Scale Of Meters Research Articles

Spatial and temporal variability of snow accumulation in East Antarctica from traverse data

AbstractRecent snow accumulation rate is a key quantity for ice-core and mass-balance studies. Several accumulation measurement methods (stake farm, fin core, snow-radar profiling, surface morphology, remote sensing) were used, compared and integrated at eight sites along a transect from Terra Nova Bay to Dome C, East Antarctica, to provide information about the spatial and temporal variability of snow accumulation. Thirty-nine cores were dated by identifying tritium/b marker levels (1965_66) and non-sea-salt (nss) SO42_ spikes of the Tambora (Indonesia) volcanic event (1816) in order to provide information on temporal variability. Cores were linked by snow radar and global positioning system surveys to provide detailed information on spatial variability in snow accumulation. Stake-farm and ice-core accumulation rates are observed to differ significantly, but isochrones (snow radar) correlate well with ice-core derived accumulation. The accumulation/ablation pattern from stake measurements suggests that the annual local noise (metre scale) in snow accumulation can approach 2 years of ablation and more than four times the average annual accumulation, with no accumulation or ablation for a 5 year period in up to 40% of cases. The spatial variability of snow accumulation at the kilometre scale is one order of magnitude higher than temporal variability at the multi-decadal/secular scale. Stake measurements and firn cores at Dome C confirm an approximate 30% increase in accumulation over the last two centuries, with respect to the average over the last 5000 years

REVIEW: The management of wild large herbivores to meet economic, conservation and environmental objectives

Summary Wild large herbivores provide goods and income to rural communities, have major impacts on land use and habitats of conservation importance and, in some cases, face local or global extinction. As a result, substantial effort is applied to their management across the globe. To be effective, however, management has to be science‐based. We reviewed recent fundamental and applied studies of large herbivores with particular emphasis on the relationship between the spatial and temporal scales of ecosystem response, management decision and implementation. Long‐term population dynamics research has revealed fundamental differences in how sex/age classes are affected by changes in density and weather. Consequently, management must be tailored to the age and sex structure of the population, rather than to simple population counts. Herbivory by large ungulates shapes the structure, diversity and functioning of most terrestrial ecosystems. Recent research has shown that fundamental herbivore/vegetation interactions driving landscape change are localized, often at scales of a few metres. For example, sheep and deer will selectively browse heather Calluna vulgaris at the edge of preferred grass patches in heather moorland. As heather is vulnerable to heavy defoliation, in the long term this can lead to loss of heather cover despite the average utilization rate of heather in a management area being low. Therefore, while herbivore population management requires a large‐scale approach, management of herbivore impacts on vegetation may require a much more flexible and site‐specific approach. Localized impacts on vegetation have cascading effects on biodiversity, because changes in vegetation structure and composition, induced by large herbivores affect habitat suitability for many other species. As such, grazing should be considered as a tool for broader biodiversity management requiring a more sophisticated approach than just, for example, eliminating grazing from conservation areas through the use of exclosures. Synthesis and applications. The management of wild large herbivores must consider different spatial scales, from small patches of vegetation to boundaries of an animal population. It also requires long‐term planning based on a deep understanding of how population processes, such a birth rate, death rate and age structure, are affected by changes in land use and climate and how these affect localized herbivore impacts. Because wild herbivores do not observe administrative or political boundaries, adjusting their management to socio‐political realities can present a challenge. Many developing countries have established co‐operative management groups that allow all interested parties to be involved in the development of management plans; developed countries have a lot to learn from the developing world's example.

