Woody buffer effects on water temperature: The role of spatial configuration and daily temperature fluctuations

Water temperature is a key driver for riverine biota and strongly depends on shading by woody riparian vegetation in summer. While the general effects of shading on daily maximum water temperature T_max are well understood, knowledge gaps on the role of the spatial configuration still exist. In this study, the effect of riparian buffer length, width, and canopy cover (percentage of buffer area covered by woody vegetation) on T_max was investigated during summer baseflow using data measured in seven small lowland streams in western Germany (wetted width 0.8–3.7 m). The effect of buffer length on T_max differed between downstream cooling and heating: T_max approached cooler equilibrium conditions after a distance of 0.4 km (~45 min travel-time) downstream of a sharp increase in canopy cover. In contrast, T_max continued to rise downstream of a sharp decrease in canopy cover along the whole 1.6 km stream length investigated. The effect of woody vegetation on T_max depended on buffer width, with changes in canopy cover in a 10 m wide buffer being a better predictor for changes in T_max compared to a 30 m buffer. The effect of woody vegetation on T_max was linearly related to canopy cover but also depended on daily temperature range T_range, which itself was governed by cloudiness, upstream canopy cover, and season. The derived empirical relationship indicated that T_max was reduced by −4.6°C and increased by +2.7°C downstream of a change from unshaded to fully shaded conditions and vice versa. This maximum effect was predicted for a 10 m wide buffer at sunny days in early summer, in streams with large diel fluctuations (large T_range). Therefore, even narrow woody riparian buffers may substantially reduce the increase in T_max due to climate change, especially in small shallow headwater streams with low baseflow discharge and large daily temperature fluctuations.     

Key factors affecting the future provision of tree-based forest ecosystem goods and services

The continuous provisioning of forest ecosystem goods and services (EGS) is of considerable interest to society. To provide insights on how much EGS provision will change with a changing climate and which factors will influence this change the most, we simulated forest stands on six climatically different sites in Central Europe under several scenarios of species diversity, management, and climate change. We evaluated the influence of these factors on the provision of a range of tree-based EGS, represented by harvested basal area, total biomass, stand diversity, and productivity. The most influential factor was species diversity, with diverse forest stands showing a lower sensitivity to climate change than monocultures. Management mainly influenced biomass, with the most intensively managed stands retaining more of their original biomass than others. All three climate-change scenarios yielded very similar results. We showed that (1) only few factor combinations perform worse under climate-change conditions than others, (2) diversity aspects are important for adaptive management measures, but for some indicators, management may be more important than diversity, and (3) at locations subject to increasing drought, the future provision of EGS may decrease regardless of the factor combination. This quantitative evaluation of the influence of different factors on changes in the provision of forest EGS with climate change represents an important step towards the design of more focused adaptation strategies and highlights key factors that should be considered in simulation studies under climate change.     

On the last explosions of carbonatite pipe G3b, Gross Brukkaros, Namibia

 Pipe G3b is part of the Upper Cretaceous carbonatitic Gross Brukkaros Volcanic Field in southern Namibia. The pipe represents the root zone of a diatreme and is located 2800 m west of the rim of Gross Brukkaros, a downsag caldera. The pipe is exposed approximately 550 m below the original Upper Cretaceous land surface. It cuts down into its own feeder dyke, 0.3 m thick. The pipe coalesced from two small pipes and in plan view is 19 m long and 12 m wide. It consists of fragmented Cambrian Nama quartzites and shales of the Fish River subgroup. Despite intensive brecciation, the stratigraphic sequence of the country rocks is almost preserved in the pipe. In addition, the feeder dyke became fragmented too and can be traced in a 2- to 3-m-wide zone full of carbonatite blocks along the southern margin of the pipe. The void space of the breccia is 30–50% in volume. Finally, after the disruption of country rocks and feeder dyke, a little carbonatite magma intruded some of the void space. The breccia of pipe G3b is considered to represent a root zone at the transition from the feeder dyke into a diatreme above. Formation of the breccia required a shock wave thought to have been associated with a last explosion of the diatreme immediately above the present level of exposure. The explosion can be shown to have been phreatomagmatic in origin. Received: 11 October 1996 / Accepted: 6 March 1997     

Elektrochemische Einschätzung des Oberflächenzustandes von Wasserreinigungskohlen

Electrochemical Characterization of the Surface of Activated Carbon Used in Water Treatment Plants. We tried to measure electrochemically those properties of activated carbons which are important for using them for water purification. A success was achieved with the electrochemical immersion potential U_i which is found to be a function of concentration of functional surface groups on the carbon surface. However, the expected direct proportionality for inert surfaces between BET surface area and amount of charge measured in recharge processes has not been observed.     

