Lateral Expansion Rate Research Articles

An Analytical Model for Tropical Cyclone Outer-Size Expansion on the f Plane

Abstract Tropical cyclones are known to expand to an equilibrium size on the f plane, but the expansion process is not understood. In this study, an analytical model for tropical cyclone outer-size expansion on the f plane is proposed. Conceptually, the storm expands because the imbalance between latent heating and radiative cooling drives a lateral inflow that imports absolute vorticity. Volume-integrated latent heating increases more slowly with size than radiative cooling, and hence, the storm expands toward an equilibrium size. The predicted expansion rate is given by the ratio of the difference in size from its equilibrium value rt,eq to an environmentally determined time scale τrt of 10–15 days. The model is fully predictive if given a constant rt,eq, which can also be estimated environmentally. The model successfully captures the first-order size evolution across a range of numerical simulation experiments in which the potential intensity and f are varied. The model predictions of the dependencies of lateral inflow velocity and expansion rate on latent heating rate are also compared well with numerical simulations. This model provides a useful foundation for understanding storm size dynamics in nature.

Rapid Saline Permafrost Thaw Below a Shallow Thermokarst Lake in Arctic Alaska

AbstractPermafrost warming and degradation is well documented across the Arctic. However, observation‐ and model‐based studies typically consider thaw to occur at 0°C, neglecting the widespread occurrence of saline permafrost in coastal plain regions. In this study, we document rapid saline permafrost thaw below a shallow arctic lake. Over the 15‐year period, the lakebed subsided by 0.6 m as ice‐rich, saline permafrost thawed. Repeat transient electromagnetic measurements show that near‐surface bulk sediment electrical conductivity increased by 198% between 2016 and 2022. Analysis of wintertime Synthetic Aperture Radar satellite imagery indicates a transition from a bedfast to a floating ice lake with brackish water due to saline permafrost thaw. The regime shift likely contributed to the 65% increase in thermokarst lake lateral expansion rates. Our results indicate that thawing saline permafrost may be contributing to an increase in landscape change rates in the Arctic faster than anticipated.

Climatic controls on the dynamic lateral expansion of northern peatlands and its potential implication for the ‘anomalous’ atmospheric CH4 rise since the mid-Holocene

Understanding the dynamic changes in peatland area during the Holocene is essential for unraveling the connections between northern peatland development and global carbon budgets. However, studies investigating the centennial to millennial-scale process of peatland expansion and its climate and environmental drivers are still limited. In this study, we present a reconstruction of the peatland area and lateral peatland expansion rate of a peatland complex in northern Sweden since the mid-Holocene, based on Ground Penetrating Radar measurements of peat thickness supported by radiocarbon (14C) dates from four peat cores. Based on this analysis, lateral expansion of the peatland followed a northwest-southeast directionality, constrained by the undulating post-glacial topography. The areal extent of peat has increased non-linearly since the mid-Holocene, and the peatland lateral expansion rate has generally been on the rise, with intensified expansion occurring after around 3500 cal yr BP. Abrupt declines in lateral expansion rates were synchronized with the decreases in total solar irradiance superimposed on the millennial ice-rafted debris events in the northern high latitudes. Supported by the temporal evolution of peatland extent in four other Fennoscandian peatlands, it appears that the northern peatland areal extent during the early to middle Holocene was much smaller compared to previous empirical model reconstructions based on basal age compilations. Interestingly, our reconstruction shows the increments of peat area since the mid-Holocene coincide with the rise in atmospheric CH4 concentration, and that abrupt variations in atmospheric CH4 on decadal to centennial timescales could be synchronized with peatland lateral expansion rates. Based on our analysis we put forward the hypothesis that lateral expansion of northern peatlands is a significant driver of dynamics in the late Holocene atmospheric CH4 budget. We strongly urge for more empirical data to quantify lateral expansion rates and test such hypotheses.

The ongoing lateral expansion of peatlands in Finland.

