Iron-rich post-perovskite and the origin of ultralow-velocity zones

The boundary layer between the crystalline silicate lower mantle and the liquid iron core contains regions with ultralow seismic velocities. Such low compressional and shear wave velocities and high Poisson's ratio are also observed experimentally in post-perovskite silicate phase containing up to 40 mol% FeSiO3 endmember. The iron-rich post-perovskite silicate is stable at the pressure-temperature and chemical environment of the core-mantle boundary and can be formed by core-mantle reaction. Mantle dynamics may lead to further accumulation of this material into the ultralow-velocity patches that are observable by seismology.     

Multiyear prediction of monthly mean Atlantic Meridional Overturning Circulation at 26.5°N

Attempts to predict changes in Atlantic Meridional Overturning Circulation (AMOC) have yielded little success to date. Here, we demonstrate predictability for monthly mean AMOC strength at 26.5°N for up to 4 years in advance. This AMOC predictive skill arises predominantly from the basin-wide upper-mid-ocean geostrophic transport, which in turn can be predicted because we have skill in predicting the upper-ocean zonal density difference. Ensemble forecasts initialized between January 2008 and January 2011 indicate a stable AMOC at 26.5°N until at least 2014, despite a brief wind-induced weakening in 2010. Because AMOC influences many aspects of climate, our results establish AMOC as an important potential carrier of climate predictability.     

Long-term change in the nitrogen cycle of tropical forests

Deposition of reactive nitrogen (N) from human activities has large effects on temperate forests where low natural N availability limits productivity but is not known to affect tropical forests where natural N availability is often much greater. Leaf N and the ratio of N isotopes (δ(15)N) increased substantially in a moist forest in Panama between ~1968 and 2007, as did tree-ring δ(15)N in a dry forest in Thailand over the past century. A decade of fertilization of a nearby Panamanian forest with N caused similar increases in leaf N and δ(15)N. Therefore, our results indicate regional increases in N availability due to anthropogenic N deposition. Atmospheric nitrogen dioxide measurements and increased emissions of anthropogenic reactive N over tropical land areas suggest that these changes are widespread in tropical forests.     

Conservation and landscape maintenance in Germany: Past,present, and future

Three main sources of landscape maintenance and nature conservation in Germany are identified: the British landscape garden, the official conservation activities, and a private association of nature park promoters. Among their achievements are the German Nature Conservation Act of 1935, the establishment of about fifty nature parks and one national park, a well-developed theory and practice of landscape planning, and three university departments of landscape architecture. The three sources, however, have not yet generated one comprehensive stream of activity, and they seem to lack a common basis of work. To overcome these difficulties, the author proposes a landscape strategy based on a pattern of ecosystems in different successional stages. The strategy is derived from the history of land-use in Central Europe and from the resulting Man-Nature relationships. They created a characteristic landscape pattern defined as the ‘European savanna’, the diversity of which provided for a high degree of ecological stability. The diversity can be maintained even in today's land-use, which consists of four main types. In a given area, one of these types is allowed to prevail, but there is repeated inclusion of the three other use-types in a finely-grained mixture. This should result in a diversified make-up of the landscape, which is both productive and ecologically stable enough to provide for an optimum natural environment of balanced Man-Nature relationships.     

The geographic origin of old Douglas-fir stands growing in Central Europe

Since the nineteenth century, Douglas-fir seed sources have been widely used for establishment of forest stands outside its natural distribution range. In Europe, some of these old Douglas-fir stands are registered as seed stands and provide seed sources for nurseries, although it is unclear from which region in North America they originate. In recent years, the interest in planting Douglas-fir has increased substantially because the species is seen as a potential adaptation option to climate change. This makes the assignment of European Douglas-fir stands of unknown seed origin to their geographic origin in North America increasingly important, because the genetic quality of these plantations must be guaranteed. In this study, we use 13 nuSSR loci to investigate the origin of 67 Austrian and German Douglas-fir stands of unknown origin. We performed a hierarchical Bayesian cluster analysis using 38 native Douglas-fir populations. The resulting clusters are used as reference populations to assign the 67 Central European Douglas-fir stands from Austria and Germany planted more than 80 years ago. Our results suggest that the majority of our investigated Douglas-fir stands come from central Washington (USA), the recommended seed zones for Central Europe. Some stands were located outside the suggested area, e.g. central Oregon and Santa Fe (New Mexico). The accuracy assessment of our approach revealed the best performance for the highest hierarchical level, e.g. assigning populations either to the coastal or the Rocky Mountain variety. As expected, the uncertainty increases with decreasing hierarchical level. The final assessment, if an admixture of seed sources within the European Douglas-fir stands is evident suggests that 23 of the Douglas-fir stands show an admixture which was not detected in our Douglas-fir reference populations growing in the natural distribution range.     

