Hyper-arid Ecosystem Research Articles

Inter- and intrapopulation variation in the response of tree seedlings to drought: physiological adjustments based on geographical origin, water supply and species.

Initiatives to restore natural ecosystems have had little success in arid and hyperarid ecosystems. In this context, the natural seedling establishment is particularly affected by drought patterns and climatic variability. Likewise, the effect of plant provenance on forest restoration success remains unclear, although previous studies have concluded that some seed locations might be better able to tolerate water stress. In this study, we examined the physiological mechanisms involved in the drought stress resistance of Prosopis tamarugo and Prosopis alba seedlings from different arid and hyperarid locations of the Atacama Desert in northern Chile. We measured the xylem water potential (Ψ), cuticular transpiration (Ec), specific leaf area (SLA) and pressure-volume curves at the intrapopulation and interpopulation levels of seedlings of both species subjected to three drought-induced treatments. In addition, plant characteristics such as seedling height (Sh), stem diameter (Sd), leaf biomass (Lb), root biomass (Rb) and seedling survival (Ss) were measured during the treatments. Seedlings of most hyperarid habitats had the highest values of Ψ and water content relative to the turgor loss point, as well as decreased SLA, especially during the strongest drought treatment. Ψ was strongly correlated with Sh in both species, and soil humidity was correlated with Sd. This study highlights the high variability of physiological responses to water stress in both species at the interpopulation and intrapopulation levels, which provides us with a powerful seed selection tool for future reforestation programmes aimed at the early selection and genetic improvement of species of the Prosopis genus.

Environmental tastes as predictors of environmental opinions and behaviors

We develop a novel way to assess how individuals perceive and utilize their local environment. Specifically, we query local residents in Scotland’s Cairngorms National Park regarding their preferences for different characteristics of their environment and examine how these preferences correlate with environmental behaviors and opinions. We identify groupings of preferred characteristics as distinct environmental tastes that, drawing upon Bourdieu's theory of taste, represent general dispositions, preferences, or orientations regarding the environment. We then test whether these tastes are useful for explaining environmental behaviors and opinions.We introduced this idea previously using survey data drawn from residents of a hyper-arid ecosystem. Here, we seek to establish whether our framework has potentially universal applications generalizable to other socio-ecological settings. We analyze survey data collected from inhabitants of the Cairngorms and, using data reduction methods, identify four distinct environmental tastes. We demonstrate how tastes constitute significant correlates of private sphere environmental behavior, engagement in outdoor activities, opinions about development, perceived economic benefit from the environment, and environmental concerns.Environmental tastes defined for the Cairngorms are similar to those drawn from previous research and we find several parallels between the two different settings in the associations between tastes and opinions and behavior. There are similarities in the way individuals with certain profiles of environmental tastes are more inclined to have certain opinions and to engage in certain activities. We suggest that tastes can be elucidating for understanding diverse preferences for environmental characteristics and their broader implications for how humans interact with the landscape.

Antarctic microbial communities are functionally redundant, adapted and resistant to short term temperature perturbations

Climate change has the potential to induce dramatic shifts in the biodiversity and functionality of soil microorganisms in polar hyperarid ecosystems. In these depauperate soil ecosystems, microbial communities are vital as they represent the dominant input sources of essential nutrients. However, the effects of changing climate on extreme edaphic environments, such as the McMurdo Dry Valleys of Antarctica, remain poorly understood. To better understand these effects, we constructed soil microcosms and simulated temperature shifts over a 40-day period. Soil physicochemical analysis revealed low levels of key nutrients, with mean organic carbon and nitrogen contents of <0.1% and 11.55 ppm, respectively. We also applied 16S rRNA gene amplicon sequencing to determine taxonomic composition and enzyme assays to measure in situ activity. Our data showed a prevalence of ubiquitous soil taxa (Actinobacteria, Chloroflexi and Deinococcus-Thermus), with a smaller proportion of autotrophic phyla (i.e. Cyanobacteria). None of the major phyla showed relative abundance changes in response to temperature. We found very low extracellular enzyme activity levels across all samples and observed no significant differences among temperature treatments. Functional predictions (using PICRUSt) revealed the putative presence of key genes implicated in the cycling of carbon (ppc, rbcl) and nitrogen (nifH, nirK), in stress response and in DNA repair throughout all treatments. Overall, our results suggest that short-term temperature fluctuations do not alter microbial biodiversity and functionality in Antarctic soils. This study provides the first evidence that microbial communities within this edaphic extreme environment may be functionally redundant, adapted and resistant to short term climatic perturbations.

