A study on an oligotrophic bacteria and its ecological characteristics in an arid desert area

An oligotrophic bacterium was isolated from the biological soil crust underlayer in the Xinjiang Gurbantunggut Desert. It was numbered SGB-5, G . Cell size is (0.328-0.746) μm×(0.171-0.240) μm. Raised colony is white, roundness and its diameter is 5 mm. The strain is a facultative aerobe. It was able to grow in conditions of 1―15 mg·C·L?1 culture medium at 10―50℃. The strain's optimum growth temperature is 37℃. The range of its optimum growth pH is 8―9. A large amount of extracellular mucopolysaccharide was secreted during growth. The chemical composition of this mucopolysaccharide consists of arabinose, X sugar, glucose, galactose and mannitol. Mole ratio of these sugars is 1:14:19:6:14. The viscosity of the mucopolysaccharide can reach 6300 mPa·s, when the strain is cultivated for 72 h. After the culture solution in which viscosity was 1500 mPa·s was sprinkled on the quicksand surface, 6 mm bacteria crust of conglutinating sand was formed. This crust could not only stabilize sand, but could also potentially slow the rate of the soil water evaporation.     

Changes in the plain river system and its hydrological characteristics under urbanization – case study of Suzhou City,China

ABSTRACT

Rapid urbanization in China has severely disturbed the underlying surface and river systems. The stream structure parameters of Suzhou City were analysed to study the evolution and spatial differentiation of a water system undergoing urbanization. The influencing pattern of different urbanization processes on river system structure and hydrological processes was detected by statistical methods and simulation analysis. The results show that urban sprawl is influenced by both the natural environment and the social economy. At different stages of urbanization, the spatial urban expansion and the natural river characteristics influence the evolution of the river network: during rapid urbanization, the decline in surface water ratio and river density is more intense. The decrease of surface water ratio and river density in rapidly urbanized areas was greatest, followed by that in area urbanized in the 1980s, with few changes in the old town. Under high urbanization, river system indicators tend to stabilize. The rivers’ hydrological features were affected by urbanization, with water yield in the study area increasing from 0.81 to 0.95 m³/m² (1991–2015). The same rainfall intensity results in higher flood levels and greater risk of flooding under rapid urbanization.     

Projected streamflow in the Huaihe River Basin (2010–2100) using artificial neural network

Climate projections for the Huaihe River Basin, China, for the years 2001–2100 are derived from the ECHAM5/MPI-OM model based on observed precipitation and temperature data covering 1964–2007. Streamflow for the Huaihe River under three emission scenarios (SRES-A2, A1B, B1) from 2010 to 2100 is then projected by applying artificial neural networks (ANN). The results show that annual streamflow will change significantly under the three scenarios from 2010 to 2100. The interannual fluctuations cover a significant increasing streamflow trend under the SRES-A2 scenario (2051–2085). The streamflow trend declines gradually under the SRES-A1B scenario (2024–2037), and shows no obvious trend under the SRES-B1 scenario. From 2010 to 2100, the correlation coefficient between the observed and modeled streamflow in SRES-A2 scenario is the best of the three scenarios. Combining SRES-A2 scenario of the ECHAM5 model and ANN might therefore be the best approach for assessing and projecting future water resources in the Huaihe basin and other catchments. Compared to the observed period of streamflows, the projected periodicity of streamflows shows significant changes under different emission scenarios. Under A2 scenario and A1B scenario, the period would delay to about 32–33a and 27–28a, respectively, but under B1 scenario, the period would not change, as it is about 5–6a and the observed period is about 7–8a. All this might affect drought/flood management, water supply and irrigation projects in the Huaihe River basin.     

