bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamics of bacteria–substrate stable isotope separation: dependence on substrate availability and implications for aquatic food web studies
Authors: McGoldrick Daryl J. , Barton David R. , Power Michael , Scott Ryan W. , Butler Barbara J. 
Published: September 2008

Heterotrophic bacteria growing without substrate limitation discriminate against the heavier stable isotopes of C and N, which is reflected in the isotopic signatures of consumers of bacteria. We measured bacteria and substrate isotopic separation (C and N) during glucose and ammonium uptake by three strains of bacteria ( Pseudomonas putida , Bacillus megaterium , and Enterobacter aerogenes ) grown in batch culture at 4 and 30 °C. Isotopic separation between bacteria and substrate was dependent on substrate availability. Higher discrimination against the heavier isotopes, and therefore more depleted δ13C and δ15N values of bacterial biomass, were observed during the exponential growth phase when the nutrient supply was in excess of the demand. We also compared the isotopic ratios of Chironomus tentans grown on aged macrophyte detritus and commercial fish food. Isotopic signatures of Chironomus larvae grown on fish food were within the ranges typical of one trophic step, whereas larvae grown on detritus were strongly depleted in13C, suggesting assimilation of bacteria that had grown on the C-rich detritus. Our results are consistent with the very few other studies of bacterial fractionation of nonlimiting nutrients and may also explain the frequent observation of unexpectedly depleted isotopic signatures in aquatic food web studies.
Intralacustrine site fidelity and nonrandom mating in the littoral-spawning northern redbelly dace (Phoxinus eos)
Authors: Massicotte Rachel , Magnan Pierre , Angers Bernard 
Published: September 2008

Natal site fidelity of the northern redbelly dace ( Phoxinus eos ), a common minnow in North America, was confirmed by combining ecological and genetic approaches. A 2-year mark–recapture experiment conducted at four sites separated by 50–450 m strongly supported the propensity of the dace to practice site fidelity during the reproductive period. Individuals recaptured at their marking sites were characterized with five microsatellite loci. Hardy–Weinberg equilibrium and allelic differentiation tests revealed that the fish from different sites significantly differed from a single panmictic and genetically uniform population, thus confirming the homing behaviour of the dace. The detection of a pattern of isolation by distance revealed that migration mostly occurred between nearby sites and decreased as distance from birth site increased. When considering the high population density of dace, their high swimming capability, the distribution of the spawning sites along the littoral zone, and the small size of the lake studied (<5 ha), these results strongly suggest natal site fidelity in this species. The detection of this phenomenon for this species is extremely useful for empirical investigations of factors affecting patterns of isolation by distance and of evolutionary perspectives of natal site fidelity in fishes.
Assessing the importance of macroinvertebrate trophic dead ends in the lower transfer of methylmercury in littoral food webs
Authors: Cremona Fabien , Planas Dolors , Lucotte Marc 
Published: September 2008

Total mercury and methylmercury concentrations ([THg], [MeHg]) were measured in littoral macroinvertebrates from Lake St. Pierre, Quebec, Canada. Functional groups (detritivore, grazer, edible predator, inedible predator) explained the greatest fraction of [MeHg] variation compared with time (year, month), and space (station and shore). Greatest [THg] and [MeHg] were found in inedible predators mostly from families of heteropterans and coleopterans. Detritivores and grazers exhibited the lowest Hg concentrations, while edible predators were intermediate. Inedible predators also had the highest percentage of MeHg ([MeHg]/[THg]), with some taxa close to 100%. Such high percentages are seldom observed in freshwater organisms other than piscivorous fish. MeHg burden (concentrations × biomass) in inedible predators accounted for 10% of the MeHg pool for the whole invertebrate community. These large quantities of MeHg are sequestrated in aquatic “trophic dead ends” and could partly explain the low [MeHg] measured in fish, compared with [MeHg] of macroinvertebrates from Lake St. Pierre and other freshwater ecosystems with large littoral zones. We recommend taking into account the inedible organisms in Hg cycling models to avoid a possible overestimation of the MeHg pool available to fish.
Postconsumption domoic acid generation by the diatom Pseudo-nitzschia multiseries as a factor in depuration models
Authors: Stewart James E. 
Published: September 2008

