Small Hollows Research Articles

Dynamics of temperate rainforest from fine resolution pollen analysis, Upper Ringarooma River, northeastern Tasmania

Abstract The relationship between sclerophyll forest and temperate rainforest in Tasmania is believed to be driven by climate, soils and fire regime; however, this has been tested infrequently on time frames relevant to the longevity of the major forest trees involved. This study uses sediments in four small hollows from within a rainforest stand in the Upper Ringarooma valley in northeastern Tasmania, Australia, to analyse vegetation dynamics and disturbance over the last 1000 years. Pollen‐vegetation relationships were investigated by comparing pollen rain and current vegetation, and the chronology was established by radiocarbon and lead‐210 dates. The lead‐210 data indicate that the two Sphagnum humus profiles were not always closed systems for inorganic inwash; however, the pollen and charcoal records are generally consistent indicating that a mixed Eucalyptus‐Nothofagus forest shifted to a Kothofagus dominated rainforest as fire became a less prominent component of the environment. About 400 years ago Leptospermum lanigerum invaded the community as canopy gaps developed, possibly as the older Nothofagus Cunninghamii trees died. There is no strong evidence of invasion by Atherosperma moschatum as suggested by some models of forest dynamics in these forests in Tasmania. In this stand of forest, fire and erosion following flooding have been the major causes of disturbance.

Identifying forest stand types using pollen from forest hollows

Methods of interpreting pollen assemblages in sediment were examined using surface samples from 66 small forest hollows in Michigan and Wisconsin. All canopy trees in the surrounding 50 m were measured to provide detailed information about the source vegetation of each surface pollen assemblage. Basal area of trees in each forest sample was used to classify them into six stand types: hemlock-dominated, sugar maple/hemlock mixed, sugar maple-dominated, and ash-, oak-, and pine-dominated stands. Various statistical procedures were tested to learn which was most successful in sorting the pollen assemblages into appropriate vegetation groups. Two ordination techniques – detrended correspondence analysis (DCA) and canonical variate analysis (CVA) – give similar overall results, although CVA more successfully separated assemblages from hemlock stands from those of sugar maple-dominated stands. Squared chord distance,0.05 also successfully identified samples from the same forest type. After stand dominants have been identified from pollen assem blages using multivariate methods, a further determination of stand composition is sometimes possible using ratios of pollen counts of individual taxa. Ratios can be calibrated by comparison with species abundances around surface samples. For instance, ratios of pine to hemlock pollen can indicate the abundance of pine within a stand dominated by hemlock, whereas pine pollen percentages alone are affected by variable abundance of other species.

八ヶ岳連峰稲子岳の凹地内における暖候期の冷気湖形成

八ヶ岳連峰稲子岳の凹地内における暖候期の冷気湖形成

Origin of the frequency branch γ of the de Haas-van Alphen effect in CeSn 3

CeSn 3 is a typical heavy-electron compound which belongs to the valence-fluctuation regime. The major experimental frequency branches of the de Haas-van Alphen effect are explained reasonably well by the large hole sheet and the large electron sheet of the Fermi surface which are derived on the basis of an itinerant 4f-electron model. In particular, it is shown by visualizing the extremal electron orbits that one of the major experimental frequency branches, i.e., the branch γ, can be explained by those orbits which run through the small hollow on the large electron sheet.

Time Domain Reflectometry Measurements of Nitrate Transport in Manure‐Amended Soil

AbstractTo obtain more detailed information about N processes in agricultural soils, nondestructive measurement techniques with high spatial and temporal resolution are needed. The ability of time domain reflectometry (TDR) in combination with small polysulfone hollow fiber (PHF) solution samplers to follow NO−3 production and transport in soil fertilized with cattle slurry and exposed to different rainfall events was investigated. The experiments were conducted in minilysimeters using a coarse sandy soil and two different slurry application methods: (i) surface application followed by harrowing (homogenous incorporation) or (ii) direct injection (incorporation as a manure string). Comparison between soil‐water electrical conductivity (ECw) obtained with TDR and the sum of NO−3 and Cl− concentrations in the soil water measured with solution samplers showed a good agreement both with respect to concentration levels and temporal and spatial development. Except for an initial leaching of the natural ion content in the soil water when water application was started, NO−3 released from the manure was the dominating anion in the soil water and changes in NO−3 corresponded well to changes in ECw. Both slurry and water application strategy had a large effect on the temporal development in nitrification and NO−3 leaching. In the case of homogeneously incorporated slurry and constant water application for 3 wk, NO−3 formation and leaching started after 4 to 5 d, while it started after 9 to 10 d in the case of directly injected slurry. If water was applied only in the last (third) week to the directly injected slurry system, a large amount of the NH+4 in the slurry was oxidized to NO−3 before water application and subsequently leached. The TDR measurements of ECw with high spatial and temporal resolution combined with a few measurements of ion concentrations by PHF solution samplers is a new, valuable method for analyzing turnover and transport of nonconservative ions in soil.

