Wood-ash recycling affects forest soil and tree fine-root chemistry and reverses soil acidification

Wood ash was applied to a forest ecosystem with the aim to recycle nutrients taken from the forest and to mitigate the negative effects of intensive harvesting. After two years, the application of 8,000 kg ha−1 of wood ash increased soil exchangeable Ca and Mg. Similarly, an increase in Ca and Mg in the Norway spruce fine roots was recorded, leading to significant linear correlations between soil and root Ca and soil and root Mg. In contrast to these macronutrients, the micronutrients Fe and Zn and the toxic element Al decreased in the soil exchangeable fraction with the addition of wood ash, but not in the fine roots. Only Mn decreased in soil and in fine roots leading to a significant linear correlation between soil and root Mn. In soil, as well as in fine roots, strong positive correlations were found between the elements Ca and Mg and between Fe and Al. This indicates that the uptake of Mg resembles that of Ca and that of Al that of Fe. With the wood ash application, the pH increased from 3.2 to 4.8, the base saturation from 30% to 86%, the molar basic cations/Al ratio (BC/Al) of the soil solution from 1.5 to 5.5, and the molar Ca/Al ratio of the fine roots from 1.3 to 3.7. Overall, all below-ground indicators of soil acidification responded positively to the wood ash application within two years. Nitrate concentrations increased only slightly in the soil solution at a soil depth of 75-80 cm, and no signs of increased heavy metal concentrations in the soils or in the fine roots were apparent. This suggests that the recycling of wood ash could be an integral part of sustainable forest management because it closes the nutrient cycle and reverses soil acidificatio

A high-reflectivity high-Q micromechanical Bragg-mirror

We report on the fabrication and characterization of a micromechanical oscillator consisting only of a free-standing dielectric Bragg mirror with high optical reflectivity and high mechanical quality. The fabrication technique is a hybrid approach involving laser ablation and dry etching. The mirror has a reflectivity of 99.6%, a mass of 400ng, and a mechanical quality factor Q of approximately 10^4. Using this micromirror in a Fabry Perot cavity, a finesse of 500 has been achieved. This is an important step towards designing tunable high-Q high-finesse cavities on chip.Comment: 3 pages, 2 figure

Force-Velocity and Power Characteristics of Rat Soleus Muscle Fibers after Hindlimb Suspension

The effects of 1, 2, and 3 wk of Hindlimb Suspension (HS) on force-velocity and power characteristics of single rat soleus fibers were determined. After 1, 2, or 3 wk of HS, small fiber bundles were isolated, placed in skinning solution, and stored at -20 C until studied. Single fibers were isolated and placed between a motor arm and force transducer, functional properties were studied, and fiber protein content was subsequently analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Additional fibers were isolated from soleus of control and after 1 and 3 wk of HS, and fiber type distribution and myosin light chain stoichiometry were determined from SDS-PAGE analysis. After 1 wk of HS, percent type I fibers declined from 82 to 74%, whereas hybrid fibers increased from 10 to 18%. Percent fast type 11 fibers increased from 8% in control and 1 wk of HS to 26% by 3 wk of HS. Most fibers showed an increased unloaded maximal shortening velocity (V(sub 0)), but myosin heavy chain remained entirely slow type I. The mechanism for increased V(sub 0) is unknown. There was a progressive decrease in fiber diameter (14, 30, and 38%) and peak force (38, 56, and 63%) after 1, 2, and 3 wk of HS, respectively. One week of HS resulted in a shift of the force-velocity curve, and between 2 and 3 wk of HS the curve shifted further such that V(sub 0) was higher than control at all relative loads less than 45% peak isometric force. Peak absolute power output of soleus fibers progressively decreased through 2 wk of HS but showed no further change at 3 wk. The results suggest that between 2 and 3 wk the HS-induced alterations in the force-velocity relationship act to maintain the power output of single soleus fibers despite a continued reduction in fiber force

Self-cooling of a micro-mirror by radiation pressure

We demonstrate passive feedback cooling of a mechanical resonator based on radiation pressure forces and assisted by photothermal forces in a high-finesse optical cavity. The resonator is a free-standing high-reflectance micro-mirror (of mass m=400ng and mechanical quality factor Q=10^4) that is used as back-mirror in a detuned Fabry-Perot cavity of optical finesse F=500. We observe an increased damping in the dynamics of the mechanical oscillator by a factor of 30 and a corresponding cooling of the oscillator modes below 10 K starting from room temperature. This effect is an important ingredient for recently proposed schemes to prepare quantum entanglement of macroscopic mechanical oscillators.Comment: 11 pages, 9 figures, minor correction

PORTABLE IMAGE-BASED HIGH PERFORMANCE MOBILE MAPPING SYSTEM IN UNDERGROUND ENVIRONMENTS – SYSTEM CONFIGURATION AND PERFORMANCE EVALUATION