A theoretical analysis of the clearance of the neurotoxin domoic acid (DA) from molluscan shellfish, notably the blue mussel ( Mytilus edulis ), indicated that the depuration simulation did not account for the maximum accumulation of DA nor for the failure to eliminate all of the DA from the mussels in the anticipated time. Subsequent examination of relatively young, neurotoxin-producing cells of Pseudo-nitzschia multiseries concentrated 8.5- to 10-fold and reincubated in the dark, however, showed significant amounts of DA were produced within the first 24 h of incubation. The possible production of DA, after ingestion, could generate an additional contribution to the toxin burden in the mollusc, which, when included in the depuration simulation, would explain part or all of the observed disparity in the depuration experiment.
A relascope for measuring canopy cover
Authors: Stenberg Pauline , Korhonen Lauri , Rautiainen Miina 
Published: September 2008

Angle count or relascope sampling has traditionally been used in forestry to estimate stand basal area. In this paper, we present an extension to the basal area relascope, the crown relascope, which differs from the normal relascope in that the relascope’s slot is very high and wide. We describe the theoretical basis of the instrument and present results from a field test in which a crown relascope with a basal area factor of 250 m2/ha (0.025) was used to estimate canopy cover of 73 sample plots in northern Finland. The crown relascope estimates had a root mean square difference of 9.3% and an average difference of –3.1% when compared with estimates obtained with the control method, line intersect sampling using the Cajanus tube. The results indicated that the crown relascope is a quick and fairly reliable instrument for canopy cover estimation, especially in relatively sparse forests where crown overlap is insignificant and visibility does not limit an efficient use of the instrument.
The effect of spacing on the growth ofEucalyptus camaldulensison salt-affected soils of the Punjab, Pakistan
Authors: Akhtar Javaid , Saqib Z. A. , Qureshi R. H. , Haq M. A. , Iqbal M. S. , Marcar N. E. 
Published: September 2008

This study compared the performance of Eucalyptus camaldulensis Dehnh. planted at four spacings (2.0 m × 2.0 m, 2.5 m × 2.5 m, 3.0 m × 3.0 m, and 3.5 m × 3.5 m) at three experimental saline sites in Punjab province of Pakistan over 5 years and assessed the impact of these planting densities on soil salinity amelioration. Tree response was assessed by measuring survival, height, and diameter at breast height (DBH) of trees at 1, 2, and 5 years as well as wood volume after 5 years. Wood volume per hectare, height, and DBH were greater at sites I and II than at site III. The 3.0 m × 3.0 m spacing resulted in taller trees, but DBH and wood volume were greater with the 3.5 m × 3.5 m spacing. The study confirmed that initial tree spacing or density has a significant impact on the subsequent height, DBH, and wood volume of E. camaldulensis plants. The study also showed that broad spacing could be a better option in saline environments. There was a definite reduction in soil salinity (electrical conductivity, ECe) at five soil depths after 5 years of tree growth at all sites and spacing treatments, with reductions varying from 46% to 47% at site I, 31% to 52% at site II, and 25% to 58% at site III. Soil ECewas generally higher in surface (0–15 cm) soils.
Nutrient fluxes via leaching from coarse woody debris in a Fagus sylvatica forest in the Solling Mountains, Germany
Authors: Kuehne C. , Donath C. , Müller-Using S. I. , Bartsch N. 
Published: September 2008