Composition and spatio temporal variability of the epiphytic macroalgal assemblage of Fucus vesiculosus Linnaeus at Clare Island, Mayo, western Ireland

The composition and the patterns of spatial and temporal variability of the epiphytic assemblages of Fucus vesiculosus of Clare Island, on the western coast of Ireland, were investigated for an annual cycle. Specimens of Fucus were collected on seven sampling dates from three sites of the island (Portlea, Kinnacorra and Portnakilly). Data of cover of the most common epiphytic species were collected and analysed by multivariate and univariate techniques. Elachista fucicola, Polysiphonia lanosa, Porphyra umbilicalis, Spongonema tomentosum and Ulva compressa were the most common species. Spatial and temporal variation was detected both for the whole assemblage and for the most abundant species. In general, the assemblage was quantitatively more abundant and diverse in spring–summer than in autumn–winter. In spring–summer, there was a clear differentiation among the assemblage of Portnakilly and the assemblages of the other two sites. Individual species were also generally more abundant in spring–summer and their distribution at the three sites was often not consistent in time; P. lanosa was the only epiphyte for which a consistent effect of site was found. Spatial variation on a scale of meters to tens of meters was the most striking pattern of distribution of the epiphytic assemblage; significant effects related to this spatial scale were detected both for the whole assemblage and for individual species. Phenological patterns of the epiphytic species determining availability of propagules and limited dispersal, leading to aggregated patterns of distribution, are considered the main factors responsible of such patchiness. The importance of the incorporation of small spatial scales in sampling designs analysing the distributional patterns of epiphytic assemblages is discussed.

The influence of ecology and genetics on behavioral variation in salamander populations across the Eastern Continental Divide.

Understanding the unique contributions of ecology and history to the distribution of species within communities requires an integrative approach. The Eastern Continental Divide in southwestern Virginia separates river drainages that differ in species composition: the more aquatic, predatory Desmognathus quadramaculatus is present only in the New River drainage (which drains to the Gulf of Mexico), while Desmognathus monticola is present in both the New River drainage and the James River drainage (which drains to the Atlantic Ocean). We investigated natural distributions, behavioral variation in experimental mesocosms, population genetic, and phylogenetic implications of community structure. The presence of D. quadramaculatus increased the terrestriality of D. monticola in natural and experimental situations but to different degrees in allopatric and sympatric populations. Our ecological data suggest that the degree of terrestriality in D. monticola is a result of a balance between the optimal aquatic habitat and risks of predation. Our genetic analyses suggest that D. monticola has experienced a recent range expansion and has only a recent history of association with D. quadramaculatus in Virginia. This is surprising given the strong behavioral variation that exists in populations experiencing unique community compositions over a scale of meters. This study demonstrates the need to combine both ecology and genetics toward an understanding of the factors affecting species distributions, behavioral variation between populations, and patterns of genetic variation across a landscape.

Spatio-temporal variability of micro- and meiobenthic communities in a White Sea intertidal sandflat

Meiobenthos (harpacticoids), microzoobenthos (ciliates) and microphytobenthos (epipelic diatoms and dinoflagellates) were collected during July 1999 using nested sampling at the scales of decimeters, meters and tens of meters. Similarity between samples decreased rapidly with distance for all groups, but unicellular organisms were distributed more heterogeneously at a large scale than meiobenthos. Microspatial (decimeter scale) variations contributed the main part of total variation of harpacticoid abundance, while the large-scale differences were less important. On the contrary, these differences yielded the main variability for ciliates and especially for microalgae. The relative role of temporal variability decreased steadily for the smaller-sized organisms. Stability of spatial structure at multiple scales was estimated by Mantel correlations, R m , between the successive similarity matrices. For harpacticoids, the results showed intensive and chaotic turnover of microaggregations. For microbenthos, rather high R m values were found in smaller scales: tens of meters—for ciliates, from meters on—for dinoflagellates, and already from decimeter scale and on—for diatoms. Thus, the general spatial pattern (that is the arrangement of micropatches) was more stable for microbenthos than for meiobenthos. Temporal variability of species structure, in contrast to the spatial one, was highest for the smallest organisms. Correlations between size groups, using both total abundance and species composition, differed for microspatial, meso-spatial or temporal distribution. At the microscale, there were slight but significant negative correlations between harpacticoids and microalgae. Meso-scale distribution of dinoflagellates and diatoms differed significantly due to their different preferences in sediment properties. Ciliates were strongly positively correlated with dinoflagellates. At the microscale, each group had an individual community pattern. At larger scales, species composition of diatoms, ciliates and harpacticoids varied in space in coordination, while dinoflagellates behaved independently. It is hypothesized that body size determines the spatio-temporal scale of the perception of environmental heterogeneity.