The contribution of soil biogenic NO and HONO emissions from a managed hyperarid ecosystem to the regional NO&amp;lt;sub&amp;gt;&amp;lt;i&amp;gt;x&amp;lt;/i&amp;gt;&amp;lt;/sub&amp;gt; emissions during growing season

Abstract. A study was carried out to understand the contributions of soil biogenic NO emissions from managed (fertilized and irrigated) hyperarid ecosystems in NW China to the regional NOx emissions during the growing season. Soil biogenic net potential NO fluxes were quantified by laboratory incubation of soil samples from the three dominating ecosystems (desert, cotton, and grape fields). Regional biogenic NO emissions were calculated bottom-up hourly for the entire growing season (April–September 2010) by considering corresponding land use, hourly data of soil temperature, gravimetric soil moisture, and fertilizer enhancement factors. The regional HONO emissions were estimated using the ratio of the optimum condition ((FN,opt(HONO) to FN,opt (NO)). Regional anthropogenic NOx emissions were calculated bottom-up from annual statistical data provided by regional and local government bureaus which have been downscaled to monthly value. Regional top-down emission estimates of NOx were derived on the monthly basis from satellite observations (OMI) of tropospheric vertical NO2 column densities and prescribed values of the tropospheric NOx lifetime. In order to compare the top-down and bottom-up emission estimates, all emission estimates were expressed in terms of mass of atomic nitrogen. Consequently, monthly top-down NOx emissions (total) were compared with monthly bottom-up NOx emissions (biogenic + anthropogenic) for the time of the satellite overpass (around 13:00 LT) with the consideration of the diurnal cycle of bottom-up estimates. Annual variation in total Tohsun Oasis NOx emissions is characterized by a strong peak in winter (December–February) and a secondary peak in summer (June–August). During summer, soil biogenic emissions were from equal to double that of related anthropogenic emissions, and grape soils were the main contributor to soil biogenic emissions, followed by cotton soils, while emissions from the desert were negligible. The top-down and bottom-up emission estimates were shown to be useful methods to estimate the monthly/seasonal cycle of the total regional NOx emissions. The resulting total NOx emissions show a strong peak in winter and a secondary peak in summer, and the second maximum in summer was only found if the soil emissions were taken into account, which provides confidence in both completely independent methods. Despite the regional character of these findings, particularly the second maximum in summer provides substantial evidence to hypothesize that biogenic emissions from soils of managed drylands (irrigated and fertilized) in the growing period may be much more important contributors to regional NOx budgets of dryland regions than thought before.

Dung Beetle (Coleoptera: Scarabaeidae) Abundance and Diversity at Nature Preserve Within Hyper-Arid Ecosystem of Arabian Peninsula

Coprophagous beetles (Coleoptera: Scarabaeidae) play an important ecological role in the management of grazing and cycling of nutrients within different ecosystems. Seasonal abundance, species richness, and alpha diversity of the dung beetles were investigated in Rawdhat Khorim Nature Preserve in the central Kingdom of Saudi Arabia (KSA). Adult beetles were trapped using UV light traps biweekly from November 2011 to October 2012 (for a total of 24 nocturnal trap samples). A total of 2,982 dung beetles were caught, representing 22 species in nine genera belonging to the subfamilies of Aphodiinae and Scarabaeinae. The total catch was dominated (58%) by Aphodius pruinosus Reitter and Aphodius wollastoni iranicus Balthasar, with the Aphodiinae constituting 94% of the total beetle richness. Most of the dung beetle species were dwellers (20 species). Aphodius luridus (F.) and Granulopsammodius plicatulus (Fairmaire) are new records for KSA. Abundance, richness, and alpha diversity of dung beetles peaked during spring. Alpha diversity increased with higher average air temperatures. Dung beetle abundance was positively correlated with the normalized difference vegetation index. Two clusters of species phenology were apparent, a summer-active group and those not active during the summer months. Our findings may enhance the understanding of dung beetle ecology in the rawdhat network within hyper-arid ecosystems of Arabian Peninsula and sustainable management of dung beetles for nutrient reincorporation through the consumption and storage of dung in the soil.