To evaluate the importance of nutrient fluxes via leaching from coarse woody debris (CWD) in an area with high atmospheric nitrogen (N) inputs, throughfall and CWD leachate from logs at different stages of decomposition were investigated over a period of 14 and 27 months, respectively, in a 160-year-old European beech ( Fagus sylvatica L.) forest in northwestern Germany. Water samples, collected from 30 zero-tension lysimeters installed in pairs along 15 logs and from 27 neighboring raingauges, were chemically analyzed in the laboratory. Generally, as CWD decay advanced, the ratio of leachate to throughfall decreased, and the amount of dissolved nutrients in the leachate increased. With the exception of ammonium (NH4+) and dissolved inorganic carbon, the element concentrations in the CWD leachate were significantly higher than those in the throughfall. The concentrations of NH4+and nitrate (NO3–) in the CWD leachate, which were very high compared with values from North American studies, were caused by the continuously high atmospheric N inputs, and the resulting N saturation in the forest ecosystem investigated. The low concentrations of the cations calcium and magnesium indicate that at this site nutrients limiting plant and fungal growth are retained and accumulated in the CWD.
Another Note on Zeno's Arrow
Authors: Magidor Ofra 
Published: September 2008

AbstractIn Physics VI.9 Aristotle addresses Zeno's four paradoxes of motion and amongst them the arrow paradox. In his brief remarks on the paradox, Aristotle suggests what he takes to be a solution to the paradox.In two famous papers, both called 'A note on Zeno's arrow', Gregory Vlastos and Jonathan Lear each suggest an interpretation of Aristotle's proposed solution to the arrow paradox. In this paper, I argue that these two interpretations are unsatisfactory, and suggest an alternative interpretation. In particular, I claim that what seems on the face of it to be Aristotle's solution to the paradox raises two puzzles to which my interpretation, as opposed to Lear's and Vlastos's, provides an adequate response.
Porphyry and Plotinus on the Seed
Authors: Wilberding James 
Published: September 2008

AbstractPorphyry's account of the nature of seeds can shed light on some less appreciated details of Neoplatonic psychology, in particular on the interaction between individual souls. The process of producing the seed and the conception of the seed offer a physical instantiation of procession and reversion, activities that are central to Neoplatonic metaphysics. In an act analogous to procession, the seed is produced by the father's nature, and as such it is ontologically inferior to the father's nature. Thus, the seed does not strictly speaking contain a full-fledged vegetative soul. Rather, it acquires its vegetative soul only while it is being actualized by an actual vegetative soul. This actualization takes place primarily at conception, where the seed as it were reverts back and becomes obedient to the mother's nature, but continues through the period of gestation. In this way, Porphyry can account both for maternal resemblance and for ideoplasty. He uses the Stoic language of complete blending to describe the mother's relation to the seed and embryo, and this reveals that he thinks of individuals as having their own unique individual natures (as opposed to sharing in a single universal nature). In the course of developing this theory, Porphyry makes significant revisions to his philosophical predecessors' views in both embryology and botany. He revises Aristotle's verdict on the relative importance of the female in generation as well as Theophrastus' explanation of the biological mechanics of grafting. Although Plotinus nowhere addresses embryology in the same detail as Porphyry does, we can conclude from his remarks on seeds and plants that his own views were similar to those of his student.
Interpreting the Atmospheric Circulation Trend during the Last Half of the Twentieth Century: Application of an Adjoint Model
Authors: Blessing Simon , Greatbatch Richard J. , Fraedrich Klaus , Lunkeit Frank 
Published: September 2008

