bluuebunny/crossref_metadata_2025 huggingface dataset:
Effets du scarifiage sur les propriétés du sol et l'ensemencement naturel dans une pessière noire à mousses de la forêt boréale québécoise
Authors: Prévost Marcel
Published: December 2007

Two types of scarification (cone and disk) were applied at two intensities (simple and double passes), in a randomized complete block design, established alongside buffer stands of spruce protective of water courses, that provided a natural seed source. Treatment effects on seedbed evolution, natural seeding of black spruce (Piceamariana (Mill.) BSP), competing vegetation, and soil physical and chemical properties were examined over a 3-year period. In situ nitrogen mineralization was also studied, using the buried-bag method. All scarification treatments created a surface horizon (0–10 cm) with 80% less organic matter content than the control treatment. However, treatments tended to loosen the exposed deep layers, creating microsites whose compactness appeared adequate for root development (1.07–1.22 Mg/m3). The organic matter loss mainly decreased exchangeable K and Mg in the surface 20 cm of scarified microsites. Scarification had little impact on total N of sampled profiles and clearcutting did not increase N mineralization with regard to the forest, during the first year after disturbance. The weak soil warming and the stability of temperatures under the unscarified humus suggest that clearcutting did not significantly enhanced microbial activity on the site. However, removal of the insulating humus layer allowed a significant summer soil warming in the furrows. Despite this, scarified microsites were characterized by N immobilization during the first growing season after treatment. However, net N production was positive during the winter period, presumably because of a N-flux phenomenon. Scarification improved black spruce regeneration by natural seeding. Three years after treatment, stocking levels reached 40 to 51% in the scarified sectors while they reached 31% in the controls, this gap being mainly attributed to the second germination year. The difference can be explained by the improved receptivity of bare mineral soil, well-decomposed humus, and mixed mineral–organic seedbeds that covered 12–20% of the scarified areas immediately after treatment. Generally, results indicate that microsites created by a light scarification are as receptive as microsites created by a severe perturbation. Finally, every scarification treatment efficiently controlled the ericaceous shrub cover during the first 3 years after treatment.
Acclimation of photosynthesis in Norway spruce and red oak grown in open-top chambers and subjected to natural drought and to elevated CO2
Authors: Thiec Didier Le , Dixon Martin
Published: December 2007

Eight-year-old Norway spruce (Piceaabies (L.) Karst.) and 6-year-old red oak (Quercusrubra L.) trees planted directly into the soil were enclosed in open-top chambers and exposed to either 350 or 700 μmol•mol−1 of CO2 for three growing seasons. During the third year a natural drought was allowed to develop, reducing the predawn leaf water potential to between −0.80 and −1.15 MPa. Intensive gas-exchange measurements were performed before, during, and after the drought. CO2 response curves revealed mesophyll limitation to photosynthesis in drought-stressed trees grown in elevated levels of CO2. The water-use efficiency was greater for trees grown at elevated CO2, but less so during drought in red oak and the same between treatments for drought-stressed spruce. Diurnal measurements showed that enhancement of assimilation rates of trees grown at 700 μmol•mol−1 depended upon the time of day that measurements were made. There was an acclimation to increased CO2 in both species that could not be explained by leaf area differences, available soil for roots, nutrient limitation, or starch accumulation.
Photosynthetic response of loblolly pine and sweetgum seedling stands to elevated carbon dioxide, water stress, and nitrogen level
Authors: Groninger J.W. , Seiler J.R. , Zedaker S.M. , Berrang P.C.
Published: December 2007

Seedling stands of loblolly pine (Pinustaeda L.) and sweetgum (Liquidambarstyraciflua L.) were grown in monoculture or mixed stands for two growing cycles in controlled-environment chambers. Treatments consisted of ambient (408 ppm) and elevated (806 ppm) CO2, concentrations, water-stressed and well-watered conditions, and low (20 kg N/ha) and high (215 kg N/ha) nitrogen application rates. Photosynthesis rates were measured under ambient and elevated cuvette CO2 concentrations for both whole stands and individual seedlings from these stands. Significant interactions between CO2 and water suggested that elevated CO2 concentration compensated for low water availability in individually measured loblolly pine and in whole seedling stands regardless of stand type. Expressing photosynthesis on a soil area versus a leaf-mass basis influenced the photosynthetic rankings of the three stand types relative to one another. Net photosynthetic rates per unit leaf mass were 390 and 880% higher in individually measured seedlings than in whole monoculture stands for loblolly pine and sweetgum, respectively. Lower photosynthetic contributions from lower canopy leaves in whole seedling stands compared with the upper canopy leaves used in individual-seedling measurements were thought to be responsible for lower photosynthetic rates in seedling stands. These results suggest that photosynthetic response is influenced by canopy dynamics that are unaccounted for by individual-seedling measurements of photosynthesis. Differences in photosynthetic response between loblolly pine and sweetgum stands and individuals are thought to be largely due to species-specific differences in canopy light extinction characteristics.
Rate of spread of Armillariaostoyae in two Douglas-fir plantations in the southern interior of British Columbia
Authors: Peet F.G. , Morrison D.J. , Pellow K.W.
Published: December 2007