The progression in urbanization increases the need for different types of underground infrastructure. Consequently, infrastructure and life cycle management are rapidly gaining in importance. Mobile reality capturing systems and cloud-based services exploiting georeferenced metric 3D imagery are already extensively used for infrastructure management in outdoor environments. These services minimise dangerous and expensive field visits or measurement campaigns. In this paper, we introduce the BIMAGE Backpack, a portable image-based mobile mapping system for 3D data acquisition in indoor environments. The system consists of a multi-head panorama camera, two multi-profile laser scanners and an inertial measurement unit. With this system, we carried out underground measurement campaigns in the Hagerbach Test Gallery, located in Flums Hochwiese, Switzerland. For our performance evaluations in two different tunnel sections, we employed LiDAR SLAM as well as advanced image-based georeferencing. The obtained absolute accuracies were in the range from 6.2 to 7.4 cm. The relative accuracy, which for many applications is even more important, was in the range of 2–6 mm. These figures demonstrate an accuracy improvement of the subsequent image-based georeferencing over LiDAR SLAM by about an order of magnitude. The investigations show the application potential of image-based portable mobile mapping systems for infrastructure inventory and management in large underground facilities

Northern Sourced Water dominated the Atlantic Ocean during the Last Glacial Maximum

Increased carbon sequestration in the ocean subsurface is commonly assumed to have been one of the main causes responsible for lower glacial atmospheric CO2 concentrations. Remineralized carbon must have been stored away from the atmosphere for thousands of years, yet the water mass structure accommodating such increased carbon storage continues to be debated. Here, we present new sediment-derived bottom-water neodymium isotope records that allow fingerprinting of water masses and provide a more complete picture of the Atlantic Meridional Overturning Circulation geometry during the Last Glacial Maximum. These results suggest that the vertical and meridional structure of the Atlantic water mass distribution only experienced minor changes since the last ice age. In particular, we find no compelling evidence supporting glacial southern-sourced water substantially expanding to shallower depths and farther into the Northern Hemisphere than today, which had been previously inferred from stable carbon isotope (δ13C) reconstructions. We argue that depleted δ13C values observed in the deep Northwest Atlantic do not necessarily indicate the presence of southern-sourced water. Instead, these values may represent a northern-sourced water mass with lower than modern preformed δ13C values that were further modified downstream by increased sequestration of remineralized carbon, facilitated by a more sluggish glacial deep circulation, corroborating previous evidence

Dynamik der Stickstoffspezies im Boden und ihre Bedeutung für die Wurzelmorphologie - was haben wir von Drew gelernt?

Harnstoff ist nach Kalkammonsalpeter der bedeutendste Stickstoffdünger in Deutschland. Insbesondere in Kombination mit Nitrifikationsinhibitoren (NI) stellt Harnstoff eine Düngeform dar, die im Unterschied zu Ammoniumsulfat weniger zu einer Versauerung führt und gleichzeitig aufgrund der potentiellen Bindung des Zwischenproduktes Ammonium eine geringere Auswaschungsgefahr birgt als Nitratdünger. Die N-Düngeform beeinflusst neben pH-Wert und Mobilität auch die Morphologie/Physiologie des Wurzelsystems. Untersuchungen auf Gelplatten und in Nährlösung mit konstantem Angebot jeweils einer N-Spezies zeigen meist eine Förderung der Anzahl Seitenwurzeln bei reiner Ammoniumernährung und eine geringere Anzahl Seitenwurzeln bei Nitraternährung; die Länge der vorhandenen Seitenwurzeln ist tendenziell erhöht. Unklar ist, inwiefern solche Ergebnisse auf das System Pflanze Boden übertragbar sind. Im Boden stellt die organische Substanz stets eine zusätzliche N-Quelle dar. Aufgrund der mikrobiellen Aktivität liegen meist beide Stickstoffspezies zeitgleich vor. Am Austauscher bzw. in den Zwischenschichten von Tonmineralen wird NH4+ gebunden, welches sich im Gleichgewicht mit der Bodenlösung befindet. Es wurden Säulenversuche (h = 25 cm, Ø = 7 cm) mit Ackerbohne und Gerste mit homogenisiertem Unterboden einer Parabraunerde und plazierter Düngung von Harnstoff ohne und mit NI durchgeführt. Eine ungedüngte Kontrolle diente als Vergleich. Die Änderung der N-Spezies und des pH über die Zeit in zwei Bodentiefen wurde über Mikrosaugkerzen in situ erfasst. Die Änderung der Wurzelmorphologie über die Zeit mit Röntgentomographie (bei Ackerbohne) bzw. über destruktive Zwischenernten und WinRHIZO (bei Gerste) erfasst. Die Verwendung von Harnstoff mit NI führte zu einer Ausgangssituation in der NH4+ in der mineralischen Stickstofffraktion dominiert, allerdings nur im Nmin-Extrakt mit 1M KCl (gelöst + austauschbar gebunden) und nicht in der Bodenlösung. Diese Variante weist dann auch eine erhöhte Anzahl von Seitenwurzeln im Bereich der Plazierung auf – tendenziell bei Ackerbohne, signifikant bei Gerste. Weitaus prägnanter zeigt sich ein hemmender Effekt hoher Nitratkonzentrationen auf die Seitenwurzelbildung bei Gerste. Die in artifiziellen Systemen (Gelplatten, Nährlösungsversuche) gemachten Beobachtungen lassen sich prinzipiell auf das System Boden übertragen. Allerdings liegen die speziellen Randbedingungen im Boden selten und meist nur während kurzer Zeiträume vor