Radial Transects Research Articles

Experimental study on the effects of pressure loss on uniformity, application rate and velocity on different working conditions using the dynamic fluidic sprinkler

An experiment was conducted to determine the effects of pressure loss, combined spacing, and.coefficients of uniformity on the dynamic fluidic sprinkler. Spline interpolation was used to convert the radial water volume into grid-type data and various pressure conditions were used to simulate the three-dimensional water distribution under square and triangular combinations of sprinklers. For each of the combinations of the sprinklers, experiments were performed at operating pressures of 0.15, 0.2, 0.25, and 0.3 MPa, respectively. To find the optimum spatial distribution of sprinklers, three different sprinkler intervals, 1R, 1.2R, and 1.4R, were performed for the square and triangular combinations. The droplet size distributions were also measured along a radial transect from the sprinkler for each operational pressure using the Thies Clima Laser Precipitation Monitor. The results demonstrated that the average values of the inclination angles of the water droplet trajectory curves were 60.78° and 68.85° as the pressure rose from 0.15 MPa to 0.3 MPa. When the pressure exceeds 0.2 MPa, the square combination's distribution uniformity coefficients of 25% low and high values were higher than those of the triangle combination. Triangular combination coefficients of uniformity (CU) values initially decreased and then increased as sprinkler spacing increased, with the CU value under 1.4R spacing reaching 73.85%. At a 1.2R interval, the CU value of a triangular combination was 8.49% lower than that of a square combination, which is a significant difference. Peak irrigation values for the square combination, when the pressure was changed from 0.1 to 0.3 MPa, were 29.97, 22.9, 19.8, 19.91, and 19.21 mm h−1, respectively. The CU values at 0.2, 0.25, and 0.3 MPa decreased at rates of 0.07%, 1.36%, and 0.8%, respectively, when the pressure was reduced by 10%.

Automatic detection of fish scale circuli using deep learning.

Teleost fish scales form distinct growth rings deposited in proportion to somatic growth in length, and are routinely used in fish ageing and growth analyses. Extraction of incremental growth data from scales is labour intensive. We present a fully automated method to retrieve this data from fish scale images using Convolutional Neural Networks (CNNs). Our pipeline of two CNNs automatically detects the centre of the scale and individual growth rings (circuli) along multiple radial transect emanating from the centre. The focus detector was trained on 725 scale images and achieved an average precision of 99%; the circuli detector was trained on 40678 circuli annotations and achieved an average precision of 95.1%. Circuli detections were made with less confidence in the freshwater zone of the scale image where the growth bands are most narrowly spaced. However, the performance of the circuli detector was similar to that of another human labeller, highlighting the inherent ambiguity of the labelling process. The system predicts the location of scale growth rings rapidly and with high accuracy, enabling the calculation of spacings and thereby growth inferences from salmon scales. The success of our method suggests its potential for expansion to other species.

Models to predict the radial variation of stiffness, strength, and density in planted noble fir, Norway spruce, western hemlock, and western red cedar in Great Britain

Key messageThis study compares the measured radial variation in wood stiffness, strength, and density of noble fir, Norway spruce, western hemlock, and western red cedar by developing mixed-effects models for each property using age as the explanatory variable. These models could be used to simulate the effect of rotation length and species choice on sawn wood properties.ContextTimber production in Great Britain relies primarily on Sitka spruce. The use of multiple species is desirable to mitigate against biotic and abiotic risks posed to a single species. When considering alternative species, quantifying and modeling radial variation in wood properties is important to determine the potential for sawn timber production at a given rotation length.AimsTo build empirical models for the radial variation in wood properties that can account for species.MethodsClear-wood samples were produced along radial transects in trees from four conifer species: Abies procera Rehder, Picea abies (L.) Karst, Tsuga heterophylla (Raf.) Sarg., Thuja plicata Donn. ex D.Don. Modulus of Elasticity, Modulus of Rupture, and density were measured on each species according to established standards. Mixed-effects models were built using ring numbers from the pith and species as explanatory variables.ResultsThe same model forms could be used across the four species. Nonlinear models were developed for the Modulus of Elasticity and density. For the Modulus of Rupture, a linear model was most appropriate. The effect of species in the models was significant.ConclusionAt similar rotation lengths, noble fir, Norway spruce, and western hemlock can produce timber with comparable properties to Sitka spruce. Overall, western red cedar would have worse properties for structural use.

