Interacting controls on innate sources of CO2 efflux from a calcareous arid zone soil under experimental acidification and wetting

More than half of global soil carbon is stored as carbonates, primarily in arid and semi-arid zones. Climate change models predict more frequent and severe rainfall events in some parts of the globe, many of which are dominated by calcareous soils. Such events trigger substantial increases in soil CO2 efflux. We hypothesised that the primary source of CO2 emissions from calcareous, arid zone soil during a single wetting event is abiotic and that soil acidification and wetting have a positive, potentially interacting, effect. We manipulated soil pH, soil moisture, and controlled soil respiration by gamma irradiating half of an 11 day incubation experiment. All manipulated experimental treatments had a rapid and enormous effect on CO2 emission. Respiration contributed ca. 5% of total CO2 efflux; the major source (carbonate buffering) varied depending on the extent of acidification and wetting. Maximum CO2 efflux occurred when pH was lowest and at intermediate matric potential. CO2 efflux was lowest at native pH when soil was air dry. Our data suggest that there may be an underestimate of soil-atmosphere carbon fluxes in arid ecosystems with calcareous soils. There is also a clear potential that these soils may become net carbon sources depending on changes in rainfall patterns, rainfall acidity, and future land management. Our findings have major implications for carbon cycling in arid zone soil and further study of carbon dynamics in these terrestrial systems at a landscape level will be required if we are to improve global climate and carbon cycling models.

Phylogeny and ecology determine morphological structure in a snake assemblage in the central Brazilian Cerrado

To investigate the role of ecological and historical factors in the organization of communities, we describe the ecomorphological structure of an assemblage of snakes (61 species in six families) in the Cerrado (a savanna-like grassland) of Distrito Federal, Brazil. These snakes vary in habits, with some being fossorial, cryptozoic, terrestrial, semi-aquatic, or arboreal. Periods of activity also vary. A multivariate analysis identified distinct morphological groups associated with patterns of resource use. We report higher niche diversification compared to snakes in the Caatinga (a semi-arid region in northeastern Brazil), with fossorial and cryptozoic species occupying morphological space that is not occupied in the Caatinga. Monte Carlo permutations from canonical phylogenetic ordination revealed a significant phylogenetic effect on morphology for Colubridae, Colubrinae, Viperidae, Elapidae, and Boidae indicating that morphological divergence occurred in the distant past. We conclude that phylogeny is the most important factor determining structure of this Neotropical assemblage. Nevertheless, our results also suggest a strong ecological component characterizes a peculiar snake fauna.

Learning from arid planning and design history and practice : from Woomera to creating the new Roxby Downs communities

The principles and knowledge about arid planning and design have much applicability to contemporary Australian planning discourses because of climate change evidence and policy shifts that sketch a hotter and more unreliable future climate with an emphasis upon a semi-arid environment for Australia. Despite this merit and intent, we appear to have learnt little from the past and are failing to draw upon the pioneering planning and design knowledge that underpinned community development and scaffolding in numerous Australian arid and semi-arid communities, and to bring this knowledge into our future planning processes and strategies.

This paper considers the essential attributes and variables of three Australian arid planning and design, drawing upon historical practice and research that have been explored in the planning of semi-arid and arid places including Port Pirie, Whyalla, Monarto, Broken Hill, Port Augusta, Leigh Creek, Andamooka, Olympic Dam Village and Roxby Downs. It specifically reviews Woomera Village (1940s) Shay Gap (1970s) and the proposed extensions to Roxby Downs (2010s) as models of how to better plan and design communities in arid environments. Instrumental in these innovations is the use of landscape-responsive urban design strategies, water harvesting and irregular rainfall capture, arid horticulture, building design, colour and materiality, orientation and shading strategies, and social community construction under difficult isolationist circumstances. The paper points to key strategies that need to be incorporated in future climate change responsive community developments and policy making.

