Longitudinal Transect Research Articles

Quantifying leaf-scale variations in water absorption in lettuce from hyperspectral imagery: a laboratory study with implications for measuring leaf water content in the context of precision agriculture

Variations in water absorption across lettuce leaves (Latuca sativa L. var. longifolia) were quantified from hyperspectral imagery acquired in the laboratory using selected spectral indices, specifically, the Moisture Stress Index (MSI), the Normalised Difference Water Index (NDWI) and the intensity of specific water absorptions at 970 nm (IA970), 1170 nm (IA1170) and 1775 nm (IA1775). Absorption was separately quantified for the midrib, the green parts of the leaves and for whole leaves. Indices were non-linearly related to water content expressed per weight of wet plant material (g g−1) but linearly to water content per unit area of leaf (g cm−2). Indices were weakly correlated with water content in the stem but strongly correlated with water in the green parts of leaves and in whole leaves. Water content in whole leaves was significantly underestimated (P < 0.01) when it was predicted from a model developed for the green parts of leaves, indicating that water content must be derived from the same leaf component used to derive the predictive model. Some indices (NDWI, MSI, IA1170) highlighted intricate reticulated patterns of water absorption across the leaves but these were poorly defined by other indices (IA970, IA1775). Indices extracted from the leaf along transverse and longitudinal transects were qualitatively similar but quantitative analysis indicated that they were significantly different (P < 0.05). The principal contribution of this study is that it highlights the implications of quantifying leaf water content from hyperspectral imagery acquired at spatial resolutions great enough to resolve individual leaf components.

Locality or habitat? Exploring predictors of biodiversity in Amazonia

Amazonia is an environmentally heterogeneous and biologically megadiverse region, and its biodiversity varies considerably over space. However, existing knowledge on Amazonian biodiversity and its environmental determinants stems almost exclusively from studies of macroscopic above‐ground organisms, notably vertebrates and trees. In contrast, diversity patterns of most other organisms remain elusive, although some of them, for instance microorganisms, constitute the overwhelming majority of taxa in any given location, both in terms of diversity and abundance. Here, we use DNA metabarcoding to estimate prokaryote and eukaryote diversity in environmental soil and litter samples from 39 survey plots in a longitudinal transect across Brazilian Amazonia using 16S and 18S gene sequences, respectively. We characterize richness and community composition based on operational taxonomic units (OTUs) and test their correlation with longitude and habitat. We find that prokaryote and eukaryote OTU richness and community composition differ significantly among localities and habitats, and that prokaryotes are more strongly structured by locality and habitat type than eukaryotes. Our results 1) provide a first large‐scale mapping of Amazonian soil biodiversity, suggesting that OTU richness patterns might follow substantially different patterns from those observed for macro‐organisms; and 2) indicate that locality and habitat factors interact in determining OTU richness patterns and community composition. This study shows the potential of DNA metabarcoding in unveiling Amazonia's outstanding diversity, despite the lack of complete reference sequence databases for the organisms sequenced.

Efecto de la cobertura vegetal de ribera en las comunidades ícticas en el bosque húmedo premontano y muy húmedo premontano del Alto Magdalena, Colombia

El objetivo de este estudio fue determinar la influencia de la cobertura vegetal en la composición, la estructura y la diversidad de la ictiofauna en las quebradas de las zonas de vida de los bosques húmedo premontano (bh-PM) y muy húmedo premontano (bmh-PM) del Alto Magdalena, Colombia. Para esto, se muestrearon 23 estaciones distribuidas en las coberturas vegetales de pastos, mosaico de cultivos, arbustos y bosques en las diferentes zonas de vida. En cada estación se establecieron transectos longitudinales (100 m/ancho variable); los peces se capturaron con un equipo de pesca eléctrica y una red de arrastre (5 m x 1,5 m, ojo de malla de 0,05 m), y se evaluaron paralelamente algunas variables ambientales. La estructura y la diversidad de la ictiofauna se calcularon mediante el uso de modelos estándar. En cuanto a la diversidad, medida con números de Hill, no hubo diferencias significativas entre las coberturas vegetales en el bh-PM. Sin embargo, en el bmh-PM la cobertura de pastos fue la más diversa. En el análisis de escalamiento multidimensional no métrico, no se evidenciaron diferencias en la estructura del ensamblaje de peces en los tipos de cobertura vegetal, sin embargo, en el análisis canónico de correspondencias se evidenció que la cobertura de dosel, la calidad de la vegetación de ribera y la elevación influyeron de manera significativa en la composición y la distribución de la ictiofauna. Si bien la cobertura de pastos presentó la mayor diversidad íctica, es un hábitat con degradación del bosque de ribera y cambios en la temperatura, idóneo para el establecimiento de especies tolerantes e invasoras. © 2018. Acad. Colomb. Cienc. Ex. Fis. Nat.