Abstract
A tangent linear adjoint for a low-resolution dynamical model of the atmosphere is used to derive the optimal forcing perturbations for all state variables such that after a specified lead time the model response has a given projection, in terms of an energy norm, on the pattern associated with the 51-yr trend in the Northern Hemisphere winter tropospheric circulation, 1948/49–1998/99. A feature of the derived forcing sensitivity is a Rossby wave–like feature that emanates from the western tropical Pacific and is associated with the deepening of the Aleutian low, whereas an annular pattern in the forcing sensitivity in the uppermost model level is shown to be associated with the pattern of the trend over the Euro-Atlantic/Asian sectors, including the upward trend in the North Atlantic Oscillation index. The authors argue that the Rossby wave–type feature is consistent with studies that have argued a role for the upward trend in tropical sea surface temperature during the 51-yr period. On the other hand, the authors interpret the annular pattern in the forcing sensitivity as being consistent with studies that have argued that the trend over the Euro-Atlantic sector was associated with influences from the stratosphere. In particular, a nonlinear model driven by the optimal forcing perturbation applied only to the top model level is successful at reproducing the trend pattern with the correct amplitude in the Euro-Atlantic sector, but implies a trend over the North Pacific toward a weaker Aleutian low, contrary to what was observed but similar to the spatial pattern associated with the northern annular mode. These results show that the adjoint approach can shed light on previous apparently different interpretations of the trend. The study also presents a successful application of a tangent linear adjoint model to a climate problem.
Internal Feedbacks from Monsoon–Midlatitude Interactions during Droughts in the Indian Summer Monsoon
Authors: Krishnan R. , Kumar Vinay , Sugi M. , Yoshimura J. 
Published: September 2008

AbstractResults from a 20-yr simulation of a high-resolution AGCM forced with climatological SST, along with simplified model experiments and supplementary data diagnostics, are used to investigate internal feedbacks arising from monsoon–midlatitude interactions during droughts in the Indian summer monsoon. The AGCM simulation not only shows a fairly realistic mean monsoon rainfall distribution and large-scale circulation features but also exhibits remarkable interannual variations of precipitation over the subcontinent, with the 20-yr run showing incidence of four “monsoon droughts.”The present findings indicate that the internally forced droughts in the AGCM emanate largely from prolonged “monsoon breaks” that occur on subseasonal time scales and involve dynamical feedbacks between monsoon convection and extratropical circulation anomalies. In this feedback, the suppressed monsoon convection is shown to induce Rossby wave dispersion in the summertime subtropical westerlies and to set up an anomalous quasi-stationary circulation pattern extending across continental Eurasia in the middle and upper troposphere. This pattern is composed of a cyclonic anomaly over west central Asia and the Indo-Pakistan region, a meridionally deep anticyclonic anomaly over East Asia (∼100°E), and a cyclonic anomaly over the Far East. The results suggest that the anchoring of the west central Asia cyclonic anomaly by the stagnant ridge located downstream over East Asia induces anomalous cooling in the middle and upper troposphere through cold-air advection, which reduces the meridional thermal contrast over the subcontinent. Additionally, the intrusion of the dry extratropical winds into northwest India can decrease the convective instability, so that the suppressed convection can in turn weaken the monsoon flow. The sustenance of monsoon breaks through such monsoon–midlatitude feedbacks can generate droughtlike conditions over India.
Sensitivity of the Upper Mesosphere to the Lorenz Energy Cycle of the Troposphere
Authors: Becker Erich 
Published: September 2008

AbstractThe concept of a mechanistic general circulation model that explicitly simulates the gravity wave drag in the extratropical upper mesosphere in a self-consistent fashion is proposed. The methodology consists of 1) a standard spectral dynamical core with high resolution, 2) idealized formulations of radiative and latent heating, and 3) a hydrodynamically consistent turbulent diffusion scheme with the diffusion coefficients based on Smagorinsky’s generalized mixing-length formulation and scaled by the Richardson criterion. The model reproduces various mean and variable features of the wave-driven general circulation from the boundary layer to the mesopause region during January.The dissipation of mesoscale kinetic energy (defined as the frictional heating due to the mesoscale flow) in the extratropical troposphere is found to indicate the tropospheric gravity wave sources relevant for the mesosphere/lower thermosphere. This motivates a sensitivity experiment in which the large-scale differential heating is perturbed such that the Lorenz energy cycle as measured by the globally integrated frictional heating becomes stronger. As a result, both the resolved gravity wave activity and the dissipation of mesoscale kinetic energy in the extratropical troposphere are amplified. These changes have strong remote effects in the summer mesopause region, where the gravity wave drag, the residual meridional wind, and the frictional heating shift to lower altitudes. Furthermore, temperatures decrease below the summer mesopause and increase farther up, which is accompanied by an anomalous eastward wind component around the mesopause.
Life Cycles of Hurricane-Like Vorticity Rings
Authors: Hendricks Eric A. , Schubert Wayne H. , Taft Richard K. , Wang Huiqun , Kossin James P. 
Published: September 2008

