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M Intervals (m + interval)
Selected AbstractsDetailed examination of lymph nodes improves prognostication in colorectal cancerINTERNATIONAL JOURNAL OF CANCER, Issue 11 2010Fania S. Doekhie Abstract Up to 30% of stage II patients with curatively resected colorectal cancer (CRC) will develop disease recurrence. We evaluated whether examination of lymph nodes by multilevel sectioning and immunohistochemical staining can improve prognostication. Lymph nodes (n = 780) from 36 CRC patients who had developed disease recurrence (cases) and 72 patients who showed no recurrence of disease for at least 5 years (controls) were analyzed. Sections of 4 levels at 200-,m interval were immunohistochemically stained for cytokeratin expression. The first level was analyzed by conventional and automated microscopy, and the 3 following levels were analyzed by automated microscopy for the presence of tumor cells. Overall, cases showed more micrometastases (3 patients) than controls (1 patient). Analysis of a second level led to the additional detection of 1 patient with micrometastases (case) and 1 patient with macrometastasis (case). Examining more levels only led to additional isolated tumor cells, which were equally divided between cases and controls. Likewise, automated microscopy resulted only in detection of additional isolated tumor cells when compared with conventional microscopy. In multivariate analysis, micrometastases [odds ratio (OR) 26.3, 95% confidence interval (CI) 1.9,364.8, p = 0.015], T4 stage (OR 4.8, 95% CI 1.4,16.7, p = 0.013) and number of lymph nodes (OR 0.9, 95% CI 0.8,1.0, p = 0.028) were independent predictors for disease recurrence. Lymph node analysis of 2 levels and immunohistochemical staining add to the detection of macrometastases and micrometastases in CRC. Micrometastases were found to be an independent predictor of disease recurrence. Isolated tumor cells were of no prognostic significance. [source] Evaluation of DRAINMOD-S for simulating water table management under semi-arid conditions,IRRIGATION AND DRAINAGE, Issue 3 2002M. A. S. Wahba modèl e dela direction dela table d'eau souterraine; le drainage conventionnel; le drainage contrôlé Abstract The water table management simulation model, DRAINMOD-S, was evaluated under semi-arid conditions using field data from the Maruit experimental field in the western delta of Egypt for three cropping seasons; maize 1999, wheat 1999/2000 and maize 2000. Two water table management systems (conventional drainage (FD) and controlled drainage (CD)) were applied in the study area. The recorded data included daily ground water table depths, drain outflows during flow events, soil salinity to depth of 1.20 m from the soil surface (0.30 m interval), and relative crop yield. DRAINMOD-S was run to simulate the applied water table management systems for the same study periods. The reliability of the model was evaluated by comparing measured and predicted values of the daily ground water table depth, cumulative outflow based on total monthly outflow, soil salinity during each season, and relative crop yield. Good agreement was found between the measured and predicted values. DRAINMOD-S predicted values within an absolute deviation ranged from 11.0 to 16.0 cm for ground water table depth, from 18 to 75 mm for drain outflows, from 0.22 to 1.08 dS m,1 for soil salinity, and from 4.62 to 4.86% for relative crop yield. The model showed the potential for long-term simulation and planning of ground water table management systems under semi-arid conditions of the western delta of Egypt. Copyright © 2002 John Wiley & Sons, Ltd. RÉSUMÉ Le modèle DRAINMOD-S pour simuler la direction de la table d'eau sous des conditions demi-arides á été évalué en utilisant le data des champs experimentaux du Mariut delta denileouest d'Égypte pendant trois saisons agricoles: le maïs 1999, le blé 1999/2000 et le maïs 2000. Deux systèmes de direction de la table d'eau (drainage conventionnel (FD) et drainage contrôlé (CD)) ontété appliqués àla superficie de l'étude. Le data qui s'est remis en ordre s'inclut les mesures des profondeurs de la table d'eau souterraine, les écoulements des drains pendant les évènements de l'écoulement, la salinité du sol au profondeur de 1.20 m souterrain aux intervalles de 30 cm, etles produits agricoles relatifs. DRAINMOD-S S'est mis en courant pour simuler l'application des systèmes de la direction pour la même période d'étude. La véracité du modèle aété évaluée en comparant