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PubMed2004

Resource pulses, species interactions, and diversity maintenance in arid and semi-arid environments.

Arid environments are characterized by limited and variable rainfall that supplies resources in pulses. Resource pulsing is a special form of environmental variation, and the general theory of coexistence in variable environments suggests specific mechanisms by which rainfall variability might contribute to the maintenance of high species diversity in arid ecosystems. In this review, we discuss physiological, morphological, and life-history traits that facilitate plant survival and growth in strongly water-limited variable environments, outlining how species differences in these traits may promote diversity. Our analysis emphasizes that the variability of pulsed environments does not reduce the importance of species interactions in structuring communities, but instead provides axes of ecological differentiation between species that facilitate their coexistence. Pulses of rainfall also influence higher trophic levels and entire food webs. Better understanding of how rainfall affects the diversity, species composition, and dynamics of arid environments can contribute to solving environmental problems stemming from land use and global climate change.

Biodiversity↗
PubMed2006

Sperm motion characteristics of GarolexMalpura sheep evolved in a semi-arid tropical environment through introgression of FecB gene.

The arid and semi-arid tropical climates of India are endowed with vast diversity of non-prolific sheep breeds. The GarolexMalpura sheep has been evolved in a semi-arid tropical environment by introgression of FecB gene via artificial insemination of Malpura ewes using diluted semen of prolific microsheep Garole and subsequently multiplied by inter se mating among GarolexMalpura halfbreds. The aim of the present study was to identify FecB mutation in sexually mature GarolexMalpura rams by forced RFLP-PCR of BMPR-1B gene and evaluate: (i) semen production and sperm motion characteristics of GM rams and (ii) influence of age and FecB genotype on their semen attributes. Semen was collected during autumn season from 12 donor rams by artificial vagina on 8 occasions at weekly interval. The overall means of traits which did not differed significantly with age or FecB genotyping were volume (0.72 ml), mass motility (4.44), sperm concentration (2721.56 x 10(6)ml(-1)), curvilinear velocity (134.51 microm/s), motility (81.3%), amplitude of lateral head displacement (6.24 microm), beat frequency (44.43 Hz), sperm head elongation (48.9%) and sperm head area (10.01 microm(2)). The FecB genotyping had a significant effect (P<0.05) on percent linearity and rapid motile sperms, which did not vary significantly with age. Although sperm concentration was higher in FecB(BB) and FecB(B+), compared to FecB(++) genotypes but the effect was non-significant. The age and FecB genotyping had significant effects (P<0.05) on straightness, average path velocity, straight-line velocity and percentage of medium or slow motile sperms. It is concluded that GarolexMalpura rams with introgressed FecB gene are capable of producing good quality semen in a semi-arid tropical climate.

Aging↗
PubMed2004

Avian reproductive failure in response to an extreme climatic event.

Recently, climate change research has emphasized the potential increase in the frequency and severity of climatic extremes. We compared the reproductive effort and output among four species of passerine birds in coastal southern California, USA, a semi-arid region, during a normal precipitation year (2001) and the driest year in a 150-year climate record (2002). Both reproductive effort and output differed dramatically between years. Mean reproductive output among the four species was 2.37 fledglings/pair in 2001 and 88.4% of all pairs observed attempted at least one nest. The birds attempted a mean of 1.44 nests per pair and were successful in 47.7% of those attempts. In 2002, only 6.7% of the pairs even attempted a nest and only 1.8% were successful, for a total output of 0.07 fledglings per pair. The abundance of suitable arthropod prey items in the environment was also much lower in 2002, suggesting that low food availability was the proximal cause of the reproductive failure. The data for one of these species, the rufous-crowned sparrow (Aimophila ruficeps), were combined with reproductive and rainfall data from a previous 3-year study (1997-1999) in the same sites. The combined data sets suggest that the response of reproduction to rainfall variation is linear, and that the low end of the precipitation range brings the population near reproductive failure. Any change in climate that would increase the frequency of extreme dry conditions would likely endanger populations of these species.

Acclimatization↗
PubMed2003

Greening of arid cities by residual water reuse: a multidisciplinary project in northern Chile.

