Rates, patterns, and impacts ofPhragmites australis expansion and effects of experimentalPhragmites control on vegetation, macroinvertebrates, and fish within tidelands of the lower Connecticut River

Phragmites expansion rates (linear at 1–3% yr⁻¹) and impacts of this expansion on high marsh macroinvertebrates, aboveground production, and litter decomposition fromPhragmites and other marsh graminoids were studied along a polyhaline to oligohaline gradient. These parameters, and fish use of creeks and high marsh, were also studied inPhragmites control sites (herbicide, mowing, and combined herbicide/mow treatments).Phragmites clones established without obvious site preferences on oligohaline marshes, expanding radially. At higher salinities,Phragmites preferentially colonized creekbank levees and disturbed upland borders, then expanded into the central marsh. Hydroperiods, but not salinities or water table, distinguishedPhragmites-dominated transects. Pooled samples ofPhragmites leaves, stems, and flowers decompose more slowly than other marsh angiosperms;Phragmites leaves alone decompose as or more rapidly than those of cattail. AbovegroundPhragmites production was 1,300 to 2,400 g m⁻² (about 23% of this as leaves), versus 600–800 g m⁻² for polyhaline to mesohaline meadow and 1,300 g m⁻² for oligohaline cattail-sedge marsh. Macroinvertebrates appear largely unaffected byPhragmites expansion or control efforts; distribution and densities are unrelated to elevation or hydroperiod, but densities are positively related to litter cover. Dominant fish captured leaving flooded marsh wereFundulus heteroclitus andAnguilla rostrata; both preyed heavily on marsh macroinvertebrates.A. rostrata andMorone americana tended to be more common inPhragmites, but otherwise there were no major differences in use patterns betweenPhragmites and brackish meadow vegetation. SAV and macroalgal cover were markedly lower within aPhragmites-dominated creek versus one withSpartina-dominated banks. The same fish species assemblage was trapped in both plus a third within the herbicide/mow treatment. Fish biomass was greatest from theSpartina creek and lowest from thePhragmites creek, reflecting abundances ofF. heteroclitus. Mowing depressedPhragmites aboveground production and increased stem density, but was ineffective for control.Phragmites, Spartina patens, andJuncus gerardii frequencies after herbicide-only treatment were 0.53-0.21; total live cover was <8% with a heavy litter and dense standing dead stems. After two growing seasonsAgrostis stolonifera/S. patens/J. gerardii brackish meadow characterized most of the herbicide/mow treatment area;Phragmites frequency here was 0.53, contributing 3% cover. Both values more than doubled after four years; a single treatment is ineffective for long-termPhragmites control.     

K/Rb-, Ca/Sr- und K/Ti-Verhältnisse in basaltoiden Gesteinen der Ostalpen und benachbarter Gebiete

Zusammenfassung Es wurden 69 basaltische Gesteine aus dem ostalpinen und westkarpatischen Orogen sowie aus dem pannonischen Zwischengebirge röntgenfluoreszenzspektrometrisch auf K, Ca, Rb, Sr und Ti analysiert. Eine Auswertung der Korrelationsdiagramme K/Rb, Ca/Sr und K/Ti ergibt für verwandte Gesteine definierte Konzentrationsfelder. Die Alkaliolivinbasalte zeichnen sich, soweit sie nicht durch sekundäre Prozesse Veränderungen erfahren haben, durch relativ enge Konzentrationsfelder aus. Als Mittelwerte wurden für 30 Proben von Alkaliolivinbasalten (<2% K) von 12 verschiedenen Vorkommen erhalten: 1,39% K, 6,58% Ca, 1,57% Ti, 48 ppm Rb und 1015 ppm Sr.Die Basalte des Orogenrandes erscheinen weniger alkalisch. Im Orogenbereich kann eine stärkere Kontamination mit sialischem Material möglich sein. Basalte des Orogenbereiches und des pannonischen Zwischengebirges weisen anscheinend mit zunehmender Sialmächtigkeit eine stärkere Tendenz zur Alkalisierung auf.

