Pond Density Research Articles

Object-based analysis of unmanned aerial vehicle imagery to map and characterise surface features on a debris-covered glacier

Debris-covered glaciers in the Himalaya may have spatially-averaged rates of surface height change that are similar to those observed on bare-ice glaciers, despite the insulating effects of thick debris. Spatially heterogeneous melt patterns caused by the development and evolution of ice cliffs and supraglacial pond systems result in substantial mass losses over time. However, mechanisms controlling the formation and survival of cliffs and ponds remain largely unknown. To study the distribution and characteristics of these surface features we deploy an unmanned aerial vehicle (UAV) over a stretch of the debris-covered Langtang Glacier, Nepal. Acquired images are processed into high-resolution orthomosaics and elevation models with the Structure from Motion (SfM) photogrammetry algorithm. Ice cliffs and ponds are classified using object-based image analysis (OBIA) and their morphology and spatial distribution are analysed and evaluated using object, pixel and point cloud approaches. Results show that ice cliffs are predominantly north-facing, and larger ice cliffs are generally coupled with supraglacial ponds, which may affect their evolution considerably. The spatial distribution of ice cliffs indicates that they are more likely to form in areas where high strain rates are expected. The spatial configuration of ponds over the entire tongue reveals high pond density near confluences, possibly due to closure of conduits via transverse compression. We conclude that the combination of OBIA and UAV imagery is a valuable tool in the semi-automatic and objective analysis of surface features on debris-covered glaciers. The technique may also have potential for upscaling to the use of spaceborne imagery, and the use of UAV-derived point clouds to analyse ice cliff undercuts is promising.

A new role for pond management in farmland bird conservation

Biodiversity declines in agricultural landscapes represent a major conservation challenge. In the UK, some agricultural landscapes contain high pond densities, but many farmland ponds have become terrestrialised since the 1960s, with input of organic material resulting in a decrease in the size and depth of ponds that eventually transform into wet woodland habitats. Pond management, including removal of overhanging scrub and sediment, has proven highly effective in enhancing freshwater biodiversity. However, the implications of this management for farmland bird assemblages are unknown.Bird surveys were undertaken at recently managed, open, macrophyte-dominated and at highly terrestrialised, macrophyte-free ponds in the intensively cultivated farmland of North Norfolk, UK. The diversity, abundance and composition of bird assemblages visiting these ponds were compared to determine responses to pond management by tree and mud removal.Avian species richness, abundance and bird-visit frequencies were all higher at open farmland ponds. The observed patterns of bird occurrence were best explained by management-induced reductions in tree shading that resulted in aquatic macrophyte-dominance likely associated with high emergent invertebrate prey abundance. Moreover, we predict that open-canopy ponds offer greater habitat heterogeneity than overgrown ponds, allowing diversified bird use. Overgrown, terrestrialised ponds were preferred by some woodland bird species. Gamma diversity across the entire pondscape exceeded all individual pond alpha diversity measures by an order of magnitude, suggesting distinct variation in the bird assemblages visiting farmland ponds during different successional stages.Pond management that generates a mosaic of pond successional stages, including open-canopy, macrophyte-dominated ponds, could help to address the long-term decline of farmland birds. We strongly advocate increased agro-ecological research in this field, combined with greater emphasis on ponds and pond management options in agri-environment schemes.

Changing land use and its impact on the habitat suitability for wintering Anseriformes in China's Poyang Lake region

As an internationally important wetland for migratory waterbirds, China's Poyang Lake region has experienced substantial changes in land use during the past two decades owing to climate change and anthropogenic disturbances. Recent dam constructions on the Yangtze River and its tributaries for agriculture and hydroelectric power exert strong effects on the hydrological regimes of this lake. However, few studies have investigated how the land-use changes through time affect the habitat suitability for wintering Anseriformes—the largest community in this region. Thus, it is necessary to timely monitor changes in the habitat quality and understand the potential factors that alter it. In this study, three periods (1995, 2005 and 2014) of typical environmental indicators that have direct impacts on foraging and resting for the Anserformes, including proximity to water (density of lakes, rivers and ponds), human disturbances (density of residences and various road networks), preferred land cover types and food availability (NDVI), are integrated to develop a habitat suitability index model for habitat mapping. The results indicate that long-term lake shrinkage in low-water periods led to greatly expanded wetlands in these years, which provided more suitable habitat for migratory waterfowl. The amount of highly suitable habitat in 2014 was nearly twice as much as in 1995. Recent survey data from 1997 to 2013 also revealed an increase in the population size, and confirmed the improvement of habitat suitability in the Poyang Lake region. Spatial analysis revealed that land use changes contributed most to the improved habitat coverage between 1995 and 2014. However, the relative significances of these transformations for highly suitable and moderately suitable habitats are strikingly different. Increases in wetland and paddy field area are the main reasons for explaining these improvements, respectively. The framework model proposed in this study will help governments to evaluate habitat conservation and restoration for protecting waterbirds in a spatially explicit way.