Dynamik und Elementgehalte von Fichtenfeinwurzeln in Kalkgesteinsböden am Wank (Bayerische Kalkalpen)

Dynamics and nutrient concentration in fine-roots of alpine spruce stands on calcareous soils (Wank-Massif/Bavarian Alps) The dynamics and the concentrations of nutrient elements in the fine roots of two stands of alpine spruce differing in vigour on calcareous soils overlying limestone in the Wank massif of the bavarian alps were measured. Selected root parameters were compared with those obtaining on acid soils. At Wank, the concentration (mg/100 ml soil) of living fine roots and root tips was maximum in the organic surface layer and the mineral horizon immediately underlying the surface layer. There were significantly more fine root biomass (kg ha^?1) on the calcareous site (Walk) than on acid soils (Solling and Fichtelgebirge). There were also marked differences between the two sites in concentration of nutrient elements in the fine roots was strongly influenced by chemical composition of the soil solution.     

The (Me5C5)Si+ cation: a stable derivative of HSi+

The reaction of decamethylsilicocene, (Me5C5)2Si, with the proton-transfer reagent Me5C5H2+B(C6F5)4- produces the salt (Me5C5)Si+ B(C6F5)4(2), which can be isolated as a colorless solid that is stable in the absence of air and moisture. The crystal structure reveals the presence of a cationic pi complex with an eta5-pentamethylcyclopentadienyl ligand bound to a bare silicon center. The 29Si nuclear magnetic resonance at very high field (delta = - 400.2 parts per million) is typical of a pi complex of divalent silicon. The (eta5-Me5C5)Si+ cation in 2 can be regarded as the "resting state" of a silyliumylidene-type (eta1-Me5C5)Si+ cation. The availability of 2 opens new synthetic avenues in organosilicon chemistry. For example, 2 reacted with lithium bis(trimethylsilyl)amide to give the disilene E-[(eta1-Me5C5)[N(SiMe3)2]Si]2(3).     

Simulation of chromium transport in the unsaturated zone for predicting contaminant entries into the groundwater

Heavy metal contaminations in the top‐soil layers can impose serious threats to groundwater quality. A seepage water prognosis of probable future contaminant entries at the groundwater surface has to take into account the emission characteristics of the source zone and the reactive transport of the contaminated leachate through the unsaturated zone. Here, a possible approach is presented, exemplarily for a site contaminated with chromium, encompassing batch elution experiments, unsaturated soil column leaching experiments with flow interruption, soil monolith lysimeter experiments, and numerical modeling of non‐equilibrium solute transport. The prognosis provides a long‐term prediction of Cr concentrations at the groundwater surface. It must be emphasized, that the modeling results are uncertain, because several of the parameters in the simulations can be determined only with significant errors. Additionally, the approach is not applicable routinely for every hazardous waste site. Our study reveals, however, that reactive contaminants can possibly reach the groundwater at hazardous concentrations within very short time.     