Artificial water points facilitate the spread of an invasive vertebrate in arid Australia

Summary: The spread of invasive species after their initial introduction is often facilitated by human actions. In some cases, invaders only become established in habitats where dominant native species have been displaced as a result of human actions or where humans inadvertently provide essential resources such as food, water or shelter. We investigated if dams that provide water for livestock have facilitated the cane toad's (Rhinella marina) invasion of a hot semi-arid landscape by providing toads with a resource subsidy and hence refuge from extreme heat and aridity. To determine the relationship between the presence of surface water and habitat occupancy by toads, we surveyed natural and artificial water features for cane toads during the annual dry season. We used radiotracking and acoustic tags to determine whether movement patterns and shelter use of cane toads were focussed around dams. To determine whether dams provide toads with refuge from extreme heat and aridity, we deployed plaster models with internal thermometers to estimate ambient temperatures and toad desiccation rates in shelter sites. To determine whether dams alleviate the stress experienced by toads, we measured plasma corticosterone levels of toads that sheltered in and away from dams. Toads were present in sites with standing water and absent from waterless sites. Most radiotracked toads sheltered within 1 m of water. Toad movements were focussed around water. Toads tracked with passive acoustic telemetry over a 6-month dry season were highly resident at dams. Plaster models placed in toad shelter sites away from the water lost 27% more mass and experienced higher temperatures than models placed near the water's edge. Toads that sheltered in terrestrial shelters exhibited higher plasma corticosterone levels compared to toads that sheltered near dams. Dams provide toads with refuge habitats where they are less at risk from overheating and dehydration. Synthesis and applications. Artificial water points can facilitate biological invasions in arid regions by providing a resource subsidy for water-dependent invasive species. Our study suggests that there is scope to control populations of water-dependent invasive vertebrates in arid regions by restricting their access to artificial water points.

Estado nutricional de escolares do semi-árido do nordeste brasileiro

SILVA, João B. da et al. Estado Nutricional de Escolares do Semi-Árido do Nordeste Brasileiro. Revista de Salud Pública, v. 11, n. 1, p. 62-71, 2009.

Efeitos da tilápia do Nilo (Oreochromis niloticus) e do enriquecimento por nutrientes sobre a comunidade planctônica em um lago artificial no semi-árido brasileiro

The major aim of this study was to test the hypothesis that the introduction of the Nile tilapia (Oreochromis niloticus) and the enrichment with nutrients (N and P) interact synergistically to change the structure of plankton communities, increase phytoplankton biomass and decrease water transparency of a semi-arid tropical reservoir. One field experiment was performed during five weeks in twenty enclosures (8m3) to where four treatments were randomly allocated: with tilapia addition (T), with nutrients addition (NP), with tilapia and nutrients addition (T+NP) and a control treatment with no tilapia or nutrients addition (C). A two-way repeated measures ANOVA was done to test for time (t), tilapia (T) and nutrient (NP) effects and their interaction on water transparency, total phosphorus, total nitrogen, phytoplankton and zooplankton. The results show that there was no effect of nutrient addition on these variables but significant fish effects on the biomass of total zooplankton, nauplii, rotifers, cladocerans and calanoid copepods, on the biovolume of Bacillariophyta, Zygnemaphyceae and large algae (GALD ≥ 50 μm) and on Secchi depth. In addition, we found significant interaction effects between tilapia and nutrients on Secchi depth and rotifers. Overall, tilapia decreased the biomass of most zooplankton taxa and large algae (diatoms) and decreased the water transparency while nutrient enrichment increased the biomass of zooplankton (rotifers) but only in the absence of tilapia. In conclusion, the influence of fish on the reservoir plankton community and water transparency was greater than that of nutrient loading. This finding suggests that biomanipulation should be a greater priority in the restoration of eutrophic reservoirs in tropical semi-arid regions

Eutrofização e capacidade de carga de fósforo de seis reservatórios a bacia do Rio Seridó, região semi-árida do Estado do RN

The eutrofization is a natural process of accumulation of nutrients in aquatic´s body that it has been accelerated for the human´s actives, mainly the related with the activities of camp, industrial and the inadequate disposition of the domestic sewage. The enrichment of the aquatic´s body with nutrients, mainly the nitrogen and the phosphorus, and the consequent proliferation of algae and Cyanobacteria can commit the quality of the water for the public provisioning, for the fish farming and for other ends. The problem becomes more critical when there is a shortage of water naturally as in the semi-arid area of the Brazilian northeast. Before that problem this work had as objective evaluates the trophic state of six reservoirs of the basin of River Seridó of Rio Grande of Norte and also estimate the capacity of load of match of the reservoir and risk probabilities based on the established limits by the resolution Conama 357/05. The results demonstrate that the six reservoirs are eutrofization, with concentration of total phosphorus and cloro a in the water upster to 50 e 12 μg l-1. The results show that space homogeneity exists in the state trophic of the reservoirs, but a significant variation interanual in function of the increase of the concentrations of nutrients and decrease of the transparency of the water with the reduction of the body of water accumulated in the reservoirs.The results of the simulation risk estocastic show that the reservoirs could receive annually from 72 to 216 Kg of P, assuming a risk of 10% of increasing in more than 30 μg l-1 the annual medium concentrations of total match in the water of these reservoirs. This load could be high in until 360 kg of P a year in case the managers assume a risk of 10% of increasing in more than 50 μg l-1 the annual medium concentrations of total phosphorus in the waters of these reservoirs