Abrupt shift in δ18O values at Medicine Lake Volcano (California, USA)

 Oxygen-isotope analyses of lavas from Medicine Lake volcano (MLV), in the southern Cascade Range, indicate a significant change in δ¹⁸O in Holocene time. In the Pleistocene, basaltic lavas with <52% SiO₂ averaged +5.9‰, intermediate lavas averaged +5.7‰, and silicic lavas (≥63.0% SiO₂) averaged +5.6‰. No analyzed Pleistocene rhyolites or dacites have values greater than +6.3‰. In post-glacial time, basalts were similar at +5.7‰ to those erupted in the Pleistocene, but intermediate lavas average +6.8‰ and silicic lavas +7.4‰ with some values as high as +8.5‰. The results indicate a change in the magmatic system supplying the volcano. During the Pleistocene, silicic lavas resulted either from melting of low-¹⁸O crust or from fractionation combined with assimilation of very-low-¹⁸O crustal material such as hydrothermally altered rocks similar to those found in drill holes under the center of the volcano. By contrast, Holocene silicic lavas were produced by assimilation and/or wholesale melting of high-¹⁸O crustal material such as that represented by inclusions of granite in lavas on the upper flanks of MLV. This sudden shift in assimilant indicates a fundamental change in the magmatic system. Magmas are apparently ponding in the crust at a very different level than in Pleistocene time. Received: 6 March 1997 / Accepted: 12 January 1998     

Pre-Variscan basement rocks in southern Poland: Where is the southeastern margin of eastern Avalonia (Cadomia)?

Summary Pre-Variscan basement in southern Poland is poorly exposed and thus known mostly from subsurface data. The availability of the latter is reviewed for terrains located between the Sudetes and the East European Platform. In these terrains the following relationships have been documented: Cadomian granitoids capped by Variscan flysch, Palaeozoic platform strata, Palaeozic folded and partly thermally altered successions, and low-grade metamorphic rocks overlain by Middle Cambrian strata. In view of their interrelationships the location of the Avalonia-Baltica suture in southeastern Poland is uncertain.     

Did the M S7.0 Lushan earthquake dynamically trigger earthquakes in the Datong volcanic region (Shanxi Province)?

Immediately following the M _S7.0 Lushan earthquake on April 20, 2013, using high-pass and low-pass filtering on the digital seismic stations in the Shanxi Province, located about 870–1,452 km from the earthquake epicenter, we detected some earthquakes at a time corresponding to the first arrival of surface waves in high-pass filtering waveform. The earthquakes were especially noticed at stations in Youyu (YUY), Shanzizao (SZZ), Shanghuangzhuang (SHZ), and Zhenchuan (ZCH), which are located in a volcanic region in the Shanxi Province,but they were not listed in the Shanxi seismic observation report. These earthquakes occurred 4–50 min after the passage of the maximum amplitude Rayleigh wave, and the periods of the surface waves were mainly between 15 and 20 s following. The Coulomb stresses caused by the Rayleigh waves that acted on the four stations was about 0.001 MPa, which is a little lower than the threshold value of dynamic triggering, therefore, we may conclude that the Datong volcanic region is more sensitive to the Coulomb stress change. To verify, if the similar phenomena are widespread, we used the same filtering to observe contrastively continuous waveform data before, and 5 h after, the M _S7.0 Lushan earthquake and M _S9.0 Tohoku earthquake in 2011. The results show that the similar phenomena occur before the earthquakes, but the seismicity rates after the earthquakes are remarkably increased. Since these weak earthquakes are quite small, it is hard to get clear phase arrival time from three or more stations to locate them. In addition, the travel time differences between P waves and S waves (S–P) are all less than 4 s, that means the events should occur in 34 km around the stations in the volcanic region. The stress of initial dynamic triggering of the M _S9.0 Tohoku earthquake was about 0.09 MPa, which is much higher than the threshold value of dynamic triggering stress. The earthquakes after the M _S9.0 Tohoku earthquake are related to dynamic triggering stress, but the events before the earthquake cannot be linked to seismic events, but may be related to the background seismicity or from other kinds of local sources, such as anthropogenic sources (i.e., explosions). Using two teleseismic filtering, the small background earthquakes in the Datong volcanic region occur frequently, thus we postulate that previous catalog does not apply bandpass filter to pick out the weak earthquakes, and some of the observed weak events were not triggered by changes in the dynamic stress field.     