Estimation of Ice Thickness of the Satopanth Glacier, Central Himalaya Using Ground Penetrating Radar

Total volume of stored ice in the Himalayan glaciers is an important quantity for water resource management of the Himalayan catchments. However, direct measurement of glacier-ice thickness is rare in the Indian Himalaya. We have estimated the ice thickness of the debris-covered Satopanth Glacier (SPG) using a ground penetrating radar (GPR). Multiple bistatic, unshielded antennae with frequencies of 16, 20, 40 and 80 MHz were used for this purpose. We have done GPR surveys at various locations over the ablation zone of SPG. However, satisfactory results were obtained only on two transects. Near the glacier snout, a transverse GPR profile shows an ice thickness of 38 ± 3.5–50 ± 3.5 m. We have obtained 98 ± 7–112 ± 7 m ice thickness at a longitudinal transect in the upper ablation zone. To measure the speed of the radar waves in ice, a common midpoint survey was carried out. Our results for the speed of the electromagnetic waves are slightly lower than the standard values of such waves through pure ice.

Growth and physiological sapling responses of eleven Quercus ilex ecotypes under identical environmental conditions

Abstract Studies with holm oak indicate that genetic variation may result in substantial differences in drought tolerance among its ecotypes. However, few trials have studied this variation under common environmental conditions. This study aimed to assess physiological and morphological responses of holm oak saplings for 11 ecotypes that represent a longitudinal transect across south-central Spain (Andalusia). Drought resistance was assessed by measuring growth, xylem water potential, chlorophyll fluorescence, and photosynthesis. Possible relationships among morphological and physiological responses across ecotypes were determined using Pearson product-moment correlations and multiple linear regressions. The response variables were used in multivariate analyses including discriminant function analysis, principal component and cluster analyses. Last, we used sparse Partial Least Squares regression (sPLS) to analyse the relationships between the morpho-physiological responses and biophysical parameters of the parent locations. Our results indicate that Q. ilex ecotypes growing in a common garden setting exhibited substantial variation in morphological and physiological traits. At the end of the growth trial (65 months post-planting), basal diameter, leaf area, and midday water potential were higher in Q. ilex ecotypes from western sites compared to eastern sites across Andalusia. PCA and clustering revealed clear morphological and physiological differentiation in response to gradients of geographical and ecological variation in ecotype origin. Variables that were related to the water regime of the ecotypes, such as seasonal precipitation and evapotranspiration, showed stronger correlations with ecotype responses. Consequently, eastern ecotypes were more likely to spread in response to projected increases in temperatures and declines in summer precipitation; however, western ecotypes would likely decrease in response to hotter and drier summers.

Restored floodplains enhance denitrification compared to naturalized floodplains in agricultural streams

Predicted changes in the timing and magnitude of storms have the potential to amplify water quality challenges associated with agricultural runoff. In agricultural streams of the Midwestern US, floodplain restoration has the potential to enhance inorganic nitrogen (N) removal by increasing the bioreactive surface area for microbially-mediated denitrification. The restoration of inset floodplains via construction of the two-stage ditch increases denitrification compared to channelized systems, however, little is known about how denitrification on restored floodplains compares to those formed naturally when stream channel management lapses. We used sacrificial microcosm incubations and membrane-inlet mass spectrometry (MIMS) to compare denitrification rates in floodplain soils collected along transects in both naturalized and restored floodplains; longitudinal transects spanned two zones in the active floodplain (near-stream, NS vs. middle, MID) and a third zone that reflected upland conditions in the riparian buffer strip (UP). Denitrification rates were 35–49% higher in the restored, inset floodplains compared to naturalized floodplains. Variation in denitrification rates were primarily explained by soil organic matter (OM) and OM was > 20% higher in restored floodplains than naturalized, highlighting the contrasts between stable, constructed floodplains with heterogeneous, depositional bars typical of naturalizing channels. Consequently, restored inset floodplains could remove > 70% more N than the naturalized floodplains during similar storm inundation events.