Myosin Rod-Packing Schemes in Vertebrate Muscle Thick Filaments

Muscle myosin filament backbones are known to be aggregates of long coiled–coil α-helical myosin rods, but the packing arrangement is not understood in detail. Here we present new data on fish muscle myosin filaments from low-angle X-ray diffraction and from freeze-fracture, deep-etch electron microscopy which put constraints on the kind of models that might explain all of the observations. In particular, it is known in the case of vertebrate striated muscle thick filaments that the myosin head array in resting muscle is not perfectly helical but contains periodic perturbations. We show by analysis of low-angle X-ray diffraction patterns from resting bony fish muscle that any radial, azimuthal, and axial perturbations of the myosin head origins on the filament surface (due to perturbed myosin rod packing) must all be rather small and that the main perturbations are in the myosin head configurations (i.e., tilts, slews, rotations) on those origins. We provide evidence that the likely arrangement of titin molecules on the myosin filament is with them aligned parallel to the filament long axis, rather than following helical tracks. We also show from freeze-fracture studies of fish muscle that the myosin filament backbone (including titin and other extra proteins) has a radius of about 65–75 Å and appears to contain a small (≈15–20 Å radius) hollow core. Together with previously published evidence showing that the myosin rods are nearly parallel to the thick filament long axis, these results are consistent with the curved crystalline layer model of Squire (J. M. Squire, 1973,J. Mol. Biol.77, 291–323), and they suggest a general structure for the C-zone part of the thick filament

The history of Fagus forest in southwestern Sweden during the last 1500 years

In the recent past, Fagus forests in southwestern Sweden were more common and widespread than today. The Fagus forest area has decreased considerably due to cultural activities, mainly during the eighteenth and nineteenth centuries. The pollen records of two small adjacent forest hollows (lying c. 50 m apart) in the Bocksten area in central Halland indicate that the pre- Fagus forest was of a rich memoral type with many woody taxa present. Quercus, Tilia, Alnus, and Corylus were important components of this forest type. Fagus became established in the area around 1450 14C years BP, and rapidly became dominant in the forest. The expansion of Fagus was remarkably rapid, and probably facilitated by slight human disturbance. The rather pure Fagus stands found today in the area are a product of recent human activities. The high pollen percentages of Tilia at one of the sites (site A) until 200 BP is remarkable, and stands in contrast to the picture seen in regional-scale pollen diagrams from Sweden. At this site, Tilia grew in a mixture with Fagus, Quercus and Corylus for almost 1200 years until the stand was suddenly cleared c. 200 BP. At the other site (B), Tilia shows a gradual decrease beginning before the establishment of Fagus, which is in agreement with the regional picture. It is evident that stand-level differences in vegetation is not possible to detect with conventional pollen diagrams based on regional-scale sites. Different grazing regimes, or human influence, may have caused these stand-scale differences in vegetation. The boreo-nemoral forest type found today in the studied area is domi nated by intensively managed Picea plantations and Fagus stands. This forest type has little resemblance to the vegetation that existed during earlier periods.

History of aPinus strobus‐dominated stand in northern New York

Abstract.Pollen, plant macrofossils and charcoal from a small forest hollow were analyzed to determine the formation and dynamics of aPinus strobus‐dominatedforest stand on outwash soil in northern New York.P. strobus, Betula papyriferaandAbies balsameacolonized the upland surrounding the hollow following a major disturbance that occurred ca. 360 yr ago. Pre‐disturbance vegetation consisted of shade‐tolerantTsuga canadensis, Fagus grandifoliaandPicea ruhens. The size‐class distribution of modern vegetation suggests continuing recruitment ofA. balsameaandAcer rubrumat the site. The status ofP. strobusandB. papyriferain the stand is uncertain, but there is no evidence for recolonization ofT. canadensis, F. grandifoliaorP. rubens. Frequent windthrow has probably played a role in stand dynamics since ca. 310 yr BP due to the high wind‐susceptibility of overstory and understory tree taxa in the modern forest patch.Vegetation change that occurred following fire(s) ca. 310 yr BP was recorded by plant macrofossils but not by pollen, indicating that the pollen assemblage was insensitive to vegetation change within at least 30 m (and potentially 60 m) of the hollow. The apparent insensitivity of this small‐hollow pollen assemblage to local vegetation change may be related to the relatively large size of the hollow (75 m2) and/or to its close proximity to a 0.24 ha kettle pond.

