Ridge Top Research Articles

Preliminary estimates of regolith generation and mobility in the Susquehanna Shale Hills Critical Zone Observatory, Pennsylvania, using meteoric 10Be

Abstract This study seeks to quantify the rate and timing of regolith generation in the Critical Zone at the Susquehanna Shale Hills Critical Zone Observatory (SSHO). Meteoric 10 Be depth profiles were determined using measurements from 30 hillslope soil and bedrock core samples in an effort to constrain 10 Be inventories. The SSHO is located in the temperate climate zone of central Pennsylvania and comprises a first-order watershed developed entirely on a Fe-rich, organic-poor, Silurian-aged shale. Two major perturbations to the landscape have occurred at SSHO in the geologically recent past, including significant and sustained periglacial activity until after the retreat of the Laurentide ice sheet (∼21 ka) and deforestation during early colonial land-use. Bulk soil samples ( n = 16) were collected at three locations along a planar hillslope on the southern ridge of the catchment, representing the ridge top, mid-slope and valley floor. Rock chip samples ( n = 14) were also collected from a 24 m deep core drilled into the northern ridge top. All meteoric 10 Be concentration profiles show a declining trend with depth, with most of the 10 Be retained in the uppermost decimeters of the soil. Meteoric 10 Be inventories are higher at the mid-slope and valley floor sample sites, at 3.71 ± 0.02 × 10 10 at/cm 2 and 3.69 ± 0.02 × 10 10 at/cm 2 , than at the ridge top site (1.90 ± 0.01 × 10 10 at/cm 2 ). The 10 Be inventory at the convex ridge top site implies a minimum residence time of ∼10.6 ka, or if erosion is steady, an erosion rate of 19.4 ± 0.2 m/My.

Habitat specificity and diversity of tree species in an African wet tropical forest

Niche differentiation with respect to habitat has been hypothesized to shape patterns of diversity and species distributions in plant communities. African forests have been reported to be relatively less diverse compared to highly diversed regions of the Amazonian or Southeast Asian forests, and might be expected to have less niche differentiation. We examined patterns of structural and floristic differences among five topographically defined habitats for 494 species with stems ≥1 cm dbh in a 50-ha plot in Korup National Park, Cameroon. In addition, we tested for species–habitat associations for 272 species (with more than 50 individuals in the plot) using Torus translation randomization tests. Tree density and basal area were lowest in areas with negative convexity, which contained streams or were inundated during rainy periods and highest in moist well-drained habitats. Species composition and diversity varied along the topographical gradient from low flat to ridge top habitats. The low depression and low flat habitats were characterized by high diversity and similar species composition, relative to slopes, high gullies and ridge tops. Sixty-three percent of the species evaluated showed significant positive associations with at least one of the five habitat types. The majority of associations were with low depressions (75 species) and the fewest with ridge tops (8 species). The large number of species–habitat associations and the pronounced contrast between low (valley) and elevated (ridgetop) habitats in the Korup plot shows that niche differentiation with respect to edaphic variables (e.g., soil moisture, nutrients) contributes to local scale tree species distributions and to the maintenance of diversity in African forests.

An Investigation into Ridge-Top Turbulence Characteristics During Neutral and Weakly Stable Conditions: Velocity Spectra and Isotropy

An investigation into high Reynolds number turbulent flow over a ridge top in New Zealand is described based on high-resolution in-situ measurements, using ultrasonic anemometers for two separate locations on the same ridge with differing upwind terrain complexity. Twelve 5-h periods during neutrally stratified and weakly stable atmospheric conditions with strong wind speeds were sampled at 20 Hz. Large (and small) turbulent length scales were recorded for both vertical and longitudinal velocity components in the range of 7–23 m (0.7–3.3 m) for the vertical direction and 628–1111 m (10.5–14.5 m) for the longitudinal direction. Large-scale eddy sizes scaled to the WRF (Weather Research and Forecasting) numerical model simulated boundary-layer thickness for both sites, while small-scale turbulent features were a function of the complexity of the upwind terrain. Evidence of a multi-scale turbulent structure was obtained at the more complex terrain site, while an assessment of the three-dimensional isotropy assumption in the inertial subrange of the spectrum showed anisotropic turbulence at the less complex site and evidence of isotropic turbulence at the more complex site, with a spectral ratio convergence deviating from the 4/3 or unity values suggested by previous theory and practice. Existing neutral spectral models can represent locations along the ridge top with simple upwind complexity, especially for the vertical wind spectra, but sites with more orographic complexity and strong vertical wind speeds are often poorly represented using these models. Measured spectra for the two sites exhibited no significant diurnal variation and very similar large-scale and small-scale turbulent length scales for each site, but the turbulence energy measured by the variances revealed a strong diurnal difference.