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K/Rb-, Ca/Sr- and K/Ti-tatios in basaltic rocks of the Eastern Alps and neighbouring regions

Summary Using x-ray fluorescence spectrometry 69 samples of basaltic rocks from the Eastern Alps, the Western Carpathian Mountains, the Hungarian Plain, and the Bakony Mountains were analysed for the elements K, Ca, Ti, Rb and Sr. The correlation diagrams show defined concentration fields for similiar rock types. Alkaliolivine basalts, which are not influenced by secondary processes, are characterized by small concentration fields. The average values of 30 samples of alkali olivine basalts (<2% K), taken from 12 volcanoes, are: 1.39% K, 6.58% Ca, 1,57% Ti, 48 ppm Rb and 1015 ppm Sr.Some basalts of the orogene border seem to be less alkalic. A higher contamination with sialic material may be possible in the region of the orogene. Basalts from the region of the orogene and from the Hungarian Plain show a strong tendency towards the formation of alkali rich rock types. A relation to the thickness of the sial seems to be probable.

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Mit 4 Abbildungen     

Hydrobiology of a salt pan from the Peninsula of Baja California, Mexico

The study site, a salt pan in the northwest of Baja California, Mexico,has a surface area of 33.2 ha and water capacity of 216,072m³. It is intermittently isolated from the adjacent ocean by asand bar, so that flooding via the coastal plain is a low frequency eventassociated with extreme storm conditions. Temporal changes in water volumewere represented by a particular expression of the mass conservationequation having as variables the volumetric capacity of the system, waterinputs by pluvial precipitation, runoff and infiltration, and water loss byevaporation; the numerical model explained over 80 per cent of observedfluctuations. The hydrobiological study covered a three-year period and twohydrological cycles; the first one was of mixed marine and pluvial origin,and the second, continental. Throughout the first cycle, phosphate andnitrate concentrations were up to one order of magnitude higher as weretotal particulate protein, chlorophyll a and phytoplankton abundance. Ingeneral, nannoplankton abundance was up to three orders of magnitude greaterthan the microphlanktonic fraction. In the former, 29 different cell formswere observed; two halophytic bacteria constituted 60–80 per cent ofthat fraction. In the microplankton, there were 27 different forms; mostwere benthic diatoms. The zooplanktonic assemblages of the first cycle hadmarine and continental elements; at 141 per mille, Artemia sp. firstappeared; at 240 per mille, it was the only faunistic element in the system.During the second cycle, Artemia was always present, co-existing with othercontinental species up to a salinity of 99 per mille. The morphology andmorphometry of Artemia were similar to those of Artemia franciscana.     

Chemical characteristics of atmospheric bulk deposition in a semi-rural area of the <Emphasis Type="Bold">Po Valley</Emphasis> (Italy)

This study provides an analysis of a five-year time series chemical composition of the bulk deposition (2009–2013), collected within a farm surrounded by industrial and urban settlements in a semi-rural area of the Po Valley, with the aim of characterizing potential emission sources affecting precipitation composition at the site. Most monitoring efforts in this region, recognized as one of the most polluted in the world both due to the intense industrialisation and urbanisation as well as to frequent air stagnation conditions, are presently devoted more to gaseous and particulate pollutants than to precipitation chemistry. The bulk deposition samples were very concentrated in chemical species, both acidic and alkaline, high compared to other polluted sites in the world and to locations in the same district. The mean ions concentrations (in μeq l^?1) are: NO₃ ^? (243) > SO₄ ^2? (220) > PO₄ ^3? (176) > Cl^? (153) > NO₂ ^? (29) > F^? (2.6); NH₄ ⁺ (504) > Ca²⁺ (489) > K⁺ (151) > Na⁺ (127) > Mg²⁺ (127). pH data shows a trend toward slightly alkaline conditions attributed to the large presence of ammonium and crustal elements, in spite of high concentrations of nitrates and sulphates. The relevant concentrations of Ca²⁺ and Mg²⁺ further suggests that these alkaline conditions might be due to the correspondingly significant concentrations of carbonates/bicarbonates in our dataset. While back-trajectories analysis suggests the stronger importance of local resuspension over long-range transport, statistical analyses on ion composition highlight the key role exerted by agricultural activity, especially in the case of NH₄ ⁺, K⁺, Ca²⁺ and PO₄ ^3? (especially linked to fertilisation practices and soil resuspension due to mechanical operations). Apart from Na⁺ and Cl^? ions which correlate well as expected, indicating their likely common origin from marine salt, the identification of the origin of the other ions is very complex due to the contribution of diverse local sources, such as industrial and residential settlements.     

