Science-based approach for credible accounting of mitigation in managed forests     

Giacomo Grassi  Roberto Pilli  Jo House  Sandro Federici  Werner A. Kurz 《Carbon balance and management》2018,13(1):8

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Microbial photosynthesis in coral reef sediments (Heron Reef, Australia)     

Ursula Werner  Anna Blazejak  Paul Bird  Gabriele Eickert  Raphaela Schoon  Raeid M.M. Abed  Andrew Bissett  Dirk de Beer   《Estuarine, Coastal and Shelf Science》2008,76(4):876-888

We investigated microphytobenthic photosynthesis at four stations in the coral reef sediments at Heron Reef, Australia. The microphytobenthos was dominated by diatoms, dinoflagellates and cyanobacteria, as indicated by biomarker pigment analysis. Conspicuous algae firmly attached to the sand grains (ca. 100 μm in diameter, surrounded by a hard transparent wall) were rich in peridinin, a marker pigment for dinoflagellates, but also showed a high diversity based on cyanobacterial 16S rDNA gene sequence analysis. Specimens of these algae that were buried below the photic zone exhibited an unexpected stimulation of respiration by light, resulting in an increase of local oxygen concentrations upon darkening. Net photosynthesis of the sediments varied between 1.9 and 8.5 mmol O₂ m⁻² h⁻¹ and was strongly correlated with Chl a content, which lay between 31 and 84 mg m⁻². An estimate based on our spatially limited dataset indicates that the microphytobenthic production for the entire reef is in the order of magnitude of the production estimated for corals. Photosynthesis stimulated calcification at all investigated sites (0.2–1.0 mmol Ca²⁺ m⁻² h⁻¹). The sediments of at least three stations were net calcifying. Sedimentary N₂-fixation rates (measured by acetylene reduction assays at two sites) ranged between 0.9 to 3.9 mmol N₂ m⁻² h⁻¹ and were highest in the light, indicating the importance of heterocystous cyanobacteria. In coral fingers no N₂-fixation was measurable, which stresses the importance of the sediment compartment for reef nitrogen cycling.  相似文献   

Shark interactions in pelagic longline fisheries   总被引：1，自引：0，他引：1  

Eric Gilman  Shelley Clarke  Nigel Brothers  Joanna Alfaro-Shigueto  John Mandelman  Jeff Mangel  Samantha Petersen  Susanna Piovano  Nicola Thomson  Paul Dalzell  Miguel Donoso  Meidad Goren  Tim Werner 《Marine Policy》2008

Substantial ecological, economic and social problems result from shark interactions in pelagic longline fisheries. Improved understanding of industry attitudes and practices towards shark interactions assists with managing these problems. Information on fisher knowledge and new strategies for shark avoidance may benefit sharks and fishers. A study of 12 pelagic longline fisheries from eight countries shows that incentives to avoid sharks vary along a continuum, based on whether sharks represent an economic disadvantage or advantage. Shark avoidance practices are limited, including avoiding certain areas, moving when shark interaction rates are high, using fish instead of squid for bait and deeper setting. Some conventionally employed fishing gear and methods used to target non-shark species contribute to shark avoidance. Shark repellents hold promise; more research and development is needed. Development of specifically designed equipment to discard sharks could improve shark post release survival prospects, reduce gear loss and improve crew safety. With expanding exploitation of sharks for fins and meat, improved data collection, monitoring and precautionary shark management measures are needed to ensure that shark fishing mortality levels are sustainable.  相似文献   

Organized bacterial assemblies in manganese nodules: evidence for a role of S-layers in metal deposition   总被引：1，自引：0，他引：1  

Xiaohong Wang  Heinz C. Schröder  Ute Schloßmacher  Werner E. G. Müller 《Geo-Marine Letters》2009,29(2):85-91

Polymetallic/ferro-manganese nodules (Mn-nodules) reach sizes of up to 10 cm in diameter and are abundantly found on the seabed. To date, the origin of Mn-nodules remains unclear, and both abiogenic and biogenic origins have been proposed. In search of evidence for a contribution of microbial processes to the formation of Mn-nodules, we analyzed those spherical nodules which contain a concentrically banded texture in their interior. The Mn-nodules were collected at a depth of 5,152 m from the Clarion-Clipperton Zone. Our high-resolution scanning electron microscopy analyses reveal first published evidence that endolithic microorganisms exist and are arranged in a highly organized manner on plane mineral surfaces within the nodules. These microorganisms are adorned on their surfaces with S-layers, which are indicative for bacteria. Moreover, the data suggest that these S-layers are the crystallization seeds for the mineralization process. We conclude that the mineral material of the Mn-nodule has a biogenic origin, and hope that these data will contribute to the development of biotechnological approaches to concentrate metals from seawater using bacteria in bioreactors.  相似文献   

Estimation of actual evapotranspiration from an alluvial aquifer of the Kouris catchment (Cyprus) using continuous streamflow records     

Anastasia Boronina  Sergey Golubev  Werner Balderer 《水文研究》2005,19(20):4055-4068

The Kouris catchment is located in the south of the Troodos massif in Cyprus. The hydrology is driven by a Mediterranean climate, a mountainous topography, and a complex distribution of hydrogeological properties resulting from complex geology. To quantify the regional water balance further, a simple method using continuous streamflow records in the River Limnatis (Kouris catchment) was applied to calculate the actual evapotranspiration rate in the dry seasons. It was found that daily cycles of streamflow, recorded by automatic pressure logger, were caused by direct evaporation from the groundwater table and by transpiration of riparian forest. The daily amounts of ‘missing’ streamflow were calculated for the period 30 October–4 November 2001 and were extrapolated to the entire dry season and to the whole Kouris catchment. The actual evapotranspiration rate from the alluvial aquifer of the region is 2·4 ± 0·5 Mm³ for April–September 2001. The validity of the assumptions and the uncertainties in the estimates used in the method are discussed. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Canopy dieback in the upper montane rain forests of Sri Lanka   总被引：2，自引：0，他引：2  