Long-term population dynamics of Fagus sylvatica at the northern limits of its distribution in southern Sweden: a palaeoecological study

Regional pollen diagrams indicate that Fagus may have been present close to its northern distri butional limits in southern Sweden for as long as 1000 years. Fagus has probably always been rare in this region, except for some small and scattered stands. Many of these outlying Fagus stands have been regarded as planted but no previous studies have investigated this in detail. At Mattarp, a small outpost Fagus stand in northern Småland, the pollen record of the deposit of a small hollow indicates that Fagus became established c. 400 BP. The local establishment was associated with an earlier phase of woodland clearance and the former system of land-use. Local factors seem to have controlled the immigration and establishment at the stand-scale at this site. Regional climate had probably been favourable for Fagus for almost 2000 years and cannot be regarded as the direct cause for establishment at this site. The complex south Swedish cultural landscape may have favoured Fagus establishment in many areas, particularly when there has been a temporary reduction in human influence. Picea became regionally established around 800 BP, but a local expansion did not occur until c. 400 BP, coinciding with the establishment of Fagus. Picea expansion also seems to have been favoured by a moderate human influence at this site. Fagus pollen influx values have steadily increased since the time of establishment. It seems likely that the Fagus stand has continually increased in size, and probably would continue to do so if this were not prevented by human activities.

The immigration of Fagus sylvatica L. and Picea abies (L.) Karst. into a natural forest stand in southern Sweden during the last 2000 years

The continental scale migrations of Fagus sylvatica L. and Picea abies (L.) Karst. are under a broad climatic control, but disturbance and local factors influence the immigration of these species into individual forest stands. Palaeoecological analysis of a small forest hollow in the boreo‐nemoral zone of southern Sweden has shown that a forest stand with largely unbroken forest continuity resisted immigration of Fagus for almost 1000 years. Two fires about 950 and 330 years ago were the disturbing factors that facilitated eventual Fagus immigration. Picea immigrated and achieved co‐dominance in a single generation, without resistance from the existing forest. Thus migrational lag is demonstrable for Fagus but not Picea. The immigration of these two dominating species coupled with a severe reduction in tree species diversity has resulted in a total change in forest competition during the last few centuries despite the maintenance of a structural forest continuity. Some of these changes are attributable to changes in the grazing regime, but the forest stand is as close to «natural» conditions as can be found in S. Sweden.

Use of transverse flow hollow fibers for bubbleless membrane aeration

A novel sealed-end transverse flow hollow fiber membrane module was evaluated for aeration of water. In this process the sealed-end fibers were held vertically from the bottom of a channel. Pure oxygen under high pressure was maintained in the fiber. The water to be aerated was pumped over the outside of the fibers. Due to the concentration gradient, oxygen transferred through the air-filled pores and dissolved directly into the water without forming bubbles. Since the primary orientation of the fiber is perpendicular to the liquid flow, a high mass transfer coefficient was achieved at low liquid velocities compared to parallel flow modules. Measured mass transfer coefficients for hollow fibers held at different angles are presented in this paper. In addition, the design equations for transverse-flow aerators are developed. The mass transfer behavior of a small scale transverse-flow bubblesless hollow fiber membrane module was measured experimentally and the results were compared with the theoretical predictions.

The Origin of Bedded Cherts of the Early Permian Gufeng Formation in the Lower Yangtze Area, Eastern China

Abstract Bedded cherts occurring in the Early Permian Gufeng Formation in the Lower Yangtze region, eastern China, are nearly 20‐80 m in thickness and contain varying amounts of radiolarians and sponge spicules. There are three types of section for the Gufeng Formation: chert, carbonate and chert ‐ carbonate mixing types. Bedded cherts mainly occur in the first and third types of section. The depocentres of silica are marked by some small (not larger than a few thousand square kilometres in area) rhombic or elliptic hollows and their formation was controlled by faults. Argillaceous volcanic rocks in cherts occur as numerous thin layers. Bedded cherts are characterized by higher Fe and lower Al contents, enrichment in such trace elements as As, Sb, Bi, Ga, Au, Ag and Cr, lower total REE abundance, negative Ce anomaly and varying degrees of HREE enrichment. These characteristics are important evidence for hydrothermal cherts. Minor amounts of substances of non ‐ hydrothermal origin are mixed in the cherts. The temperatures of sea water range approximately from a few tens of degrees to over 160°C. during the deposition of siliceous sediments.