Detection of a global aquatic invasive amphibian, Xenopus laevis, using environmental DNA

Detection is crucial in the study and control of invasive species but it may be limited by methodological issues. In amphibians, classical survey techniques exhibit variable detection probability depending on species and are often constrained by climatic conditions often requiring several site visits. Furthermore, detection may be reduced at low density because probability capture (passive traps), or activity (acoustic surveys) drop. Such limits may impair the study of invasive species because low density is typical of the onset of colonisation on a site. In the last few years, environmental DNA (eDNA) methods have proved their ability to detect the presence of aquatic species. We developed here an eDNA method to detectXenopus laevisin ponds. This austral African species is now present worldwide because of its use in biology and as a pet. Populations have settled and expanded on several continents so that it is now considered as one of the major invasive amphibians in the World. We detected the presence ofX. laevisat density as low as 1 ind/100 m2and found a positive relationship between density in ponds and rate of DNA amplification. Results show that eDNA can be successfully applied to survey invasive populations ofX. laeviseven at low density in order to confirm suspected cases of introduction, delimit the expansion of a colonized range, or monitor the efficiency of a control program.

Impact of cyprinid herpesvirus 3 (Koi herpesvirus) on wild and cultured fish.

Abstract Common carp is a widespread freshwater fish inhabiting lower and mid streams of rivers and shallow confined waters in Eurasia. Carp aquaculture in shallow, man-made ponds has a long history and now common carp is the most widely cultured freshwater fish species in the world. In many regions, carp aquaculture secures food for the population and carp ponds constitute characteristic elements in the landscape, which contribute to local biodiversity and water balance. Farmed and natural populations of common carp can be threatened by the cyprinid herpesvirus 3 (CyHV-3, syn. Koi herpesvirus (KHV)), the cause of KHV disease. Carp affected by this disease develop severe clinical signs and suffer from high morbidity and mortality. The infection was rapidly dispersed into naive populations by healthy appearing latently infected individuals. During initial outbreaks, the disease killed farmed carp in Europe, Israel and Indonesia as well as a high percentage of carp from natural populations in China, Europe, Japan and the USA. However, in subsequent years the number of carp mortalities declined in affected populations. In carp aquaculture, economic losses related to fish mortalities, reduced stocking density in ponds at risk of infection and trade restrictions incurred upon infected carp populations, are still significantly challenging the economic basis of carp farming. Possible control measures include disinfection of contaminated ponds by quick lime and re-stocking with virus-free fish, the development of effective vaccines and the breeding of disease-resistant carp lines.

Study on <i>Panax notoginseng</i> F.H.Chen Cultivation Under Forest

To overcome the Panax notoginseng F.H.Chen facility cultivation high cost and the consecutive monoculture problems of cultivated land, to satisfy the market demand, to save the production cost, improve the utilization rate of forest land, increase the income of forest farmers, protect the ecological environment, we has been used Yunnan wenshan Panax notoginseng F.H.Chen high quality seedlings for carring out cultivation technology research under forests, according to plant spacing 25 cm ×30 cm to planting, used randomized block design, repeated three times. We choice the Nut forest and China fir forest that the altitude is above 1000m and forests canopy density pond are 0.8 in shuping township Hongjiang, Gracp forest and Kiwi fruit forest that the altitude is 900m and forest canopy density of 0.6 and 0.5 respectively in tangwan township. The test results in 4 forests showed that cultivation growth of nut forest cultivation of Panax notoginseng F.H.Chen, crown diameter, survival rate, three years raw tuber weight were higher than the other three kinds of forests land, China fir forest is better than that of grape and Kiwi fruit forest, grapes forest is higher than the kiwi fruit forest at crown diameter and survival rate, but high growth and tuber weight below the kiwi fruit forest. when we cultivated Panax notoginseng F.H.Chen for scale cultivation under forests, Research results show that we should preference chioce Nut forest in Nut forest, China fir forest, Gracp forest and Kiwi fruit forest at Panax notoginseng F.H. Chen cultivation. because the nut are broadleaf deciduous tree species, lots of fallen leaves decomposed by decaing, increased the soil humus content that makes more loose fertile soil, better permeability, and damp, cool, more diffuse light and scattered light under forests. It is comformed to Panax notoginseng F.H.Chen ecological habit and the rule of the growth and development, and the Panax notoginseng F.H.Chen liked cloudy, joied the cool shade under forests, avoid direct light, liked oblique or scattered light. The Panax notoginseng F.H.Chen large scale cultivations undergrowth can overcome the facility cultivation cost high, production input more, technology is difficulty disadvantages such as, it’s can save the production cost, improve the utilization efficiency of forest land and increase the income of forest farmers, drive to get rich of local forest farmers, protect the ecological environment, promote the sustainable development of Panax notoginseng F.H.Chen industry.