The rate of spread of Armillariaostoyae (Romagnesi) Herink was calculated from observations over 20 years on plots in two Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) plantations in the southern interior of British Columbia. Average rates of spread in active disease centers ranged from 0.7 to 1.3 m/year.
A simple and efficient method to estimate microsite light availability under a forest canopy
Authors: Parent Sylvain , Messier Christian
Published: December 2007

This study presents a new, simple, and efficient method for estimating microsite light availability in the understory of a forest. The percentage of above-canopy photosynthetic photon flux density (%PPFD) transmitted above 16 microsites in the understory of a mixed conifer–broadleaf forest was measured every minute between 07:00 and 19:00 for both a completely overcast and a cloudless day. Instantaneous measures of %PPFD were also taken at different times on 3 overcast days. The instantaneous measures of %PPFD were strongly and directly related (P < 0.001) among themselves and with mean daily %PPFD values. These results demonstrate the usefulness of using an instantaneous measure of %PPFD taken under overcast sky conditions for estimating the mean daily %PPFD at any microsite under a forest canopy.
Chloroplast-dependent and light-independent expression of the tobacco rbcS promoter–GUS chimeric gene in black spruce
Authors: Gray-Mitsumune Madoka , Yoo Bong Y. , Charest Pierre J.
Published: December 2007

The tobacco rbcS (ribulose bisphosphate carboxylase small subunit) promoter, fused to the β-glucuronidase (GUS) reporter gene, was delivered to black spruce (Piceamariana (Mill.) BSP) tissues via microprojectile DNA bombardment, and its regulation was studied. The expression of the tobacco rbcS promoter–GUS chimeric gene was dependent on the presence of chloroplasts in black spruce tissues, as demonstrated in two ways: (i) there was no GUS activity expressed in zygotic embryos where no chloroplasts were observed, whereas it was expressed in light- and dark-grown seedlings that contained mature or immature chloroplasts; (ii) a herbicide, Norflurazon, destroyed chloroplast structure in seedlings and inhibited the expression of the tobacco rbcS promoter–GUS chimeric gene. A control chimeric gene, the cauliflower mosaic virus (CaMV) 35S promoter–GUS fusion gene was not inhibited by Norflurazon. Unlike in angiosperms, light had no effect on the expression of tobacco rbcS promoter–GUS chimeric gene. Both light- and dark-grown seedlings showed GUS activity, and expression in dark-grown seedlings was not enhanced by light. These results suggest that the tissue-specific regulation of the rbcS promoter may be conserved between angiosperms and conifers, but that the light regulation of this promoter may not be conserved.
Comparison and evaluation of five methods of estimation of the Johnson system parameters
Authors: Zhou Bailin , McTague John Paul
Published: December 2007

The Johnson system of distributions was used to fit both diameter and height data collected from 226 sample plots located in the ponderosa pine (Pinusponderosa P. Laws, ex C. Laws.) and mixed-conifer forest types in New Mexico and Arizona. To estimate the Johnson system parameters, five methods (namely the four-percentile method, Knoebel–Burkhart method, mode method, maximum likelihood estimation method, and a new method developed in the study, linear regression method) were compared and evaluated. For these sample plots, the linear regression method was superior for estimating parameters of SB distributions for both diameter and height.
Role of lammas growth in recovery of Douglas-fir seedlings from deer browsing, as influenced by weed control, fertilization, and seed source
Authors: Roth Brian E. , Newton Michael
Published: December 2007

This study examined the effects of weed control, nitrogen fertilization, and seed source on lammas growth (second flushing) in Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) seedlings. It also assessed the occurrence of deer browsing as related to these silvicultural treatments and examined the role of lammas growth in seedling recovery and escapement from deer browsing. Weed control significantly increased the occurrence of lammas growth, presumably because of greater soil moisture and nutrient availability. Nitrogen fertilization decreased lammas growth significantly, at least in part by favoring weed growth. Lammas growth was not influenced by seed source. The increased lammas growth associated with weed control mediated the effects of deer browse. Although multiple-year browsing occurred more commonly on weeded than unweeded seedlings, after two growing seasons weeded seedlings that were repeatedly browsed were twice as large as nonbrowsed, nonweeded seedlings. On one site, stock of wild origin was more heavily browsed than that from a seed orchard.
Decomposition of woody debris in Western Australian forests
Authors: Brown Sandra , Mo Jiangming , McPherson James K. , Bell David T.
Published: December 2007