A catalog of aftershock sequences in Greece (1971–1997): Their spatial and temporal characteristics

A complete catalog of aftershock sequences is provided for main earthquakes with M_L 5.0, which occurred in the area of Greece and surrounding regions the last twenty-seven years. The Monthly Bulletins of the Institute of Geodynamics (National Observatory of Athens) have been used as data source. In order to get a homogeneous catalog, several selection criteria have been applied and hence a catalog of 44 aftershock sequences is compiled. The relations between the duration of the sequence, the number of aftershocks, the magnitude of the largest aftershock and its delay time from the main shock as well as the subsurface rupture length versus the magnitude of the main shock are calculated. The results show that linearity exists between the subsurface rupture length and the magnitude of the main shock independent of the slip type, as well as between the magnitude of the main shock (M) and its largest aftershock (Ma). The mean difference M–Ma is almost one unit. In the 40% of the analyzed sequences, the largest aftershock occurred within one day after the main shock.The fact that the aftershock sequences show the same behavior for earthquakes that occur in the same region supports the theory that the spatial and temporal characteristics are strongly related to the stress distribution of the fault area.     

A volumetric water budget of Devils Lake (USA): non-stationary precipitation–runoff relationships in an amplifier terminal lake

Devils Lake, a terminal lake in eastern North Dakota, rose more than 9 m between 1992 and 2013, producing a 286% increase in lake area, and causing more than US$1 billion in direct damages. An annual volumetric lake water budget is developed from monthly hydroclimatological variables for the period 1951–2010 to investigate the rapid lake expansion. The lake is an amplifier terminal lake in which long-term climatic changes are amplified by positive feedback mechanisms, causing the lake to transition from a precipitation-dominated to a runoff-dominated water budget. Factors specific to the Devils Lake Basin further amplify this positive feedback relationship. These include principles of fill–spill hydrology that operate between individual sub-basins within the closed basin, and between the innumerable wetland complexes within each sub-basin. These factors create a pronounced non-stationary precipitation–runoff relationship in the basin during both long-term wetting and drying phases.     

Active surface faulting or landsliding in the Lower Tagus Valley (Portugal)? A solved controversy concerning the Vila Chã de Ourique site

The Lower Tagus Valley has experienced significant (M 6–7) historical seismicity, evidencing the presence of seismogenic faults. These are still deficiently known due to the low strain rates and the recent alluvial sedimentation of the Tagus River that buries most of the structures, though Paleoseismic evidence was allegedly found by a research team in the Tagus valley, at a site 60 km N of Lisbon, near Vila Chã de Ourique (VCO). According to this team, trenching at the VCO site exposed an active thrust fault, evidencing the surface rupture of a large earthquake that occurred in 1531. Our studies performed at this site, comprising field observations with a reappraisal of the trench outcrops previously excavated, borehole drilling, soil mechanics laboratory testing, and seismic reflection acquisition, pointed to the alternative interpretation that the outcropping structures are gravitational and not of tectonic origin. The interpretation of new outcrops crosscutting the structures exposed at the trenches, as well as newly acquired high-resolution seismic reflection data, definitely exclude the active thrust fault explanation and support a gravitational slip model for all the observed structures. Gravitational slip in the river bank slope was promoted by low shear strength clays and high pore water pressure coupled with slope toe river erosion. Gravitational slides must have occurred prior to development of the present sedimentation level of the Tagus alluvial plain, which was attained in the last few thousand years as indicated by borehole data and estimations of sedimentation rates.     

The Microstructural Characteristics of Fault Rocks from the Wasatch Fault Zone in Utah (USA) Under Polarizing and Electronic Microscope and Its Seismogeologic Significance

The microstructures of fault rocks from the Wasatch fault zone in Utah (USA) have been studied using a polarizing microscope,a scanning electron microscope (SEM) and an ultrahigh-voltage electron microscope (HVHM).This fault zone may be recognized as one a with long history of seismic activity according to the microstructural characteristics such as type, deformation characteristics,melting structure and surface textures of the fault rocks.However,the main fault now present seems not to have been noticeably active since the late Pleistocene (Q_3),as shown by the eroded-surface texture on the quartz fragments in the fault gouge.Meanwhile,those faults supposed to be strongly active in modern times are branching faults much closer to the basin side and are covered by the Holocene sediments in the basin.     