Spatial and temporal variation of phytoplankton in subtropical stabilization ponds

Abstract Aim: This study aimed at analyzing the phytoplankton community in two stabilization ponds of a subtropical region regarding spatial and temporal composition, richness, and abundance, as well as the respective relationships with local abiotic factors. For this purpose, we tested the hypothesis that eutrophic discharges of sewage results in the maintenance of high-density phytoplankton community, mainly Cyanobacteria and Chlorophyceae, both spatially and seasonally, as well as the occurrence of a spatial and seasonal similarity between phytoplankton richness and density in stabilization ponds. Methods: We carried out monthly samplings of the phytoplankton community and environmental variables, between March 2011 and February 2012, in two stabilization ponds located in the city of Cascavel, West Paraná State, Brazil. Results: We observed that the sampled months presented a clear distinction regarding environmental variability, which did not occur for the ponds. We identified 39 taxa, with Cyanobacteria as the most representative group both in richness and density. We records low diversity and evenness of species and low phytoplankton spatial and temporal variability without significant differences between the richness and density mean values according to the periods and sampling station. Conductivity, nutrients, dissolved oxygen and turbidity were the major structuring environmental variables of phytoplankton. Conclusion: Our results corroborated our hypotheses considering the similar spatial and temporal phytoplankton distributions because of abiotic conditions behaving similarly, as well as the direct connection of the ponds. This paper points out the importance of such studies to proper management, including cyanobacteria control and operational decisions regarding stabilization ponds and the export of undesirable inoculum for receiving water bodies.

Small farm ponds: overlooked features with important impacts on watershed sediment transport

AbstractDespite their size, small farm ponds are important features in many landscapes. Yet hydrographical databases often fail to capture these ponds, and their impacts on watershed processes remain unclear. For a 230‐km2 portion of central Texas, United States (U.S.), we created a historical inventory of ponds and quantified the accuracy of automated detection methods under varying drought conditions. In addition, we documented pond dredging/enlargement events and identified sites that had been abandoned. We also analyzed sediment cores from downstream reservoirs to track changes in watershed sediment transport. Over 75 years, pond densities increased more than 350% — to among the highest documented in the U.S. — and the ability of automated methods to detect these ponds was highly dependent on drought severity (R2 = 0.96). Approximately 5% of ponds present in the 1950s were no longer present in 2012, while 33% were dredged between 1937 and 2012. Downstream reservoir sedimentation has decreased by an average of 55% as ponds have increased in number. These findings suggest that small ponds and the maintenance of trapping efficiency have large‐scale impacts on sediment dynamics. Accurately accounting for these storage effects is vital to water resource planning efforts.

ECOLOGICAL DETERMINANTS OF AVIAN INFLUENZA VIRUS, WEST NILE VIRUS, AND AVIAN PARAMYXOVIRUS INFECTION AND ANTIBODY STATUS IN BLUE-WINGED TEAL (ANAS DISCORS) IN THE CANADIAN PRAIRIES