The role of the Kupferschiefer in the formation of hydrothermal base metal mineralization in the Spessart ore district, Germany: insight from detailed sulfur isotope studies

The Spessart district (SW Germany), located at the southwestern margin of the Permian Kupferschiefer basin in Central Europe, hosts abundant stratabound and structurally controlled base metal mineralization. The mineralization styles identified are (1) stratabound Cu-Pb-Zn-(Ag) ores in Zechstein sedimentary rocks, (2) structurally controlled Cu-As-(Ag) ores in Zechstein sedimentary rocks, (3) crosscutting Co-Ni-(Bi)-As and Cu-Fe-As veins, (4) stratabound metasomatic Fe-Mn carbonate ores in Zechstein dolomite, (5) barren barite veins, and (6) Fe-Mn-As veins in Permian rhyolites. Building on previous work that involved mineralogical, textural, and chemical characterization of the major mineralization types, we have performed a comprehensive sulfur isotope study that applied both conventional and novel laser-ablation multi-collector inductively coupled plasma mass spectrometry techniques. The δ³⁴S values of sulfide minerals from the different ore types are consistently negative and highly variable, in the range between −44.5‰ and −3.9‰, whereas the δ³⁴S values of barite are all positive in the range between 4.7‰ and 18.9‰. Remarkably, stratabound and structurally controlled mineralization in Zechstein sedimentary rocks has the least negative δ³⁴S values, whereas vein-type deposits have consistently more negative δ³⁴S values. The observed pattern of sulfide δ³⁴S values can be best interpreted in terms of fluid mixing at the basement-cover interface. Hydrothermal fluids originating from the crystalline basement migrated upward along subvertical fault zones and were periodically injected into groundwaters that were flowing in the post-Variscan sedimentary cover. These groundwaters had interacted with the Zechstein sedimentary rocks, resulting in fluids characterized by elevated concentrations of reduced sulfur (with negative δ³⁴S values) and alkaline pH. Repeated mixing between both chemically contrasting fluids caused rapid and efficient precipitation of sulfide ore minerals in hydrothermal veins with highly variable but distinctly negative δ³⁴S values.     

Use of biological marker distributions to study thermal history of the Permian Kupferschiefer of the Lower Rhine Basin

In the Central European Zechstein Basin, the Permian Kupferschiefer has been deposited under marine anoxic conditions. From a lagoon at the southwest border of the Zechstein Sea, today part of the Lower Rhine Basin, 30 core samples have been studied by means of organic geochemical methods. Within the area investigated, the depth of the Kupferschiefer horizon increases from about 350 m in the south to about 1000 m in the north. Furthermore, the Kupferschiefer has been thermally affected in the western part by the intrusive body of the so-called Krefeld High. This geological situation opens the possibility to investigate differences of short term and long term temperature effects on the biological marker distribution within a sediment layer of a largely uniform faciès type. Depth related changes in the hopane, sterane and diasterene/diasterane distributions are compared to those changes induced by the Krefeld High. The composition of aromatic steroid hydrocarbons is used to discuss time-temperature effects. It is shown that depth related values of maturation parameters can only be interpreted by taking into account post-depositional tectonic events. Samples from tectonic horst structures show higher maturation values than one would expect from the present day depth.

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Zusammenfassung Aus dem Bereich der heutigen Niederrheinischen Bucht wurden an 30 Kernproben des Kupferschiefers organischgeochemische Untersuchungen durchgeführt. Innerhalb des Untersuchungsgebiets nimmt die Teufe des Kupferschieferhorizonts von 350 m im Süden auf über 1000 m im Norden zu. Organisch-geochemische Reifeparameter zeigen an, daß der Kupferschiefer im Westen durch den Intrusivkörper des Krefelder Gewölbes thermisch beeinflußt worden ist. Aufgrund dieser Situation bietet sich die Möglichkeit, Unterschiede im Einfluß von kurzzeitigen und langzeitigen Temperatureinwirkungen auf die Verteilung von Chemofossilien in einem faziell einheitlichen Horizont zu studieren. Teufenabhängige Variationen der Hopan-, Steran-, Diasteran- und Diasterenverteilungen lassen sich mit den zusätzlich durch den Intrusivkörper verursachten Veränderungen vergleichen. Die Verteilungsmuster der aromatischen Steroide werden zur Deutung von Zeit-Temperatur-Effekten im Verlauf der Diagenese herangezogen. Die ermittelten Meßwerte der Reifeparameter lassen sich nur interpretieren, wenn postsedimentäre tektonische Bewegungen nach der Ablagerung des Kupferschiefers in Betracht gezogen werden. Die aus Horsten stammenden Proben zeigen höhere Reifegrade an als entsprechend ihrer heutigen Teufe zu erwarten.