Transport and deposition of the fire biomarker levoglucosan across the tropical North Atlantic Ocean

Biomass burning impacts biogeochemical cycling, vegetation dynamics and climate. However, interactions between fire, climate and vegetation are not well understood and therefore studies have attempted to reconstruct fire and vegetation history under different climatic conditions using sedimentary archives. Here we focus on levoglucosan, a thermal by-product of cellulose generated during biomass burning, and, therefore, a potential fire biomarker in the marine sedimentary archive. However, before levoglucosan can be applied as a biomass burning proxy in marine sediments, there is a need for studies on how levoglucosan is transported to the marine environment, how it is reflecting biomass burning on continents, as well as the fate of levoglucosan in the marine water column and during deposition in marine sediments. Here we present analyses of levoglucosan, using an improved Ultra High Pressure Liquid Chromatography-Electro Spray Ionization/High Resolution Mass Spectrometry (UHPLC-ESI/HRMS) method, in atmospheric particles, in particulate matter settling through the water column and in marine surface sediments on a longitudinal transect crossing the tropical North Atlantic Ocean at 12°N. Levoglucosan was detected in the atmosphere, although in low concentration, possibly due to the sampled particle size, the source area of the aerosols, or the short time interval of sampling by which large burning events may have been missed. In sinking particles in the tropical North Atlantic Ocean we find that levoglucosan deposition is influenced by a mineral ballast effect associated with marine biogenic particles, and that levoglucosan is not transported in association with mineral dust particles. Highest levoglucosan concentrations and seasonal differences in sinking particles were found close to continents and low concentrations and seasonal differences were found in the open ocean. Close to Africa, levoglucosan concentration is higher during winter, reflecting seasonal burning in northwestern Africa. However, close to South America levoglucosan concentrations appear to be affected by riverine transport from the Amazon River. In surface sediments close to South America, levoglucosan concentration is higher than in the middle of the Atlantic Ocean, implying that here the influence from the South American continent is important and perennial. Our study provides evidence that degradation of levoglucosan during settling in the marine water column is not substantial, but is substantial at the sediment–water interface. Nevertheless, levoglucosan was detected in all surface sediments throughout the tropical North Atlantic, indicating its presence in the marine sedimentary record, which reveals the potential for levoglucosan as a biomass burning proxy in marine sediments.

Ameliorative, Ecological and Landscape Roles of Făget Forest, Cluj-Napoca, Romania, and Possibilities of Avoiding Risks Based on GIS Landslide Susceptibility Map

In the case of forests located in the close proximity of urban centres, the functions and conventional roles of the forests have to be largely reconsidered. An experimental study area was located in Făget Forest, near the city of Cluj-Napoca, North-West of Romania, as a subject to evaluate different natural risks, especially landslides. Although most of this area is stabilized, human activity became in the last period the most aggressive and active factor that can induce changes in slopes stability. The evaluation based on new changes on the terrain and constructions has clearly revealed the effect of the unprecedented urban sprawl and the expansion of infrastructure elements and residential buildings. Landslide susceptibility map was elaborated using a multivariate statistical analysis and the Geographical Information System (GIS) technology on a predetermined path inside the forest, as well as obtaining valuable information about the tree species. Based on 14 surveys, each of them covering an area of 500 m2 on a longitudinal transect of the forest, there were identified relatively few tree species with a significant share: Carpinus betulus (42.9%), Fagus sylvatica (24.9%), Quercus petraea (23.2%), Q. robur (6.3%), Prunus avium (1.2%). Their positive roles on avoiding or limiting the flow on slopes, flooding, landslides etc. are different depending on the position, terrain, forest composition, trees density, slope, exposition, but it is fundamental beneficial. However, these species can assure productive (as wood), ameliorative, ecological, landscape, cultural, educational, relaxation roles, and consequently inestimable values.