les valeurs mésurées avec lcelles des produits agricoles sur le profondeur de la table d'eau quotidien, l'écoulement cumulatif basé sur l'écoulement total du mois, la salinité du sol pendant chaque saison, et les produits agricoles relatifs. On a trouvé un bon accord entre les valeurs mésurées et celles qu'on avait prédites avec une déviation absolue qui rangeait de 11.0 à 16.0 cm pour la profondeur de la table d'eau, de 18 à 75 mm pour l'écoulement du drains, et de 0.22 à 1.08 dS m,1, pour la salinité du sol et de 4.62 à 4.86% pour les produits agricoles relatifs. Le modèle a indiqué une éfficacité pour une simulation allongée et pour projeter les systèmes de la direction dela table d'eau souterraine auprès les conditions demi-arides du delta ouest en Egypte. Copyright © 2002 John Wiley & Sons, Ltd. [source] Demographic genetics of American beech (Fagus grandifolia Ehrh.) IV.PLANT SPECIES BIOLOGY, Issue 3 2008Development of genetic variability, gene flow during succession in a coastal plain forest in Maryland Abstract Genetic recovery of an American beech (Fagus grandifolia) population in deciduous forests that were once pastures was studied using 16 allozyme loci from 410 individuals in a 600 m × 600 m study plot in Maryland, USA. We also examined the spatio-temporal genetic structure of the American beech population at a regional scale. Overall genetic diversity of mature trees was measured by estimating average heterozygosity (H = 0.156). Rare alleles were observed in five loci, Lap, 6Pdgh3, Pgi, Adh1 and Got3. Mature individuals were divided into three size classes based on d.b.h. The genetic component of each size class was compared and it was revealed that several alleles (Pgm-a, 6Pgdh3-a and Lap-b) were shared only in specific size classes. The spatial distribution of the genotypes demonstrated a conspicuous localization in three loci (Aco, Adh1 and Idh). Spatial autocorrelation analyses were carried out among the mature trees for a 20 m interval, and were positive for 0,120 m and negative for >180 m. Distrograms indicated that a unique genetic localization occurs among mature individuals. Seven hundred and seventy-five seedlings in the 10 m × 120 m transect were analyzed to measure gene flow via seed and/or pollen. We obtained a genetic neighborhood area of 1.17 ha and an effective population size of 32.4. The temporal and spatial modes of genetic recovery of the population are discussed in the context of conservation biology. [source] Gas Hydrates in the Qilian Mountain Permafrost, Qinghai, Northwest ChinaACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 1 2010Youhai ZHU Abstract: Qilian Mountain permafrost, with area about 10×104 km2, locates in the north of Qinghai-Tibet plateau. It equips with perfect conditions and has great prospecting potential for gas hydrate. The Scientific Drilling Project of Gas Hydrate in Qilian Mountain permafrost, which locates in Juhugeng of Muri Coalfield, Tianjun County, Qinghai Province, has been implemented by China Geological Survey in 2008,2009. Four scientific drilling wells have been completed with a total footage of 2059.13 m. Samples of gas hydrate are collected separately from holes DK-1, DK-2 and DK-3. Gas hydrate is hosted under permafrost zone in the 133,396 m interval. The sample is white crystal and easily burning. Anomaly low temperature has been identified by the infrared camera. The gas hydrate-bearing cores strongly bubble in the water. Gas-bubble and water-drop are emitted from the hydrate-bearing cores and then characteristic of honeycombed structure is left The typical spectrum curve of gas hydrate is detected using Raman spectrometry. Furthermore, the logging profile also indicates high electrical resistivity and sonic velocity. Gas hydrate in Qilian Mountain is characterized by a thinner permafrost zone, shallower buried depth, more complex gas component and coal-bed methane origin etc. [source] Development of the saltation system under controlled environmental conditionsEARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2002Samantha ArnoldArticle first published online: 24 JUN 200 Abstract The transport of sand by the wind occurs predominantly by the process of saltation. Following the entrainment of sand by an above threshold wind, the saltation system is regulated by the mutual interaction of the atmospheric boundary-layer, the sand cloud and the sand bed. Despite existing data on the spatial and temporal development of the sand transport system, very little is known about the development of the