Metagenomic analysis provides insights into functional capacity in a hyperarid desert soil niche community

In hyperarid ecosystems, macroscopic communities are often restricted to cryptic niches, such as hypoliths (microbial communities found beneath translucent rocks), which are widely distributed in hyperarid desert environments. While hypolithic communities are considered to play a major role in productivity, the functional guilds implicated in these processes remain unclear. Here, we describe the metagenomic sequencing, assembly and analysis of hypolithic microbial communities from the Namib Desert. Taxonomic analyses using Small Subunit phylogenetic markers showed that bacterial phylotypes (93%) dominated the communities, with relatively small proportions of archaea (0.43%) and fungi (5.6%). Refseq-viral database analysis showed the presence of double stranded DNA viruses (7.8% contigs), dominated by Caudovirales (59.2%). Analysis of functional genes and metabolic pathways revealed that cyanobacteria were primarily responsible for photosynthesis with the presence of multiple copies of genes for both photosystems I and II, with a smaller but significant fraction of proteobacterial anoxic photosystem II genes. Hypolithons demonstrated an extensive genetic capacity for the degradation of phosphonates and mineralization of organic sulphur. Surprisingly, we were unable to show the presence of genes representative of complete nitrogen cycles. Taken together, our analyses suggest an extensive capacity for carbon, phosphate and sulphate cycling but only limited nitrogen biogeochemistry.

Use of Spatial Analysis to Test Hypotheses on Plant Recruitment in a Hyper-Arid Ecosystem

Mounds originating from wind-blown sediment accumulation beneath vegetation (nebkhas) often indicate land degradation in dry areas. Thus far, most nebkha research has focused on individual plants. Here, we aimed to explore population-scale processes (up to scales of about 100 m) that might explain an observed nebkha landscape pattern. We mapped the Rhazya stricta Decne. population in a 3 ha study site in a hyper-arid region of Saudi Arabia. We compared the spatial patterns of five different cohorts (age classes) of observed nebkha host plants to those expected under several hypothesized drivers of recruitment and intraspecific interaction. We found that all R. stricta cohorts had a limited fractional vegetation cover and established in large-scale clusters. This clustering weakened with cohort age, possibly indicating merging of neighboring vegetation patches. Different cohort clusters did not spatially overlap in most cases, indicating that recruitment patterns changed position over time. Strong indications were found that the main drivers underlying R. stricta spatial configurations were allogenic (i.e. not driven by vegetation) and dynamic. Most likely these drivers were aeolian-driven sand movement or human disturbance which forced offspring recruitment in spatially dynamic clusters. Competition and facilitation were likely active on the field site too, but apparently had a limited effect on the overall landscape structure.

Differences in Perceptions, Attitudes, and Use of Ecosystem Services among Diverse Communities in an Arid Region: A Case Study from the South of Jordan

The aim of this study was to understand how local people interact with their surrounding ecosystem. The researchers focused on a dry terrestrial environment (Wadi Araba and Aqaba in southwest Jordan) and analyzed an assortment of communities in order to reveal how different groups perceive and use their environment in varying ways. The analytical tools in this study—derived from the social sciences—included preliminary interviews and a field survey of 150 randomly selected respondents from Wadi Araba (rural) and Aqaba (urban). The survey, based on a structured questionnaire, consisted of eight sets of nested multiple choice questions focusing on respondents’ perceptions of, and attitudes toward, the surrounding hyper-arid ecosystem. Responses from rural residents reflected a greater average concern of, and awareness toward, their environment than responses from urban residents.

Seasonal diet of the burrowing owl Athene cunicularia Molina, 1782 (Strigidae) in a hyperarid ecosystem of the Atacama desert in northern Chile

Located in the Atacama desert of northern Chile, Pampa del Tamarugal is a hyperarid ecosystem characterized by extreme arid conditions (<0.7 mm of annual precipitation) and relatively scarce vegetation, dominated by arboreal species of Prosopis tamarugo. These unfavorable environmental conditions can affect the quantity and diversity of prey available for carnivores, making Pampa del Tamarugal an interesting environmental scenario for the study of the trophic ecology of raptors. Our analyses of the seasonal diet of the burrowing owl Athene cunicularia (Molina, 1782) indicate that insects and scorpions were the most common prey (58.3% and 27.5%, respectively). However, the rodent Phyllotis darwini was the most important prey in biomass (49.5%). Significant differences were observed in diverse trophic statisticians between summer and winter seasons. Unlike similar studies carried out in arid areas of South America and North America, we observe that the diet of the burrowing owl in Pampa del Tamarugal shows a higher trophic niche breadth and trophic diversity, but a lower species-prey richness.