ШИРОТНЫЕ ИЗМЕНЕНИЯ РАЗНООБРАЗИЯ ГРИБОВ НА МОДЕЛЬНОЙ ТРАНСЕКТЕ ЕВРАЗИИ, "Известия Российской академии наук. Серия географическая"

Changes in taxonomic, morphological and substrate specificity of distribution of clavarioid fungi were studied at the Oman-Ural longitudinal transect covered over 6300 km from 20° to 80° northern latitude, along 58° eastern longitude. The works were carried out in two scales. First of scale is cells by 100000 km2 inside 12 latitudinal zones, each by 5° latitude, from the tropical deserts of Arabic Peninsula to the Arctic deserts of Novaya Zemlya Islands. Second scale is 50 localities, by 100 km2 area, situated inside 12 latitudinal cells (as in previous scale). For both scales peaks of species richness of fungi in the close ranges of latitudes, from 50 to 60° N latitude for cells in taiga and south-taiga forests, and 50–65° N latitude, are established. The number of species is reduced to almost zero with decreasing latitude. Such results indicate that the distribution of clavarioid fungi from North to South does not correspond to the “classical” latitudinal gradient of diversity. The number of species in the cells of the Arctic and tropical deserts is similar, and the mean number of species in the localities situated in the tropical deserts is lower than in the Arctic counterparts. The richest localities correspond to cells with average annual temperatures from +1.1 to +4.5 °C. The share of species with small and unbranched fruitbodies positively correlated with latitude, as well as the share of species of saprotrofic grassinhabited taxons. The negative correlation is established for leaves-inhabited taxons, and the share of ground species is relatively constant throughout the entire transect. The share of widespread species, for both scales, is maximal at the desert “ends” of transect, whereas is minimal in the middle latitudes, characterized by the highest number of species. This distribution of the microbiota reflects the bioclimatic specificity of transect: a wide spreading of cryo- and arid deserts, and steppes, in which there are no specific species. The distribution of fungi in a greater degree demonstrates no pattern of changes in diversity with latitude, but the rule of limiting under extreme conditions, which is characterized by a decrease in species richness with increasing pessimal conditions.

植物核DNA含量在全球尺度上的纬度变异式样及其气候适应意义——以菊科植物为例

PDF HTML阅读 XML下载 导出引用 引用提醒 植物核DNA含量在全球尺度上的纬度变异式样及其气候适应意义——以菊科植物为例 DOI: 10.5846/stxb201704270777 作者: 作者单位: 上海师范大学,上海师范大学,上海师范大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31070479） Latitudinal variation patterns of plant nuclear DNA amount on a global scale and their environmental adaptation significance: a case study with Asteraceae Author: Affiliation: College of Life and Environmental Sciences,Shanghai Normal University,Shanghai Normal University,College of Life and Environmental Sciences,Shanghai Normal University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:核DNA含量是重要的生物学概念，涉及DNA C-值和基因组大小。前人有关植物核DNA含量在纬度梯度上的变异规律存在着矛盾的报道，而且多数将核DNA含量与纬度、海拔、气候等因素之间的关系描述成线性关系。核DNA含量是否具有环境适应上的意义，也还存在争议。先前有关核DNA含量与环境因素间关系的矛盾性报道可能与取样过小、地理范围过窄、研究对象遗传背景差异过大有关。如果对一个遗传背景相近的类群在全球范围内进行取样，核DNA含量会呈现有规律的纬度梯度变化，可能与大的气候因素之间存在非线性关系。菊科（Asteraceae）是被子植物的最大科，是一个广泛认可的自然分类群。为揭示全球空间尺度上植物核DNA含量在纬度梯度上的变异规律，以及这种变异是否具有环境适应意义，以菊科为对象开展了核DNA含量与纬度、生物气候因素关系的统计分析。从"植物DNA C-值数据库"检索到822种菊科植物的核DNA含量数据；在全球范围内，沿经度方向上设立10条样带，每条样带横跨15个经度，每条样带又均分成22个样块，每个样块纵跨7.5个纬度；其次，从"世界气候数据网站"下载1950-2000年时间段14个生物气候因子数据，应用ArcGIS 9.3获得每个样块14个生物气候因子的平均值；根据"全球生物多样性信息网站"记录，计算每个样块菊科植物平均的核DNA含量数据。为避免气候变量之间的多重共线性对数据分析的影响，应用主成分分析对数据进行了降维，发现最冷季度平均温度、最干季度雨量分别是第一、二主成分上荷载最大的因子，去除与它们相关性在-0.7至+0.7之间的其他气候因子后获得了最冷季度平均温度、最干季度雨量和最湿月份雨量三个变量用于进一步数据分析。结果发现，菊科植物在全球10个样带上的核DNA含量与纬度关系密切，与最冷季度平均温度、最干季度雨量和最湿月份雨量呈现极显著的单峰型的非线性关系，可以用二项式进行拟合。因此，全球空间尺度上植物核DNA含量沿着纬度梯度有规律性的非线性变化，这种变化具有很强的气候适应意义。 Abstract:Nuclear DNA amount is an important biological concept that includes DNA C-value and genome size. There are conflicting reports about latitudinal variation patterns of plant nuclear DNA amount. Relationships of plant nuclear DNA amount with latitude, altitude, and climatic variables have been reported as linear. Disputes also exist as to whether nuclear DNA amount of plants is of environmental adaptation significance. We speculated that the conflicting reports were due to insufficient sampling of the taxa, limitations in the geographical range, and different genetic backgrounds of the samples. Asteraceae is not only the largest family within angiosperms, but also a widely accepted natural taxa. To clarify the latitudinal variation patterns of plant nuclear DNA amount on a global scale, and to explore the possible climatic adaptation significance of these patterns, we conducted a study with Asteraceae to analyze the relationships of nuclear DNA amount with latitude and bioclimatic variables. First, we obtained the data of nuclear DNA amounts of 822 species of Asteraceae from the Plant DNA C-value database. We selected ten global longitudinal transects, each with a span of 15 longitudinal degrees, and evenly divided each transect(from 82.5°N to 82.5°S) into 22 blocks. We obtained geographical records of the 822 species from the Global Biodiversity Information Faculty, together with fourteen bioclimatic factors within these blocks from the Worldclim Global Climate Database. We calculated the average DNA 1C-values and genome sizes of each species in each block. To avoid multicollinearity among the fourteen climatic variables, we performed principal component analysis(PCA) to reduce the dimensionality of the variables. We found that the mean temperature of the coldest quarter and the precipitation of the driest quarter had the highest loads in the first two principal components. The climatic variables with low correlation coefficients(-0.7 to 0.7) with the above two variables were included in the analyses. We found that the nuclear DNA amounts of Asteraceae had a regular latitudinal variation that could be expressed by polynomial functions. The relationships of nuclear DNA amount with the mean temperature of the coldest quarter, the precipitation of the driest quarter, and the wettest month were typically nonlinear with a unimodal pattern, and could be expressed by binominal equations. Therefore, on the global scale, plant nuclear DNA amount changes regularly on latitudinal gradients, which has distinct climatic adaptation significance. 参考文献 相似文献 引证文献