saltation system towards equilibrium. Results are presented from wind-tunnel experiments that were designed to address the simultaneous spatial and temporal development of the saltation system, with and without artificial sand feed. The development of the saltation system was monitored over a streamwise length of 8 m during a period of 3600 s. Mass flux data were measured simultaneously at 1 m intervals by the downwind deployment of seven Aarhus sand traps. Wind velocity data were collected throughout the experiments. The downwind spatial development of the saltation system is manifested by an overshoot in mass flux and friction velocity prior to declining towards a quasi-equilibrium. Mass flux overshoots at approximately 4 m downwind, in remarkable agreement with existing data of a comparable scale. Friction velocity overshoots at approximately 6 m downwind, a result not previously witnessed in saltation studies. The overshoot of mass flux prior to the overshoot in friction velocity is a spatial manifestation of the time lag between the entrainment of grains and the deceleration of the wind by the grains in transport. Temporally, the development of the saltation system is controlled by the availability of entrainable grains from the sand bed. Through time the saltation system develops from a transport-limited to a supply-limited system. The depletion of the sand bed through time limits the appropriateness of the assumption of ,equilibrium' for the universal prediction of mass flux. Copyright © 2002 John Wiley & Sons, Ltd. [source] Crosswell seismic waveguide phenomenology of reservoir sands & shales at offsets >600 m, Liaohe Oil Field, NE ChinaGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2005P. C. Leary SUMMARY Crosswell seismic data recorded at 620,650 m offsets in an oil-bearing sand/shale reservoir formation at the Liaohe Oil Field, northeast China, provide robust evidence for waveguide action by low-velocity reservoir layers. Crosswell-section velocity models derived from survey-well sonic logs and further constrained by observed waveguide seismic wavegroup amplitudes and phases yield plausible evidence for interwell reservoir,sand continuity and discontinuity. A pair of back-to-back Liaohe crosswell vector-seismic surveys were conducted using a source well between two sensor wells at 650 and 620 m offsets along a 200-m-thick reservoir formation dipping 7° down-to-east between depths of 2.5 and 3 km. A downhole orbital vibrator generated seismic correlation wavelets with frequency range 50,350 Hz and signal/noise ratio up to 5:1 over local downhole ambient noise. The sensor wells were instrumented with a mobile 12- to 16-level string of clamped vector-motion sensor modules at 5 m intervals. Using 5 m source depth increments, crosswell Surveys 1 and 2 cover source/sensor well intervals above and through the reservoir of, respectively, 600 m/600 m (13 000 vector traces in 9 common sensor fans) and 300 m/560 m (7000 vector traces in 7 common sensor fans). Survey 1 common sensor gathers show clear, consistent high-amplitude 20 ms waveletgroup lags behind the first-arrival traveltime envelope. Such arrivals are diagnostic of seismic low-velocity waveguides connecting the source and sensor wells. Observed Survey 1 retarded wavegroup depths tally with source and sensor depths in low-velocity layers identified in sonic well logs. Finite-difference acoustic model wavefields computed for waveguide acoustic layers constrained by well-log sonic velocity data match the observed waveguide traveltime and amplitude systematics. Model waveforms duplicate the observed m-scale and ms-scale sensitivity of waveguide spatio-temporal energy localization. Survey 2 crosswell data, in contrast, provide no comparable evidence for waveguide action despite a sensor-well sonic well log similar to that of Survey 1. Instead, acoustic wavefield modelling of Survey 2 data clearly favours an interpreted waveguide model with 10° downdip interrupted by a 75,100 m throw down-fault near the sensor well. The absence of clear waveguide arrivals is adequately explained by dispersal of waveguide energy at the fault discontinuity. Auxiliary well sonic velocity and lithologic logs confirm the model-implied 75,100 m of down-throw faulting near the sensor well. [source] Stocks and dynamics of SOC in relation to soil redistribution by water and tillage erosionGLOBAL CHANGE BIOLOGY, Issue 10 2006JIANHUI ZHANG Abstract Soil organic carbon (SOC) displaced by soil erosion is the subject of much current research and the fundamental question, whether accelerated soil erosion is a source or sink of atmospheric CO2, remains unresolved. A toposequence of terraced fields as well as a long slope was selected from hilly areas of the Sichuan Basin, China to determine effects of soil redistribution rates and processes on SOC stocks and dynamics. Soil samples for the determination of caesium-137 (137Cs), SOC, total N and soil particle size fractions were collected at 5 m intervals along a transect down the two toposequences. 