The first multi-model ensemble of regional climate simulations at kilometer-scale resolution part 2: historical and future simulations of precipitation

This paper presents the first multi-model ensemble of 10-year, “convection-permitting” kilometer-scale regional climate model (RCM) scenario simulations downscaled from selected CMIP5 GCM projections for historical and end of century time slices. The technique is to first downscale the CMIP5 GCM projections to an intermediate 12–15 km resolution grid using RCMs, and then use these fields to downscale further to the kilometer scale. The aim of the paper is to provide an overview of the representation of the precipitation characteristics and their projected changes over the greater Alpine domain within a Coordinated Regional Climate Downscaling Experiment Flagship Pilot Study and the European Climate Prediction system project, tasked with investigating convective processes at the kilometer scale. An ensemble of 12 simulations performed by different research groups around Europe is analyzed. The simulations are evaluated through comparison with high resolution observations while the complementary ensemble of 12 km resolution driving models is used as a benchmark to evaluate the added value of the convection-permitting ensemble. The results show that the kilometer-scale ensemble is able to improve the representation of fine scale details of mean daily, wet-day/hour frequency, wet-day/hour intensity and heavy precipitation on a seasonal scale, reducing uncertainty over some regions. It also improves the representation of the summer diurnal cycle, showing more realistic onset and peak of convection. The kilometer-scale ensemble refines and enhances the projected patterns of change from the coarser resolution simulations and even modifies the sign of the precipitation intensity change and heavy precipitation over some regions. The convection permitting simulations also show larger changes for all indices over the diurnal cycle, also suggesting a change in the duration of convection over some regions. A larger positive change of frequency of heavy to severe precipitation is found. The results are encouraging towards the use of convection-permitting model ensembles to produce robust assessments of the local impacts of future climate change.

     

Localised strain in fissured clays: the combined effect of fissure orientation and confining pressure

Acta Geotechnica - This paper reports the main results of an experimental study on the mechanics of intensely fissured natural clays, extending our previous studies on scaly clay from Santa Croce...     

Physical structure and vertical distribution of chlorophyll a in winter sea ice from the northwestern Weddell Sea, Antarctica

The investigation on sea-ice biology in combination with physics, chemistry and ecology was carried out in the northwestern Weddell Sea, Antarctica, during the cruise ANT/XX III-7 on board POLARSTERN in the austral winter (August-October) in 2006. The distribution of chlorophyll a was measured and related to sea ice texture. The mean concentrations of chlorophyll a in the sea ice varied considerably with ice texture. The concentration of chlorophyll a per core ranged from 2.10– 84.40 μg/dm 3 with a mean of 16.56 μg/dm 3 . And the value of R (chlorophyll a / gross chlorophyll) ranged from 0.79–0.83. These high winter chlorophyll values indicate that primary production is considerable and confirms that there is significant primary production in Antarctic sea ice during winter. Thus this constitutes a major proportion of southern ocean primary production and carbon flux before the sea ice retreats.     

Mediterranean warm-core cyclones in a warmer world

Regional climate model projections over the Mediterranean region are analysed for the presence of intense, warm-core lows that share some of the characteristics of tropical cyclones. The results indicate that the number of such systems decreases in a warmer world, particularly in winter. Comparison of the simulated numbers to changes in relevant climate diagnostics suggests that numbers decrease due to an increasingly hostile environment for storm formation, combined with a general poleward shift in the incidence of wintertime lows over western Europe.