Changes in mass and nutrients in experimental logs of six tree species during 5 years of exposure in the three major forest production regions of southwest Western Australia were measured to determine how climate, substrate quality, and substrate size interact to regulate decomposition of woody debris in this Mediterranean-type climate. Branch (3–5 cm in diameter) and bole (10–15 cm in diameter) material of the six species was set out in representative areas of a regenerating clear-cut Eucalyptusdiversicolor F. Muell. wet sclerophyll forest, selectively cut Eucalyptusmarginata Donn ex Smith dry sclerophyll forest, and clear-cut areas of a former Pinuspinaster Aiton plantation. Experimental logs were collected at about 0.5, 2, and 5 years after placement and were separated into bark and wood components. Samples of initial material were analyzed for moisture content, water-soluble and NaOH-soluble extractives, and nutrient concentrations (N, P, K, Ca, and Mg). At each collection, moisture content and changes in mass and nutrient concentration were determined for the sample logs. Eucalyptuscalophylla R.Br, the major associate of the two native forests, lost the most mass during this time, up to 65% of the initial mass (decomposition coefficient k = 0.22 year−1). Decomposition was least in P. pinaster and E. marginata, at about 24–26% of original mass (k = 0.05 year−1 and 0.07 year−1, respectively). Mass losses were greatest in Manjimup, the wettest site, and least at Gnangara, the driest site, but differences in overall levels of decomposition were small despite the range in climatic moisture regimes. Small logs decomposed faster than large logs. Changes in nutrient concentrations occurred in all logs at all sites, indicating activity by decomposer organisms and (or) leaching losses. Nitrogen was the only element to be immobilized over the 5-year period. Mineralization rates were of the order P ≈ Ca < Mg < K. Concentrations of compounds extractable in cold water and NaOH decreased during the 5 years of exposure. Differences in decomposition rates were partly explained by initial concentrations of N only; there appeared to be no relationship between decomposition and concentration of the other elements and extractives.
Variation in the induced resin response of white spruce, Piceaglauca, to attack by Pissodesstrobi
Authors: Alfaro René I. , Kiss G.K. , Yanchuk A.
Published: December 2007

The intensity of the traumatic resin response in white spruce, Piceaglauca (Moench) Voss, to attack by the white pine weevil, Pissodesstrobi Peck, was studied in trees with different severities of attack. The response level was highest in trees where the attacks failed, i.e., where eggs were laid but the brood was killed and no adults emerged. Successfully attacked trees had, on average, only 62% of the response intensity of trees with failed attacks. Response intensity in trees that had been subjected only to feeding was much lower, at 42% of the failed attack response. Healthy unattacked trees showed no or little traumatic resin response. Response intensity varied in a nonlinear fashion with the number of eggs laid, increasing rapidly from zero in healthy trees, being highest in trees having between 10 and 60 egg punctures, and progressively lower again in trees with higher numbers of egg punctures. For a given number of egg punctures, resistant white spruce trees had a consistently higher traumatic resin response than susceptible trees. The number of eggs laid on a leader was inversely related to the intensity of the traumatic resin response and to the timing of the attack. Fewer eggs were laid on leaders with high traumatic resin response or attacked late in the season than on leaders with lower resin response or attacked early in the season.
Effects of tomato mosaic Tobamovirus infection on red spruce seedlings
Authors: Bachand George D. , Castello John D. , Schaedle Michail , Stehman Stephen V. , Livingston William H.
Published: December 2007

Height, weight, root volume, shoot length, needle length and weight, and total chlorophyll content were measured for both control and tomato mosaic Tobamovirus (ToMV)-inoculated red spruce (Picearubens Sarg.) seedlings in each of five, 3-month growth periods. Mean bud-break rating was determined for each seedling in growth period 5. In January 1995 the freezing tolerance of control and ToMV-infected seedlings was determined. Approximately 85% of the inoculated seedlings became infected with ToMV, as determined by enzyme-linked immunosorbent assay of young root tissue. Reduction in seedling height, weight, root volume, bud break, and mean shoot length of infected seedlings was observed when compared with control seedlings. The rate of increase over time in height, weight, and root volume was lower (54, 57, and 52%, respectively) in infected seedlings compared with control seedlings. Additionally, needles of infected seedlings were less susceptible to freezing damage than those of control seedlings. However, virus infection had no effect on the freezing tolerance of roots.
Backcountry recreationists' valuation of forest and park management features in wilderness parks of the western Canadian Shield
Authors: Boxall Peter C. , Watson David O. , Englin Jeffrey
Published: December 2007

The economic value of four forest ecosystems, fire-damaged forests, cut blocks, and several park management features was estimated for backcountry recreationists, primarily canoeists, in Nopiming Provincial Park in eastern Manitoba. The analysis was conducted using the travel cost random utility model. It revealed that the forest ecosystems associated with jack pine (Pinusbanksiana Lamb.) and white spruce (Piceaglauca (Moench) Voss) were valued by recreationists. On the other hand, the analysis predicted that recreationists would pay to avoid black spruce (Piceamariana (Mill.) BSP) and aspen (Populustremuloides Michx.) ecosystems, fire-damaged forests, portages, and cottages. The results provide weak statistical evidence that cut blocks that are not in the line of site of recreationists provide positive benefits. While park management variables play a role in determining recreation values, the ages and types of forests located at recreation sites are more important. These findings support a major role for fire in determining recreation economic benefit flows from forests in the Canadian Shield.
Effects of nitrogen availability on northern red oak seedling growth in oak and pine stands in northern Lower Michigan
Authors: Kim Choonsig , Sharik Terry L. , Jurgensen Martin F. , Buckley David S. , Dickson Richard E.
Published: December 2007