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Résumé Dans le bassin du Zechstein d'Europe Centrale, les Kupferschiefer permiens ont été déposés dans des conditions marines anoxiques. Dans un paléo-lagon situé à la bordure sud-ouest de la mer du Zechstein, et qui fait partie aujourd'hui du Bassin du Bas-Rhin, 30 échantillons, provenant de carottes, ont fait l'objet d'une étude de géochimie organique. Dans la région ainsi étudiée, la profondeur de l'horizon des Kupferschiefer augmente, du sud au nord, de 350 m à 1.000 m. D'autre part, les Kupferschiefer ont subi, dans leur partie ouest, l'influence thermique du corps intrusif du «Dôme de Krefeld». Cette situation géologique fournit la possibilité d'étudier les effets à long terme et à court terme de la température sur la distribution des marqueurs biologiques au sein d'un niveau sédimentaire de faciès uniforme. Les modifications dans la répartition de l'hopane, du stérane et du diastérène/diasterane en fonction de la profondeur sont comparées à celles qui sont provoquées par le Dôme de Krefeld. Les effets temps-température sont discutés à partir de la composition des hydrocarbures stéroïdes aromatiques. Les auteurs montrent que la valeur des paramètres de maturation liés à la profondeur ne peuvent être interprétés sans que l'on prenne en considération les événements tectoniques postsédimentaires. Des échantillons provenant de structures en horst montrent un degré d'évolution plus élevé que celui auquel on s'attend d'après leur profondeur actuelle.

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Zur Genese neuentdeckter Vulkanschlote in der Umgebung des Donnersberges/Pfalz

Zusammenfassung Einige neuentdeckte Vulkanschlote im Rotliegenden der Umgebung des Donnersberges in der Saar-Nahe-Senke/Pfalz wurden hinsichtlich Aufbau, Alter und Genese untersucht. Es sind calderaartig abgesunkene Pyroclastica von Schlotbreccien zu unterscheiden, von denen Ablagerung aus einer Gas-Partikel-Suspension angenommen wird. Die Breccien setzen sich aus einer Mischung von Lapilli und z. T. aufgearbeitetem Nebengestein zusammen. In fast allen Schloten wurde die Aktivität durch das Eindringen von Schmelzen abgeschlossen.Als Beispiel wird der Schlot des Rödern beschrieben.

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In the Lower Permian of the Saar-Nahe-Senke (Palatinate, SW Germany) several recently discovered volcanic necks have been investigated. In this preliminary report structure, composition, and age relationship of the breccias are described as well as their mode of emplacement which is believed to be due partly to fluidization and partly to calderalike subsidence of subaerially deposited tephra. In some of the necks magmatic intrusion terminated the volcanic activity.The volcanic neck of the Rödern is described as an example.

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Résumé Plusieurs cheminées récemment découvertes dans le Permien inférieur des alentours du Donnersberg dans la Saar-Nahe-Senke (Palatinat, Sud-ouest d'Allemagne) ont été étudiées. Leur composition et les problèmes de l'âge et de la genèse sont discutés. Il faut distinguer des sédiments pyroclastiques des caldères d'effondrement et des brèches formées à l'intérieur des cheminées. Celles-ci se composent des lapillis et des fragments des roches encaissantes. Leur formation est le résultat d'un dégagement de gaz tenant en suspension des particules solides.La fin de l'activité est marquée en général par l'intrusion des laves. La cheminée du Rödern est décrite à titre d'exemple.

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The response of fishes to physicochemical changes in the mangroves of northeast Florida Bay

Historically, large volumes of fresh water from the Everglades reached Florida Bay in the form of overland sheet flow. South Florida's extensive canal system has diverted fresh water from its historic course, resulting in shorter hydroperiods and higher salinities than would have occurred in an unaltered system. The mixing zone between the freshwater Everglades and euryhaline Florida Bay is primarily characterized as a dwarf red mangrove forest. The small, demersal fishes found in this habitat are an important food source for a variety of predators and are excellent bioindicators for both short-term and long-term perturbations in the system. I examine the effect of fluctuating water level, salinity, and temperature on this fish community in order to better understand the impact water diversion has had on the ecotone. Fish were collected at four sites within the ecotone over a t-yr period using a 9-m² drop trap. Principal components analysis was used to generate 10 composite variables (PCs) from a temporal array of 59 physicochemical variables. These composite variables were used in regression analyses to evaluate spatial and temporal changes in the fish community. Regression analysis indicated fish density was significantly related to short-term and long-term changes in water level and with long-term temperature variation (r²=0.50). An ANOVA of density between sites supports the regression results, indicating that sites with longer hydroperiod had higher density than sites with shorter hydroperiod. The impact of changes in density on biomass was reflected by regression analysis, which indicated that increased water level and decreased variability in depth were correlated with higher biomass (r²=0.61). Biomass was also influenced by changes in the salinity regime, presumably through increases in individual fish body size or through a shift in the community toward heavier-bodied fish species. An ANOVA of biomass between sites indicates sites with longer freshwater periods had higher biomass than sites with shorer freshwater periods. The first two axes of a detrended correspondence analysis on community biomass explained 59.2% of the variance in the community and supported the hypothesis that salinity was a primary determinant of community structure. These results indicate historic changes in water deliver could have altered the mangrove fish community, thereby lowering prey availability for higher trophic levels.