This paper describes a project in northern Chile aimed to promote the development of appropriate green areas and gardens for arid regions under prevalent conditions of shortage of water and high salt content in soil and water. Field studies were conducted to test the suitability of selected salt-tolerant native and introduced plants for ornamental use. Plant growth, water and soil quality, marine spray, climate, wastewater treatment and irrigation operating problems were the subject of specific studies and discussion.

Chile↗
PubMed2003

[Clinical efficiency and tolerance of hydrogen sulfide balneotherapy in hypertensive patients living in arid zone].

AIM: To examine clinical efficiency and safety of moderate hydrogen sulfide (HS) baths in the treatment of hypertensive patients living in arid zones. MATERIAL AND METHODS: Sixty patients with stable essential hypertension (EH) of stage I-II according to WHO classification living in arid climate took sparing HS baths. Efficiency of the baths was assessed by changes in blood pressure (BP), 24-h monitoring of BP. RESULTS: It is shown that systolic and diastolic BP after HS balneotherapy fell significantly both in daytime and at night. The 24-h profile of BP improved, heart rate decreased by 4.3%, physiological fluctuations of BP and BP variability were not damaged. CONCLUSION: Moderate HS baths are recommended for wider use in a hot climate of the arid zone as an effective and safe method of balneotherapy which can be adjuvant to basic medication of EH.

Adult↗
PubMed2004

[Decline regularity and causes of Pinus sylvestris var. mongolica plantation on sandy land].

The study showed that the decline of Pinus sylvestris var. mongolica plantation out of its natural distribution area was a phenomenon of premature senility. The infected harm of shoot blight was the direct cause of Pinus sylvestris var. mongolica dying, but wasn't the basic reason. The decline of Pinus sylvestris var. mongolica was caused by the interaction of biological and other factors, which was "the third disease" beyond infectious and non-infectious diseases, namely, "decline disease of forest". Climate difference, improper management, unbalanced usage of soil water, and high content of N settled from air were the inducing factors, among which, climate difference and unbalanced usage of soil water were the main ones, while insect harm and shoot blight were the promoting factors.

Agriculture↗
PubMed2004

[Efficacy and safety of hydrogen sulfide balneotherapy in ischemic heart disease the arid zone].

AIM: To evaluate efficacy of hydrogen sulfide (HS) balneotherapy in patients with coronary heart disease (CHD) in conditions of heat discomfort. MATERIAL AND METHODS: The study included 72 CHD patients aged 35 to 60 years with stable angina pectoris of the second functional class taking balneotherapy in summer under arid climatic conditions. Before and after balneotherapy the patients were examined with estimation of clinical symptoms, stress bicycle exercise (SBE) parameters, number of nitroglycerine tablets. RESULTS: The balneotherapy resulted in a significant prolongation of SBE (p < 0.0018), in longer time to depression of the ST segment by 1 mm (p < 0.01), to an anginal attack in the course of SBE (p < 0.0036), shorter duration of pain after SBE (p < 0.001), less number of anginal attacks (p < 0.0002) and reduced need in short-acting nitrates (p < 0.0002). CONCLUSION: In a hot climate of the arid zone use of moderate HS baths raises tolerance of CHD patients to exercise, attenuates clinical manifestations of CHD and, consequently, reduces daily need in nitrates.

Adult↗
PubMedDate not supplied

[The central hemodynamic reaction of patients with ischemic heart disease to the climatic and weather conditions of an arid zone].

Central hemodynamics of coronary patients living in the arid zone (215 males aged 40-72 and 150 females aged 40-75) was assessed in comfortable weather conditions, 1-2 days before the invasion of the dust storm, upon its invasion and in hot weather season (+26-30 degrees C). Angina of effort functional class I, II and III was in 102, 198 and 65 patients, respectively. Atmospheric conditions before the invasion of the dust storm form a hypoxic type of weather while on the day of the storm the weather appears spastic resulting in arterial hypertension, elevated total peripheral resistance and heart beat in diminution of cardiac output and stroke volume. Hot weather brings about a hypotensive response, total peripheral resistance falls, cardiac output increases at the expense of enhanced heart beat as stroke volume decreases. It is concluded that under the climatic conditions of an arid zone coronary patients develop a complex of hemodynamic responses which function with strain to supply blood to organs and tissues.

Adult↗
PubMed2003

Efficacy of microencapsulated insecticides against the sandfly, Phlebotomus papatasi Scopoli.