The nitrogen (N) status and dry weight increment of northern red oak (Quercusrubra L.) seedlings in relation to N availability were examined at various levels of canopy cover and understory removal treatments under field conditions in red oak and red pine (Pinusresinosa Ait.) stands. Net N mineralization rates over two growing seasons following canopy cover treatments were determined by the in situ buried bag technique. Canopy removal increased N mineralization in both oak and pine stands. Net N mineralization rates were ≈1.2–2.2 times higher in the clearcut and the other partial canopy cover treatments than in the uncut stands. Net N mineralization in the same canopy cover treatments was ≈2–3 times higher in red oak stands than in red pine stands. However, red oak seedlings from the same canopy cover treatments in both stand types had similar dry weight, N concentrations, N content, and N-use efficiency despite differences in soil N availability. The only exception was ≈2 times greater seedling dry weight and N content in the red oak clearcuts compared with the red pine clearcuts. The similarity in seedling performance within partial canopy removal or uncut stands may have been due to limiting factors other than N in the red oak stands. Red oak seedlings from litter removal treatments within the clearcuts had significantly higher N-use efficiency than those from the herb and shrub removal treatments. These results suggest that (i) canopy manipulation increases soil N availability; (ii) increases in dry weight and N uptake by red oak seedlings when forest canopies are completely removed are due, in part, to increased available soil N; (iii) red oak seedling response to soil N availability resulting from no or only partial canopy removal may be the same in different stand types (e.g., red oak vs. red pine) because factors other than N, such as light, are limiting.
Conditions for the start and spread of crown fire
Authors: Wagner C. E. Van
Published: December 2007

Some theory and observations are presented on the factors governing the start and spread of crown fire in conifer forests. Crown fires are classified in three ways according to the degree of dependence of the crown phase of the fire on the ground surface phase. The crown fuel is pictured as a layer of uniform bulk density and height above ground. Simple criteria are presented for the initiation of crown combustion and for the minimum rates of spread and heat transfer into the crown combustion zone at which the crown fire will spread. The theory is partially supported by some observations in four kinds of conifer forest.
Control of plot edge bias in forest stand growth simulation models
Authors: Martin G. L. , Ek A. R. , Monserud R. A.
Published: December 2007

Techniques for reducing edge bias are discussed and a new approach, termed the linear expansion method, is presented. This method is applicable to a wide variety of plot shapes and sizes and is unbiased under very general assumptions about the forest tree spatial pattern. The accuracy and efficiency of the linear expansion method were compared with (i) no edge bias correction and (ii) corrections by plot image translation techniques for several forest stands and spatial patterns. Results indicated translation and the linear expansion method behaved equally well on square plots 0.08 ha in size. As the plot size diminished or its shape deviated from square, the linear expansion method provided greater accuracy and lower bias than translation techniques. The linear expansion method also provided useful accuracy on circular plots where translation was not feasible.
Closure rates of yellow birch pruning wounds
Authors: Solomon Dale S. , Blum Barton M.
Published: December 2007

In August 1963, 135 yellow birch trees (Betulaalleghaniensis Britt.), averaging 5.08 cm in diameter at 1.37 m aboveground were pruned to two-thirds of their total height. Larger pruning wounds had a faster rate of closure but required more time to close than small wounds. The width and length of the pruning wound, as well as the diameter growth of the tree, were significantly related to closure rate. Although shade had no significant effect on closure rate, it reduced formation of epicormic branches.
Influence of light intensity, temperature, and leaf area on stomatal aperture and water potential of woody plants
Authors: Pereira J. S. , Kozlowski T. T.
Published: December 2007

Leaf diffusion resistance and shoot water potential of seedlings of six species of woody angiosperms were studied in a 4 × 4 design of crossed gradients of light intensity (1507, 4306, 10 764, and 21 528 lx) and temperature (18, 22.5, 26, and 30 °C). In all species, leaf diffusion resistance generally increased with decreasing light intensity and increasing temperature, but the effects of light intensity were much greater. Highly significant differences on leaf diffusion resistance were found for light intensity, temperature, time of day, and various interactions of these. Shoot water potential of all species decreased with increasing light intensity and temperature. Both leaf resistance and water potential under light and temperature stress varied among species. Despite high leaf resistance under environmental stress, indicating rapid stomatal closure, Acersaccharum with an extensive leaf area developed high shoot water deficits. Stomatal opening and closing in responses to changes in light intensity varied among five species of woody angiosperms but were not consistently correlated with species shade tolerance.
Stomatal infiltration pressures versus diffusion porometer measurements of needle resistance in Douglas-fir and lodgepole pine foliage
Authors: Lassoie James P. , Fetcher Ned , Salo David J.
Published: December 2007

The use of the infiltration technique to estimate coniferous stomatal activity is investigated by comparing simultaneous measurements of stomatal infiltration pressure (inversely related to aperture) with leaf resistance determined using an aspirated diffusion porometer. The infiltration technique is shown to be incapable of accurately estimating leaf resistances but is able to describe adequately whether stomata are open or closed in both Douglas-fir and lodgepole pine. Furthermore, the infiltration technique allows the collection of information about stomatal status during times when the use of the diffusion porometer is impossible, such as periods marked by cold temperatures, dew, or precipitation.
DYNAMICAL EFFECTS OF MYOCARDIAL ISCHEMIA IN ANISOTROPIC CARDIAC MODELS IN THREE DIMENSIONS
Authors: COLLI FRANZONE PIERO , PAVARINO LUCA F. , SCACCHI SIMONE
Published: December 2007