Peatlands are the most dense terrestrial carbon stock and since the last glacial epoch northern peatlands have accumulated between 400 and 1000 Gt of carbon. Although the horizontal development history of the peatlands during the Holocene has been previously researched, these studies have overlooked the current peatland margins. This has led to a long-standing view that the lateral expansion of the peatlands has halted or significantly slowed down. However, no concentrated effort focusing on the recent development of the peatland margins has been conducted. To fulfil this knowledge gap, we studied the development of peatland margins in five Finnish peatlands. In addition, we studied the effect of peatland subsoil characteristics and past forest fires on the peatland expansion. We sampled 15 transects with a total of 47 peat cores utilizing 14 C radiocarbon dating on the basal layers of these peat cores. Our results show that the Northern peatlands are still expanding with four of our study sites having recent, post-1950's basal ages in the peatland margins. In addition, the rate of peatland lateral expansion has increased during the last 1500 years in our study sites, challenging the current knowledge of the recent peatland expansion dynamics. We recorded lateral expansion rates of 0.1-6.4 cm/year from the sites studied. The rate of lateral expansion was restricted by local characteristics, especially the steepness of subsoil (p = .0108). Forest fires likely played an important role as the trigger for lateral expansion in southern study sites with large number of charcoal found at the basal layer of the peat cores. Depending on the scope of this recent lateral expansion across the vast northern peatlands, the effect on the carbon balance could be significant and should be taken into account when estimating the development of carbon pools in these crucial ecosystems.

Carbon accumulation dynamics and development processes of peatland established after the Changbaishan Millennium eruption

The Changbaishan Millennium eruption (946–947 CE) was one of the strongest volcanic activities over the past 2000 years, which greatly influenced the nearby wetland ecosystems. However, the carbon accumulation dynamics and development processes of these peatlands have rarely been investigated. This study tried to reveal the carbon accumulation dynamics and development processes of peatland established after the Changbaishan Millennium eruption. Here we selected the Yueliangwan peatland as study object. Results suggest that the Yueliangwan basin was a lake after the Changbaishan Millennium eruption. Then, a arid climate event occurred between 1250 and 1300 CE and dried out the water of this basin. During 1300–1384 years CE, the carbon accumulation rate (CAR) was low because of the peat initiation process. During 1384–1600 years CE, the CAR reached the highest over the past 700 years. Peat plants further rapidly expanded on the flat areas. During 1600–1750 years CE, the CAR showed a decreasing trend. The lateral expansion rate significantly slowed down because of the restriction of complex morphology. During 1750–1850 years CE, the CAR reached the lowest values. The lateral expansion of this peatland was over. During 1850–2019 years CE, the Yueliangwan peatland developed into bog stage. The CAR slightly increased during this period. These processes suggest that peatlands can rapidly develop after volcanic eruption. Additionally, correlation analyses indicate that regional precipitation controlled by the total solar irradiance and El Niño Southern-Oscillation (ENSO) activity played an important role in influencing the carbon accumulation dynamics and vegetation succession of the peatlands in Northeast China. This study would expand our understanding of long-term interactions between carbon accumulation dynamics and lateral expansion of peatlands, hydroclimate and volcanic activity.

Enhanced properties of tailored MoAlB ceramics by hot forging

In this work, hot forging texture of pre-sintered MoAlB ceramics (relative density, 97.9%) were achieved by spark plasma sintering (SPS). The radial compression and lateral expansion rates reached − 54.8% and 25.8%, respectively. The X-ray diffraction results exhibited a preferred orientation of tailored samples. The b-axis of grains were prone to be parallel to the pressure and the grains grew along the a- and c-axis directions. Therefore, the Lotgering orientation factor of f(0k0) on the textured top surface (TTS) get 0.66. The properties of tailored MoAlB exhibited obvious anisotropic characteristics. Remarkably, the electrical conductivity perpendicular to the b-axis reached 4.34 × 106 S/m (25 °C). Compared with untextured MoAlB (5.45 MPa·m1/2), the fracture toughness parallel to the b-axis reached 8.04 MPa·m1/2. Additionally, the tailored surface perpendicular to the b-axis presented better oxidation resistance with thinner oxide layer when exposed at 1400 °C for 20 h in air.