Efeitos de manipulações ascendentes e descendentes sobre a comunidade fitoplanctônica em um reservatório eutrófico no semi-árido brasileiro

Top-down (grazing) and bottom-up (nutrient, light) controls are important in freshwater ecosystems regulation. Relative importance of these factors could change in space and time, but in tropical lakes bottom-up regulation has to been appointed as more influent. Present study aimed to test the hypothesis that phytoplankton growths rate in Armando Ribeiro reservoir, a huge eutrophic reservoir in semi-arid region of Rio Grande do Norte state, is more limited by nutrient available then zooplankton grazing pressure. Bioassay was conduced monthly from September (2008) to August (2009) manipulating two levels of nutrients (with/without addition) and two level of grazers (with/without removal). Experimental design was factorial 2X2 with four treatments (X5), (i) control with water and zooplankton from natural spot ( C ), (ii) with nutrient addition ( +NP ), (iii) with zooplankton remove ( -Z ) and (iv) with zooplankton remove and nutrient addition ( -Z+NP ). For bioassay confection transparent plastic bottles (500ml) was incubate for 4 or 5 days in two different depths, Secchi`s depth (high luminosity) and 3 times Secchi`s depth (low luminosity). Water samples were collected from each bottle in begins and after incubates period for chlorophyll a concentration analysis and zoopalnktonic organisms density. Phytoplankton growths rates were calculated. Bifactorial ANOVA was performance to test if had a significant effect (p<0,005) of nutrient addition and grazers remove as well a significant interaction between factors on phytoplankton growths rates. Effect magnitude was calculated the relative importance of each process. Results show that phytoplankton growth was in generally stimulated by nutrient addition, as while zooplankton remove rarely stimulated phytoplankton growth. Some significant interactions happening between nutrient additions and grazers remove on phytoplankton growth. In conclusion this study suggests that in studied reservoir phytoplankton growth is more controlled by ascendent factors than descendent

Comunidades zooplanctônicas como bioindicadoras da qualidade da água de quatro reservatórios da região semi-árida do Rio Grande do Norte

The response of zooplankton assemblages to variations in the water quality of four man-made lakes, caused by eutrophication and siltation, was investigated by means of canonical correspondence analysis. Monte Carlo simulations using the CCA eingenvalues as test statistics revealed that changes in zooplankton species composition along the environmental gradients of trophic state and abiogenic turbidity were highly significant. The species Brachionus calyciflorus, Thermocyclops sp. and Argyrodiaptomus sp. were good indicators of eutrophic conditions while the species Brachionus dolabratus, Keratella tropica and Hexarthra sp. were good indicators of high turbidity due to suspended sediments. The rotifer genus Brachionus was the most species-rich taxon, comprising five species which were associated with different environmental conditions. Therefore, we tested whether this genus alone could potentially be a better biological indicator of these environmental gradients than the entire zooplankton assemblages or any other random set of five species. The ordination results show that the five Brachionus species alone did not explain better the observed pattern of environmental variation than most random sets of five species. Therefore, this genus could not be selected as a target taxon for more intensive environmental monitoring as has been previously suggested by Attayde and Bozelli (1998). Overall, our results show that changes in the water quality of man-made lakes in a tropical semi-arid region have significant effects on the structure of zooplankton assemblages that can potentially affect the functioning of these ecosystems

Arthropoda de solo em um ecossistema semi-árido da região neotropical: composição, variabilidade temporal e estratificação