Small‐scale variation in growing season length affects size structure of scarlet monkeyflower

Growing season length can control plant size over altitudinal and biogeographic scales, but its effect at the scale of meters is largely unexplored. Within the riparian zone of a northern California river, scarlet monkeyflower, Mimulus cardinalis, grows significantly larger at sites high in the channel as compared to sites low in the channel, and even larger where tributaries meet the main stem of the river. We explored the hypothesis that markedly different growing season length controls this size variation. Due to the very gradual retreat of the water level following winter flooding, emergence time is three months longer for plants growing at tributary confluences than for plants growing at low elevations in the channel. Consistent with the growing season length hypothesis, we found no difference in transplant growth between river and tributary confluence sites in an experiment where we equalized growing season length at these locations. Moreover, a second experiment showed that individuals planted earlier in the year gain a distinct size advantage over those planted later, even though growing conditions are less ideal. These results suggest that emergence time may be a key determinant of plant size structure along rivers, an important result considering forecasted variation in water flows with climate change.

Spatio-temporal variability of micro- and meiobenthic communities in a White Sea intertidal sandflat

Meiobenthos (harpacticoids), microzoobenthos (ciliates) and microphytobenthos (epipelic diatoms and dinoflagellates) were collected during July 1999 using nested sampling at the scales of decimeters, meters and tens of meters. Similarity between samples decreased rapidly with distance for all groups, but unicellular organisms were distributed more heterogeneously at a large scale than meiobenthos. Microspatial (decimeter scale) variations contributed the main part of total variation of harpacticoid abundance, while the large-scale differences were less important. On the contrary, these differences yielded the main variability for ciliates and especially for microalgae. The relative role of temporal variability decreased steadily for the smaller-sized organisms. Stability of spatial structure at multiple scales was estimated by Mantel correlations, R m , between the successive similarity matrices. For harpacticoids, the results showed intensive and chaotic turnover of microaggregations. For microbenthos, rather high R m values were found in smaller scales: tens of meters—for ciliates, from meters on—for dinoflagellates, and already from decimeter scale and on—for diatoms. Thus, the general spatial pattern (that is the arrangement of micropatches) was more stable for microbenthos than for meiobenthos. Temporal variability of species structure, in contrast to the spatial one, was highest for the smallest organisms. Correlations between size groups, using both total abundance and species composition, differed for microspatial, meso-spatial or temporal distribution. At the microscale, there were slight but significant negative correlations between harpacticoids and microalgae. Meso-scale distribution of dinoflagellates and diatoms differed significantly due to their different preferences in sediment properties. Ciliates were strongly positively correlated with dinoflagellates. At the microscale, each group had an individual community pattern. At larger scales, species composition of diatoms, ciliates and harpacticoids varied in space in coordination, while dinoflagellates behaved independently. It is hypothesized that body size determines the spatio-temporal scale of the perception of environmental heterogeneity.

Geochemical controls on the environmental mobility of Sb and As at mesothermal antimony and gold deposits

Antimony and arsenic are commonly mobilised into the environment from mesothermal mineral deposits. Both these metalloids are potentially toxic in the environment when dissolved in water at low levels (<0·01 mg/l). Mobility of antimony, in comparison to that of arsenic, is documented at mine sites in four different mesothermal systems in low grade Palaeozoic-Mesozoic metamorphic terranes of New Zealand (Globe Hill, Reefton; Macraes, Otago; and Endeavour Inlet, Marlborough) and Australia (Hillgrove, New South Wales). Dissolved antimony can reach ~50 mg/kg in mine waters where evaporative concentration occurs in oxidised near-neutral pH mine waters in contact with stibnite. Such waters are chemically saturated with respect to antimony oxides, and antimony oxide precipitation occurs locally. Most mine waters have lower dissolved Sb concentrations, especially where high rainfall causes dilution. However, high rainfall areas have widespread diffuse mobilisation of both Sb and As to give elevated background levels (0⋅1–0⋅01 mg/kg) in downstream waters. Dissolved Sb is decreased by adsorption of Sb to hydrated iron oxide (HFO) precipitates in streams. Bulk distribution coefficient, Kd, for this Sb adsorption ranges up to at least 105, and is similar to that of As adsorption in the same settings. Attenuation of dissolved Sb by HFO results in an order of magnitude decrease in Sb concentrations on a scale of metres. In the absence of HFO, dissolved Sb can be transported in streams for many kilometres. Elevated dissolved Sb concentrations can arise distant (tens of kilometres) from a mine site because of dissolution of antimony-bearing minerals physically transported downstream. Hence, without HFO attenuation, environmentally toxic levels of Sb can be readily leached from mine sites and distributed widely.