Composition, Diversity, and Value of Ecological Importance in Andean Grassland Ecosystems according to the Altitudinal Gradient in the Huacracocha Micro-Watershed, Peru

Aims: determine the composition and floristic diversity, the similarity between sites based on the distribution of species in the altitudinal gradient, and determine the value of ecological importance, in Andean grassland ecosystems.
 Study Design: Original research.
 Place and Duration of Study: This study took place in the Huacracocha micro-watershed in the Central Highlands of Peru, during the rainy season (January - March 2022).
 Methodology: The agrostological evaluation points were determined taking into account twelve sites of interest were determined, located from the lowest part of the micro-watershed (4091.8 masl) to the part with the highest vegetation cover (4512.27 masl), the agrostological reading process at each evaluation site was carried out using the radial transect method with the line and intercept point technique.
 Results: We observed the presence of the presence of 78 vascular species, included in 51 genus and 21 families, was found. The dominance of certain species characterized the type of grassland vegetation, and at least 3 species determined the similarity between sites. The alpha diversity index was low, and the value of ecological importance ranged between 0.0062 and 0.2194.
 Conclusion: It was concluded that the Andean grassland ecosystems are constituted by a complex community of grasslands based on numerous floristic families, genus, and species, likewise, the dominance of species among the shared sites characterizes the vegetation type, and the diversity index and the IVI determine the complex structural characteristics with great biodiversity.

Novel aerial sampling method to detect flowering Bambusa vulgaris (Schrad. ex J.C. Wendl.) in Trinidad and Tobago, West Indies

Little to no records of Bambusa vulgaris (Schrad. ex J.C. Wendl.) flowering events have been published for Trinidad and Tobago, West Indies. This paper aims to document past flowering events on these islands and to record environmental conditions surrounding an individual flowering event in north-west Trinidad. A novel systematic sampling approach using aerial surveys was adopted. An unmanned drone was used to establish a 500 m radial transect at the first flowering clump and this method was continued until no more flowering bamboo clumps/clusters were identified. Additional aerial surveys and site visits along major roads were also conducted to search for flowering clumps/clusters on both islands. Much research is still warranted (using similar methodologies and guidelines) to record environmental cues associated with B. vulgaris flowering on the islands as the present study was only able to provide a baseline for future studies.

Effects of best land management practices on the structure, composition and diversity of woody vegetation in agroforestry parklands: case of Dan Saga and Tabofatt villages in Niger republic

The large-scale use of best land management practices has been instrumental in the accession of recent regreening in certain Sahelian areas. This study therefore aimed at highlighting the effect of the wide use of these practices on the structural and ecological parameters of the woody flora in agroforestry parklands. To this end, an inventory of ligneous vegetation was carried out on radial transects in an East–West and North–South direction in the villages clusters of Dan Saga and Tabofatt in Niger Republic. A variance comparison test was applied on the values from plots with practice compare to those from plots without practice (controls). In Dan Saga site, the results obtained show the significant effect of the practice of assisted natural tree regeneration on the density of trees (97 against 58 plants/ha for the control plots), on the basal area (3.04 against 1.98 m2/ha for the control plots), on regeneration (61.96% against 40.91% for the controls) and on floristic diversity (2.93 against 2.41 bits for the control plots) with a clear dominance of Combretaceae. On the other hand, this effect is relatively less significant in the case of Tabofatt site’s where the practice of planting trees coupled with water and runoff collection structures induced positive effect particularly on the basal area (2.29 against 1.90 m2/ha for plots controls), on the structure of the vegetation stood by the abundance of plants with average diameter (class from 5 to 10 cm) as well as the species diversity (2.54 against 2.18 bits for the controls) with a dominance of species of the Mimosaceae family. These results can be used as decision support tools to guide actions to scale up regreening in the Sahelian context.