The interaction between the presence of moderate or severe subendocardial ischemic regions and the anisotropic structure of the cardiac muscle is investigated here by means of numerical simulations based on anisotropic Bidomain and Monodomain models. The ischemic effects on cardiac excitation, recovery and distribution of action potential duration are discussed, showing the presence of ischemic epicardial markers. Extracellular potential distributions during the ST and TQ intervals are computed separately using non-stationary models. During the ST interval, the extracellular potential patterns differ from those simulated with stationary models used in the literature. These differences are explained by decomposing the cardiac current sources into conormal, axial and orthogonal components and by determining which component is dominant during the ST and TQ intervals.
TWO-DIMENSIONAL INCOMPRESSIBLE IDEAL FLOWS IN A NONCYLINDRICAL MATERIAL DOMAIN
Authors: FERNANDES F. Z. , LOPES FILHO M. C.
Published: December 2007

The purpose of this work is to prove the existence of a weak solution of the two-dimensional incompressible Euler equations on a noncylindrical domain consisting of a smooth, bounded, connected and simply connected domain undergoing a prescribed motion. We prove the existence of a weak solution for initial vorticity in Lp, for p > 1. This work complements a similar result by C. He and L. Hsiao, who proved existence assuming that the flow velocity is tangent to the moving boundary, see Ref. 6.
A DELAY MODEL FOR THE EFFECTS OF ENVIRONMENTAL TOXICANT ON BIOLOGICAL SPECIES
Authors: GAKKHAR SUNITA , SAHANI SAROJ KUMAR
Published: December 2007

A three-dimensional time delay mathematical model consisting of a biological species, toxicant in the environment as well as in the species, has been proposed and analyzed. Investigation of the dynamical model reveals that the otherwise stable system can be destabilized by introduction of time lag in the system. The possibility of chaos arising from periodic input of toxicant has been explored. Further, the instability or chaos can be controlled by some external negative feedback on the environmental toxicant.
Symmetry of Strong Interactions
Authors: Nakamura Seitaro , Sato Shigeo
Published: December 2007

The symmetry of strong interactions and weak interactions is formulated in terms of the four-dimensional charge space of SU(2) × SU (2) or O (4), where the isospin, τ, and the “hypercharge spin”, ζ, are considered as two independent spin matrices. The wave functions of baryons and mesons in this charge space are assumed to be composed of the eigenfunctions t of τ3 and s of ζ3, and to transform according to the representations (1/2, 0) and (0, 1/2), respectively. As the basic wave functions which span an irreducible representation space allowing the reflection operations in the charge space, which give rise to the transformations we need sixteen kinds of baryons and also sixteen kinds of mesons, if we assume that the ground state particles are described in terms of the bilinear products t*t, s*s t*s and s*t. The sixteen kinds of particles are made of a singlet, a triplet and a quartet which correspond to an octet in SU (3) symmetry and their countermultiplets which come out by exchanging t⇄s. Among the latter multiplets, a “hypercharge spin” triplet of baryons Z+ (Y=+2), Λ*(Y=0), Ω−(Y = −2) and of mesons D+ (Y=+2), D°(Y=0), D−(Y=−2) are introduced as the countermultiplets of ∑ hyperon and π meson, respectively. We also attempt to classify baryon isobars and meson isobars in terms of the higher configurations of t, t* and s, s*. It is remarkable that a new selection rule of “hypercharge independence” is very powerful in explaining the suppression of some of the decay modes which are otherwise hard to understand. It may also be satisfactory to see that the allowed modes are described in terms of Symmetric interactions, while the forbidden modes of decay are invoked in terms of the meso-strong symmetry breaking interactions on the basis of the present scheme of SU(2) × SU (2) symmetry. The possible experiments which could afford tests of the present scheme are cited within the framework of strong interactions only.

We extend the theorem by Okun and Pomeranchuk for high energy scattering in the asymptotic region to include hypercharge independence in addition to charge independence, and obtain good results in the case of kaon-nucleon scattering; we also obtain predictions which can be easily tested by the experiments in the case of antiproton (proton)-nucleon scattering in the asymptotic region. Discussions are made on the various results deduced from the present scheme of SU (2) × SU (2), in comparison with those obtained from the SU (3) scheme.
Gross Theory of β-Decay and Shell Effects
Authors: Kondoh Takayoshi , Yamada Masami
Published: December 2007

General properties of nuclear β-decay are discussed on the basis of the gross theory. It is demonstrated that the agreement with experimental data is greatly improved by a good choice of the Q-values and by inclusion of the shell effects. Various aspects of the shell effects are discussed in considerable detail. Based on a fairly general single-particle scheme, several systematics are derived for the β strength functions and half-lives.
New data on
Kimberella
, the Vendian mollusc-like organism (White Sea region, Russia): palaeoecological and evolutionary implications
Authors: Fedonkin M. A. , Simonetta A. , Ivantsov A. Y.
Published: December 2007