137Cs data showed that along the long slope transect soil erosion occurred in upper and middle slope positions and soil deposition appeared in the lower part of the slope. Along the terraced transect, soil was lost over the upper parts of the slopes and deposition occurred towards the downslope boundary on each terrace, resulting in very abrupt changes in soil redistribution over short distances either side of terrace boundaries that run parallel with the contour on the steep slopes. These data reflect a difference in erosion process; along the long slope transect, water erosion is the dominant process, while in the terraced landscape soil distribution is mainly the result of tillage erosion. SOC inventories (mass per unit area) show a similar pattern to the 137Cs inventory, with relatively low SOC content in the erosional sites and high SOC content in depositional areas. However, in the terraced field landscape C/N ratios were highest in the depositional areas, while along the long slope transect, C/N ratios were highest in the erosional areas. When the samples are subdivided based on 137Cs-derived erosion and deposition data, it is found that the erosional areas have similar C/N ratios for both toposequences, while the C/N ratios in depositional areas are significantly different from each other. These differences are attributed to the difference in soil erosion processes; tillage erosion is mainly responsible for high-SOC inventories at depositional positions on terraced fields, whereas water erosion plays a primary role in SOC storage at depositional positions on the long slope. These data support the theory that water erosion may cause a loss of SOC due to selective removal of the most labile fraction of SOC, while on the other hand tillage erosion only transports the soil over short distances with less effect on the total SOC stock. [source] Structure and Functioning of the "Egg Bank" of a Fairy Shrimp in a Temporary Pool: Chirocephalus ruffoi from Pollino National Park (Southern Italy) as a Case StudyINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 1 2004Graziella Mura Abstract To investigate their distribution and total numbers, resting eggs of the anostracan Chirocephalus ruffoi were collected from the bed of a temporary pool in southern Italy. Samples were taken at 0.5 m intervals along six transects oriented at 30° from each other, by means of a cylindrical core sampler. The horizontal distribution of intact resting eggs was extremely patchy, with cyst number per core ranging from 191 to 1,400 (CV = 32.7%), corresponding to a mean of between 0.8 and 4.3 cysts cm,3. Differences observed were related to core position and transect orientation, total cyst numbers being markedly higher in the leeward area of the pool compared to the windward area. Marked variation was also evident in vertical distribution, a significant, though weak correlation was recorded between egg density and sediment depth. Cyst-bank size (± 95% confidence limits) of the pool bed, estimated from the mean cyst number cm,3 obtained for the 6 transects, ranged between 1.0 × 108 and 1.3 × 108 cysts. Hatching in the laboratory was very erratic. Despite significant differences in hatching, the observed variation was unrelated to most of the variables considered (position within sections, cores and transects, pre-incubation treatment) and was explained only by initial sediment conditions (moist/dry). In none of the experimental conditions tested was synchronous hatching obtained. Possible causal factors (mixing of the bottom sediments by cattle, egg age, storage conditions, differential exposure to environmental cues as well as variability in hatching response even at clutch level) are discussed. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Vegetation Change and Soil Nutrient Distribution along an Oasis-Desert Transitional Zone in Northwestern ChinaJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 11 2007Bao-Ming Chen Abstract Many studies have focused on soil nutrient heterogeneity and islands of fertility in arid ecosystems. However, few have been conducted on an oasis-desert transitional zone where there is a vegetation pattern changing from shrubs to annual herbs. The goal of the present study was to understand vegetation and soil nutrient heterogenity along an oasis-desert transitional zone in northwestern China. Three replicated sampling belts were selected at 200 m intervals along the transitional zone. Twenty-one quadrats (10 × 10 m) at 50 m intervals were located along each sampling belt. The vegetation cover was estimated through the quadrats, where both the soil under the canopy and the open soil were sampled simultaneously. The dominated shrub was Haloxylon ammodendron in the areas close to the oasis and Nitraria tangutorum dominated the areas close to the desert. In general, along the transitional zone the vegetation cover decreased within 660 m, increased above 660 m and decreased again above 1 020 m (close to the desert). The soil nutrients (organic matter, total N, NO3, and NH4+) showed significant differences along the zone. The soil nutrients except the soil NH4+ under the canopy were higher than those in open soil, confirming "islands of fertility" or nutrient enrichment. Only a slight downward trend of the level of "islands of fertility" for soil organic matter appeared in the area within 900 m. Soil organic matter both under canopy and in interspace showed a positive correlation with the total vegetation cover, however, there was no significant correlation between the other soil nutrients and the total vegetation cover. We also analyzed the relationship between the shrubs and annuals and the soil nutrients along the zone. Similarly, there was no significant correlation between them, except soil organic matter with the annuals. The results implied that annual plants played an important role in soil nutrient enrichment in arid ecosystem. [source] Investigating the Fate and Transport of Escherichia coli in the Charles River, Boston, Using High-Resolution Observation and Modeling,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 2 2008Ferdi L. Hellweger Abstract:, The processes affecting the fate and transport of Escherichia coli in surface waters were investigated using high-resolution observation and modeling. The concentration patterns in Boston's Charles River were observed during four sampling events with a total of 757 samples, including two spatial surveys with two along-river (1,500 m length) and three across-river (600 m length) transects at approximately 25-m intervals, and two temporal surveys at a fixed location (Community Boating) over seven days at hourly intervals. The data reveal significant spatial and temporal structure at scales not resolved by typical monitoring programs. A mechanistic, time-variable, three-dimensional coupled hydrodynamic and water quality model was developed using the ECOMSED and RCA modeling frameworks. The computational grid consists of 3,066 grid cells with average length dimension of 25 m. Forcing functions include upstream and downstream boundary conditions, Stony Brook, and Muddy River (major tributaries) combined sewer overflow (CSO) and non-CSO discharge and wind. The model generally reproduces the observed spatial and temporal patterns. This includes the presence and absence of a plume in the study area under similar loading, but different hydrodynamic conditions caused by operation of the New Charles River Dam (downstream) and wind. The model also correctly predicts an episode of high concentrations at the time-series station following seven days of no rainfall. The model has an overall root mean square error (RMSE) of 250 CFU/100 ml and an error rate (above or below the USEPA-recommended single sample criteria value of 235 CFU/100 ml) of 9.4%. At the time series station, the model has an RMSE of 370 CFU/100 ml and an error rate of 15%. [source] Demographic genetics of the American beech (Fagus grandifolia Ehrh.) III.PLANT SPECIES BIOLOGY, Issue 1 2003Genetic substructuring of coastal plain population in Maryland Abstract Spatiotemporal genetic substructurings were investigated in the American beech population of the east-central coastal plain in Maryland. All trees including seedlings, various sizes of juveniles, and mature trees within the study site (10 × 100 m) were mapped, diameters measured, and leaves collected for allozyme analyses. Eleven polymorphic loci in eight enzyme systems were examined: 6Pgdh2, 6Pgdh3, Acp2, Adh1, Adh2, Fum, Got1, Got3, Lap, Pgi, and Pgm2. A