Distinct Rainfall Interception Profiles among Four Common Pacific Northwest Tree Species

Forest tree canopies have a critical influence on water cycles through the interception of precipitation. Nevertheless, radial patterns of canopy interception may vary interspecifically. We analyzed canopy interception using catchments along radial transects underneath four common forest tree species (Acer macrophyllum, Alnus rubra, Pseudotsuga menziesii, and Thuja plicata) in the Pacific Northwest over two years. Near the center of the canopy in the leaf-off season, interception was 51.6%–67.2% in conifer species and only 20.1%–40.1% in broadleaf species, and interception declined to 19.9–29.9 for all species near the edge of the canopy. One deciduous species (A. rubra) showed spatially uniform interception during the leaf-off period (19.9%–20.96%), while another varied from 23.1%–40.1%. Patterns were more pronounced in the leaf-on period (under high vapor pressure deficit conditions), where conifers intercepted 36.5%–95.9% of precipitation, depending on the species and position under the canopy. Deciduous species similarly intercepted 42.1%–67.7% of rainfall, depending on species and canopy position. Total throughfall was curvilinearly related to the amount of rainfall near canopy centers for conifer trees but less so for deciduous trees. Soil moisture was predictably related to interception across and within species. These data highlight interspecific differences in radial interception patterns, with consequences for soil moisture, hydrologic processes, and ecosystem function.

Effects of scattered Faidherbia albida and Cordia africana Tree on Soil Properties under their Canopies in Fedis District, Easte Hararghe Zone, Oromia

The study was conducted to investigate the effect of scattered trees under their canopies on soil fertility status at Fedis district, East Hararghe Zone, oromia, Ethiopia. Accordingly, six isolated and nearly identical Faidherbia albida and Cordia africana trees were selected and the canopy coverage of each tree was divided into four radial transects. Soil samples from three horizontal distances levels: 2.5m, 5m and 25m with two soil depths levels (0–20cm and 20-40cm) were taken for analysis of soil physical and chemical properties and tree species with two levels with factorial arrangement in RCBD replicated six times were employed. The result revealed soil texture was not influenced significantly (P>0.05) by tree species. Soil bulk density was significantly (p<0.05) influenced by both tree species. Soil moisture was significantly (p<0.05) higher under canopy of trees than open field and in surface than in subsurface soils. Soil chemical properties;- electric conductivity, organic carbon, organic matter, soil carbon stock, total nitrogen, available phosphorus and exchangeable cation (Mg, Ca, Na and K) for surface and subsurface soil layers of under F.albida and C. africana trees were significantly (p<0.05) higher in canopy than open field and in surface than subsurface. Soil pH was not significantly (p>0.05) influenced by both tree species. It can be concluded that these tree species have the potential to improve soil fertility beneath its canopy. This may be important for the agricultural landscape health and demonstrated the scattered trees to retain on crop fields to improve soil fertility status under its canopy and on farm biodiversity conservation in agricultural landscapes conditions.

Effects of Recreational Camping on the Environmental Values of National Parks in Sri Lanka.

Camping is a popular activity in the contemporary nature-based tourism domain and rapidly gaining momentum as a key recreational activity in Sri Lanka’s national parks (NPs). Recreational uses such as camping in natural areas can induce significant and often localised resource impacts that can affect soil, vegetation, wildlife and water, with the severity of such impacts varying according to the intensity of use. Hence, monitoring of the biophysical conditions of campsites has become an important component in the reserve management agenda in many places, especially in developed countries. To the best of our knowledge, this is the first study to examine the biophysical impacts associated with the recreation ecology of camping in Sri Lanka. Ten campsites from three dry zone NPs were selected to assess biophysical impacts of camping activities. Field measurements were based on the fixed radial transect method. Gathered data included the total area of the campsite, erosion potential measured as the area of exposed soil (devoid of vegetation or organic litter), number of exposed roots and human damage to trees, number of fireplaces/ fire scars on the ground, visual counts of litter, soil compaction measured by penetrometer, loss of woody debris. This study reports significant levels of environmental degradation related to all the indictors of biophysical impacts at both high and low use campsites. There was no evidence for any difference in the level of environmental degradation associated with high and low use campsites. The loss of natural values associated with campsites negatively impacted visitors’ nature-based experience. These findings highlight the importance of managing biophysical impacts in campsites to provide a high-quality visitor experience, while sustainably managing tourism activities in NPs.