A Model for Variations in Gelifluction Rates with Temperature and Topography: Implications for Global Change

A model is proposed for gelifluction rates, in terms of active layer depths and sub-surface runoff. It is concluded that the flow of soil during melting can generally be assumed to be under saturated conditions, so that active layer depth is the dominant driver. Erosional slope profiles produced by gelifluction should be convex, with no tendency for small hollows to enlarge into valleys at any scale. This model has been applied, using a global database of monthly climate, to estimate regional variations in gelifluction rates under current conditions, and with both increases and decreases in mean temperatures. It is concluded that wide bands, roughly between 40–65°N and S, should have experienced a period of very intense gelifluction during the postglacial warming.

Infrared surface waves in circular hollow waveguides with small core diameters

An asymptotic form of the characteristic equation that describes wave propagation at near-infrared wavelengths in small core hollow circular waveguides is developed. Analytic solutions for the transverse and axial propagation constants are obtained. These demonstrate the transition of the TE/sub 11/ and TM/sub 01/ modes to surface waves as the guide radius is increased to values much greater than at cutoff. Relative power density distributions illustrating these mode transitions are shown.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The origin of hydrothermal metalliferous sediments associated with the early Mesozoic Othris and Pindos ophiolites, mainland Greece

Metalliferous sediments and sulphides are associated with the Jurassic Othris and Pindos ophiolites, central and northern Greece. These ophiolites formed at an Early Mesozoic spreading ridge within a small. Pindos ocean basin created by rifting of the northern margin of Gondwanaland. Ubiquitous terrigenous silt was derived from adjacent continental margins mainly the Pelagonian microcontinent to the east. In the Othris area, disseminated, massive and vein sulphides occur within and above MORB-type pillow lavas and volcaniclastic sediments. Sulphide was precipitated in quartz veins within fault-controlled stockworks. Episode (with local epidosite) is locally very abundant in extrusives immediately underlying thick SiFe-rich hydrothermal sediments. Massive sulphides were precipitated as small fault-controlled bodies. that are directly overlain by Fe-rich mudstones and Fe-rich cherts, strongly depleted in Mn. Mudstones, relatively enriched in hydrothermal Fe, Mn, Cu, Zn, Pb, REE and Ba, were ponded into small fault-controlled hollows around the fringes of the sulphide-precipitating field. Elsewhere (e.g. northern Othris), manganese-rich layers in ribbon radiolarites are strongly enriched in Mn and trace-elements. Metal-enriched deposits are also found within slices of mid-ocean ridge-type lavas associated with melange (Avdella Melange) structurally underlying the Pindos ophiolite, NW Greece. Sulphides there are restricted to tiny massive deposits overlying pillow lava and sulphide veins within ophiolitic extrusives. Pillow lavas are overlain by volcanic talus breccias, shed from submarine fault scarps. Overlying metalliferous mudstones are enriched in Fe and other hydrothermal constituents, probably derived from nearby sulphide precipitating zones and mixed with lithogenous sediments. The metalliferous deposits preserve a variety of hydrothermal deposits within an Early Mesozoic small ocean basin. The Pindos sediments reflect mixing of ferruginous hydrothermal constituents with terrigenous sediment, possibly during the earlier stages of basin opening. The Othris sulphide and ferruginous oxide-sediments record evidence of a small, high-temperature hydrothermal field, formed near the spreading axis when the ocean neared its maximum width. Manganese-rich cherts in the northern Othris area reflect widespread accumulation of hydrothermal constituents on the abyssal plain, derived from axial high-temperature hydrothermal fields and/or related to low-temperature (off-axis?) discharge.