Trophic interactions between two medium-sized mammals: the case of the native Dolichotis patagonum and the exotic Lepus europaeus in a hyper-arid ecosystem

As medium-sized herbivores, the exotic Lepus europaeus (European hare) and the native Dolichotis patagonum (mara) have been considered ecological equivalents. These species coexist in Ischigualasto Provincial Park, a hyper-arid ecosystem with scarce food resources. Our objective was to evaluate diet composition, relationship between diets and food availability, and trophic relationships between both herbivores. Collection of feces and vegetation sampling were made in the Mesquite woodland community. Diet composition was analyzed by microhistological analysis of feces. In both seasons, shrub species represented the most abundant cover type in the area, and annual forbs and grasses appeared in the wet season. Herbivores showed similar dietary ecology: shrubs were the main food items along the year, showing a higher plasticity compared to their diets in other ecosystems, where they selected mostly grasses. The mara selected shrubs such as Atriplex sp. and Prosopis torquata, whereas the European hare selected Cyclolepis genistoides, Atriplex sp., and Bulnesia retama. During the wet season, both herbivores supplemented their diets with grasses and annual forbs. In the dry season, there was increased consumption of cacti, such as Tephrocactus sp. The mara and the European hare are likely close ecological equivalents, in terms of dietary similarity, and they showed strong dietary overlap across the dry season (over 60 %). Thus, we can assume the existence of a potential trophic competition between mara and European hare, especially during the season when food resources are scarce. These results can be important for the management of drylands in South America, where populations of threatened herbivorous species, such as the mara, coexist with exotic animals, sharing spatial and trophic resources even in protected areas.

Natural history of coastal Peruvian solifuges with a redescription of Chinchippus peruvianus and an additional new species (Arachnida, Solifugae, Ammotrechidae)

Two species of Chinchippus (Ammotrechidae) were studied in central Peru. Both species are endemic to the hyper-arid coastal desert and appear to derive most of their energy and nutrients from maritime prey, such as intertidal amphipods feeding on beach-cast algae or as arthropod scavengers feeding upon seabird and pinniped carcasses. Data on the spatial distribution of the two species were obtained from analyzing stomach contents of one common predator, the gecko Phyllodactylus angustidigitus, and suggest that both species are more abundant in insular than in mainland habitats. We redescribe Chinchippus peruvianus Chamberlin 1920, known only from a female specimen and describe the male for the first time while C. viejaensis is recognized as new. The new species is distinguished from C. peruvianus by its darker coloration, smaller size, and differences in cheliceral dentition. In the process of investigating the ecology of terrestrial organisms in the coastal desert and guano islands of central Peru, we have come across a series of Chinchippus peruvianus Chamberlin 1920 and a closely related species. These solifuges, along with other terrestrial predators, thrive in places that could be defined as a barren land of gravel, sand, and granitic outcrops - a moonscape where arachnids and lizards somehow manage to survive, reproduce, and colonize new habitats. The western coast of South America is among the driest places on Earth (Dietrich & Perron 2006), where arid conditions have persisted for the last 14 million years (Alpers & Brimhall 1988). Facing this hyper-arid ecosystem is one of the world's most productive marine ecosystems, the Peru-Chile cold current (Tarazona & Arntz 2001). The stark contrast in productivity promotes the exchange of energy and nutrients between these two adjacent ecosystems, and marine-derived resources subsidize terrestrial predators along the Peruvian coast (Catenazzi & Donnelly 2007a) and in other coastal deserts (Polis & Hurd 1996). In this study we describe the taxonomy and natural history of the two Chinchippus species and explore their distribution in relation to the availability of marine-derived resources. The genus Chinchippus was established by Chamberlin (1920) based on a single female from the Peruvian island of Chincha. He considered it to belong to the African family Daesiidae. Roewer (1934) included Chinchippus in the ammotrechid subfamily Saronominae based on the segmenta- tion of legs I, II, and IV and the palpal spination. Muma (1976) tentatively included it with the saronomines although its placement was still based on Chamberlin's sole female. Based on Chamberlin's single female, the genus Chinchippus can be recognized by: all the legs having a single tarsal segment, no claws on leg I, stridulating ridges on the mesal surface of the chelicera, lateral plates of the ''rostrum'' shorter than the median plates, and a recurved cephalothorax.