Residue Management Impacts on Field-Scale Snow Distribution and Soil Water Storage

Spatial variation of soil water affects crop performance, fertilizer use efficiencies, and other important economic and environmental factors. Soil water storage could be increased and field variability reduced by residue management practices such as no tillage (NT), as surface residues can retain more snow, enhance water infiltration, and reduce evaporation as compared to conventional tillage (CT). Our objectives were to evaluate the residue effects on snow distribution and the spatial variation of soil water storage for two adjacent fields near Pullman, Washington: one under NT, and the other under CT. The fields were surveyed during the winter and spring of 2007-2008 to assess topographic variations in snow depth, snow water equivalent (SWE), and soil water storage. Standing stubble under NT retained 10 to 20 cm more snow on ridge tops and steeply sloped ground than CT, and the snowpack was distributed more evenly with less spatial variation. SWE followed the same pattern of larger spatial variation in CT than in NT. Soil water (0 to 1.5 m) in the spring was lowest for ridge tops and highest in valleys for NT and CT. Under NT, however, soil water varied less across different field locations than under CT, and overall water storage was 60, 29, and 13 mm more for NT than CT on ridge top, south slope, and valley locations, respectively. Although many factors can contribute to the spatial variation of soil water, standing wheat residue under NT retained more snow on ridge tops and steeply sloped areas, reduced soil water spatial variation, and increased soil water recharge.

C1 Route corridor and alignment selection

As outlined in Section A2, there are several factors that determine the selection of route corridors and the design of the alignment within them. These include road network planning and traffic forecasts, construction and maintenance costs and engineering, socio-economic, environmental and political considerations. The following discussion focuses on route corridor and alignment design in relation to topography and geometric standards, and describes how these considerations interface with those of slope stability and ground conditions. The selection of the route corridor is the most critical element in any road construction project in hilly or mountainous terrain. It affects route length, construction quantities, cost and alignment stability, as well as environmental and social impact. In many circumstances the selection of the route corridor may be straightforward, for example for roads linking villages and towns on ridge tops or valley floors. In other cases, however, several alternatives will present themselves. These will be determined, inter alia , by topography, hydrology and river crossings, land use and the location of landslides and other difficult ground conditions. The availability of suitable naturally occurring construction materials may also be a consideration in route corridor selection in some circumstances. ### C1.2.1 Topography Usually the objective will be to avoid the steepest areas and to develop an alignment that follows the lineaments or grain of the topography, as controlled by the underlying geology. In fold mountain belts, for example, there is usually a distinct topographic grain; in the Himalayas it is essentially east–west and in the Andes it is north–south. Where there is a choice, alignments that follow this grain will normally require less rise and fall. Earthworks quantities and slope stability hazards will also tend to be less if, for example, a ridge or valley floor alignment can be followed. Where roads are required to cross the grain of the …

Cone-beam Computed Tomography Evaluation of the Soft Tissue Thickness and Neurovascular Bundle's Position at the Palatal Region