The baseline and residual activity of micro-encapsulated insecticides was assessed on a sandfly colony originating in the Jordan Valley, Israel. Lethal doses were calculated for formulations of the pyrethroids permethrin and cypermethrin and the organophosphates diazinon and chlorpyrifos. Cypermethrin was found to be more toxic than permethrin and chlorpyrifos was more toxic than diazinon. Accordingly, the residual activity of chlorpyrifos and cypermethrin was tested after 1 and 4 wk exposure of impregnated filter papers under three environmental conditions: Jerusalem-indoors, Jerusalem-outdoors and semi-arid conditions. The results showed that environmental and climatic conditions play a major role in the persistence of toxicity of micro-encapsulated insecticides. A significant loss of toxicity for both compounds was noted after 4 wk of exposure under semi-arid conditions.

Animals↗
PubMed2003

Environmental and human factors influencing thermal comfort of office occupants in hot - humid and hot - arid climates.

The effects of environmental and individual factors on thermal sensation in air-conditioned office environments were analysed for two large, fully compatible thermal comfort field studies in contrasting Australian climates. In the hot - humid location of Townsville, 836 office workers were surveyed; 935 workers participated in hot - arid Kalgoorlie-Boulder. Overall perceived work area temperature and measured indoor operative temperature correlated moderately with thermal sensation for Townsville (T) subjects but only perceived temperature correlated with Kalgoorlie-Boulder (KB) sensation. Multiple regression analyses confirmed that indoor climatic variables (including Predicted Mean Vote) contributed to actual thermal sensation vote (24% T; 15% KB), with operative temperature having more of an effect in T than in KB. Subsequent analyses of individual characteristics showed no linear contributions to thermal sensation. The remaining variances were significantly related to perceived work area temperature (7% additional explained variance in T; 12% in KB). Mann - Whitney analyses (after correction for climatic variables) showed that T subjects with higher job satisfaction had thermal sensations closer to 'neutral'. Males, healthier subjects, non-smokers, respondents with earlier survey times and underweight occupants had lower median thermal sensations in KB. Townsville occupants appeared more adapted to their outdoor climatic conditions than Kalgoorlie-Boulder respondents, perhaps due to limited home air-conditioning. Further research into non-thermal impacts on gender-related thermal acceptability is suggested.

Adolescent↗
PubMedDate not supplied

[Microcirculatory changes in patients with the initial manifestations of cerebral circulatory failure under the conditions of an arid zone].

Microcirculation was studied in 53 ICCD patients: 28 lived in comfortable weather conditions while 25 patients lived in heat discomfort in arid climatic zone. It is shown that heat discomfort led to compensatory microvascular reactions providing proper supply of oxygen to organs and tissues: tortuosity and dilation of the microvessels, opening of the capillaries, shunting in relative hypoxia and hyperthermia.

Adaptation, Physiological↗
PubMed1976

Water conservation in xerophilic birds.

Adaptation of birds to dry climates involves decrease in relative evaporative water loss (mechanism unknown); decrease in GFR; and high urine osmolality in the dehydrated state in conjunction with cloacal resorption parameters, which allows the urine to enter the cloaca without a further water loss. The net result of the adaptations is such that the best adapted birds, such as the budgerygah (12) and the zebra finch (13) fed dry seeds alone can live without water. Similar features have been observed also in the best adapted desert rodents (27). Finally, birds tolerate a 7 to 13% increase in plasma osmolality (9). Tucker (28) has calculated that the budgerygah has fuel for 14 h flight; we have calculated that it also has water for 14 h (12) at neutral temperature and humidity. This is better than the Jumbo Jet, which can only fly for 12 h.

Adaptation, Physiological↗
PubMed2005

[Spermatophyte flora in Hunshandake sand].

This paper studied the spermatophyte flora in the Hunshandake sand of central Inner Mongolia agriculture-animal husbandry ecotone, and compared it with the flora in whole Inner Mongolia. The results showed that there were 1191 species of spermatophyte in the sand, belonging to 402 genera and 84 families. The geographic element of the flora was of multiplicity, and predominant with temperate floristic element, among which, North Temperate distribution elements had a higher percentage, and Compositae and Gramineae had the greatest proportion. The temperate floristic element had a trend of laying in big families, indicating that the plant distribution of Hunshandake sand had adapted to the climate of this area. The dominant families of the spermatophyte belonged to different elements, but most of them were the worldwide element. The original of the element was very ancient, and the geographic element was complex and transitive. In addition, the plant flora was significantly vulnerable.