Short-term changes in the aerosol characteristics at Kharagpur (22°19′N, 87°19′E) during winter

In-situ measurements of number density, size distribution, and mass loading of near-surface aerosols were carried out at Kharagpur, a site on the eastern part of Indo-Gangetic Plains during the winter month of December 2004. The data have been used to investigate wintertime characteristics of aerosols and their effects on the occurrence of haze. The aerosol number density is found to be of the order of 10⁹ m^?3 and mass loading is ~265±70 μg m^?3 (5–8 times that reported from south Indian sites). The diurnal patterns and day-to-day variations in aerosol number density and mass loading are closely associated with atmospheric boundary layer height. During haze events, the number density of submicron particles is found to be 2–5 times higher than that during non-hazy period. This could be attributed to the enhanced concentration of anthropogenic aerosols, low atmospheric boundary layer height/ventilation coefficient and airflow convergence.     

Surface exposure dating of young basalts (1–200 ka) in the San Francisco volcanic field (Arizona,USA) using cosmogenic 3He and 21Ne

K–Ar ages of young basalts (<500 ka) are often higher than the actual eruption age, due to low potassium contents and the frequent presence of excess Ar in olivine and pyroxene phenocrysts. Geological studies in the San Francisco and Uinkaret volcanic fields in Arizona have documented the presence of excess ⁴⁰Ar and have concluded that K–Ar ages of young basalts in these fields tend to be inaccurate. This new study in the San Francisco volcanic field presents ³He_c and ²¹Ne_c ages yielded by olivine and pyroxene collected from three Pleistocene basalt flows – the South Sheba (∼190 ka), SP (∼70 ka), and Doney Mountain (∼67 ka) lava flows, – and from one Holocene basalt, the Bonito Lava Flow (∼1.4 ka) at Sunset Crater. These data indicate that, in two of three cases, ⁴⁰Ar/³⁹Ar and K–Ar ages of the young basalts agree well with cosmic-ray surface exposure ages of the same lava flow, thus suggesting that excess ⁴⁰Ar is not always a problem in young basalt flows in the San Francisco volcanic field. The exposure age of the Bonito lava flow agrees within uncertainty with dendrochronological and archeological age determinations. K–Ar and cosmogenic ³He and ²¹Ne ages from the SP flow are in agreement and much older than the OSL age (5.5–6 ka) reported for this lava flow. Furthermore, if the non-cosmogenic ages are assumed to be accurate, the subsequent calculated production rates at South Sheba and SP flow sample sites agree well with values in the literature.     

Soil characteristics and site effect assessment in the city of Delhi (India) using H/V and f–k methods

Local site conditions substantially affect the characteristics of seismic waves and its potential to cause earthquake damage. To accurately identify the variation of seismic hazard at different locations within the cities, measurements from a three-component station may be used for estimating the resonance frequencies and evaluate the expected level of damage at each site. This information can also be complemented with array measurements of ambient noise in order to estimate the V_s profiles and characterize the corresponding sediment layers at each site.     

Vegetation water sources in California's Sierra Nevada (USA) are young and change over time,a multi-isotope (δ18O, δ2H, 3H) tracer approach.