Supramolecular dendritic liquid quasicrystals

A large number of synthetic and natural compounds self-organize into bulk phases exhibiting periodicities on the 10(-8)-10(-6) metre scale as a consequence of their molecular shape, degree of amphiphilic character and, often, the presence of additional non-covalent interactions. Such phases are found in lyotropic systems (for example, lipid-water, soap-water), in a range of block copolymers and in thermotropic (solvent-free) liquid crystals. The resulting periodicity can be one-dimensional (lamellar phases), two-dimensional (columnar phases) or three dimensional ('micellar' or 'bicontinuous' phases). All such two- and three-dimensional structures identified to date obey the rules of crystallography and their symmetry can be described, respectively, by one of the 17 plane groups or 230 space groups. The 'micellar' phases have crystallographic counterparts in transition-metal alloys, where just one metal atom is equivalent to a 10(3)-10(4)-atom micelle. However, some metal alloys are known to defy the rules of crystallography and form so-called quasicrystals, which have rotational symmetry other than the allowed two-, three-, four- or six-fold symmetry. Here we show that such quasiperiodic structures can also exist in the scaled-up micellar phases, representing a new mode of organization in soft matter.

Online calibration and pre-processing of TAMA data

The TAMA300 gravitational wave detector, a pioneer among hundred-plus metre scale interferometric detectors, observed over 1000 h with sufficient sensitivity to monitor sources within our galaxy (Tagoshi et al 2001 Phys. Rev. D 63 062001, Ando et al 2001 Phys. Rev. Lett. 86 3950). This was an important step to the first direct detection of gravitational waves. In such long-term observations, online calibration and pre-processing of data are important for both the detector operation and the gravitational wave signal search. By focusing on the most promising source of neutron star binaries, such online processes were developed and were running during the long-term observation in 2003. As a result, the average sensitivity to inspiralling neutron star binaries can be maintained at 73% of our best sensitivity.

Green and senescent leaf phenolics showed spatial autocorrelation in a Quercus robur population in northwestern Spain

Intraspecific variation in polyphenols may be important both for the resistance of plants to herbivory and for nutrient cycling in terrestrial ecosystems. The spatial pattern and scale of polyphenol concentration in natural populations are practically unknown, despite multiple evidence that resources influencing leaf phenolics (such as light or nutrient availability) show spatial dependence at the scale of meters to tens of meters. By using geostatistical methods, we evaluated the spatial variability in polyphenol concentration in green and senescent leaves in a pedunculate oak (Quercus robur L.) population of 125 individuals. The spatial pattern of light and nutrient availability for plants was also evaluated. Leaf polyphenols were more variable than other leaf properties, and green polyphenols were significantly correlated with radiation, leaf mass per unit area and leaf N concentration. Both green and senescent leaf polyphenol concentration showed spatial dependence at distances below 6 to 10 m, with structural (spatial) variance explaining between 50 and 80% of the total variance. The variance not explained by space was assumed to be due to individual genotypic variability. Stochastic maps of leaf phenolics in the area showed that the probability of finding high phenolics level was not random. These findings may be important to understand the spatial heterogeneity of plant-herbivore interactions, leaf litter decomposition and mineralization rate.