The Canadian prairies are one of the most important breeding and staging areas for migratory waterfowl in North America. Hundreds of thousands of waterfowl of numerous species from multiple flyways converge in and disperse from this region annually; therefore this region may be a key area for potential intra- and interspecific spread of infectious pathogens among migratory waterfowl in the Americas. Using Blue-winged Teal (Anas discors, BWTE), which have the most extensive migratory range among waterfowl species, we investigated ecologic risk factors for infection and antibody status to avian influenza virus (AIV), West Nile virus (WNV), and avian paramyxovirus-1 (APMV-1) in the three prairie provinces (Alberta, Saskatchewan, and Manitoba) prior to fall migration. We used generalized linear models to examine infection or evidence of exposure in relation to host (age, sex, body condition, exposure to other infections), spatiotemporal (year, province), population-level (local population densities of BWTE, total waterfowl densities), and environmental (local pond densities) factors. The probability of AIV infection in BWTE was associated with host factors (e.g., age and antibody status), population-level factors (e.g., local BWTE population density), and year. An interaction between age and AIV antibody status showed that hatch year birds with antibodies to AIV were more likely to be infected, suggesting an antibody response to an active infection. Infection with AIV was positively associated with local BWTE density, supporting the hypothesis of density-dependent transmission. The presence of antibodies to WNV and APMV-1 was positively associated with age and varied among years. Furthermore, the probability of being WNV antibody positive was positively associated with pond density rather than host population density, likely because ponds provide suitable breeding habitat for mosquitoes, the primary vectors for transmission. Our findings highlight the importance of spatiotemporal, environmental, and host factors at the individual and population levels, all of which may influence dynamics of these and other viruses in wild waterfowl populations.

Effects of Stocking Density on Production Traits of Channel Catfish×Blue Catfish Hybrids

AbstractChannel Catfish Ictalurus punctatus × Blue Catfish I. furcatus hybrid fingerlings (mean weight, 47 g) were stocked in 0.4‐ha ponds at densities of 7,425, 12,375, 17,325, 22,275, and 27,225 fish/ha in three replicate earthen ponds for each density. Fish were fed a 28% protein diet to apparent satiation once daily. Ponds were equipped with electric paddlewheel aerators (12.5 hp/ha) that were turned on when dissolved oxygen (DO) levels reached <5.0 mg/L; additional aeration was provided by power‐takeoff tractor‐driven paddlewheels at DO < 2.5 mg/L. Feeding was terminated at the end of October and fish were harvested and weighed. Stocking density had no significant effect on feed conversion (overall average, 1.97), survival (≥93% in all treatments), or processing yield (carcass yield = 66.2%, shank fillet yield = 34.8%, nugget yield = 10.5%). Harvest weight was not significantly different between 7,425 and 22,275 fish/ha (average, 0.85 kg) but was less at 27,225 fish/ha (0.72 kg). Net production increased significantly with increased density from 7,425 to 22,275 fish/ha but was not different between 22,275 and 27,225 fish/ha. Percentage of submarketable fish (<0.45 kg) was not significantly different from pond densities of 7,425 through 22,275 fish/ha (average, 2.3%), but was higher at 27,225 fish/ha (8.8%). Aeration hours increased and minimum DO levels decreased significantly as stocking density increased. The smaller average weight at 27,225 fish/ha may have been due to fish behavior associated with crowding, lack of equal access to feed, or degraded water quality. However, past research has demonstrated a “threshold” relationship between minimum DO levels and catfish feeding and growth. Data from this study indicate a similar DO threshold–growth relationship, suggesting the observed effect of density on growth may have been at least partially due to minimum DO levels being below that needed for optimal growth at 27,225 fish/ha.

Object-based detection of Arctic sea ice and melt ponds using high spatial resolution aerial photographs