Occurrence of potential nest trees and their use by birds in sclerophyll forest in north-east Tasmania

Abstract Breeding of hollow-nesting birds and the distribution and availability of tree hollows were investigated in an area of sclerophyll forest in north-eastern Tasmania. The occurrence of potential tree hollows was assessed from the ground and used as an index of actual hollows. Entrance size was categorized as small, medium or large corresponding to the differing requirements of the birds present on the site. Smaller hollows were more abundant than larger hollows. The distribution of hollows amongst trees was highly clumped. Diameter at breast height and the presence of a fire scar explained one-third of the variation in numbers of hollows per tree. Streamside and non-streamside areas did not differ in the number of hollows/tree or the sizes of hollows present. Thirty trees were found that were utilized as nest sites by striated pardalotes Pardalotus striatus, laughing kookaburras Dacelo novae- gaineae, green rosellas Platycercus caledonicus and yellow-tailed black cockatoo Calyptorhynchus funereus. In comparison with a representative sample of trees, nest trees were larger, had a greater number of potential hollows, a greater proportion of larger hollows and a greater proportion were fire scarred. Eucalyptus viminalis was used as a nest tree to a greater extent than expected from its relative abundance. Hollows appeared to be far in excess of the requirements of the birds present. Trees remaining in streamside reserves after logging would probably provide enough hollows to support the number of hollow-nesting birds present before logging. However, only 13% of striated pardalotes and none of the other species utilized streamside areas for nesting in the undisturbed forest.

The weathering effects of the lichen Lecidea aff. Sarcogynoides (Koerb.) on magaliesberg quartzite

AbstractThe effect of the weathering processes generated by Lecidea aff. Sarcogynoides (Koerb.) on the substrate was studied by means of a scanning electron microscope. The elements present in the substrate (Magaliesberg quartzite) and in the lichen thallus were determined by X‐ray fluorescence spectrometry for the purpose of comparison. The elements present were mostly similar although a few were present in the thallus which were not observed in the quartzite. It is possible that those elements present in the lichen thallus which were not present in the substrate may have been extracted from the atmosphere. The occurrence of small hollows (weathering pits) in which the early stages of plant development occurs, and the disintegration of the rock indicate that Lecidea aff. sarcogynoides (Koerb.) contributes to the chemical weathering processes by chelation and mechanically by the penetration and expansion of hyphae. A model is proposed in which a possible mechanism for these weathering processes is suggested.

The history and vegetation dynamics of a yew wood (Taxus baccata L.) in S.W. Ireland.

Reenadinna Wood is one of the largest Taxus baccata dominated woods in the British Isles. It is therefore of considerable ecological and conservation interest. To investigate the history and dynamics of the wood, pollen data from a small hollow within the wood are described. These data are compared with the regional pollen record and local historical and archaeological information. The yew wood appears to have developed at least 3000, but probably 5000 years ago from a wood previously dominated by pine, oak, elm and hazel. There is evidence to suggest that the wood has been disturbed by periods of patch cultivation and site occupancy.

Le tumulus I des Combes, Les Bondons (Lozère)

ABSTRACT The circumference of the tumulus (diameter: 5 to 6 metres) is bounded by a structure composed of large leaning slabs, placed edge to edge in a narrow trench dug into the substratum. The actual sepulchral surface is indicated by a covered ring of stones. The funerary urn contains the remains of a cremated individual and was found lying flat, with its mouth towards the bottom of a small artificial hollow. Date: end of the seventh century B.C.

Growth of fibrous hydroxyapatite in the gel system

Hydroxyapatite (HAP) was prepared in the agar gel system, where Ca2+ ions were incorporated in the gel and PO 4 3− solution was layered over the gel. When the concentration of Ca2+ was lower than 1.0 M and the initial solution Ca/P molar ratio was lower than about unity, fibrous HAP several centimetres to several tens of centimetres in length was grown upwards in the PO 4 3− solution from the gel phase, while at the larger Ca2+ concentration and initial Ca/P molar ratio CaHPO4 · 2H2O (DCPD) in the form of gelatinous precipitate, particulate precipitates or needle-like crystals were preferred to HAP. The fibrous HAP was calcium deficient and composed of small elongated hollow ovals linked in a zigzag row. This was considered to be formed in the following manner. First, Ca2+ ions supplied through pores in the gel reacted with PO 4 3− ions to form a small spherulite at the pore exit, then the spherulite was bloated and elongated by the osmotic pressure or capillary force until a part of the oval was broken for Ca2+ ions to be gushed out into the PO 4 3− solution. The above two processes were repeated to form elongated hollow ovals linked to the preceding ones.