Productivity of Capsicum annuum under Grewia optiva-Based traditional agroforestry system in mid hill zone of Himachal Pradesh (India)

Agroforestry is relatively a new name for a set of old practices. The multifarious trees deliberately retained by the farmers on the farm bund form the agroforestry combinations, which supplement the fodder, fuel, fiber, fruits and flosses as their life support system. Grewia optiva is an important fodder tree retained on farm bunds by farmers in Western Himalayan region. The present investigation was aimed to study the effect of G. optiva based traditional agroforestry system i.e. agri-silviculture, on the productivity of bell pepper (Capsicum annuum). The crown spread of tree was considered major factor and categorized into different classes for quantifying its effect on crop growth and production along radial transects from tree trunk. Results revealed that the crown classes significantly affected the yield of bell pepper causing about 33% reduction in yield under tree canopy as compared to the open condition.

Scaling up Assisted Natural Regeneration to Intensify Agroecologically Agrosystems Productivity

As an agroecological intensification technique, the scaling up of trees assisted natural regeneration (ANR) could help to protect Sahelian agrosystems and to ensure crop production in the context of high demographic pressure and climatic variability. This study aims to evaluate agronomic and environmental performances of a multi-specific agroforestry parkland arising from a Maradi local community innovations in tree resources management to support their ongoing scaling up. The study site is located in central-south of Maradi region's (Niger) with annual rainfall average amount of 600 mm and is derived from more than thirty years of trees ANR practice. Pearl millet is the dominant cereal most often in association with cowpea, sorghum or groundnut. Woody trees density was evaluated on radial transects. Water profile and soil bulk density in ANR and non-ANR areas were determined from rainy and dry season soils sampling at depths of 0-50 cm, 50-100 cm, 100-150 cm and 150- 200cm. Pearl-millet growth and it yield parameters were monitored in 100 m2 (10x10m) plots due to 50 plots in ANR and 50 non- ANR areas. Results showed that the two zones had the same composition for dominant woody trees but the average density was higher in the ANR than non-ANR areas. Tree density was lower in fields in the vicinity of the village than those that are far away in all context. Soil water content was higher in ANR areas under and out of tree canopy than in non-ANR area in surface horizons. However, in deep horizons up to 200 cm, soil water content was higher in H ANR and HC ANR areas than in SC ANR areas, respectively. Apart from seeding density (F = 1.20, P-value = 0.2756), all measured agronomic performance parameters were significantly higher in the ANR than in the non-ANR area. These results show that the ANR practice improve agrosystems productivity in a sustainable manner through increases of crop yield as well as direct incomes to smallholders through wood exploitation from enhanced pruning.

Effects of Ziziphus Spina-Christi (L.) on Selected Soil Properties and Sorghum Yield in Habru District, North Wollo, Ethiopia

Ziziphus spina-christi is a multipurpose tree which grows naturally on the farm lands in Habru district. Since, the effects of this tree on soil and crop have not scientifically quantified; this study has been carried out with the aim of assessing the effect of Ziziphus spina-christi on soil physicochemical properties, grain and biomass yield of sorghum.Five isolated and nearly identical Ziziphus spina-christi tree growing on farm lands with similar site condition were selected and canopy coverage of each tree was divided into four radial transects. Soil samples from three horizontal distances: 1.2m, 2.9m and 15m with two soil depths (0–15cm and 15-30cm) were taken for analysis of soil physico- chemical properties. Three quadrates 1m x1m at each transect and distances were laid for sorghum grain yield and biomass estimation. The result shows that soil pH, EC, CEC and soil texture were not significantly (p>0.05) influenced by Ziziphus spina-christi tree, whereas soil bulk density, soil moisture content, total nitrogen, organic carbon, available phosphorus and exchangeable cation (Mg, Ca and K) were significantly (P<0.05) influenced mainly due to higher organic matter input through litter fall, root biomass, uptake and return of nutrients from deeper soil profiles under the tree canopies. While the grain yield of sorghum and above ground biomass were not statistically significant (p>0.05).Hence, retaining of this tree on crop land improves the soil fertility status.