The taphonomic varieties of over 800 specimens of
Kimberella
(collected from the Vendian rocks of the White Sea region) provide new evidence of the animal's anatomy such as: shell morphology, proboscis, mantle, possibly respiratory folds and possibly musculature, stomach and glands. Feeding tracks, crawling trails and, presumably, escape structures preserved along with the body imprint provide insights on the mode of locomotion and feeding of this animal. The shield-like dorsal shell reached up to 15 cm in length, 5–7 cm in width, and 3–4 cm in height. The shell was stiff but flexible. Evidence of dorso-ventral musculature and fine transverse ventral musculature suggests arrangement in a metameric pattern. Locomotion may have been by means of peristaltic waves, both within the sediment and over the surface of the sea floor, by means of a foot resembling that of monoplacophorans. Respiration may have been through a circumpedal folded strip (possibly an extension of the mantle). Feeding was accomplished by a retractable proboscis bearing terminal hook-like organs and provided with a pair of structures interpreted here as glands. Whilst feeding,
Kimberella
moved backwards. The structural complexity of
Kimberella
poses questions about the time of origin of the triploblastic metazoans.
The provenance and palaeobiology of a new multi-vaned, chambered frondose organism from the Ediacaran (later Neoproterozoic) of South Australia
Authors: Jenkins R. J. F. , Nedin C.
Published: December 2007

The new, large, frondose and stalked, Ediacaran (late Neoproterozoic) ‘petalonamid’
Pambikalbae hasenohrae
gen.
et
sp.
nov
. is preserved in a three-dimensional manner within sandy channel fills occurring directly below the Ediacara Member of the Rawnsley Quartzite on the ‘Nilpena’ pastoral property at a western outlier of the Flinders Ranges, South Australia.
Pambikalbae hasenohrae
was made up of numerous chambered vanes supported by a tapering axial stem and an anchoring stalk. Chambers forming the vanes were commonly infilled with sediment, though variably flattened; groups of vanes representing individual specimens can extend as much as
c
. 3.7 cm deep through the hosting sandstone matrix. Several series of chambers present in each vane abut at zigzag sutures.
Pambikalbae
is clearly not a cnidarian sea pen, but nevertheless exhibits characteristics suggestive of an evolutionary grade comparable to that of known modern cnidarian divisions. Though the serial geometric configuration of its thin integument seems ideally suited to house symbiotic microbial photoautotrophs, our appraisal of the palaeoecology of
Pambikalbae
is supportive of its being a heterotrophic suspension feeder.
Pambikalbae
may plausibly be a highly derived hydrozoan, part of the ancestral stock of the Siphonophorida, or a sister group to the early Chondrophorina.
Upper Vendian assemblages of carbonaceous micro- and macrofossils in the White Sea Region: systematic and biostratigraphic aspects
Authors: Leonov M. V. , Ragozina A. L.
Published: December 2007

Complexes of microfossils, consisting of spheromorphic acritarchs, and coccoid and filamentous cyanobacterial colonies, characterize distinct levels of the Upper Vendian sequence (Ediacaran) of the White Sea region. Three discrete assemblages of algal macrofossils have been recognized in this succession. The oldest assemblage is characteristic of the Lyamtsa Formation of Early Redkino age, the middle assemblage, the Verkhovka, Zimnegory and lowermost Yorga formations of Late Redkino age, and (provisionally) the youngest assemblage, preserved in the upper part of the Yorga Formation of Early Kotlin age. The Vendian succession studied here can be correlated with a similar succession in the Podolia region of Ukraine.
Climates and climate zonality of the Vendian: geological evidence
Authors: Chumakov N. M.
Published: December 2007

In view of the difficulties of stratigraphic correlation, the absence of being able to position continents reliably, the scarcity of climate indicators, and the fact that Vendian sequence crops out over a wide area and can be far apart, it has only so far been possible to identify the most general climatic features for three Vendian units. Late Vendian (Nemakit–Daldyn), and possibly Early Tommotian (Early Cambrian), time was characterized by a glacial climate with pronounced climatic zonation. It appears that there were northern and southern cold zones and a low-latitude, possibly mid-latitude warmer zones. Throughout the time the Middle Vendian sequence was being deposited (Redkino–Kotlin), a warm, possibly arid zone was characteristic of low and mid- palaeolatitudes. In southern high latitudes, there is evidence of a warm humid climate at some periods during this time. The Early Vendian (Laplandian or Varangian) time was characterized by a glacial climate. Some palaeocontinental reconstructions based on magnetism suggest that these glaciations affected high, middle and most of the low latitudes, extending to the palaeoequator. The timing of glacial events in the late Neoproterozoic and their extent across the globe and severity is a topic of great debate at the moment—some researchers suggesting glaciations that lasted for millions of years that locked the entire Earth in solid ice (‘Snowball Earth’). Others suggest that some ice-free oceans were present even during the most severe of glacial events and certainly some geological evidence seem to fit this latter hypothesis well.
Ediacaria booleyi
: weeded from the Garden of Ediacara?
Authors: MacGabhann B. A. , Murray J. , Nicholas C.
Published: December 2007

Sole markings from the Upper Cambrian Booley Bay Formation at Booley Bay, Co. Wexford, Ireland, previously described as the Ediacaran-type fossil
Ediacaria booleyi
appear to possess a number of morphological characteristics which are not consistent with assignment to the genus
Ediacaria
, nor any other known Ediacaran taxon. An inorganic origin for the structures has been proposed by several workers; we tentatively consider them to be at least in part organic, and are currently working to evaluate this hypothesis critically. If organic, the organisms must have had a density similar to that of the sediment in which they were emplaced, and to survive the transport process, they must have had a rigid integument. Neither of these properties appears to be consistent with an interpretation as an Ediacaran-type organism. We suggest here that the Booley Bay specimens should be removed from the genus
Ediacaria
. If
Ediacaria booleyi
is not related to known Ediacaran organisms, this would remove a key aspect of the argument against a mass extinction at the Precambrian/Cambrian boundary.
Seeing ghosts: Neoproterozoic bilaterian body plans
Authors: Valentine J. W.
Published: December 2007