Der Einfluß von Wind und Windschutz auf den CO2-Gehalt der bodennahen Luftschicht über Feldkulturen

Zusammenfassung Mit Hilfe des Ultrarotabsorptionsschreibers (URAS) wurde die CO₂-Konzentration in der bodennahen Luftschicht unter dem Einfluß von Wind und Windschutz gemessen. In der Nacht ist die CO₂-Konzentration im Windschutz gegenüber dem Freiland erhöht, da dort die Atmungskohlensäure vor Verwehung geschützt ist. Bei unbewachsenem Boden bleibt jedoch in Lee die CO₂-Konzentration durch Behinderung der Zufuhr aus der Umgebung geringer als in Luv. Für den Verlauf des Aufbaues eines CO₂-Gefälles vom Boden her ist die Höhe der Windgeschwindigkeit bestimmend. Das rasche Absinken der CO₂-Konzentration in den Morgenstunden muß zuerst durch die Photosynthese, die schon kurz nach Sonnenaufgang einsetzt, verursacht werden. Nach Erwärmung der untersten Luftschichten geht dann durch den Vertikalaustausch der größte Teil des während der Nacht angesammelten Kohlendioxyds den Pflanzen für die Photosynthese verloren. Am Tage besteht im Windschutz gegenüber dem Freiland meist ein CO₂-Defizit, das zeitweise durch die erschwerte Erneuerung der Bestandesluft durch Advektion, in erster Linie jedoch durch die stärkere Assimilation der Pflanzen in Lee zustande kommt. Diese Mitteilung wird durch eine weitere ergänzt werden, welche das photosynthetische Verhalten von Pflanzen mit und ohne Windschutz behandelt.

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CO₂-content in the air layer above the ground with crop cultures in open field and under the lee

Summary By means of ultra-red absorption recorder (URAS) the CO₂-concentration of the air near the ground under the influence of wind and wind shelter was investigated. During the night the CO₂-concentration under the lee has been found increased in comparison with open field. Behind a shelter the CO₂ is not so much blown away as outside. Indeed, above soil without any plant growth the CO₂-concentration inside the sheltered area remains lower in consequence of the hindrance of horizontal transport of air. The wind speed is important to the formation of a CO₂-gradient above the ground. The rapid decrease of CO₂-concentration in the early morning must be caused primarily by photosynthesis of plants beginning almost immediately after sunrise. Later on by vertical air movement the greatest part of CO₂, accumulated during the night, is lost for photosynthesis by warming the air near the ground. During the day under the lee there exist mostly a CO₂-deficite in comparison with the open field. This is partly rendered by difficulty of air transport by advection, at first, indeed, by an increased rate of photosynthesis under the lee. The present communication will be continued by a second one concerning the photosynthetic behaviour of plants inside and outside of wind shelter.

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Transendoscopic injection of poly-L-lactic acid into the soft palate in horses: A new therapy for dorsal displacement of the soft palate?

The purpose of this study was to establish a minimal invasive, transendoscopic technique for injection of poly-L-lactic acid into the free edge of the soft palate that can be performed on the standing sedated horse. Furthermore, whether the implant material induces an increase in fibrous tissue at the injection site, resulting in a greater rigidity of the soft palate, was determined.In 4 horses, the injection was performed bilaterally along the caudal margin of the soft palate, and the influence of the treatment on the soft palate function was determined. Clinical, radiographic and endoscopic examinations at rest were performed before and up to 168 days after injection according to a standardized examination protocol.In 6 horses, the implant material was injected unilaterally into the right half of the caudal margin of the soft palate. After clinical and endoscopic follow-up examinations, 2 horses each were killed 28, 84, and 168 days after the implantation procedure. At necropsy, macroscopic comparison of the treated and the untreated halves of the soft palate showed the influence on the size of the ostium intrapharyngeum and on the soft palate thickness. The localization of the implant material in the soft palate and the tissue response to the poly-L-lactic acid were evaluated histologically.Transendoscopic injection into the soft palate requires neither general anesthesia nor wound management, and it is noted for minimal tissue trauma. After injection, no alteration of the soft palate function was observed in horses with normal upper airway mechanics. One horse with intermittent dorsal displacement of the soft palate showed an improvement of the soft palate function for 112 days after implantation. No significant alteration in the size of the ostium intrapharyngeum was evident in any horse. Histologic assessment indicated the presence of implant material during the entire observation period of 168 days. The implant was accompanied by a granulomatous inflammation, and it was encapsulated by fibrous tissue. This may result in an increase in stiffness, and subsequent a greater rigidity of the soft palate, preventing it from displacement. The injection may therefore be considered an alternative to established therapies in horses showing dorsal displacement of the soft palate because of its unstable free edge.