Land use in relation to composition and abundance of phlebotomines (Diptera: Psychodidae) in five foci of domiciliary transmission of cutaneous leishmaniasis in the Andean region of Colombia

American cutaneous leishmaniasis is a public health concern in Colombia, its incidence being sustained or focally increased principally by the emergence of domestic transmission concomitantly with the adaptation of the phlebotomine vectors to habitat transformation around households. The objective of the study is to scale up a rapid characterization methodology for evaluating the relationship of land use around the house to the composition and abundance of phlebotomines. Five sites with a history of domestic leishmaniasis transmission in the Andean area of Colombia were selected. The peri-domestic habitat was evaluated at 10 m intervals along eight radial transects, centered on each house, at 45° intervals using a web pattern. Phlebotomines were captured by placing three CDC light traps over two nights both indoors and outdoors (10 m from the house). Blood source and infection were determined by PCR. Spearman rank correlation coefficients and negative binomial regression were used to quantify associations between the phlebotomine abundance and habitat categories. The study demonstrated that the vectors were largely anthropophagic (62% of 79 were human blood) and that a single species in each site was favored by the pertaining agriculture monoculture. Specifically, Pintomyia (Pifanomyia) quasitownsendi was associated with sugar cane in Novillero and La Esmeralda; while Pi. (Pif.) longiflocosa was associated with coffee plantations in Agua Bonita and El Cucal. Honda Alta had a more diverse array of land use and forest coverage with a lower number of specimens but higher species diversity. In terms of distance from the house to an area of a given land use, the abundance of Pi. (Pif.) quasitownsendi was inversely related to the distance to sugar cane plantation (Spearman correlation coefficient, ρ = -0.56, p < 0.001 for outdoor catches, and ρ = -0.50, p < 0.001 indoors). A similar inverse relationship was observed for Pi. (Pif.) longiflocosa with regard to technified coffee (ρ = -0.51, p < 0.001 outdoors, and ρ = -0.48, p < 0.001 indoors).This rapid characterization methodology could guide public heath decision makers in identifying those houses at higher risk of domestic transmission, and also educate farmers to increase the distance between their crops and any neighboring houses.

A Systematic Review of Remotely Operated Vehicle Surveys for Visually Assessing Fish Assemblages

Anthropogenic activities and greater demands for marine natural resources has led to increases in the spatial extent and duration of pressures on marine ecosystems. Remotely operated vehicles (ROVs) offer a robust survey tool for quantifying these pressures and tracking the success of management intervention while at a range of depths, including those inaccessible to most SCUBA diver-based survey methods (∼>30 m). As the strengths, limitations, and biases of ROVs for visually monitoring fish assemblages remain unclear, this review aims to evaluate ROVs as a survey technique and to suggest optimal sampling strategies for use in typical ROV-based studies. Using the search engines Scopus™ and Google Scholar™, 119 publications were identified that used ROVs for visual surveys of fish assemblages. While the sampling strategies and sampling metrics used to annotate the imagery in these publications varied considerably, the total abundance of fish recorded over strip transects of varying dimensions was the most common sampling design. The choice of ROV system appears to be a strong indicator of both the types of surveys available to studies and the success of ROV deployments. For instance, larger, more powerful working-class systems can complete longer and more complex designs (e.g., swath, cloverleaf, and polygonal transects) at greater depths, whereas observation-class systems are less expensive and easier to deploy, but are more susceptible to delays or cancellations of deployments. In more severe sea state conditions, radial transects, or strip transects that employ live-boating or a weight to anchor the tether to the seafloor, can be used to improve the performance of observation-class systems. As these systems often employ shorter tethers, radial transects can also be used to maximize sampling area at greater depths and on large vessels that may rotate substantially while anchored. For highly mobile species, and in survey designs where individuals are likely to be recounted (e.g., transects along oil and gas pipelines), relative abundance (MaxN) may be a more robust sampling metric. By identifying subtle, yet important, differences in the application of ROVs as a tool for visually surveying deep-water marine ecosystems, we identified key areas for improvement for best practice for future studies.