Meiofauna abundance and community patterns along a transatlantic transect in the Vema Fracture Zone and in the hadal zone of the Puerto Rico trench

Despite the increasing sampling effort that occurred in the deep-sea environment during the last decades, knowledge about meiofauna ecology in trenches and Fracture Zones is still scarce. Based on the lack of this information, a longitudinal transect across the Vema Fracture Zone in the North Atlantic was sampled to test whether meiofauna abundances differ between Northeast and Northwest Atlantic basins, separated by the Mid-Atlantic Ridge. Also, for examination of meiofauna depth pattern, the Puerto Rico trench floor, its upper trench slope and the Western North Atlantic abyssal were investigated.In this study, meiofauna communities were dominated by Nematoda (93%) and Copepoda (4%). The highest total abundance of meiofauna was found in the Puerto Rico trench and the lowest in the Western basin. We found significant differences between the Eastern and Western Atlantic basins, which were potentially caused by differences in current regimes. Stronger currents observed in the Western basin possibly led to the coarser sediment grain size observed in this region, and consequently to the lower abundances of the major groups found there. Besides grain size, the total abundance of meiofauna was significantly correlated with total nitrogen, total organic carbon, and water depth. Moreover, our study reveals a trend of increasing abundance of total meiofauna with increasing water depth in the Puerto Rico trench. Also, significant differences between the Western abyssal and the Puerto Rico trench were discovered. Generally, the meiofauna abundance in the investigated area decreased from East to West but increased with increasing water depth in the Puerto Rico trench. Due to funnelling of organic sediments increased food availability towards deeper regions in trenches could occur and promote higher abundance.