Shallow-water aragonite recorded in bundles of limestone–marl alternations—the Upper Jurassic of SW Germany

Characteristically, limestone–marl alternations are conspicuous in outcrop because of differential weathering, the marls being predisposed to stronger deterioration. Superimposed on the bedding rhythms are in many cases lower-frequency meter-scale rhythms, so-called bundles. These bundles are eye-catching from a distance, and are typified by variations in thickness of limestone beds and marl interbeds. The palaeoenvironmental significance of the bundles received markedly less attention in the literature than the origin of the small-scale couplets. Here we focus on the palaeoenvironmental significance of the bundles by reconstructing the initial mineralogical composition. As an example, we present a classical limestone–marl alternation from the Upper Jurassic (Oxfordian–Kimmeridgian) of SW Germany that is typified by two orders of bundles superimposed on the limestone–marl couplets. Our method of reconstruction of the original mineralogical composition of the precursor sediment of limestone–marl alternations is based on a diagenesis model that assumes dissolution of aragonite and reprecipitation as calcite cement as the major mechanism of early diagenesis. Calculated initial clay, aragonite, and calcite contents show rhythmic variations on a scale of several meters that correspond to the bundles as seen in the outcrop. Limestone-dominated parts of the bundles correspond to intervals of elevated aragonite content in the precursor sediment, but not necessarily to elevated calcite contents. Additionally, an overlain fluctuation in initial mineralogy on the order of tens of meters (mega-bundles), reflecting the former local subdivision of the SW German Upper Jurassic into “Weißjura alpha”, “beta”, and “gamma”, is observed. The limestone-dominated “Weißjura beta” (lower Kimmeridgian) is the interval with highest initial aragonite content. Our new method allows for quantification of initial mineralogical composition. As aragonite and calcite usually have different sources (shallow-water benthic versus planktic), this approach potentially adds significant new possibilities for palaeoceanographic interpretation of calcareous rhythmites. In the Jurassic example, the observed variations in reconstructed aragonite content are interpreted as variations in flooding events and related export of aragonitic material from marginal shallow-water platforms.

A distinct class of avalanche scars on Mars

We report observations of a set of surface features on Mars that form a distinct class of avalanche scars. These features have a horizontal scale of hundreds of meters, but a depth scale of meters distinguishes them from the shallower features known as slope streaks. The meters-thick avalanche scars have escaped previous attention because of weak contrast between the interiors of the scarred regions and their surroundings. Often the most visible feature is a shadow cast by the trough wall, a band 1–3 pixels wide in Mars Orbiter Camera narrow angle images, indicating maximum depths of 4–10 m. We investigate the morphology of more than 500 such features. Slopes upon which the avalanches occur average about 27°. Impact craters are seen at the heads of some avalanche scars; this subset exhibits statistically wider opening angles. The scars span an estimated several Ma in age. Those found so far occurred mainly in the Olympus Mons lower aureole. We compare shapes of slope streaks to shapes of meters-thick avalanches, and the results support the notion that the two classes are distinct. The newly-discovered avalanches resemble some terrestrial flows of loose, dry material such as dry snow and glass beads. On the basis of these analogs, we suggest a physical model.

Carbon movement and assimilation by invertebrates in estuarine habitats at a scale of metres

Theories of large-scale (kilometres) movement of carbon within and from estuaries are often not supported by empirical data, and this provided the basis for a smaller-scale (i.e. 30 m), intermediate (2 to 30 m) and fine (<2 m). The carbon stable isotope signatures of 2 crab and 2 gastropod species were measured at different positions in saltmarsh and mangrove habitats (centre, intermediate and edge in the saltmarsh, intermediate and centre positions in adjacent mangroves) at 5 sites. The δ13C signatures of crabs collected from the saltmarsh (-15.6 ± 0.2‰) were significantly more enriched than those of crabs from the mangrove habitat (-22.1 ± 0.3‰), but did not differ between positions within each habitat. The δ13C signatures of crabs in the saltmarsh were similar to those of the dominant macrophyte, the salt couch grass Sporobolus virginicus (-14.9 ± 0.1‰). The δ13C signatures of crabs in the mangrove habitat were enriched relative to those of the mangroves (-27.6 ± 0.2‰), but were similar to those of the microphytobenthos in that habitat (-24.6 ± 0.7‰). The crabs thus fitted the fine-scale model of assimilation of carbon produced in their immediate vicinity, although the signatures for crabs in the mangrove habitat were also consistent with a food source comprising a mixture of mangroves and a more enriched source, possibly the salt couch grass S. virginicus. Gastropods were found only in the saltmarsh habitat. Their δ13C signatures did not differ among central and intermediate positions (-15.3 ± 0.2‰) but were lower at edge positions (-17.0 ± 0.1‰). The δ13C signatures of gastropods indicated assimilation of carbon from sources 2 to 15 m away, at the lower end of the intermediate scale. The extent of carbon movement and assimilation varies among estuaries, and our results show that in some situations it occurs at scales much smaller than previously realised.