Sierra Nevada forests transpire a significant amount of California's water resources, sparking interest in applying forest management to improve California's water supply. Determining the source water of evapotranspiration enables forest managers to make informed decisions. To this end, a significant interest in critical zone science is to develop new methods to work across time scales to predict subsurface water storage and use. In this study, forest vegetation accessed young water and switched sources depending on availability, suggesting that forest drought vulnerability may depend on the range of water sources available (rain, snowmelt and deeply stored water). This finding also suggests that changes in transpiration rates may have immediate effects on water sources in close proximity to vegetation, and delayed effects on storage and runoff. New δ¹⁸O, δ²H and ³H data were used to track precipitation, runoff, evapotranspiration and storage through the critical zone seasonally, including seasons where evapotranspiration and snowmelt were in phase (winter snowmelt) and out of phase (seasonally dry summer). The main source of this headwater catchment's runoff is derived from its meadow saturated zone water, which was dominated by snowmelt. Water that originated as snowmelt contributed to transpiration, unless other sources, such as recent rain, became available. In cases where xylem δ¹⁸O and δ²H signatures matched those of deeper saturated zone water, ³H data showed that xylem water was distinctly younger than the deep saturated zone water. During 2016, which experienced relatively normal snowpack in winter and seasonally dry summer conditions, mean summer saturated zone water and vegetation water were similar in δ¹⁸O, −12.4 ± 0.04 ‰ and − 12.5 ± 0.3 ‰, respectively, but were distinctly different in ³H, 5.5 ± 0.2 pCi/L and 13.7 ± 1.1 pCi/L, respectively. While δ¹⁸O shows that vegetation and meadow saturated zone water have similar origins, ³H shows they have dissimilar ages.     

Problems associated with extrapolating ecological traits to higher-than-species level exemplified in the description of the larvae of Potamophylax haidukorum Malicky, 1999, Potamophylax winneguthi (Klapálek, 1902) and Melampophylax austriacus Malicky, 1990

Functional diversity, e.g. based on feeding types, is frequently used for assessment procedures. By using Trichoptera genera Potamophylax and Melampophylax as examples, we demonstrate that functional diversity, based on mandible morphology, is low in the former, but high in the latter. When using functional feeding types for assessment procedures, this strictly questions identification at higher than species level and underlines the importance of providing taxonomic information by describing hitherto unknown larvae.Based on mandible morphology, the close species pair Potamophylax haidukorum and P. winneguthi, both endemics of the Dinaric Western Balkan, are omnivorous shredders, a character shared with all other known larvae of genus Potamophylax. In existing keys, P. haidukorum and P. winneguthi may be separated from morphologically close species (e.g. Allogamus spp., Micropterna spp., Potamophylax spp., Leptotaulius gracilis Schmid and Parachiona picicornis (Pictet)) by the lack of a large posterior sclerite at the lateral protuberance, by the lack of additional face setae at mid and hind femora, by the absence of numerous black spines at the pronotal surface and by the shape of metanotal sclerites. Melampophylax austriacus, an endemic of the Eastern Alps, has spoon-shaped scraper mandibles lacking teeth. This character is shared with M. mucoreus (Hagen) and M. nepos (McLachlan), whereas in M. melampus (McLachlan) teeth are present at the mandibles as it is common for omnivorous shredders. Such intra-generic functional diversity questions trait classifications on higher taxonomic units like genus or family.     

Solar radiation,longwave radiation and emergent wetland evapotranspiration estimates from satellite data in Florida,USA / Estimations à partir de données satellitales du rayonnement solaire,du rayonnement de grande longueur d’onde et de l’évapotranspiration d’une zone humide de Floride (EUA)

Abstract

Abstract Routine estimates of daily incoming solar radiation from the GOES-8 satellite were compared to locally measured values in Florida. Longwave radiation estimates corrected using GOES-derived cloud amount and cloud top temperature products improved net radiation estimates as compared to a clear sky longwave approach. The Penman-Monteith, Turc, Hargreaves and Makkink models were applied using GOES-derived estimates of solar radiation and net radiation to predict daily evapotranspiration and were compared to evapotranspiration measured with an eddy-correlation system in an emergent wetland experimental site in north-central Florida under unstressed conditions. While the Penman-Monteith model provided the best estimates of evapotranspiration (R ² = 0.92), the empirical Makkink method demonstrated nearly comparable agreement (R ² = 0.90) using only the GOES solar radiation and measured temperature. The results show that it is possible to generate spatially distributed daily potential evapotranspiration estimates using GOES-derived solar radiation and net radiation with limited additional surface measurements.