total of 1945 trees were analyzed and 595 multilocus genotypes were detected. Six size-classes and 10 spatial blocks were discriminated for spatiotemporal analyses. Parameters for genetic variations (heterozygosity, Simpson's index, Shannon-Weaver's index, and inbreeding coefficient) decreased in larger size-classes. These genetic parameters fluctuated in spatial blocks of 10 m intervals, in which certain alleles were characteristic of specific blocks. The spatial autocorrelation by Moran's I and coancestry revealed the ranges of genetic relatedness to be only 20,30 m. Multilocus genotype analyses showed that higher genetic variations occur in larger size-classes and at gap openings where seed shadows for mother trees are overlapped. The relationships among reproductive trees, seedlings and juveniles suggested that the seed dispersal range of the American beech is normally in the range of 30,40 m. The mechanisms of a remarkably high genetic polymorphism maintained in this once artificially disturbed and grazed forest are discussed as related to conservation biology. [source] Three-dimensional reconstruction of immunolabeled neuromuscular junctions in the human thyroarytenoid muscleTHE LARYNGOSCOPE, Issue 11 2003Andrew D. Sheppert MD Abstract Objectives/Hypothesis: The objective was to reveal the location of the neuromuscular junctions in a three-dimensional reconstruction of the human thyroarytenoid muscle within the true vocal fold. Study Design: Immunohistochemical analysis of serially sectioned human true vocal folds was performed, followed by reconstruction in three dimensions using computer imaging software. Methods: Six fresh human larynges from autopsy were harvested, fixed in formalin, and embedded in paraffin. Eight vocal cords were studied from these six larynges. Five-micron serial sections were collected throughout the entire vocal cord in an axial plane at 500-,m intervals. Immunohistochemical analysis was performed with anti-synaptophysin antibody. A computer-controlled imaging and reconstruction system was used to create a three-dimensional reconstruction from the serial sections and to represent the location of the clustered band of neuromuscular junctions within each true vocal fold. The vocal cord was divided into equal thirds from anterior to posterior for statistical analysis. Results: The most neuromuscular junctions (74%) we're located in the middle third, and the least (7%) were found in the anterior third. The difference in anterior-to-posterior distribution was statistically significant in all eight specimens by ,2 analysis (P < .001). Conclusion: The distribution of neuromuscular junctions is not random within the human thyroarytenoid muscle. Because neuromuscular junctions are most highly concentrated in a band within the mid belly of the muscle, botulinum toxin type A (Botox) injection in patients with spasmodic dysphonia should be targeted to this region. [source] Resistivity imaging survey of the Roman barrows at Bartlow, Cambridgeshire, UKARCHAEOLOGICAL PROSPECTION, Issue 1 2007Timothy Astin Abstract Resistivity imaging was carried out on four large Roman barrows at Bartlow in Cambridgeshire. The geophysical survey formed part of a wider research project designed to record and assess the landscape context of the largest surviving Roman burial mounds in Britain. The barrows today range in height from 6.6,m to 13.2,m and their steep profile posed particular practical and modelling challenges. Data were obtained using a Campus Geopulse resistance meter with up to 50 electrodes spaced at 1,m intervals and lines up to 76,m long. A total of 24 lines was obtained. Topographic corrections were applied to the pseudosections, which were inverted using Res2Dinv and Res3Dinv. Resistivity imaging was particularly successful in identifying evidence for the antiquarian explorations of the site. Central collapse features or in-filled tunnels image as high resistance features in all barrows and in one (Barrow IV) there is also a low resistance feature in the approximate position of a known antiquarian tunnel. Barrow VI had a thick covering of high-resistivity that may relate to nineteenth century landscaping and reconstruction of this monument. Resistivity imaging also revealed possible evidence for ancient revetments in all four large barrows. Copyright © 2006 John Wiley & Sons, Ltd. [source] Combined seismic tomographic and ultrashallow seismic reflection study of an Early Dynastic mastaba, Saqqara, EgyptARCHAEOLOGICAL PROSPECTION, Issue 4 2005Mohamed Metwaly