Plasma density-electric field turbulence in the low-latitude ionosphere from the observation on satellites; possible connection with seismicity

Based on plasma density data from the Cosmos-900 satellite we have analyzed the spatial distribution of the ionospheric turbulence in a form k − b , where k is wave number and b is the fractal index. In this case spatial scales (∼ k −1) are ranging from 15 to 300 km at the satellite height h=450–500 km. Depending on season, local time and seismic activity the index 〈 b〉 varies in the interval 1.3–1.9. Then we have considered the slope of the spatial distribution for electric field turbulence observed on board the IK-24 satellite ( h=500–700 km, scales of several meters). Supposing a simple connection between the power spectrum density of the plasma and the electric field we find 〈 b〉=1.2–1.7. Remembering that from observation on board the Aureol-3 satellite ([Radio Science 20 (1985) 755]; h=500–700 km, scales 10–300 m) b=1.7–1.9 both for the plasma density and electric field variations, we conclude that the ionospheric turbulence is a unique process in a large interval of scales from hundreds km to several meters and the b-dependence is similar to the classic Kolmogorov's turbulence b=5/3. Intensification of the turbulence near the magnetic equator is definitely connected with the presence of the equatorial density anomaly (EA) but existence of the regular moderate level aside of EA and at the mid-latitude ionosphere invokes a possibility of another energy source, probably atmospheric gravity waves.

The live, the dead, and the very dead: taphonomic calibration of the recent record of paleoecological change in Lake Tanganyika, East Africa

High-resolution (annual to decadal) paleoecological records of community composition can contribute a long-term perspective to conservation biology on baseline ecological variability and the response of communities to environmental change. We present here a detailed comparison of species assemblage characteristics (species richness, abundance, composition, and occurrence frequency) in live, dead, and recent fossil ostracode samples from Lake Tanganyika, East Africa. This study calibrates the fidelity of paleoecological samples (i.e., both death and fossil assemblages) to live diversity patterns for the purpose of reconstructing community dynamics through time. Both life and death assemblages were collected from rocky sites in a mixed substrate habitat (total of ten sampling visits over 22-month period) over spatial scales of less than a meter to about 3-12 meters. Fossil assemblages were derived from sediment cores collected in sandy substrates adjacent to the rocky sites. Species richness in paleoecological assemblages is comparable to that in a year's accumulation of life assemblages sampled approximately monthly. The temporal reso- lution of the fossil samples in Lake Tanganyika could thus be as short as one year. Species abun- dance distributions were statistically indistinguishable among data sets. Rank abundance tests demonstrated that death and fossil assemblages were quite similar, although life assemblages dif- fered substantially in the composition of their dominant species. Species composition differences between life and paleoecological assemblages appear to reflect the area of spatial integration rep- resented by an assemblage—i.e., death and fossil assemblages are integrated over multiple habitat types, whereas life assemblages dominantly represent the rocky habitats where they were collected. Species occurrence frequencies in paleoecological data identified ecologically persistent species and may be useful for delimiting local species pools. Analysis of sampling efficiency indicates that approximately 28% of species in each paleoecological assemblage are ''unique''; i.e., they are not likely to be present in an additional subsample from the same sample. Ordination reveals that life assemblages of ostracodes are characterized by high spatiotemporal heterogeneity. Variability in species composition was lower in paleoecological assemblages, presumably as a result of spatial and temporal averaging. Death and fossil assemblages of Lake Tanganyika appear to preserve many characteristics of liv- ing benthic ostracode assemblages with high fidelity. Spatiotemporal averaging allows paleoeco- logical assemblages to render information about the average composition of ostracode communities over short timescales, at spatial scales of several meters, and across habitat types. Sampling shell assemblages in surficial sediments thus represents a more efficient way of assessing the average ecological conditions at a locality than repeated live sampling. Furthermore, paleoecological anal- yses can generate novel insights into long-term community variability and membership with direct relevance to conservation.