Bilaterians originated before 560 Ma. By 520–530 Ma, the fossil record reveals a fauna teeming with bilaterians with highly disparate body plans, in which most living phyla must have been represented. Between these dates, few bilaterian body fossil types have been found, although trace fossils indicate the presence of vermiform animals, small-bodied before the beginning of the Cambrian. The diversity of Cambrian lineages implies a branch-rich phylogenetic tree, yet organisms representing branch nodes of phyla and ancestral alliances of phyla are unknown, and most of the branches are inhabited by ‘ghosts’. The body plans of these ghosts must be precursory to the body plans of crown phyla, and their genomes must be precursory to crown genomes. Bilaterian Hox genes mediate anteroposterior regionation and are usually found in transcriptionally colinear clusters, a feature conserved even when clusters have been broken up during evolution. When body sections mediated by Hox genes are reduced during morphological evolution, the corresponding gene is sometimes deleted. It may be possible to reconstruct the anteroposterior regionation of ghost lineages from Hox clusters modifications. More information on Hox gene assemblages and functions in small-bodied crown phyla, such as acoelomorphs and others, is required to explore this possibility more fully.
Non-destructive method to detect the cycle of lamination in sedimentary rocks: rhythmite sequence in Neoproterozoic Cap carbonates
Authors: Katsuta N. , Tojo B. , Takano M. , Yoshioka H. , Kawakami S. , Ohno T. , Kumazawa M.
Published: December 2007

Environmental changes were flagged by lamination within Precambrian sedimentary rocks sequences using a high-resolution method. A continuous sample was collected and embedded in epoxy resin to form sample plates in order to investigate 2D laminations on sample surfaces. Elemental distributions in laminated samples were determined and recorded as XRF profiles, using the scanning X-ray analytical microscope (SXAM) and an image processing lamination tracer.

These methods were used to study a rhythmite sequence at the base of a Neoproterozoic cap carbonates, which immediately overlies glacial deposits in Namibia, to determine profiles of Si, Ca, Mn, Ti, Fe, and Sr. At the base and top of each interval, the concentrations of six elements were relatively constant. In the middle of the interval, Ca–Sr and Mn, which reflect presence of calcite and dolomite respectively, fluctuated. This reflects seventeen cycles. The cyclic fluctuations of Ca–Sr and Mn were interpreted as calcite–dolomite cycles. Strontium also recorded two cycles. Furthermore, the fluctuations of Ca–Sr and Mn in calcite–dolomite cycles were laterally traceable. Possibly, these calcite–dolomite cycles were deposited synchronously and regionally. New methods allow the extraction of data that record cyclic- and event-phenomena from long sequences of laminated sedimentary rocks; this is not isolated to the Neoproterozoic but also throughout Earth's history.
Rugosoopsis
: a new group of Upper Riphean animals
Authors: Hermann T. N. , Podkovyrov V. N.
Published: December 2007

The Upper Riphean Lakhanda biota (from the Uchur-Mayai region of SE Siberia) contains abundant, well preserved and highly biodiverse microfossil assemblages including
Rugosoopsis
microfossils, characterized by a uniform shape, with prominent closely transversely spaced wrinkles on the outer surface.
Rugosoopsis
are the oldest, microscopic vermiform organisms, with a typical morphology of closely spaced wrinkles on the body's outer surface resembling the Late Vendian–Early Cambrian
Sabellidites
, and even more the smallest representatives in the genus
Sokolovina
Kirjanov, 1968 (Sokolov 1997). Different types of
Rugosoopsis
preservation can be explained by the presence of numerous bacterial microorganisms on the body of
Rugosoopsis
and on organic films.
Rugosoopsis
organisms inhabited the bottom, where they likely existed alongside saprophytic microbes in finely dispersed organic debris. The community of
Rugosoopsis
and bacteria appears to represent a stable trophic system. The exceptional preservation of these microfossils is due to the favourable sedimentary environment in the Lakhanda Basin.
δ
13
C stratigraphy of the Birmania Basin, Rajasthan, India: implications for the Vendian–Cambrian transition
Authors: Maheshwari A. , Sial A. N. , Mathur S. C.
Published: December 2007

The Birmania Basin is an oval-shaped, isolated remnant of the Marwar Basin (Neoproterozoic–Early Palaeozoic), located in the heart of the Thar Desert of western Rajasthan, India. The Birmania Basin comprises a 900 metre-thick sedimentary sequence of siliciclastic, carbonate and phosphorite facies. δ
13
C and δ
18
O-values are presented in this paper, based on samples of phosphorite and carbonate collected at close intervals along two sample lines near Birmania and Kohra in the Birmania Basin, Rajasthan, India. The carbonates of the Birmania Basin sampled have suffered neither deep burial nor alteration and may provide pristine samples of the C-cycle at the time of their deposition. These values can be useful in inter-regional correlation, particularly for unfossiliferous successions. The carbon isotopic pattern observed in the Birmania succession appears to be similar to that observed in well-established Precambrian–Cambrian boundary sections globally. A worldwide phase of phosphogenesis, at or near the Precambrian–Cambrian boundary, supports the inference that biological controls driven by ocean fertility changes influenced the marine carbon reservoir.
‘Ediacaran’ as a name for the newly designated terminal Proterozoic period
Authors: Jenkins R. J. F.
Published: December 2007