Caatinga is an important laboratory for studies about arthropods adaptations and aclimatations because its precipitation is highly variable in time. We studied the effects of time variability over the composition of Arthropods in a caatinga area. The study was carried out at a preservation area on Almas Farm, São José dos Cordeiros, Paraíba. Samples were collected in two 100 m long parallel transects, separated for a 30 m distance, in a dense tree dominated caatinga area, between August 2007 and July 2008. Samples were collected in each transect every 10 m. Ten soil samples were taken from each transect, both at 0-5 cm (A) and 5-10 cm (B) depth, resulting in 40 samples each month. The Berlese funnel method was used for fauna extraction. We registered 26 orders and the arthropods density in the soil ranged from 3237 to 22774 individuals.m-2 from January 2007 to March 2008, respectively. There was no difference between layers A and B regarding orders abundance and richness. The groups recorded include groups with few records or that had no records in the Caatinga region yet as Pauropoda, Psocoptera, Thysanoptera, Protura and Araneae. Acari was the most abundant group, with 66,7% of the total number of individuals. Soil Arthropods presented a positive correlation with soil moisture, vegetal cover, precipitation and real evapotranspiration. Increases in fauna richness and abundance were registered in February, a month after the beginning of the rainy season. A periodic rain events in arid and semiarid ecosystems triggers physiological responses in edafic organisms, like arthropods. Edafic arthropods respond to time variability in the Caatinga biome. This fauna variation has to be considered in studies of this ecosystem, because the variation of Arthropods composition in soil can affect the dynamics of the food web through time

Biologia alimentar e morfohistologia do tubo digestório do mussum, synbranchus marmoratus, bloch (osteichthyes: synbranchidae) no açude Marechal Dutra Gargalheiras , localizado no semi-árido brasileiro

Food habits and morpho-histology of the digestive tract of marbled swamp eel, Synbranchus marmoratus (Block, 1917) were investigated. The fish samples were captured during August, 2007 to July, 2008 in the Marechal Dutra reservoir, Acari, Rio Grande do Norte. The rain fall data was obtained from EMPARN. The fish captured, were measured, weighed, dissected, eviscerated and individual stomach weights were registered. The stomach contents analyses were carried out based on volumetric method, points, frequency of occurrence and applying the Index of Relative Importance. The degrees of repletion of the stomachs were determined besides the Index of Repletion relating to feeding activity variations and frequency of ingestion during the rainy and dry seasons. The rainfall varied from 0 mm a 335 mm with a mean value of 71.62 mm. Highest rainfall of 335.5 mm was registered in March, 2008 and August to December was the dry period. During the dry period the study species presented high degrees of repletion of the stomachs, with a peak value in the month of September (mean = 4.54; ± SD = 0.56). The minimum mean value of = 3.99 ± SD = 0.25 was registered in the month of May during the rainy period. The stomach contents of S. marmoratus registered show that this fish prefers animals, 78.22% of crustaceans 2.85% of mollusks, 3.25% of fish, 1.4% of insects and 13.5% of semi-digested organic matter, thus characterizing the study species as a carnivore with a preference for crustaceans. The morpho-histological aspects of the digestive tract of S. marmoratus indicate that the mouth is terminal adapted to open widely, thin lips with taste buds, small villiform teeth forming a single series on maxillas, four pairs of branchial arches with short and widely spaced branchial rays. The oesophagus is short and cylindrical with a small diameter. The oesophagus wall is thick with mucas surface and internal parallel folds. The stomach is retilinical in form, presenting cardiac, caecal and pyloric portions. The caecal portion is long and is intermediary in position between the cardiac and pyloric portions. The cardiac portion of the stomach is short and cylindrical formed of simple epithelial cylindrical mucus cells. The caecal portion is long with narrow walls, a big cavity and smaller folds which give rise to gastric glands. The phyloric portion has no glands and primary or secondary mucas folds. The morphohistological aspects of the digestive tract of S. marmoratus indicate its adaptation to a carnivorous feeding habit

Relações de poder, fragmentação e gestão do território no semi-árido nordestinho: um outro olhar sobre o Cariri paraibano

This study aims to analize the Cariri Paraibano territory, as a product of relations of power that were being established along its historic process of territory formation. In this process, the fragmentation and the territory management are fundamental elements to socioterritorial reality comprehension. The theoretical-conceptual basis is based on notions of territory, region, power and territory management, which are articulated to the opinions and empiric confirmations origined from interviews made with several social actions. They also were made photographical records and researches on books, newspapers and magazines, as well on other information sources related to the object of studying. Obtained data confirm the pressuposement on which the relations of dominations and the used methods by the power s owners in the region created a little fruitful political practice and little adequate to the process of active participation of the local population on the territory management, even being on disagreement with the new political-institutional mechanisms, which take to political-administrative more democratic and participative in the country

Padrões distintos de congruência climática em duas espécies invasoras de prosopis em zonas semi-áridas da América do Sul