Reproducibility of Ba/Ca variations recorded by northeast Pacific bamboo corals

AbstractTrace elemental ratios preserved in the calcitic skeleton of bamboo corals have been shown to serve as archives of past ocean conditions. The concentration of dissolved barium (BaSW), a bioactive nutrientlike element, is linked to biogeochemical processes such as the cycling and export of nutrients. Recent work has calibrated bamboo coral Ba/Ca, a new BaSW proxy, using corals spanning the oxygen minimum zone beneath the California Current System. However, it was previously unclear whether Ba/Cacoral records were internally reproducible. Here we investigate the accuracy of using laser ablation inductively coupled plasma mass spectrometry for Ba/Cacoral analyses and test the internal reproducibility of Ba/Ca among replicate radial transects in the calcite of nine bamboo corals collected from the Gulf of Alaska (643–720 m) and the California margin (870–2054 m). Data from replicate Ba/Ca transects were aligned using visible growth bands to account for nonconcentric growth; smoothed data were reproducible within ~4% for eight corals (n = 3 radii/coral). This intracoral reproducibility further validates using bamboo coral Ba/Ca for BaSW reconstructions. Sections of the Ba/Ca records that were potentially influenced by noncarbonate bound Ba phases occurred in regions where elevated Mg/Ca or Pb/Ca and coincided with anomalous regions on photomicrographs. After removing these regions of the records, increased Ba/Cacoral variability was evident in corals between ~800 and 1500 m. These findings support additional proxy validation to understand BaSW variability on interannual timescales, which could lead to new insights into deep sea biogeochemistry over the past several centuries.

Mapping urban form and function at city block level using spatial metrics

This paper focuses on the potential of urban metrics describing the presence and the configuration of built-up and open space areas for mapping distinct types of urban form and function at city block level. Next to traditional, patch-based metrics used in landscape ecology, alternative metrics are proposed, measuring the presence and the spatial arrangement of built-up and open space areas along a set of radial transects, along contours parallel to the urban block boundary and along the block's perimeter, as well as metrics describing the internal composition of the built-up area. Use of the proposed metrics for identifying different types of urban form and function was tested on the Brussels Capital Region. Large-scale vector data was used to define built-up structures and to analyse the morphological properties of the built-up area at block level. Decision tree classification was applied in conjunction with bootstrap aggregation to gain insight in the distinctive character of the defined metrics, and the robustness of land use and urban form classification based on these metrics. Our study points out the shortcomings of traditional landscape ecological metrics for mapping urban form and emphasizes the need for alternative approaches for analysing urban landscapes, more explicitly describing the morphological characteristics of the urban fabric.

FLORA MELÍFERA Y SU OFERTA DE RECURSOS EN CINCO VEREDAS DEL MUNICIPIO DE PIENDAMÓ, CAUCA

The honey plants present in the municipality of Piendamo was determined as the basic criterion for honey production planning. Monthly visits were made to 12 apiaries during 2014. The plants were selected based on producers’ knowledge, bibliography and beeworking observation. Plots of 100 square meters were plotted, according to the Gentry method, in different coverings with radial transect of 1 km around the apiary, was carried out the herborization of the melliferous species and monitoring of floristic elements of importance for the hive (coverage, resource offered, Frequency of visits and degrees brix). A total of 150 plants belonging to 30 species, 24 genera and 13 families were collected, the most representative being Asteraceae (20%) and Fabaceae (20%). The floristic elements were analyzed by descriptive statistics and Pearson’s coefficient, stating that the species are mainly present in the coverings of Rastrojo (50%) and wood (26%). The supply is considered nectar-pollinate (70%), with ranges of medium sweetness between 30 and 43 degrees brix (36%) and an average visit frequency (46%), evidencing the honey potential of the region and the importance of the resources offered for the honey harvest.

Using otolith microchemistry to differentiate between stocked and unstocked Australian bass (Percalates novemaculeata)

Understanding the contribution of stocking to fish populations is an essential part of any program to increase fish numbers and abundance. However, subsequent assessments that aim to quantify the success of fish stocking are rarely considered. Juvenile-sized (<200mm) Australian bass (Percalates novemaculeata), from the upper Snowy River, southern New South Wales (NSW), Australia (assumed to be stocked), wild mature-sized (>400mm) fish from estuarine areas of the Snowy River, juveniles (15–30mm) from a commercial Australian bass hatchery facility known to have supplied fish for past stockings in the Snowy River, and wild fish (>400mm) considered as controls from the Clarence River in northern NSW were used for otolith microchemical analysis. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to measure Sr:Ca and Ba:Ca ratios at the otolith core and across radial transects to verify natal origins of fish and more specifically, to confirm the origin of fish caught in the river that were assumed to have originated from a recent stocking program. Otolith core Sr:Ca ratios of juvenile fish collected from the upper Snowy River and hatchery fish were not significantly different suggesting they originated from the same source. Significant differences were found in core Sr:Ca and Ba:Ca between known origin hatchery fish and wild fish. Significantly higher Sr:Ca ratios were found at otolith cores compared to the edges in fish collected from the upper Snowy River, suggesting early life was spent in more saline conditions prior to stocking compared to wild fish. Otolith transect data showed a consistent decrease in Sr:Ca ratios and a simultaneous increase in Ba:Ca ratios at approximately 17–59mm from the core, corresponding with the size at which these fish were stocked. This study has demonstrated that otolith microchemistry can successfully distinguish stocked fish from wild recruits and reveals the timing of natural migrations or artificial translocations.