Avoiding to damaging the neurovascular bundle (NB) while harvesting soft tissue graft (STG) from palatal area which is considered as a donor site for periodontal plastic surgery is important. The size of STG that can be related the position of NB and thickness of palatal mucosa (PMT). The aim of this study was to evaluate PMT and NB morphology from cone-beam computerized tomography (CBCT) images for established the ideal zone for STG. Measurements performed at 122 patients’ CBCT images. PMT evaluated according to age, gender and teeth zone. The relation of the distance among NB to top of maxillary alveolar ridge (NBD) and palate vault depth (PVD) and the angle between the alveolar bone and the palatal plane (PA) were evaluated. The mean PMT from second molar to first premolar teeth were detected as 3.8, 3.2, 3.6 and 3.1 mm respectively. PMT at second molar and second premolar teeth were statistically different from other zones (p< 0.05). The mean PMT was significantly thicker in males. Except for NBD of first premolar zone, NBD showed positive correlation with PVD. No significant relationship among PA with NBD and PVD established. The highest NBD detected 11.2 mm at second molar zone and the lowest was detected 8.05 mm at first premolar zone. The second premolar to second molar teeth zones observed as the suitable graft area considering the mean PMT. It should be careful when the STG harvested from the first premolar zone since NBD decreased to 8mm.

Hydrometeorology and structure of tropical montane cloud forests under contrasting biophysical conditions in north‐western Costa Rica

AbstractTropical cloud forests have received increasing attention because of their significance for freshwater supply. This study aimed to understand hydro‐meteorological gradients in relation to spatial changes in forest structure in north‐western Costa Rica. Seven climate stations (measuring rainfall, horizontal precipitation, throughfall, temperature and soil moisture) were installed along a 2·5 km transect between 1200 and 1500 m.a.s.l. on the Atlantic (windward) slope and the Pacific (leeward) slope of the Tilarán mountains. Forest structure was investigated on seven 10 × 50 m plots. Epiphytic vegetation was assessed on six trees at 1450 m and at 1200 m on the Pacific slope. Annual rainfall ranged from 3690 mm on the leeward slope to 6390 mm on the windward side. Horizontal precipitation was 3560 mm at the ridge, where it exceeded rainfall during the dry season, compared to 330 mm and 28 mm at the lowest windward and leeward plots, respectively. Throughfall remained below rainfall on the lower slopes but exceeded rainfall on the ridge. Soil water content ranged between 70% and 80% on the ridge top, where waterlogging occurred frequently. The studied forests were classified as lower montane rain forest, lower montane cloud forest and elfin cloud forest. The greatest canopy heights and basal areas occurred on the leeward slope between 1200 and 1450 m and at the lowest windward plot. Tree heights remained below 15 m on the ridge, where stilt roots occurred frequently. Near the ridge, epiphyte abundance and species richness were greater, compared to the lower leeward slope. These findings prove the importance of horizontal precipitation in the study area, confirm the important role of epiphytes as indicators for moisture gradients and elucidate the variability of forest structure under the given biophysical conditions. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Relationship between topographic factor and land use—A case study of Zhuanyaogou watershed

以黄土丘陵沟壑区的砖窑沟流域为例, 依据2003年和2008年两期土地利用现状图, 采用地理信息系统(GIS)软件和统计分析(SPSS)软件, 进行了基于10 m×10 m栅格单元的土地利用与地形因子关系的研究, 探讨了土地利用格局的演变及其驱动力。结果表明: 基于栅格的土地利用类型与坡度、坡向和海拔关系的综合分析是从数量上准确剖析土地利用空间分布特征及其演化规律的有效方法; 砖窑沟流域的海拔、坡度、坡向的平均值分别为1 069 m、19.24°和279°(西坡); 采用各种土地利用类型的sin(坡向)和cos(坡向)平均值绘制坡向分布图, 可直观地显示各种土地利用类型坡向分布特征。分析表明, 农田和宜林荒山共占流域总面积的80%左右, 二者的分布和变化控制着整个流域土地利用的地形分布格局。农田主要以坡地和梯田的形式分布于坡上、峁顶和梁顶, 坡度较低, 而海拔较高, 与坡度呈显著负相关, 与海拔呈显著正相关; 而宜林荒山往往分布于坡度较大而海拔较低的位置, 与坡度呈显著正相关, 而与海拔呈显著负相关。研究结果反映了黄土丘陵沟壑区土地利用的地形地貌特征。生态建设项目的实施可在短时间使土地利用的空间分布发生较大变化。

Sustained, Full-Water-Column Observations of Internal Waves and Mixing near Mendocino Escarpment