Distribution and activity of hypolithic soil crusts in a hyperarid desert (Baja California, Mexico)

Widespread and ecologically important, biological soil crusts include those microbial communities living on the surface of the soil and those that live beneath semitranslucent rocks (a.k.a. hypolithic crusts). We examined the distribution, abundance, physiology, and potential soil N contributions of hypolithic, biological crusts in hyperarid ecosystems of the Baja California peninsula and islands in the midriff region of the Gulf of California, Mexico (Sonoran desert). Crusts were limited in distribution to areas with translucent quartz rocks less than 3 cm thick, were not found on areas of islands with seabird guano deposition, but covered as much as 1% (12,750 m2) of the surface area of one island. The percent of available rocks colonized by crusts was similar between the mainland (38%) and islands without seabird guano (26%). Carbon fixation rates in the field, which have not been previously reported, ranged between 0 and 1.23 μmol m−2 s−1, and in the lab ranged between 0.66 and 0.94 μmol m−2 s−1. Evidence of low rates of N fixation was inferred from δ15N values of crust and soil. Hypolithic crusts were found to have minimal, if any, influence on soil salinity, pH, and \( {\text{NO}}^{ - }_{3} \), but may represent up to 14% of the biomass of primary producers on these islands and provide C and N to the belowground and possibly aboveground heterotrophic communities where crusts exist. The results of this study suggest a limited but potentially important contribution of hypolithic soil crusts to hyperarid ecosystems.

Soils and Brine Geochemistry and Mineralogy of Hyperarid Desert Playa, Ouargla Basin, Algerian Sahara

The Ouargla basin is located in hyperarid north Africa and characterized by an endoreic landscape (playa) with Solonchak (accumulated soluble salts) and Gypsisol (accumulated gypsum) soils, and subsurface groundwater. The chemical and mineralogical specificity of this hyperarid ecosystem has been compared to other areas under arid environment (Tunisian sub-Sahara and Algerian steep-lands). Chemical data on the major and minor elements, such as Sr2+, were obtained, and geochemical studies of groundwater, soil solution samples and brines have been performed. In total, 84 samples (42 groundwater, 39 soil solutions, 3 brines) were collected. X-ray diffraction and micromorphological observations (SEM with microprobe) were also performed in order to analyze soils and efflorescence. The concentrations of chemical components showed a strong variability (standard deviation of 1.15 for Cl− and 1.08 for Na+) which was reduced by an increasing ratio between concentrated and diluted samples. The Principal Component Analyses showed that an increase in the concentration of soluble ions was responsible for 56% of the total variance. When the soluble salt concentration increased, the chemical composition changed from Ca-sulfate dominance to Na-chloride dominance. Thermodynamic equilibrium data indicated that these salt solutions were controlled by the following precipitation sequence: calcite > gypsum > mirabilite > halite. This sequence was confirmed by X-ray diffraction and micromorphology. Genesis of dehydrated forms of CaSO4 · 2H2O were recognized by: (1) partial dehydration of gypsum by sun radiation on the soil surface, and (2) a decrease in water activity (<1) relating to an increase in ionic strength (>3 molc kg−1 of H2O) of concentrated solutions. The presence of mixed sulfates (glauberite, bloedite, and others) appears to be a distinctive feature of the hyperdesert soil. In this environment they are more stable than simple sulfates. A discrete mineral involving a minor element was observed, and celestite (SrSO4) was thermodynamically predicted. This mineral results from the coprecipitation of Sr2+ with gypsum. Micromorphologically, celestite crystals occur as inclusions and within the periphery of gypsum crystals. The seasonal and daily thermal amplitudes in the desert environment determine the precipitation pattern into the Na–Ca–SO4–H2O system (mirabilite-thenardite-halite paragenesis), controlling the process of dissolution/ precipitation of gypsum. The hyperarid environment has a remarkable chemical and mineralogical reactivity because of the high solubility and hydration status of minerals, and its sensitive reactivity to climate variation. Based on these results, dehydrated CaSO4 is proposed as a diagnostic pedological criterion for delineating hyperarid and arid ecosystems.