Biodiversity↗
PubMed2001

Climate controls on dust storm occurrence in Maowusu Desert, Inner Mongolia, north China.

Dust storms occurring in arid and semi-arid regions play a main role in the evolution of landscapes. Climate is generally regarded to be important factors influencing the occurrence of dust storm, however, the way of climate controlling dust storms had been poorly understood. In this paper, we present the Ew Index model to describe the relationship between climate variables and dust storm frequency using the available meteorological data from three meteorological stations in Maowusu Desert. This index model explains 83.6%, 69.5% and 65.09% of the variance of dust storm frequency in three regions from the north to the south, respectively and this difference is probably caused by the difference of the human disturbance. The Ew Index model is an effective predictor of dust storm frequency and provides us a quite good understanding on the occurrence of dust storms in Maowusu Desert.

China↗
PubMed1989

Laboratory evaluation of controlled-release repellent formulations on human volunteers under three climatic regimens.

Six controlled-release personal-use topical insect/arthropod repellent formulations of diethylmethylbenzamide (deet) were evaluated in an environmental chamber on volunteers for repellency against the mosquitoes Aedes aegypti and Ae. taeniorhynchus under three climatic regimens: basic variable high humidity (tropical environment), basic constant high humidity (forested and wet environment) and basic hot (hot-dry environment). The best protection under all the climatic regimens was provided by the Biotek formulation. In a tropical environment, some formulations induced more biting from mosquitoes than the concurrent untreated control in the late hours of the testing. Repellency was not directly related to the deet concentration in the various controlled-release repellent formulations.

Aedes↗
PubMed1988

[Epidemiology of Bietti's keratopathy. Study of risk factors in Central Africa (Chad)].

Climatic Droplet keratopathy (synonyms: spheroidal degeneration, Bietti's keratopathy) is a corneal degeneration characterized by an opacification at the level of the Bowman's membrane in the area of the palpebral fissure. It is particularly common in areas of bright sunlight and in Labrador; ultraviolet light thus being thought at its genesis. Two objectives were included in this study: studying the Climatic Droplet Keratopathy (CDK) prevalence by looking for the influence of the climatic factor; looking for possible association with three other degenerative ocular diseases: cataract, open-angle, glaucoma and exfoliation syndrome. A random cluster sampling survey was carried out in different climatic areas in Chad (N = 3,241 people). The resulting analysis showed a significant relation between the CDK prevalence and the kind of climate: the more the climate is dry; the more the higher the frequency: subdesert area = 1.57%, Sahelian area = 0.73%, tropical area = 0.18% (p less than 0.0001, rate standardized to age). The CDK occurs earlier in the subdesert area (mean age = 60.0) than in the Sahelian one (mean age = 66.7) (p less than 0.05). The CDK only exists among people age 40 or older, and is more frequent among males than females (p less than 0.005). The cataract is more frequent among individuals having a CDK than among those without it: relative risk = 4.3 (C.I.: 2.3-7.9 p less than 0.00001) (Mantel-Haenszel's method with adjustment to climate, age and sex). As for open-angle glaucoma, it is more frequent among individuals suffering from CDK: relative risk = 4.2 (p = 0.05). Finally, we noticed that the exfoliation syndrome was 5 times more frequent among chadians suffering from a CDK (p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2005

First approach of a method to assess water quality for arid climate bay in the Gulf of California.

This work proposes a water quality model based on the pooled effects of nitrate, nitrite, ammonium, and orthophosphate concentration as the main causatives of environmental water quality changes. One of the main characteristics of the model is assigning an environmental weight for each variable (zeta(i)) according to threshold concentrations of nutrients capable of inducing water changes condition. The model validation demonstrated adequate sensitivity to different data arrangements; as observed in an arid climate bay, showing annual stratification resulting in a variable content in nitrogen-forms and phosphorous. The model can be continuously calibrated over time by adding more N and P data to specific nutrient functions, and tested on sites with high NO(3), NO(2) or NH(4) concentrations.

Desert Climate↗