Abstract
The asymmetric dynamics of potential vorticity mixing in the hurricane inner core are further advanced by examining the end states that result from the unforced evolution of hurricane-like vorticity rings in a nondivergent barotropic model. The results from a sequence of 170 numerical simulations are summarized. The sequence covers a two-dimensional parameter space, with the first parameter defining the hollowness of the vortex (i.e., the ratio of eye to inner-core relative vorticity) and the second parameter defining the thickness of the ring (i.e., the ratio of the inner and outer radii of the ring). In approximately one-half of the cases, the ring becomes barotropically unstable, and there ensues a vigorous vorticity mixing episode between the eye and eyewall. The output of the barotropic model is used to (i) verify that the nonlinear model approximately replicates the linear theory of the fastest-growing azimuthal mode in the early phase of the evolution, and (ii) characterize the end states (defined at t = 48 h) that result from the nonlinear chaotic vorticity advection and mixing. It is found that the linear stability theory is a good guide to the fastest-growing exponential mode in the numerical model. Two additional features are observed in the numerical model results. The first is an azimuthal wavenumber-2 deformation of the vorticity ring that occurs for moderately thick, nearly filled rings. The second is an algebraically growing wavenumber-1 instability (not present in the linear theory because of the assumed solution) that is observed as a wobbling eye (or the trochoidal oscillation for a moving vortex) for thick rings that are stable to all exponentially growing instabilities. Most end states are found to be monopoles. For very hollow and thin rings, persistent mesovortices may exist for more than 15 h before merging to a monopole. For thicker rings, the relaxation to a monopole takes longer (between 48 and 72 h). For moderately thick rings with nearly filled cores, the most likely end state is an elliptical eyewall. In this nondivergent barotropic context, both the minimum central pressure and maximum tangential velocity simultaneously decrease over 48 h during all vorticity mixing events.
Internal Atmospheric Variability and Interannual-to-Decadal ENSO Variability in a CGCM
Authors: Yeh Sang-Wook , Kirtman Ben P. 
Published: September 2008

Abstract
The interactive ensemble coupling strategy has been developed specifically to determine how noise due to internal atmosphere dynamics impacts climate variability within the context of coupled general circulation models (CGCMs). In this study the authors investigate the impact of internal atmospheric variability on the ENSO variability using four CGCM simulations. In the control simulation, the interactive ensemble strategy is applied globally, thereby reducing the noise at the air–sea interface at each ocean grid point. In the second and third CGCM simulations, the interactive ensemble strategy is applied locally in the extratropics versus the tropics only, respectively. In addition, those results were compared with a standard CGCM.
The results suggest that tropical internal atmospheric variability strengthens the interannual-to-decadal ENSO variability and leads to a broader spectral peak. However, the noise due to internal atmospheric dynamics plays different roles when the interannual and decadal ENSO variability is considered separately. There are noise-induced changes in the SST–zonal wind stress feedbacks from interannual to decadal time scales. The tropical atmospheric internal variability largely modifies the frequency as opposed to the amplitude of the ENSO variability on interannual time scales. In contrast, tropical internal atmospheric variability is effective in forcing decadal ENSO variability, resulting in a significant decrease of decadal ENSO amplitude in the central tropical Pacific in a CGCM when the noise is reduced. The authors argue that the decadal ENSO variability is directly affected by the low-frequency noise over the western part of the tropical Pacific in a linear sense. On the other hand, the impact of extratropical atmospheric noise on the ENSO variability is weaker than the noise in the tropics.