The ‘International Geological Commission on Stratigraphy Working Group on the Terminal Proterozoic Period’ held a series of ballots to vote for criteria identifying the new Period. These included establishing the international site and direct locality for the ‘Global Stratotype Section and Point’ (GSSP), as well as its stratigraphic level and the official name of the new period. Information included in the present note was submitted for circulation to members of the voting committee in April 2003 for their consideration on the occasion of the formal vote to ratify the name, and was a successful proposal for the designation ‘Ediacaran’.

The name Ediacara is historically established as an alliteration of the Aboriginal reference to an ephemeral lake recorded on the first geological map of the Flinders Ranges, and subsequently transmitted through references in Parliament, historical pastoral runs (named properties), and the surveying of a new mining town. During this history its application moved some 60 km south. The name refers to a place of water, possibly in the context of ancestral time. Aspects of the subsequent history of concepts embraced in the original presentation are included.
Recovery of skeletal muscle mass after extensive injury: positive effects of increased contractile activity
Authors: Richard-Bulteau Hélène , Serrurier Bernard , Crassous Brigitte , Banzet Sébastien , Peinnequin André , Bigard Xavier , Koulmann Nathalie
Published: December 2007

The present study was designed to test the hypothesis that increasing physical activity by running exercise could favor the recovery of muscle mass after extensive injury and to determine the main molecular mechanisms involved. Left soleus muscles of female Wistar rats were degenerated by notexin injection before animals were assigned to either a sedentary group or an exercised group. Both regenerating and contralateral intact muscles from active and sedentary rats were removed 5, 7, 14, 21, 28 and 42 days after injury ( n = 8 rats/group). Increasing contractile activity through running exercise during muscle regeneration ensured the full recovery of muscle mass and muscle cross-sectional area as soon as 21 days after injury, whereas muscle weight remained lower even 42 days postinjury in sedentary rats. Proliferator cell nuclear antigen and MyoD protein expression went on longer in active rats than in sedentary rats. Myogenin protein expression was higher in active animals than in sedentary animals 21 days postinjury. The Akt-mammalian target of rapamycin (mTOR) pathway was activated early during the regeneration process, with further increases of mTOR phosphorylation and its downstream effectors, eukaryotic initiation factor-4E-binding protein-1 and p70s6k, in active rats compared with sedentary rats ( days 7–14). The exercise-induced increase in mTOR phosphorylation, independently of Akt, was associated with decreased levels of phosphorylated AMP-activated protein kinase. Taken together, these results provided evidence that increasing contractile activity during muscle regeneration ensured early and full recovery of muscle mass and suggested that these beneficial effects may be due to a longer proliferative step of myogenic cells and activation of mTOR signaling, independently of Akt, during the maturation step of muscle regeneration.
Important role of p38 MAP kinase/NF-κB signaling pathway in the sepsis-induced conversion of cardiac myocytes to a proinflammatory phenotype
Authors: Yang Min , Wu Jun , Martin Claudio M. , Kvietys Peter R. , Rui Tao
Published: December 2007

Septic plasma can convert murine cardiac myocytes to a proinflammatory phenotype. These myocytes 1) have increased nuclear levels of nuclear factor-κB (NF-κB), 2) release CXC chemokines, and 3) promote polymorphonuclear neutrophil (PMN) transendothelial migration. The purpose of the present study was to evaluate the role of the mitogen-activated protein (MAP) kinases [p38 MAP kinase, extracellular signal-regulated kinase (ERK) 1/2, and c-Jun NH2-terminal kinase (JNK)] as upstream intracellular signaling components involved in this phenomenon. Feces-induced peritonitis (FIP) was employed as a model of sepsis. In vitro, cardiac myocytes were treated with plasma (20%) obtained 6 h after either sham (saline) or FIP procedures. Myocyte supernatants were used for 1) detection of the CXC chemokines (enzyme-linked immunosorbent assay) and 2) assessment of their ability to promote PMN transendothelial migration. In vivo, myocardial PMN accumulation was assessed by measuring myeloperoxidase (MPO) activity and function (dF/d t and heart work). Treatment of cardiac myocytes with septic plasma activated p38 MAP kinase and ERK1/2, but not JNK. Blockade approaches (inhibitors or small-interference RNA) indicated that only p38 MAP kinase played a role in the conversion of the myocytes to a proinflammatory phenotype. Time course studies indicated that phosphorylation of p38 MAP kinase preceded the phosphorylation of NF-κB p65. Inhibition of p38 MAP kinase (SB-202190) blocked both NF-κB p65 phosphorylation and NF-κB nuclear translocation. Confirmatory studies in vivo indicated that FIP resulted in an increase in myocardial MPO activity and dysfunction, events reversed by the inhibitor of p38 MAP kinase. Collectively, these data indicate that the cardiomyocyte p38 MAP kinase/NF-κB signaling pathway plays an important role in the sepsis-induced conversion of myocytes to a proinflammatory phenotype.