Recent Lateral Expansion of Sphagnum Bogs Over Central Fen Areas of Boreal Aapa Mire Complexes

We investigated recent changes in spatial patterning of fen and bog zones in five boreal aapa mire complexes (mixed peatlands with patterned fen and bog parts) in a multiproxy study. Comparison of old (1940–1970s) and new aerial images revealed decrease of flarks (wet hollows) in patterned fens by 33–63% in middle boreal and 16–42% in northern boreal sites, as lawns of bog Sphagnum mosses expanded over fens. Peat core transects across transformed areas were used to verify the remote sensing inference with stratigraphic analyses of macrofossils, hyperspectral imaging, and age-depth profiles derived from 14C AMS dating and pine pollen density. The transect data revealed that the changes observed by remote sensing during past decades originated already from the end of the Little Ice Age (LIA) between 1700–1850 CE in bog zones and later in the flarks of fen zones. The average lateral expansion rate of bogs over fen zones was 0.77 m y−1 (range 0.19–1.66) as estimated by remote sensing, and 0.71 m y−1 (range 0.13–1.76) based on peat transects. The contemporary plant communities conformed to the macrofossil communities, and distinct vegetation zones were recognized as representing recently changed areas. The fen-bog transition increased the apparent carbon accumulation, but it can potentially threaten fen species and habitats. These observations indicate that rapid lateral bog expansion over aapa mires may be in progress, but more research is needed to reveal if ongoing fen-bog transitions are a commonplace phenomenon in northern mires.

Experiments on the characteristics of breach variations due to natural dam overtopping

Natural dams are a common geological disaster that can threaten the safety of people and buildings for several hundreds of kilometres downstream. However, the failure characteristics of natural dams are still unclear, especially the variation characteristics of breaches. In this paper, 20 groups of flume experiments are conducted. Based on the experimental results, the longitudinal and lateral variations of breaches during overtopping are studied. In addition, the relationship between the width and depth of breaches is quantitatively analysed. The results are as follows: during the process of a natural dam overtopping failure, the relationship between the breach depth and time is controlled by the slope of the flume. It is demonstrated that there is an “S” shape when the slope is small and a straight line when the slope is large. In terms of the rate of lateral expansion of the breach, it is demonstrated that the rate of lateral expansion of the breach is smaller in the earlier stage and later stage and is larger in the middle stage. The relationship between width and time is S-shaped. The slope at the bottom of the breach fluctuates during the entire process. The main reason is that the dam break is accompanied by backward erosion, but the slope remains below the underwater angle of repose of the material. Based on the experimental data, the quantitative relationship between the width and depth of breach is investigated. On the basis of the quantitative relationships, a mathematical model of dam breaks is established. The rationality of the model is verified by comparison with actual cases, and the relationship between the width and depth of breaches is proved to be reasonable.

Provision of contrasted nitrogen-related ecosystem services among grain legumes

Legumes deliver unique functions that are complementary to those of other groups of species (cereals and oil-rich crops), providing many ecosystem services related to nitrogen. However, the choice of grain legumes according to their ability to provide these ecosystem services remains difficult due to a lack of references for a variety of species. During two legume – wheat successions established between 2014 and 2017, five nitrogen pools were measured, and considered as proxies of nitrogen functions supporting ecosystem services and dis-services. Nitrogen pools were analyzed together with several of their explanatory shoot and root characteristics (i.e. plant traits and properties). For the first time, a wide range of grain legumes could be characterized by their contrasted functional profiles relative to nitrogen. For each species, synergies and trade-offs between the different nitrogen functions were highlighted and related to the explanatory plant characteristics. Shoot and root characteristics explained 76.1% of the variability of nitrogen functions among legumes species. Chickpea, common bean, and soybean had high capacity to take up soil nitrogen during their growth cycles, reducing the risk of nitrogen losses after their harvest. These species were characterized by a high root lateral expansion rate and their capacity to invest a large proportion of belowground biomass in nodules. Conversely, common vetch, faba bean, lentil, pea and Narbonne vetch, were less able to take up soil nitrogen, with higher risks of nitrogen losses, but these species induced high amounts of nitrogen in the following wheat crop and were characterized by high crop residue nitrogen concentration. Larger amounts of nitrogen fixed and exported in seeds were measured for species characterized by high shoot dry matter, high nitrogen harvest index, high seed nitrogen concentration, and large seeds. Hence, this study should facilitate the selection of legume species according to the expected objectives.