Abstract The relative strength and spatiotemporal structure of near-inertial waves (NIW) and internal tides (IT) are examined in the context of recent moored observations made 19 km south of Mendocino Escarpment, an abrupt ridge/step feature in the eastern Pacific. In addition to strong internal tide generation, steps and ridges give rise to the possibility of “shadowing,” wherein near-inertial energy is prevented from reaching depths beneath a characteristic intersecting the ridge top. A combination of two moored profilers and a long-range acoustic Doppler current profiler (ADCP) yielded velocity and shear measurements from 100 to 3640 m (60 m above bottom) and isopycnal depth, strain, and overturn-inferred turbulence dissipation rate from 1000 to 3640 m. Sampling intervals (20 min in the upper 1000 m and 1.5 h below that) were fast enough to minimize aliasing of higher-frequency internal-wave motions. The 67-day-long record is easily sufficient to isolate NIW and IT via bandpass filtering and to capture low-frequency variability in all quantities. No near-inertial shadowing was observed. Instead, energetic near-inertial waves were observed at all depths, radiating both upward and downward. A strong upward internal tide beam, showing a pronounced spring–neap cycle, was also seen near the expected depth. Case studies of each of these are presented in depth and isopycnal-following coordinates. Except for immediately above the bottom and in the “beam,” where IT kinetic energy shows marked peaks, kinetic energy in the two bands is within a factor of 2 of each other. However, because of the redder NIW vertical wavenumber spectrum, NIW shear exceeded IT shear at all depths by a factor of 2–4. Dissipation rate was strongly enhanced in the bottom 1000 m and in the depth range of the internal tide beam. However, except for very near the bottom and possibly in one NIW event, no clear phase relationship was observed between dissipation rate and wave shear or strain, suggesting that turbulence occurs through a cascade process rather than by direct breaking at most locations.

Terrain Sculptor: Generalizing Terrain Models for Relief Shading

Shaded relief derived from high-resolution terrain models often contains distracting terrain details that need to be removed for medium- and small-scale mapping. When standard raster filter operations are applied to digital terrain data, important ridge tops and valley edges are blurred, altering the characteristic shape of these features in the resulting shaded relief. This paper introduces Terrain Sculptor, a software application that prepares generalized terrain models for relief shading. The application uses a generalization methodology based on a succession of raster operations. Curvature coefficients detect and accentuate important relief features. Terrain Sculptor offers a graphical user interface to adjust the algorithm to various scales and terrain resolutions. The freeware application is available at http://www.terraincartography.com/terrainsculptor/.

Modelling and mapping critical loads and exceedances for the Georgia Basin, British Columbia, using a zero base-cation depletion criterion

Critical load (CL) and exceedance maps of sulphur (S) and nitrogen (N) for upland soils were generated for the Georgia Basin, British Columbia, Canada, by synthesizing available data layers for atmospheric deposition, climate (precipitation, temperature), soil, site classification and elevation. Critical loads were determined using the steady-state mass-balance model and a criterion based on zero-tolerance for further base-cation depletion. The resulting CL values were generally lowest on ridge tops and increased towards valleys. Critical load exceedance ranged from 13% of the Georgia Basin under wet deposition to 32% under modelled total (wet and dry) deposition. Moreover, exceedance increased by an additional 10% when considering upland areas only for the Georgia Basin. Significant portions of the Georgia Basin are predicted to experience exceedance-enhanced base-cation depletion rates above 200 eq ha–1 y–1 and turn-over times to a final new base saturation state within 200 years under continued atmospheric S and N deposition.

Soil erosion rates on forested mountain hillslopes estimated using 137Cs and 210Pb ex