High resolution aerial photographs used to detect and classify sea ice features can provide accurate physical parameters to refine, validate, and improve climate models. However, manually delineating sea ice and melt ponds is time-consuming and labor-intensive. In this study, an object-based classification algorithm is developed to automatically extract sea ice and melt ponds efficiently from 163 aerial photographs taken during the Chinese National Arctic Research Expedition in summer 2010 (CHINARE 2010) in the Arctic Pacific Sector. The photographs are selected from 599 cloud-free photographs based on their image quality and representativeness in the marginal ice zone (MIZ). The algorithm includes three major steps: (1) the image segmentation groups the neighboring pixels into objects according to the similarity of spectral and textural information; (2) the random forest ensemble classifier distinguishes four general classes: water, general submerged ice (GSI, including melt ponds and submerged ice along ice edges), shadow, and ice/snow; and (3) the polygon neighbor analysis further separates melt ponds and submerged ice from the GSI according to their spatial relationships. The overall classification accuracy for the four general classes is 95.5% based on 178 ground reference objects. Furthermore, the producer's accuracy of 90.8% and user's accuracy of 91.8% are achieved for melt pond detection through 98 independent reference objects. For the 163 photos examined, a total of 19,438 melt ponds larger than 1m2 are detected, with a pond density of 867.2km−2, mean pond size of 32.6±0.03m2, and mean pond fraction of 0.06±0.006; a total of 42,468 ice floes are detected, with the mean floe size of 173.3±0.1m2 (majority in 1–30m2) and mean ice concentration of 46.1±0.5% (ranging from 18.6–98.6%). These results matched well with ship-based visual observations in the MIZ in the same area and time. The method presented in the paper can be applied to data sets of high spatial resolution Arctic sea ice photographs for deriving detailed sea ice concentration, floe size, and melt pond distributions over wider regions, and extracting sea ice physical parameters and their corresponding changes between years.

The exotic weevil Stenopelmus rufinasus Gyllenhal, 1835 (Coleoptera: Curculionidae) across a “host-free” pond network

The exotic weevil Stenopelmus rufinasus Gyllenhal, 1835 (Coleoptera: Curculionidae) across a “host-free” pond network The presence of the exotic weevil Stenopelmus rufinasus (Coleoptera: Curculionidae) is closely related to the occurrence of the exotic red water fern, Azolla filiculoides. In this paper, we present the first records of S. rufinasus in Donana National Park (SW Spain), based on sampling of macroinvertebrates in 91 temporary ponds, including monthly samples of 22 ponds, during two successive years (2005-2007). The exotic weevil was present in 21% of the sampled ponds where the host plant, A. filiculiodes, was not detectable. Because A. filiculoides can reach high densities in an adjacent area of marsh, we suggest that the occurrence of the exotic weevil in these ponds is a consequence of dispersal from nearby marshes. Our study demonstrates that S. rufinasus adults can occur at relatively high densities in ponds where the host plant is not present, suggesting that such apparently “host-free” sites may act as stepping stones for the spread of this species.

Exotic Fish in Exotic Plantations: A Multi-Scale Approach to Understand Amphibian Occurrence in the Mediterranean Region.

Globally, amphibian populations are threatened by a diverse range of factors including habitat destruction and alteration. Forestry practices have been linked with low diversity and abundance of amphibians. The effect of exotic Eucalyptus spp. plantations on amphibian communities has been studied in a number of biodiversity hotspots, but little is known of its impact in the Mediterranean region. Here, we identify the environmental factors influencing the presence of six species of amphibians (the Caudata Pleurodeles waltl, Salamandra salamandra, Lissotriton boscai, Triturus marmoratus and the anurans Pelobates cultripes and Hyla arborea/meridionalis) occupying 88 ponds. The study was conducted in a Mediterranean landscape dominated by eucalypt plantations alternated with traditional use (agricultural, montados and native forest) at three different scales: local (pond), intermediate (400 metres radius buffer) and broad (1000 metres radius buffer). Using the Akaike Information Criterion for small samples (AICc), we selected the top-ranked models for estimating the probability of occurrence of each species at each spatial scale separately and across all three spatial scales, using a combination of covariates from the different magnitudes. Models with a combination of covariates at the different spatial scales had a stronger support than those at individual scales. The presence of predatory fish in a pond had a strong effect on Caudata presence. Permanent ponds were selected by Hyla arborea/meridionalis over temporary ponds. Species occurrence was not increased by a higher density of streams, but the density of ponds impacted negatively on Lissotriton boscai. The proximity of ponds occupied by their conspecifics had a positive effect on the occurrence of Lissotriton boscai and Pleurodeles waltl. Eucalypt plantations had a negative effect on the occurrence of the newt Lissotriton boscai and anurans Hyla arborea/meridionalis, but had a positive effect on the presence of Salamandra salamandra, while no effect on any of the other species was detected. In conclusion, eucalypts had limited effects on the amphibian community at the intermediate and broad scales, but predatory fish had a major impact when considering all the scales combined. The over-riding importance of introduced fish as a negative impact suggests that forest managers should prevent new fish introductions and eradicate fish from already-occupied ponds whenever possible.

Intermediate pond sizes contain the highest density, richness, and diversity of pond-breeding amphibians.