X-ray characterization of physical-vapor-transport-grown bulk AlN single crystals.

AlN slices from bulk crystals grown under low thermomechanical stress conditions via the physical vapor transport (PVT) method were analyzed by X-ray methods to study the influence of the growth mode on the crystal quality. Defect types and densities were analyzed along axial [0001] as well as lateral growth directions. X-ray diffraction (0110) rocking-curve mappings of representative wafer cuts reveal a low mean FWHM of 13.4 arcsec, indicating the generally high crystal quality. The total dislocation density of 2 × 103 cm-2 as determined by X-ray topography is low and dislocations are largely threading edge dislocations of b = 1/3〈1120〉 type. The absence of basal plane dislocations in homogeneous crystal regions void of macroscopic defects can be linked to the low-stress growth conditions. Under the investigated growth conditions this high crystal quality can be maintained both along the axial [0001] direction and within lateral growth directions. Exceptions to this are some locally confined, misoriented grains and defect clusters, most of which are directly inherited from the seed or are formed due to the employed seed fixation technique on the outer periphery of the crystals. Seed-shaping experiments indicate no apparent kinetic limitations for an enhanced lateral expansion rate and the resulting crystal quality, specifically with regard to the growth mode on a-face facets.

Deformation mechanisms and evolution of mechanical properties in damaged advanced ceramics

We investigated the uniaxial compressive behavior of damaged and intact alumina using quantitative X-ray computed tomography (XCT) analysis coupled with digital image correlation (DIC) for mechanical characterization. Internal three-dimensional crack characteristics such as crack surface area and orientation were quantified using XCT to assess the level of damage. From the quasi-static and dynamic stress–strain results, the primary effects of crack damage are to reduce the initial stiffness and rate of lateral expansion in damaged alumina. With increasing axial strain, crack closure was found to lead to a recovery of elastic properties, in some cases to intact levels, in the damaged specimens. Localized deformation mechanisms related to the crack structure, including lateral crack closure, axial crack opening and closing, and inclined crack sliding, were visualized in-situ and connected to XCT reconstructions. High-speed imaging also revealed a mixed fracture mode for damaged alumina that included axial splitting and failure along pre-existing cracks.

Rapid Recruitment of Symbiotic Algae into Developing Scleractinian Coral Tissues

While the early acquisition of Symbiodiniaceae algae into coral host tissues has been extensively studied, the dynamics of the migration of algal cells into rapidly expanding coral tissues still lacks a systematic study. This work examined two Red Sea branching coral species, Pocillopora damicornis and Stylophora pistillata, as they were growing and expanding their tissue laterally on glass slides (January–June, 2014; 450 assays; five colonies/species). We measured lateral tissue expansion rates and intratissue dinoflagellate migration rates. Tissue growth rates significantly differed between the two species (with Stylophora faster than Pocillopora), but not between genotypes within a species. Using a “flow-through coral chamber” under the microscope, the migration of dinoflagellates towards the peripheral edges of the expanding coral tissue was quantified. On a five-day timescale, the density of the endosymbiotic dinoflagellate cells, presenting within a 90 µm region of expanding coral tissue (outer edge), increased by a factor of 23.6 for Pocillopora (from 1.2 × 104 cells cm‒² to 2.4 × 105 cells cm‒²) and by a factor of 6.8 for Stylophora (from 3.6 × 104 cells cm‒² to 2.4 × 105 cells cm‒²). The infection rates were fast (5.2 × 104 and 4.1 × 104 algal cells day-1 cm‒², respectively), further providing evidence of an as yet unknown pathway of algal movement within coral host tissues.