Although the excess of lead-210 ( 210Pb ex) has been described as an alternative or complementary nuclide to cesium-137 ( 137Cs) for soil erosion assessment, the potential use of 210Pb ex in forested environments has not been examined sufficiently. In this study, to investigate the potential use of 210Pb ex for the assessment of soil erosion on various forested hillslopes, we compared soil erosion rates derived from 210Pb ex to those from 137Cs obtained in forest stands. The study was conducted in four types of forest: a Japanese cypress stand with a bare forest floor, a Japanese cypress stand with a fern understory, a Japanese cedar stand with sufficient litter cover, and a natural broadleaf forested stand in the Tsuzura River basin of southeastern Japan. 137Cs and 210Pb ex inventories for seven potential reference sites on flat ridge tops and along transects in each stand were measured using gamma-ray spectrometry to calculate soil erosion rates. To describe the behavior of organic matter in each stand, the amounts of eroded sediment and organic matter were observed for approximately 2 years in erosion plots (1.7–2.0 m long, 0.5 m wide) in the Japanese cypress stand (bare), Japanese cedar stand, and broadleaf forest stand. From the preliminary assessment of potential reference sites, spatial variability in 210Pb ex was comparable to that of 137Cs. Mean erosion rates estimated from both Cs and Pb were highest in the Japanese cypress stand (bare), followed by the Japanese cypress stand (fern), the broadleaf forest stand, and the Japanese cedar stand. This magnitude relationship was consistent with that of observation results of eroded sediment in erosion plots. In the Japanese cypress stand (bare), a significant correlation was found between Cs- and Pb-based soil erosion rates in the Japanese cypress stand (bare) while no significance was found in the other three stands. These results provide evidence of the feasibility of 210Pb ex for soil erosion assessment in forest stands with bare forest floors. In the other three stands, the preferential loss of 210Pb ex associated with organic matter may explain the poor correlation between the two erosion rates.

Regolith production rates calculated with uranium-series isotopes at Susquehanna/Shale Hills Critical Zone Observatory

In the Critical Zone where rocks and life interact, bedrock equilibrates to Earth surface conditions, transforming to regolith. The factors that control the rates and mechanisms of formation of regolith, defined here as material that can be augered, are still not fully understood. To quantify regolith formation rates on shale lithology, we measured uranium-series (U-series) isotopes ( 238U, 234U, and 230Th) in three weathering profiles along a planar hillslope at the Susquehanna/Shale Hills Observatory (SSHO) in central Pennsylvania. All regolith samples show significant U-series disequilibrium: ( 234U/ 238U) and ( 230Th/ 238U) activity ratios range from 0.934 to 1.072 and from 0.903 to 1.096, respectively. These values display depth trends that are consistent with fractionation of U-series isotopes during chemical weathering and element transport, i.e., the relative mobility decreases in the order 234U > 238U > 230Th. The activity ratios observed in the regolith samples are explained by i) loss of U-series isotopes during water–rock interactions and ii) re-deposition of U-series isotopes downslope. Loss of U and Th initiates in the meter-thick zone of “bedrock” that cannot be augered but that nonetheless consists of up to 40% clay/silt/sand inferred to have lost K, Mg, Al, and Fe. Apparent equivalent regolith production rates calculated with these isotopes for these profiles decrease exponentially from 45 m/Myr to 17 m/Myr, with increasing regolith thickness from the ridge top to the valley floor. With increasing distance from the ridge top toward the valley, apparent equivalent regolith residence times increase from 7 kyr to 40 kyr. Given that the SSHO experienced peri-glacial climate ∼ 15 kyr ago and has a catchment-wide averaged erosion rate of ∼ 15 m/Myr as inferred from cosmogenic 10Be, we conclude that the hillslope retains regolith formed before the peri-glacial period and is not at geomorphologic steady state. Both chemical weathering reactions of clay minerals and translocation of fine particles/colloids are shown to contribute to mass loss of U and Th from the regolith, consistent with major element data at SSHO. This research documents a case study where U-series isotopes are used to constrain the time scales of chemical weathering and regolith production rates. Regolith production rates at the SSHO should be useful as a reference value for future work at other weathering localities.