An Experiment on the Spatial Variability of Water Balance Terms in a Small Grass-Covered Area

By analyzing the time series of measurements of soil moisture at a point along with precipitation and potential evaporation using the bucket with a bottom hole (BBH) model, we evaluated water balance terms at the point. The estimates of those terms made at nine points on a 1.5m grid in a small grass-covered area showed their own spatial variations. The results obtained are summarized as follows.(a) Ranking of the spatial variability of the water balance terms involved in the BBH model was W (soil moisture) < E (evaporation) < Rs (surface runoff) < Gd (gravity drainage).(b) Clear patterns showing the spatial variation in surface runoff and gravity drainage in a 3×3m patch were obtained, which suggests that subsurface water below the ASSL (30cm thick) has flow systems on spatial scales of a few meters.(c) The spatial variation patterns of the water balance terms obtained by the parameterization of the BBH model did not necessarily agree with that of soil moisture but showed ones peculiar to the terms. This means that the parameterization takes the effects of other factors than soil moisture such as the micro topographic relief, vegetation cover, soil texture and structure into account appropriately, because such factors should by nature exhibit spatially not random but organized variations.(d) Daily evaporation estimates made by the BBH model were in good agreement with the measurements taken for reference by the Bowen ratio method, though it was conducted by the expedient of disregarding an insufficiency of fetch and neglecting the heat flux into the soil.

Estimating scale-dependency in disturbance impacts: El Niños and giant kelp forests in the northeast Pacific.

Recent discussions on scaling issues in ecology have emphasized that processes acting at a wide range of spatial and temporal scales influence ecosystems and thus there is no appropriate single scale at which ecological processes should be studied. This may be particularly true for environmental disturbances (e.g. El Niño) that occur over large geographic areas and encompass a wide range of scales relevant to ecosystem function. However, it may be possible to identify the scale(s) at which ecosystems are most strongly impacted by disturbances, and thus provide a measure by which their impacts can be most clearly described, by assessing scale-dependent changes in the patterns of variability in species abundance and distribution. This, in turn, may yield significant insight into the relative importance of the various forcing factors responsible for generating these impacts. The 1997-98 El Niño was one of the strongest El Niños ever recorded. I examined how this event impacted giant kelp populations in the northeast Pacific Ocean at 90 sites ranging from central Baja California, Mexico to central California, USA. These sites spanned the geographic range of giant kelp in the Northeast Pacific and were surveyed just before, immediately following, several months after, more than 1 year after, and nearly 2 years after the El Niño. I used a hierarchical sample design to compare these impacts at five spatial scales spanning six orders of magnitude, from a few meters to more than 1,000 km. Variance Components Analyses revealed that the El Niño shifted control over giant kelp abundance from factors acting at the scale of a few meters (local control) to factors operating over hundreds to thousands of kilometers (regional control). Moreover, El Niño resulted in the near-complete loss of all giant kelp throughout one-half of the species' range in the northeast Pacific Ocean. Giant kelp recovery following El Niño was far more complex and variable at multiple spatial scales, presumably driven by numerous factors acting at those scales. Recovery returned local control of giant kelp populations within 6 months in southern California, and within 2 years in Baja California.

