 2032 bp were amplified from 74 individuals of 14 populations across the entire range of C. holacantha as well as nine individuals that represented the other two species in its clade (C. wendtii and Acanthothamnus aphyllus) and two outgroups. Results suggest that a Canotia common ancestor occurred on the landscape, which underwent a population contraction ca. 15 kya. The Isla Tiburón C. holacantha population and the Chihuahuan Desert microendemic C. wendtii have the greatest genetic differentiation, are sister to one another, and basal to all other Canotia populations. Three haplotypes within C. holacantha were recovered, which correspond to regional geography and thus identified as the Arizona, Sonora, and Tiburón haplotypes, within which Acanthothamnus aphyllus is nested rather than as a sister genus. These results indicate a once broad distribution of Canotia/Acanthothamnus when the current peripheral desert ecotone habitat was more widespread during the Pleistocene, now present in relict populations on the fringes of the southern desert, in the Chihuahuan Desert, with scattered populations on desert peaks, and a common or abundant distribution at the northern boundary of the Sonoran Desert. These results suggest Canotia has tracked the shift of the desert's edge both in latitude and elevation since the end of the last Ice Age.