The role of mass movements on landscape evolution in the Central Karakoram: Discussion and speculation

Mass movement constitutes an important process in the evolution of landscapes in mountain regions. However, the role of massive slope failures in denudational unloading and landscape evolution has not been extensively studied. Large-scale mass movements in one of the greatest mountain ranges on Earth, the Central Karakoram in Pakistan, were therefore examined to help evaluate their role in landscape evolution in high mountains. Specifically, four major mass-movement complexes (Ghoro Choh rock avalanche, Busper sackung and slope failure, Gomboro slope failure, and Urdokas rockslide), each comprising 10 6 m 3 of debris, were assessed and mapped in detail. Two of these mass-movement complexes, the Ghoro Choh rock avalanche and Gomboro slope failure, were dated using terrestrial cosmogenic nuclides. The ages of occurrence of the mass-movement complexes studied in the Central Karakoram date from the late Pleistocene to the Holocene. The four major mass-movement complexes all involved the removal of mass from the tops of mountain ridges and peaks that failed and were subsequently transported towards the bottom of their respective valleys. Such massive movement of mass is anomalous compared to other forms of mass movement and is generally spatially coincident with exposed deeply buried gneiss-dome structures. These large-scale movements appear to be part of a coupled system involving river incision and glacial debuttrussing, although earthquakes might have triggered these mass movements. This study illustrates the role of climate forcing, which is part of a coupled system of denudational unloading, but it is unclear whether high-magnitude, low-frequency events such as these initiate the isostatic and tectonic influx of mass, or if sustained high-magnitude denudation resulting from a coupled system is responsible for the exhumation of buried structures.

Spatial Variation of the Morphometric Parameters of Simple Transverse Dunes over the Tall-complex Longitudinal Ridges in the Hinterland of the Taklimakan Desert

In order to explore the morphologic features of small-scale aeolian-sand landforms and their spatial variation,in this paper,the morphologic features of the simple transverse dunes over the cross-section of the tall-complex sand ridges in the hinterland of the Taklimakan Desert are researched.The real-time kinematic technology was used to measure the morphometric parameters of the simple transverse dunes in field,and the software South Survey was used to calculate the main parameters.The result shows that there are the spatial variations in the morphometric parameters of the simple transverse dunes and their interrelations.There are the significant differences between the morphometric parameters measured at 8 different geomorphologic sites(excluding those measured at the windward slope),especially between those measured at the ridge top,leeward slope of the ridge and other morphologic sites(including the inter-ridge lowland and windward slope of ridge).Geomorphologic sites,intensity of sand blown by wind and movement intensity of dunes are the driving factors of spatial variation of the morphometric parameters of the simple transverse dunes.There is a negative logarithmic relation between height and cosine of the dune wingspan,and there are also the negative linear relations between the development index and the height and windward slope of ridge.However,the significant extents of these correlations are high for the ridge top and the leeward slope of ridge but low for the inter-ridge lowland and the windward slope of ridge.

Night-time airflow in a forest canopy near a mountain crest

Night-time airflow within a deep and dense canopy near the top of a mountain ridge is investigated based on measurements at Bily Kriz, Czech Republic. The site is characterized by a young Norway spruce forest on a 13° slope and the occurrence of almost exclusively upslope or downslope flows. The forest canopy reaches the ground surface. A decoupled two-layer structure of canopy flow typically develops at night. While the above-canopy flow is most frequently an upslope-directed larger-scale flow over the ridge, the lower-canopy flow is downslope (katabatic). However, the lower-canopy flow can be forced upslope when the wind speed above the canopy exceeds a well-defined limit. Less frequently, on the lee slope to the larger-scale flow, both the above-canopy and the lower-canopy flow are usually downslope, although a flow reversal in the lower canopy is also observed, accompanied with a large shear stress (friction velocity) above the canopy. The occurrence of opposing flows is not limited to sunset/sunrise transition periods. In a simplified modelling approach to the dynamics of the nocturnal lower-canopy flow decoupled from above, local equilibrium is assumed of solely two opposing driving forces – one induced by the negative buoyancy (due to radiative cooling of the canopy) and the other by the hydrodynamic pressure gradient (resulting from the larger-scale flow over the ridge) – and the canopy drag as a retarding force. The diagnostic model gives realistic values of the major driving terms for Bily Kriz, and the downslope or upslope direction and speed of the lower-canopy flow that agree well with the measurements. The model contributes to better interpretation of the experimental results, which are in accordance with recent publications on the flow patterns on forested hills. Knowledge of the lower-canopy flow behaviour and of the degree of its decoupling from the flow aloft is necessary for assessing the contribution of advection to the CO 2 budget at sloping forest sites, and for analysis of the flux footprint.