We present data on amphibian density, species richness, and diversity from a 7140-ha area consisting of 200 ponds in the Midwestern U.S. that represents most of the possible lentic aquatic breeding habitats common in this region. Our study includes all possible breeding sites with natural and anthropogenic disturbance processes that can be missing from studies where sampling intensity is low, sample area is small, or partial disturbance gradients are sampled. We tested whether pond area was a significant predictor of density, species richness, and diversity of amphibians and if values peaked at intermediate pond areas. We found that in all cases a quadratic model fit our data significantly better than a linear model. Because small ponds have a high probability of pond drying and large ponds have a high probability of fish colonization and accumulation of invertebrate predators, drying and predation may be two mechanisms driving the peak of density and diversity towards intermediate values of pond size. We also found that not all intermediate sized ponds produced many larvae; in fact, some had low amphibian density, richness, and diversity. Further analyses of the subset of ponds represented in the peak of the area distribution showed that fish, hydroperiod, invertebrate density, and canopy are additional factors that drive density, richness and diversity of ponds up or down, when extremely small or large ponds are eliminated. Our results indicate that fishless ponds at intermediate sizes are more diverse, produce more larvae, and have greater potential to recruit juveniles into adult populations of most species sampled. Further, hylid and chorus frogs are found predictably more often in ephemeral ponds whereas bullfrogs, green frogs, and cricket frogs are found most often in permanent ponds with fish. Our data increase understanding of what factors structure and maintain amphibian diversity across large landscapes.

Phytoplankton colonization patterns. Is species richness depending on distance among freshwaters and on their connectivity?

Phytoplankton assemblages in two Sicilian water bodies were compared to test the hypothesis that colonization events and the successful establishment of a new species in an aquatic ecosystem may depend on the number of water bodies in a given area and on their relative distance. The two ecosystems are both natural, shallow lakes and they are protected sites hosting a rich avifauna. Lake Biviere di Gela is located in an area with a high density of ponds, whereas Lake Pergusa is an isolated waterbody without other aquatic ecosystems in its surroundings. Both lakes had almost disappeared about 10 years ago because of the over-exploitation of their main inflows. They were therefore re-filled using water from other catchments and their phytoplankton has been sampled since their re-filling. The results show that Lake Pergusa has maintained a species-poor phytoplankton assemblage since its re-filling, whereas Lake Biviere di Gela has been showing progressively richer phytoplankton assemblages during time. The composition of samples collected in nearby located temporary ponds suggests that phytoplankton in this area belongs to a species-rich metacommunity which favored its re-establishment in the lake. Aquatic ecosystems conservation plans cannot thus neglect the role of small waters located in the catchments.

Beaver impact on stream fish life histories: the role of landscape and local attributes

The Eurasian beaver (Castor fiber) has been reintroduced into the Carpathian Mountains and has once again become an important factor for modifying streams. Forty-three sampling sites were compared with 10 reference sites in streams not settled by beavers. Models related to the impacts of beavers on various fish life history stages and a model presenting attributes influencing the ichthyofauna structure in streams with and without beavers were generated. Significant differences in the fish species composition were found between beaver ponds versus the running sections of streams. The changes associated with pond aging caused decrease of Siberian bullhead (Cottus poecilopus) density. For brown trout (Salmo trutta), beaver ponds were the only location where large individuals were found, while the upstream parts of the beaver complexes provided spawning habitat and an area for fry growth. Common minnow (Phoxinus phoxinus) and stone loach (Barbatula barbatula) had higher density in ponds than in streams. The decisive factors for the ichthyofauna in the mountain streams settled by beavers were local attributes related to beaver activity. Our results illustrate interactions among beaver, landscape context, and fish life history in influencing the response of the stream fish assemblages to beaver recolonization. It also helps answer the question of how Eurasian beaver influence stream fish assemblages, at a much larger scale than previous studies.