Tidal and Meteorological Influences on the Growth of Invasive Spartina alterniflora: Evidence from UAV Remote Sensing

Rapid invasion of Spartina alterniflora into Chinese coastal wetlands has attracted much attention. Many field and remote sensing studies have examined the spatio-temporal dynamics of S. alterniflora invasion; however, spatially explicit quantitative analyses of S. alterniflora invasion and its underlying mechanisms at both patch and landscape scales are seldom reported. To fill this knowledge gap, we integrated multi-temporal unmanned aerial vehicle (UAV) imagery, light detection and ranging (LiDAR)-derived elevation data, and tidal and meteorological time series to explore the growth potential (lateral expansion rates and canopy greenness) of S. alterniflora over the intertidal zone in a subtropical coastal wetland (Zhangjiang estuarine wetland, Fujian, China). Our analyses of patch expansion indicated that isolated S. alterniflora patches in this wetland experienced high lateral expansion over the past several years (averaged at 4.28 m/year in patch diameter during 2014–2017), and lateral expansion rates ( y , m/year) showed a statistically significant declining trend with increasing inundation ( x , h/day; 3 ≤ x ≤ 18 ): y = − 0.17 x + 5.91 , R 2 = 0.78 . Our analyses of canopy greenness showed that the seasonality of the growth potential of S. alterniflora was driven by temperature (Pearson correlation coefficient r = 0.76 ) and precipitation ( r = 0.68 ), with the growth potential peaking in early/middle summer with high temperature and adequate precipitation. Together, we concluded that the growth potential of S. alterniflora was co-regulated by tidal and meteorological regimes, in which spatial heterogeneity is controlled by tidal inundation while temporal variation is controlled by both temperature and precipitation. To the best of our knowledge, this is the first spatially explicit quantitative study to examine the influences of tidal and meteorological regimes on both spatial heterogeneity (over the intertidal zone) and temporal variation (intra- and inter-annual) of S. alterniflora at both patch and landscape scales. These findings could serve critical empirical evidence to help answer how coastal salt marshes respond to climate change and assess the vulnerability and resilience of coastal salt marshes to rising sea level. Our UAV-based methodology could be applied to many types of plant community distributions.

Some Like It Hot: Maternal-Switching With Climate Change Modifies Formation of Invasive Spartina Hybrids.

Climate change can induce temporary, spatial or behavioral changes in species, so that only some species can adapt to the new climatic conditions. In the case of invasive species, it is expected that they will be promoted in a context of global change, given their high tolerance to environmental factors and phenotypic plasticity. Once in the invaded range, these species can hybridize with native species thus introducing their genotype in the native biota. However, the effects that climate change will have on this process of invasion by hybridization remain unclear. We evaluated the historical establishment of the reciprocal hybrids between the native Spartina maritima and the invasive S. densiflora in the Gulf of Cadiz (SW Iberian Peninsula) and we related it to climatic changes during the period 1955–2017. Our results showed that, according to their dating based on their rate of lateral expansion rates, the establishment of S. maritima × densiflora and S. densiflora × maritima in the Gulf of Cadiz has occurred in the last two centuries and has been related to changes in air temperature and rainfall during the flowering periods of their parental species, with antagonist impacts on both hybrids. Thus, the hybrid S. densiflora × maritima has been established in years with mild ends of spring and beginning of summer when the flowering of S. maritima lengthened and its pollen production was higher, and it coincided with the beginning of the flowering period of S. densiflora. Moreover, the establishment of this hybrid was related to higher spring/summer rainfalls, probably due to the reduction in salinity in middle marshes. However, the hybrid S. maritima × densiflora, was established mainly in warmer spring/summers in which the proportion of pollen:ovule of S. maritima was reduced favoring its pollination by S. densiflora. As a consequence of the promotion of S. maritima × densiflora with climate change, the native and endangered species S. maritima would be threatened, as both taxa share the same habitat and the hybrid shows a remarkably higher competitive potential.