Abstract Mastabas were large rectangular structures built for the funerals and burials of the earliest Pharaohs. One such mastaba was the basic building block that led to the first known stone pyramid, the,>4600-year old Step Pyramid within the Saqqara necropolis of Egypt. We have tested a number of shallow geophysical techniques for investigating in a non-invasive manner the subsurface beneath a large Early Dynastic mastaba located close to the Step Pyramid. After discovering that near-surface sedimentary rocks with unusually high electrical conductivities precluded the use of the ground-penetrating radar method, a very high-resolution seismic data set was collected along a profile that extended the 42.5,m length of the mastaba. A sledgehammer source was used every 0.2,m and the data were recorded using a 48-channel array of single geophones spaced at 0.2,m intervals. Inversions of the direct- and refracted-wave travel times provided P-wave velocity tomograms of the shallow subsurface, whereas relatively standard processing techniques yielded a high-fold (50,80) ultrashallow seismic reflection section. The tomographic and reflection images were jointly interpreted in terms of loose sand and friable limestone layers with low P-wave velocities of 150,650,m,s,1 overlying consolidated limestone and shale with velocities,>,1500,m,s,1. The sharp contact between the low- and high-velocity regimes was approximately horizontal at a depth of ca. 2,m. This contact was the source of a strong seismic reflection. Above this contact, the velocity tomogram revealed moderately high velocities at the surface location of a friable limestone outcrop and two low-velocity blocks that probably outlined sand-filled shafts. Below the contact, three regularly spaced low velocity blocks probably represented tunnels and/or subsurface chambers. Copyright © 2005 John Wiley & Sons, Ltd. [source] Does alpine grazing reduce blazing?AUSTRAL ECOLOGY, Issue 8 2006A landscape test of a widely-held hypothesis Abstract ,Alpine grazing reduces blazing' is a widely and strongly held view concerning the effects of livestock grazing on fuels, and therefore fire behaviour and impact, in Australia's high country landscapes. As a test of this hypothesis, we examined the patterns of burning across the alpine (treeless) landscapes of the Bogong High Plains in Victoria, following the extensive fires of January 2003. Data were collected from multiple transects, each 3,5 km long, with survey points located randomly at either 50, 200 or 500 m intervals. The transects traversed the major regions of the Bogong High Plains, both grazed and ungrazed. At each point, we recorded whether the point was burnt or unburnt, the vegetation type (closed-heath, open-heath, grassland or herbfield), the estimated prefire shrub cover, slope, aspect, and a GPS location. At burnt heathland sites, we recorded the minimum twig diameter (an a posteriori measure of fire severity) in a sample of common shrubs. In total, there were 108 km of transect lines, 419 survey points and 4050 twig measurements, with sample points equally distributed across grazed and ungrazed country. The occurrence of fire (i.e. burnt or unburnt) in grazed and ungrazed areas was analysed by logistic regression; the variation in twig diameters by anova. Approximately half of all points were burnt. There was no statistically significant difference between grazed and ungrazed areas in the proportion of points burnt. Fire occurrence was determined primarily by vegetation type, with the proportion burnt being 0.87 for closed-heath, 0.59 for open-heath, and 0.13 for grassland and all snow-patch herbfield points unburnt. In both closed-heath and open-heath, grazing did not significantly lower the severity of fire, as measured by the diameter of burnt twigs. We interpret the lack of a grazing effect in terms of shrub dynamics (little or no grazing effect on long-term cover of taller shrubs), diet and behaviour of cattle (herbs and dwarf shrubs eaten; tall shrubs not eaten and closed-heath vegetation generally avoided), and fuel flammability (shrubs more flammable than grass). Whatever effects livestock grazing may have on vegetation cover, and therefore fuels in alpine landscapes, they are likely to be highly localized, with such effects unlikely to translate into landscape-scale reduction of fire occurrence or severity. The use of livestock grazing in Australian alpine environments as a fire abatement practice is not justified on scientific grounds. [source] | |||||||||||||||||||