Composición y estructura de peces de la microcuenca del río Anchique, Tolima, Colombia

The distribution and abundance of fish is influenced by multiple factors at temporal and spatial scales, and their community composition represent good river integrity indicators. The main objective of this study was to describe the composition and structure of fish assemblages along the Anchique river sub-basin (that drains to Magdalena river), and to test the hypothesis that these communities vary temporally and spatially. For this, four sites (E1, E2, E3 and E4) were sampled along the river (from river birthplace to Magdalena river), during the periods of high and low waters, in 2014. In each site, longitudinal transects (100 m long x 2 m wide, 60 min) were established and fishing was made with both electrofishing and trawl (10 m x 1 m, 0.05 m) nets. Fish samples were fixed and transported to the laboratory for posterior taxonomic identification with the use of keys; fish diversity and structure composition were calculated with the use of standard models. Besides, substrate composition and environmental variables were also considered. A total of 652 fish belonging to 36 species were recorded; high water showed higher values (325 fish with 32 species) than low water period (300 fish with 31 species). Siluriformes was dominant (51 %), followed by Characiformes (32 %), Gymnotiformes (5 %), Cyprinidontiformes and Cichliformes (6 %). Most abundant families were Characidae (28.3 %; 9 spp.), Loricariidae (23.4 %; 8 spp.) and Trichomycteridae (15.0 %; 2 spp.). Kruskal-Wallis test indicated that there is no significant difference among some environmental variables at the temporal level. The values of structural complexity and substrate composition indices showed that E4 had the highest values (0.8), followed by E1 (0.6), and E2 and E3 (0.4). Moreover, E4 had the highest richness and diversity, according to Hill’s number. The canonical correspondence analysis showed that the substrate, and the complexity and width of the river channel, had a significant influence on fish composition and distribution. The fish community richness and diversity did not change temporarily, but did spatially, which could be related to the different structural features of sampling sites.

Changes in standing stock and vertical distribution of benthic foraminifera along a depth gradient (58–2750 m) in the southeastern Arabian Sea

Benthic foraminifera are a reliable proxy to reconstruct past oceanographic conditions. The ecological preferences of benthic foraminifera are usually studied from the core-top samples. The habitat of living benthic foraminifera, however, can be much deeper. Here, we document the vertical distribution of living benthic foraminifera from the Gulf of Mannar, Southeastern Arabian Sea, to find out the sediment depth that contains representative living assemblage and to understand the relationship between ecological parameters and foraminiferal abundance. Additionally, as the region has a well-developed oxygen minimum zone, we also assess the effect of dissolved oxygen, organic carbon (%Corg) and other associated parameters on living benthic foraminifera. The multi-core samples were collected along a longitudinal transect covering the shelf, and slope (58–2750 m), during the post southwest monsoon season. We report that at stations where dissolved oxygen is low (≤1.5 mL/L), >85% of the total living benthic foraminiferal population is confined to the top 0–1 cm section of the sediment and the average living depth decreases up to 0.6 cm. However, in the well-oxygenated waters, especially in the lower slope region, a substantial fraction of the total living benthic foraminiferal population inhabits deeper sections of the sediments. The calcareous benthic foraminifera dominates the foraminiferal population both within and outside the oxygen minimum zone. The absolute abundance of agglutinated benthic foraminifera is more on the continental slope, as compared to the shelf. The infaunal and epifaunal calcareous and agglutinated foraminifera show a different trend. We report that while the bottom water dissolved oxygen and depth controls the absolute abundance of benthic foraminifera, both the %Corg and ambient temperature, affect the relative abundance of living calcareous and agglutinated benthic foraminifera in the Gulf of Mannar.

Drop Size Distribution Climatology in Cévennes-Vivarais Region, France

Mediterranean regions are prone to heavy rainfall, flash floods, and erosion issues. Drop size distribution (DSD) is a key element for studying these phenomena through the hydrological variables which can be derived from it (rainfall rates and totals, kinetic energy fluxes). This paper proposes a five-year (2012–2016) DSD climatology, summarized by scaling parameters for concentration, size, and shape. The DSD network is composed of two longitudinal transects of three OTT Parsivel optical disdrometers each, across the Mediterranean Cevennes–Vivarais region. The influence of several factors are analysed: location (distance from the sea, orographic environment), season, daily synoptic weather situation (derived from geopotential heights, at 700 and 1000 hPa), rainfall type (analysed from 5 min radar data), as well as some combinations of these factors. It was found and/or confirmed that the orographic environment, season, weather patterns associated with the exposure to low level atmospheric flows, and rainfall types influenced the microphysical processes, leading to rainfall, measured at the ground. Consequently, the DSD characteristics, as well as the relationships between the rainfall rate and reflectivity factor, are influenced by these factors.