Old nurses always die: impacts of nurse age on local plant richness

Palatable exotic shrubs plantation in heavily degraded rangeland has been massively managed in arid and semi-arid Algeria. An associated effect observed to these managements is an increase of plant richness in these plantations due to positive interactions involving nurse species that ameliorate stressful environmental conditions. Our objective was to assess the importance and impact of nurse age on the recovery of herbaceous plant species richness. The impact of the shrub presence on the spatial repartition of herbaceous plant richness was quantified, and we tested whether it remains constant with nurse growth and ageing. Using cumulative species richness on radial transects from the nurse centre to nurse external canopy we described the spatial patterns of plant species richness around different Atriplex canescens from saplings to senescent individuals. Resulting cumulative radial species curves were modelled using linear and non-linear models and tested against null models. Nurse volumes and overall plot species richness exhibited a sigmoid shape from 2 to 15 years. The best-fitted models of the radial cumulative species richness changed with the nurse age. In young life stages, a strong positive effect under the shrub was detected. At intermediate life stages, the richness in the subcanopy was significantly impoverished whereas cumulative richness sharply grew under the shrub external canopy. At senescent life stage, cumulative species richness did not indicate a remaining effect of the shrub. An improved description of planted shrubs nurse effect consequences on plot richness is provided and suggests that late plantation opening to stock can concur to the maximization of species richness in afforested plots.

Diffusive transfer of oxygen from seamount basaltic crust into overlying sediments: An example from the Clarion–Clipperton Fracture Zone

The Clarion–Clipperton Fracture Zone (CCFZ) in the Pacific Ocean is characterized by organic carbon-starved sediments and meter-scale oxygen penetration into the sediment. Furthermore, numerous seamounts occur throughout its deep-sea plain, which may serve as conduits for low-temperature hydrothermal seawater circulation through the oceanic crust. Recent studies in deep-sea environments of the Pacific and Atlantic Oceans have suggested and presented evidence of dissolved constituent exchange between the seawater flowing in the basaltic crust and the pore water of the overlying sediments. Through high-resolution pore-water oxygen and nutrient measurements, we examined fluxes and geochemical interactions between the seamount basaltic basement and pore waters of the overlying sediments at three sites located on a radial transect from the foot of Teddy Bare, a small seamount in the CCFZ. At three sites, located 1000, 700 and 400 m away from the foot of the seamount, we found that oxygen concentrations initially decrease with sediment depth but start to increase at depths of 3 and 7 m toward the basaltic basement. Nitrate (NO3−) concentrations mirror the oxygen concentration profiles, as they increase with sediment depth but decrease towards the basement. These profiles suggest an upward diffusion of oxygen from seawater circulating within the seamount crust into the overlying basal sediments and a downward diffusion of NO32− from sediment pore water into the basaltic crust. At one site, we determined that the 87Sr/86Sr ratios of the bottom water and of the deep sediment near the basaltic crust are similar, further supporting diffusive exchange between basaltic crust fluids and sediment pore water.Transport-reaction modeling performed at two of the study sites revealed that (1) the diffusive flux of oxygen from the basaltic basement outpaces the oxygen consumption through organic matter oxidation and nitrification in the basal sediments and (2) the nutrient exchange between the sediment and the underlying basaltic crust occurs at orders-of-magnitude lower rates than between the upper sediment and the overlying bottom water. These results further show that the diffusion of oxygen from the seamount basaltic basement into the overlying pore waters affects the preservation of organic compounds and helps to maintain a completely oxygenated sedimentary column at all 3 sites near the seamount.