Comparative effect of inorganic N on plant growth and N2 fixation of ten legume crops: towards a better understanding of the differential response among species

A better understanding of how plant growth, N nutrition and symbiotic nitrogen fixation (SNF) are influenced by soil inorganic N availability, for a wide range of legume species, is crucial to optimise legume productivity, N2 fixation, while limiting environmental risks such as N leaching. A comparative analysis was performed for ten legume crops, grown in a field experiment and supplied with four N fertiliser rates. Dry matter, N concentration and SNF were measured. In parallel, root elongation rates were studied in a greenhouse experiment. For most species, N fertilisation had little effect on plant growth and N accumulation. SNF was reduced by soil inorganic N available at sowing but with large differences in the magnitude of the response among species. The response varied according to plant N requirements for growth and plant ability to retrieve inorganic N. Accordingly, root lateral expansion rate measured in RhizoTubes was highly correlated with plant ability to retrieve inorganic N measured in the field experiment. Combining SNF response to soil inorganic N, shoot N and plant ability to retrieve inorganic N, allowed a robust evaluation of differential response to soil inorganic N among a wide range of legume species.

Expansion of three reaction zones during underground coal gasification with free and percolation channels

During underground coal gasification (UCG), the expansion of the three reaction zones (oxidation zone, reduction zone, and dry distillation zone) is closely related to the stability of the gasification process and to the calorific value of the producer gas. The gasification channel structure also greatly affects the expansion process. In this article, the temperature field map and changes in producer gas components were monitored and analyzed in real time in an experimental model of UCG. A free channel and percolation channel were used and compared. The three reaction zones were found to expand during stable gasification, including the area ratios of the three zones and their forward and lateral expansion rates. The differences in the expansion of the three zones between free channel and percolation channel are here explained from the viewpoint of mass transfer. The results showed that, during the gasification of Ulanqab lignite in an oxygen- and CO2-rich environment, the average area ratios of the oxidation zone, reduction zone, and dry distillation zone in free and percolation channels were 1:1.20:1.43 and 1:1.73:2.18, respectively, the corresponding forward expansion rates were 0.077m/h and 0.019m/h, and lateral expansion rates were 0.007m/h and 0.0065m/h, respectively. Unlike in the free channel, the porous media structure of percolation channel increased the convective mass transfer rate between gasification agent and coal seam, and the stability of the gasification process and the calorific value of the producer gas. This is why the reaction zone expanded further in the percolation channel than in the free channel.

Saltmarshes Response to Human Activities on a Prograding Coast Revealed by a Dual-Scale Time-Series Strategy

On many prograding coasts, human activities such as alien species introduction and tidal flat reclamation, as countermeasures against land scarcity, are having a major impact on saltmarshes. Despite their capacity for regeneration given ample sediment supply, saltmarshes are likely to disappear if they continue to be impacted by such activities without effective monitoring and protection. However, effective monitoring requires a combination of saltmarsh species mapping and short timespan change analyses, which are difficult to accomplish due to the widespread, rapid, and complex characteristics of saltmarsh replacement in the region. Integrating multi-source remote sensing data with a times-series strategy, this study constructed saltmarsh species maps for the Jiangsu middle coast with 89.4 % overall accuracy (∼16.1 % higher than that achieved by the individual image classification method). Subsequently, we used these maps to explore the interaction between saltmarshes and human activities by a dual-scale analysis: macroscale analysis, aiming at saltmarsh ecosystem wide processes, to reflect the general evolutionary trend for all saltmarsh species, and microscale analysis, focusing on a species-specific process, to reveal the focal response mechanism for Spartina alterniflora. The results show that: (1) In the past 20 years, over 97.6 % (227.72 km2) of the loss of native saltmarshes (Phragmites australis and Suaeda salsa) was caused by tidal flat reclamation, and the invasion of S. alterniflora poses a potential threat to the future well-being of the native saltmarshes. The limited remaining area of the native saltmarshes, together with their long regeneration time, suggests that future land replacement will be dominated by the interaction between S. alterniflora and reclamation. (2) Intertidal reclamation promotes the expansion of S. alterniflora, as revealed by high linear correlations (mainly with R 2 > 0.6) between the lateral expansion rate of S. alterniflora and reclamation. The prerequisite for this correlation was a sufficient width of S. alterniflora (850–1000 m for most of the coasts), and we propose that by maintaining this critical width, S. alterniflora will be capable of relatively rapid invasion after reclamation.