Wolfgang L. Werner Dr. 《GeoJournal》1988,17(2):245-248

In 1978 a patch of dying upper montane rain forest had been observed on the slope of Thotupolakanda above Horton Plains. Patches in the upper montane rain forests of Sri Lanka were also recorded in 1980/81. All these sites were on windswept western slopes and ridges with stunted tree growth and shallow soil. From 1971 to 1983 Sri Lanka experienced some exceptionally dry years. The severe droughts of 1976 might have cause or “triggered” that dieback. After heavy rains between 1983 and 1986, these forests showed signs of recovery. Some trees had survived and sprouted again. Tree saplings were found, but regeneration was very low and further impeded by serious frost in February 1986. The influence of drought and frost clearly indicates the vulnerability of the stunted upper montane rain forest in the highest and wind-exposed regions of Sri Lanka.  相似文献   

Archean regional transpression and paleomagnetism in northwestern Ontario, Canada     

G.J. Borradaile  T. Werner  J.F. Dehls  R.N. Spark 《Tectonophysics》1993,220(1-4):117-125

The Archean metamorphic rocks of the Superior province of the Canadian Shield occur in lithologically defined belts or subprovinces. The tectonically more stable interiors of belts possess consistent primary components of magnetic remanence. In the case of the Quetico belt, these stable directions are tightly grouped about 005°/55° with some minor dispersion and most were acquired during the cooling that followed syntectonic recrystallisation.

This study examines the directions of primary remanence components for rocks along the margins of the Quetico belt, within 4 km of the strongly deformed vertical, ENE-trending boundaries. The boundaries are known to have experienced dextral transpression involving penetrative single-phase deformation which out-lasted metamorphism. Within a few kilometres of the belt boundaries, the primary remanence components are re-distributed along a vertical ENE-trending, great-circle girdle which is nearly parallel to the plane of transpressive shear and regional schistosity. It is suggested that the effects of transpression have mechanically deflected the components of primary remanence toward this plane.  相似文献   

57Fe-Moessbauer spectra,electronic and crystal structure of members of the CuS2-FeS2 solid solution series     

Peter Schmid-Beurmann  Werner Lottermoser 《Physics and Chemistry of Minerals》1993,19(8):571-577

Members of the (Cu, Fe)S₂ solid solution crystallize in the pyrite structure type, space group Pa 3, Cu and Fe being statistically distributed on the metal sites. Within this series, a semiconductor to metal transition can be detected between 25 and 38 mole% CuS₂. Compositional dependent ⁵⁷Fe-Moessbauer spectra reveal Fe²⁺ in low-spin configuration. A minimum of the quadrupole splitting and the slope in the ⁵⁷Fe-isomer shift in the intermediate part of the system, near 30 mole% CuS₂, can be correlated with the onset of metallic conductivity, whereas the structural parameters are not influenced by this transition. The analysis of the compositional dependency of the quadrupole splitting, in comparison to the isotypic system (Co, Fe)S₂, leads to the conclusion that Cu in solid (Cu, Fe)S₂ compounds is Cu⁺ with an Ar -3 d¹⁰ electronic configuration.  相似文献   

Explorations into the formal structure of drainage basins     

Christian Werner 《地球表面变化过程与地形》1994,19(8):747-762

Every basin of higher than first order is drained by a channel network composed of two subnetworks. Their basins are separated by a drainage divide line, called the basin divider, which is the primary organizing feature of the main basin. Each basin of magnitude n contains n – 1 subnetworks of higher order, and is therefore organized by a set of n – 1 dividers. The dividers and the basin boundary are interconnected in a graph called the divider network of the basin; in graph-theoretic terms this network forms a tree and has the same magnitude and link numbers as the channel network draining the basin. While the subbasins and subnetworks of a drainage basin form a nesting hierarchy, the corresponding dividers do not; indeed, any two dividers share at most one node in common, and whether they do so is independent of whether the corresponding subbasins are nesting or disjoint. However, the dividers of nesting basins are linked by recursive relationships which permit the derivation of a set of algebraic equations; these equations relate the dividers of a basin to other basin components; for example, their combined length is equal to half the length of all first-order basin boundaries minus the length of the main basin boundary. The second part of the paper explores the dependence of the divider length on other basin parameters. The expected length, as predicted by the assumption of topological randomness, is clearly rejected by the data. An alternative approach (regression) is based on the observed magnitudes of the subbasins separated by each divider, and is reasonably successful in estimating divider length. The last section introduces the concept of the standardized basin defined by a boundary length of unity; the estimated lengths of the basin divider and the basin boundary permit an approximate reconstruction of the idealized basin shape and the location of the divider in it.  相似文献   

4He diffusion in specular hematite     

Hans J. Lippolt  Rolf S. Wernicke  Werner Boschmann 《Physics and Chemistry of Minerals》1993,20(6):415-418

In order to test the chronometer qualities of speculante for the (U + Th)/He dating method, ⁴He release experiments by stepwise heating of two specularites from the Rimbach mineralization locality in the southern Vosgues (France) have been carried out. The diffusion coefficients define linear Arrhenius plots within a temperature interval of 250 to 830 °C, which is suggestive of volume diffusion. Extrapolation of the diffusion behavior to 20° C yields diffusion coefficients (D₂₀ values) smaller than 10^?26 [cm² s^?1] for both hematites with activation energies at 116 [kJ/mole]. The results of our study suggest that specularite is a very helium retentive hematite variety which is capable of quantitatively retaining radiogenic helium over geologic periods of time.  相似文献