The potential influence of shallow gas and gas hydrates on sea floor erosion of Rock Garden, an uplifted ridge offshore of New Zealand

Regional erosion of the Rock Garden ridge top, a bathymetric high within New Zealand’s Hikurangi Subduction Margin, is likely associated with its gas hydrate system. Seismic data reveal gas pockets that appear partially trapped beneath the shallow base of gas hydrate stability. Steady-state fluid flow simulations, conducted on detailed two-dimensional geological models, reveal that anomalous fluid pressure can develop close to the sea floor in response to lower-permeability hydrate-bearing sediments and underlying gas pockets. Transient simulations indicate that large-scale cycling of fluid overpressure may occur on time scales of a few to tens of years. We predict intense regions of hydro-fracturing to preferentially develop beneath the ridge top rather than beneath the flanks, due to more pronounced overpressure generation and gas migration through hydrate-bearing sediments. Results suggest that sediment weakening and erosion of the ridge top by hydro-fracturing could be owed to fluid dynamics of the shallow gas hydrate system.

Habitat association of trees in a 50-ha Malaysian rain forest plot

We studied species-habitat associations by dividing a 50-ha forest plot in the Pasoh Forest Reserve, Malaysia, into 5000, 10 × 10 m2 quadrats and assigned each quadrat to one of three habitats based on parent materials and drainage: well-drained hilly parts and ridge tops (habitat 1), moderately drained, topographically flat sites (habitat 2), and poorly drained riverine sites (habitat 3). Torus-translation tests revealed that 60.0% of 492 species had significant positive or negative associations with habitats in at least one of the three habitats. Differences in species density among the three habitats led to differences among habitats in the relative importance of species. For example, the most abundant species on habitat 2 (Anaxagorea javanica Blume) was the 52nd and 2nd most abundant species on habitats 1 and 3, respectively. We can thus conclude that species-habitat associations play a role in the distribution of tree species in the 50-ha plot and in determining variations in local floristic composition of the Pasoh forest.

High-Power Single-Mode 1.3-$\mu$m InGaAsP–InGaAsP Multiple-Quantum-Well Laser Diodes With Wide Apertures

A wide-aperture ridge waveguide structure was applied to 1.3-mum InGaAsP-InGaAsP multiple-quantum-well laser diodes (LDs) to increase their maximum kink-free output power under single-lateral-mode operations. As a result, a kink-free output power up to 140 mW and an external efficiency of 0.3 W/A were achieved from a single facet of the LD with a 7-mum-wide ridge top and a 1.5-mm-long uncoated cavity.

New insight into oil and gas exploration in Miocene and Late Oligocene strata in Qiongdongnan basin

Oil and gas exploration prospect for the Miocene and Late Oligocene strata in Qiongdongnan (琼东南) basin are evaluated. The structural-sedimentary and reservoir characteristics are discussed and helpful conclusions are drawn. It was proved that there are mainly two reservoir and capping assemblages in Qiongdongnan basin by drilled wells, i.e., one assemblage of the second and the third members of Lingshui (陵水) Formation, upper Sanya (三亚) and Meishan (梅山) formations. According to hydrocarbon evaluation from burial history and well data, all source rocks in Yacheng (崖城) and Lingshui formations have reached the mature-overmature stage. High temperature and overpressure provide dynamic conditions for oil and gas migration, while the long-term activity of basin controlling faults is adverse to their accumulation in upheaved areas. However, because the secondary faults in the basin ceased their activities at the end of the Sanya Period, and the Sanya Formation was later covered by the regional overlying layer of the Meishan Formation, the blocks and low uplifts near the secondary faults were favorable for oil and gas accumulation. Furthermore, as another important pointed area for gas migration, the highest position of a structural ridge should reasonably be a range that is covered by marine mudstone or sandy mudstone during the whole subsiding period, and therefore, the reservoir bed should not be in that position but at its inferior eminence or adjacent slope zone. Therefore, we can draw a conclusion that the inferior low uplifts and structural ridges rather than the upheavals or the top of a structural ridge, probably, have huge reservoirs, and should be chief exploration targets in the Qiongdongnan basin.