Landscape context influences the abundance of amphibians and the strength of their food web interactions in small ponds

Many species, including most amphibians, undergo an ontogenetic niche shift (ONS) from an aquatic larval stage to a terrestrial adult stage. We use the ratio of aquatic to terrestrial habitat in a landscape as a tool to understand the influence of landscape context on the population growth of ONS species. The aquatic to terrestrial ratio (ATR) of habitats can be viewed as an analog to the influence of resource ratios on the population growth of consumers and depends on the degree to which each habitat type limits the growth of a given population. Population growth rates of shorter‐lived species tend to be more limited by demographic rates in early (aquatic) life stages. As a result, increasing the ATR should lead to a higher total population size in the landscape (and higher densities in the terrestrial habitat), but have little influence on the density of individuals in any given aquatic habitat. Alternatively, population growth rates of longer‐lived species tend to be more limited by demographic rates in later (terrestrial) life stages and increasing the ATR should have little influence on the total population size in the landscape, but decrease the density of individuals in any given aquatic habitat. We show that among‐landscape variation in the breeding‐pond densities of three widespread amphibians with contrasting life histories is consistent with this framework. Within‐pond densities of Pseudacris crucifer, a species with short‐lived adults, were not influenced by ATR, whereas within‐pond densities of Hyla versicolor, a longer‐lived member of the same family (Hylidae), declined as ATR increased. Ambystoma maculatum, a long‐lived salamander, also had lower densities in ponds with higher ATR. Because A. maculatum larvae are important predators in ponds, we use structural equation modeling to show that landscape context (ATR) can moderate community structure via direct (amphibian abundances) and indirect (prey species richness) effects.

Observational bias and the apparent distribution of ponds on Eros

Over 300 “ponds” have been identified on 433 Eros: smooth deposits that sharply embay the bounding depressions in which they lie. The known ponds are largely concentrated near the equator at the ends of the long axis of the asteroid. Here, we examine the pixel scale of images available at the pond locations, and compare the observed distribution of ponds on Eros to that of the image pixel scale. We find that the majority (60%) of ponds are found in the regions covered by images with pixel scales less than 2m/px, a total of only 13% of the surface area. The correlation between pond density and image pixel scale suggests a significant observational bias in the identification of small ponds. These findings suggest that the distribution of ponds on Eros may not be as clear-cut as previously reported, and that it may be best not to use this distribution to assess existing models regarding their formation of these landforms.

Comprehensive Characterization of Pond Ash and Pond Ash Slurries for Hydraulic Stowing in Underground Coal Mines

In this study, the physicochemical and self-heating characteristics of pond ashes from Talcher Thermal Power Station (TTPS), located in the Angul district of the Indian state of Odisha are studied. The study revealed that the TTPS pond ashes belong to Class F fly ash category consisting mainly of SiO2, Al2O3, and Fe2O3, with a small amount of CaO. The presence of mineral phases, namely, quartz, mullite, magnetite, and hematite in the pond ash are confirmed by x-ray diffraction. Based on the pond ash properties, various properties of the slurries of one representative pond ash, namely, density, volume concentration, and viscosity are determined by varying the ash concentration from 45% to 65% with an increment of 5%. As well, the critical deposition velocities of slurries as a function of slurry concentration and pipe diameter are determined. The results showed that the slurry viscosity increases exponentially with increase in solid content and the critical velocity increases linearly with increase in slurry concentration and pipe diameter. The relationships generated through regression analysis can be used to quickly predict the critical velocity of similar types of ash slurries for any known slurry concentrations and pipe sizes.

Benthic community changes following the 2010 Hainan flood: Implications for reef resilience

In the future, coastal coral reefs in Southeast Asia will be exposed to both climate change and more severe and frequent floods associated with heavy rainfall. Floodwaters have caused severe coral mortality in many near-shore coral reefs throughout the world. However, previous studies have largely ignored the effects of floodwaters on macroalgae and calcified algae and the indirect effects on benthic community interactions following flood events. In October 2010, heavy rainfall of more than 1600 mm in 9 days caused the largest flood on record in eastern Hainan Island. Long-term video transects indicate that the floodwater was responsible for severe benthic community mortality in Wenchang, northeast Hainan Island. Mean live coral cover decreased from 15.2% to 9.8% and showed strongest degradation at stations proximal to areas with a high density of aquaculture ponds (i.e. stations 3S–4S decreasing from 15.0% to 0.8%). Branching corals (Acropora and Pocillopora damicornis) were the most sensitive, while massive corals (e.g. Porites, Galaxea, Platygyra and Favia) were most tolerant of floodwaters. Calcified algae were almost completely removed at all stations; coverage decreased from 28.1% to 1.7%, while macroalgae were not influenced by floodwaters. Thus, remnant coral communities that survived the flooding in Wenchang are likely to be subject to increased competition with macroalgae and benefit less from calcified algae promoting juvenile coral recruitment.