Based on climate data and occurrence records, ecological niche models (ENM) are an important opportunity to identify areas at risk or vulnerable to biological invasion. These models are based on the assumption that there is a match between the climatic characteristic of native and invaded regions predicting the potential distribution of exotic species. Using new methods to measure niche overlap, we chose two exotic species fairly common in semi-arid regions of South America, Prosopis juliflora (Sw.) D.C. and Prosopis pallida (H. ; B. ex. Willd) HBK, to test the climate matching hypothesis. Our results indicate that both species occur with little niche overlap in the native region while the inverse pattern is observed in the invaded region on South America, where both species occur with high climatic overlap. Maybe some non-climate factor act limiting the spread of P. pallida on the native range. We believe that a founder effect can explain these similarities between species niche in the invaded region once the seeds planted in Brazil came from a small region on the Native range (Piura in Peru), where both species occur sympatric. Our hypothesis of a founder effect may be evident when we look at the differences between the predictions of the models built in the native and invaded ranges. Furthermore, our results indicate that P. juliflora shows high levels of climate matching between native and invaded ranges. However, conclusions about climate matching of P. pallida should be taken with caution. Our models based on climatic variables provide multiple locations suitable for occurrence of both species in regions where they still don t have occurrence records, including places of high interest for conservation.

Avaliação das barragens subterrâneas no regime de um curso d água na região do semi-árido do RN

The Serido is a region of northeastern Brazil highlighted by its problems related to water scarcity because of its semi-arid region, large rates of evaporation and rainfall irregular and scarce. Thus, the underground dams, become a strategically important resource with a simple and inexpensive technique for storage of water. They act in a positive way in the development of inland cities that suffer from drought, because in addition to exercise a great improvement in the social role of these families, can enjoy the type of soil (silt) and provides water for both irrigation and for human consumption throughout the year. Is therefore essential to its monitoring and studies to assess its effectiveness in accordance with its purposes, along with their wells Amazons, as can occur in conditions of physical degradation, chemical and microbiological appropriate, according to the Ordinance No 518/04 Ministry of Health, however, the proposed work aims to analyze the underground dams in the municipality of Sierra Negra North-RN (semi-arid region) as to their uses and their influences on the quality and quantity of water in periods of drought and rain. Analyzing monthly these parameters: determination of pH, conductivity, calcium, magnesium, sodium, potassium, chloride, sulfate, RAS (sodium adsorption ratio), turbidity, total iron, nitrite, nitrate, total dissolved solids (STD), bicarbonate (HCO3), fecal coliform and pesticides compared to the standards allowed by the Ordinance in force for quality for human consumption. While at the risk of salinity and sodicity on the model proposed by the United Salinity Laboratory (USSL). Although efficient, it was found that results varied annually on water quality which may influence their specific uses, whether or irrigation water supply in the city

Avaliação da resposta comportamental, morfofisiológica e produção de leite de cabras puras e mestiças da raça Saanen no semi-árido do Rio Grande do Norte

Goat breeding in the state of Rio Grande do Norte, Brazil has promising economic possibilities, with the proper handling of the natural resources. The introduction of specialized animals has been one of the ways used to improve herd genetics and increase productivity. However, climate has been one of the regional factors that most interferes with the adaptation of the new genetic prevalence resulting from the introduction of exotic breeds, because in their country of origin, the air temperature during most of the year is lower than the animals body temperature. With this in mind, the aim of this study was to characterize behavioral, physiological and morphological profiles and milk production of female Saanen goats belonging to different genetic groups raised in the semi-arid region of Rio Grande do Norte in Northeast Brazil. The study was conducted in the city of Lages (5° 42 00 S and 36° 14 41 W). We used 25 lactating female Saanen goats, distributed into 3 genetic groups: 5 purebred animals, 11 three-quarter bred and 9 half-bred. Behavioral observations were made over three consecutive days in the months of August and September, between 09:00 and 11:30h, when the animals were grazing. Physiological and meteorological data were recorded in the last three days of June, July, August and September at 05:00h and at 16:00h. In the semi-intensive breeding system, the animals from different genetic groups were similar in both field behavior and physiological response patterns. Although the purebred goats had longer hair, they did not show symptoms of thermal discomfort. Their white hair helped to reflect the short wavelength rays and thus eliminate those at the longer wave lengths. We concluded that the animals raised in the semi-intensive milk production system in this study seem to have adapted to the climatic conditions of the semi-arid region of Rio Grande do Norte, Brazil