Stratigraphy and sedimentology of shoreface and fluvial conglomerates: insights from the Cardium Formation in NW Alberta and adjacent British Columbia

ABSTRACT In this paper we describe little-studied exposures of the Upper Cretaceous Cardium Formation in the northern Foothills and Peace River Plains, located north of Twp. 58. We correlate sixteen principal outcrop sections along the Foothills and across the northern escarpment of the Cardium as far east as the Smoky River. Correlations are based on tracing bounding erosion surfaces, initially observed in well logs and cores, and later extended into outcrop. The Kakwa Member is conglomeratic in many of these sections. The member displays a spectrum of conglomerate types, of both shallow marine and fluvial origin. Depositional environments are differentiated on the basis of stratigraphic context, conglomerate texture, sedimentary structures, stratification style and paleogeographic setting. We describe in detail four localities exemplifying the main paleoenvironments. At Bay Tree, a 12 m thick section consists primarily of clast-supported conglomerates representing a wave-dominated shoreface and beachface. This environment is dominated by broadly horizontal stratification with horizontal facies heterogeneity on a metre scale. At Cutbank Lake, swaley-stratified shoreface sandstones contain pebble-lined scours that show an upward increase in thickness and lateral continuity and represent rip current deposits. At Mount Niles, conglomerate forms a 2-6 m thick, >200 m wide, channelized body consisting of heterolithic matrix-supported conglomerates and pebbly sandstones capped by gravel wave ripples. Deposition may have been in a river-mouth setting. At 'Horseshoe Mountain', the upper part of the Kakwa Member consists of metre-scale crossbedded pebbly sandstone and matrix-supported conglomerate deposited in a pebbly fluvial system lacking marine influence. For the entire study area, paleocurrent observations indicate a strong NW to SE alongshore transport of gravel, with storm waves approaching from the NE. Fluvial crossbedding is directed towards the NE. Some of the outcrop facies can also be recognized in core from the adjacent subsurface. Our descriptions of conglomerate facies in outcrop facilitate interpretation of the depositional environment of comparable units in subsurface. Unfortunately, the limited extent of exposures does not allow us to determine with precision the geometry of conglomeratic units. However, a broad conglomerate-rich zone >90 km in dip extent and 10-20 km in strike extent can be traced across the northern outcrop belt and probably records the position of a major and long-lasting pebbly fluvial system. Subsurface analogs would be exploration fairways. At the reservoir scale, conglomerate bodies showing greater influence of wave reworking would tend to be more elongate, and have greater facies continuity/permeability, in a shore-parallel direction. The outcrops display lateral textural heterogeneity at scales of metres to 10s of metres. This heterogeneity would affect reservoir performance, but could not be captured (for reservoir modeling) using typical development well spacing. End_Page 437------------------------

Characterizing fish–habitat associations in streams as the first step in ecological restoration

Abstract Habitat availability is often regarded as the primary factor that limits population and community recovery in degraded ecosystems, and physical habitat is thus often targeted in restoration. The identification of which habitat(s) to attempt to restore is a critical step in the restoration process, but one for which there is often a paucity of useful information. Here we examine the distribution of fish in three lowland streams in Victoria, Australia, that have been degraded by severe sedimentation. We aim to identify habitats that are associated with high abundances of native fish, and that thus might be appropriate to target in habitat restoration. Associations between native fish abundances and physical habitat characteristics were examined at three spatial scales (among streams, among sites and within sites) to determine the types of habitat to which fish respond, and the scales over which these responses occur. Of the four species of native fish found in the streams, three (Galaxias olidus Günther, Gadopsis marmoratus (Richardson) and Nanoperca australis Günther) showed significant habitat associations at small spatial scales (i.e. within sites). In particular, these species were generally found in deeper water, and in close proximity to cover (typically either coarse or fine woody debris or vegetation). Differences in habitat availability among sites and streams were less influential, except in the case of G. marmoratus, which was completely absent from both the ephemeral streams. Although our results suggest that these species collectively respond to habitat at several spatial scales, fish distributions were allied to the presence of habitat structure at the scale of metres, the smallest spatial scale examined. We hypothesize that fish abundances are currently limited by the low availability of habitat at these small spatial scales. It may therefore be possible to increase fish abundances in these creeks by augmenting the amount of available habitat via stream restoration.