DSM derived stereo pair photogrammetry: Multitemporal morphometric analysis of a quarry in karst terrain

Bukit Merah karst has been deteriorating dramatically over 40years due to intensification of human activities as a result of fast rate of lateral urbanization and extensive dimensional expansion of surface mining activities for instance, quarrying. Application of morphometric techniques to karst landforms provides a quantitative measurement and analysis of the configuration of karst landform variations. The objective of this study is to demonstrate the viability of using an integrated approach based on digital terrain model (DTM) derived time-series of steriopair aerial photography for monitoring the long-term geological karst response to environmental changes. The aerial photo stereo pairs were used to extract digital terrain model of the years 1981 and 2004, which in turn produced the TIN profiles of selected karst sites in the study area to define the karst morphology changes and to develop 3D representation and visualization. A detailed visualization of the karst terrain and its surface changes were represented using 3D virtual reality tool to substantiate the impact of surface mining in the Bukit Merah. Topographical characteristics of limestone hills, mountainous areas and flat areas were presented in 3D prospective. The results show the simulation topographical analysis results have confirmed that there were changes in elevation over the period from 1981 to 2004 especially in the limestone hill area as detected by the digital elevation model. It showed a dramatic variation in elevation has increased over a time interval. This means there has occurred an interference with the terrain attributed to human intervention or natural causes during the time interval. The result shows that the digital terrain model (DTM) derived time-series of steriopair aerial photography is able to delineate the changes in karst topography.

Investigation on Impact Energy of S30403 Austenitic Stainless Steel at Different Temperatures

In this paper, a series of impact tests on S30403 austenitic stainless steel at 20/−196/−269 °C were performed to determine the effects of cryogenic temperatures on the material properties. Both base plate and welded joint including weld and heat-affected zone were tested to obtain the Charpy impact energy KV2 and lateral expansion rate at the cross section. It was found that when the test temperature decreased from 20 °C to −196 °C or −269 °C, both the Charpy impact energy KV2 at the base plate and welded joint decreased drastically. Specifically, the impact energy KV2 decreased by 20% at the base plate and decreased by 54% at the welded joint from 20 °C to −196 °C, but the impact energy of base plate and welded joint did not decrease, even increased when test temperature decreased from −196 °C to −269 °C. Either at 20 °C or −196 °C, the impact energy KV2 with 5 × 10 × 55 mm3 specimens was about 0.53 times that of the 7.5 × 10 × 55 mm3 specimens, much lower than 2/3, the ratio of two specimens’ cross section areas.

Field assessment of environmental factors constraining the development and expansion of Schoenoplectus californicus marsh at a California tidal freshwater restoration site

The effective restoration of wetland habitats requires understanding the establishment requirements, growth responses, and expansion dynamics of targeted plant species. This is particularly true when restoring areas that have been previously managed for other activities, such as agriculture, which can have legacy effects on the local environment. We investigated environmental factors (specifically hydrology and soil physicochemical conditions) that may influence the establishment, growth and expansion of Schoenoplectus californicus in a tidal freshwater marsh restoration site in the Sacramento–San Joaquin Delta, California, USA. This study site was previously leveed, drained, and utilized for agricultural production. A 1997 levee breach restored tidal connectivity and wetland vegetation has re-established in portions of the area. Our approach coupled an intensively-sampled transect study in S. californicus-dominated marshes with a spatially-extensive survey of S. californicus lateral expansion rates and elevation. Lateral expansion of S. californicus marsh edge was significantly less in lower elevation areas (0.61 ± 0.04 m NAVD88), whereas the marsh edge at higher elevations (0.84 ± 0.03 m NAVD88) exhibited greater expansion, often at rates greater than 1.0 m year−1. These elevation means correspond to percentages of time that the marsh surface was flooded of 100 and 94 %, respectively. Although marsh edge expansion was influenced by elevation and the resultant hydrology, other factors, such as physical exposure of marsh shorelines and compacted agricultural soils also appear to be important. However, once established, S. californicus appears to be able to ameliorate high soil bulk densities over time as the advancing marsh platform develops.