Characterization and modelling of soil CO2 efflux in old and young irrigated citrus orchards

Soil respiration (Rs) represents the largest CO2 efflux to the atmosphere of terrestrial ecosystems. The regular alternation of wet and dry soil strips prevailing in irrigated orchards is a singular case-study among ecosystems as it may help to understand the impact of the spatial variability of abiotic factors on soil respiration in orange orchards having contrasting age and structural heterogeneity. We characterised Rs in adult (AO) and young (YO) drip-irrigated orange orchards with special focus on the main factors driving Rs site-by-site and across-sites. Tree structure (leaf area index, LAI) was measured fortnightly during two years, whereas Rs, soil temperature (Ts) and moisture (θs) were measured during the same period in dry and wet longitudinal transects parallel to the tree rows. The data sets collected in the field were used to carry out a modelling exercise aimed to predict Rs from only abiotic factors (here Ts and θs) or from a combination of abiotic and biotic (LAI) factors. The modelling results indicated that the seasonal changes of Rs were temperature-driven in predominantly wet transects and moisture-driven in predominantly dry ones; and that the emerging seasonal pattern of spatially-weighted mean soil respiration (Rs,mean) was mainly explained by abiotic factors. An abiotic model assuming a constant value of the reference respiration (Rb,10=Rs at Ts=10°C) was found suitable to describe the temporal variations in Rs,mean within an orchard, but was not able to reproduce the differences in Rs between orchards (R2=0.20). The model fitness was strongly improved (R2=0.80) when Rb,10 was assumed an increasing function of LAI, suggesting that LAI might be a suitable biotic variable for predicting the magnitude of soil respiration in citrus orchards.

The Dominance of Food Supply in Changing Demographic Factors across Africa: A Model Using a Systems Identification Approach

Demographic indicators linked to general health have been strongly linked to economic development. However, change in such indicators is also associated with other factors such as climate, water availability, and diet. Here, we use a systems modelling approach, bringing together a range of environmental, economic, dietary, and health factors, to seek possible dominant causes of demographic change across Africa. A continent-wide, north-south transect of countries allows for the exploration of a range of climates, while a longitudinal transect from the Atlantic to the Red Sea provides a range of socio-economic factors within the similar climatic regime of Sahelian Africa. While change in national life expectancy and death rate since 1960 is modelled to be linked to a varying number and type of factors across the transects, the dominant factor in improving these demographic indicators across the continent is food availability. This has been strongly modulated by HIV infection rates in recent decades in some countries.

Treatment of funnel chest in children

Background. Funnel chest has a relatively high prevalence in the Russian population. Given the high percentage of the unsatisfactory results of thoracoplasty, further research for the development of new treatment methods is needed.&#x0D; Aim. To improve the treatment results for funnel chest in children.&#x0D; Materials and methods. We analyzed the treatment results of 230 children with funnel chest after thoracoplasty. We used 2 surgical techniques: classic thoracoplasty by Nuss (114 children) and its modified version by the authors (116 children). The modified technique included two-sided thoracoscopy, partial resection of the deformed rib cartilages, and endoscopic longitudinal transection of the sternal cortical plate, resulting in subcutaneous emphysema along the sternum.&#x0D; Results. The comparison of the 2 surgical techniques showed no significant difference in terms of duration and invasiveness of the procedure. Recurrent episodes of funnel chest were observed in children who had undergone thoracoplasty before 7 years of age, regardless of the technique used.&#x0D; Conclusion. This study revealed that the author’s modified thoracoplasty method was more effective in children &gt; 14 years of age with rigid funnel chest because it allowed the surgeon to decrease the thoracic pressure on the plate and the plate itself on the ribs, facilitating the repositioning of the sternum and preventing the deformation and development of pressure sores on the ribs.

Isotopic Characterization of Mercury Downstream of Historic Industrial Contamination in the South River, Virginia.

Historic point source mercury (Hg) contamination from industrial processes on the South River (Waynesboro, Virginia) ended decades ago, but elevated Hg concentrations persist in the river system. In an effort to better understand Hg sources, mobility, and transport in the South River, we analyzed total Hg (THg) concentrations and Hg stable isotope compositions of streambed sediments, stream bank soils, suspended particles, and filtered surface waters. Samples were collected along a longitudinal transect of the South River, starting upstream of the historic Hg contamination point-source and extending downstream to the confluence with the South Fork Shenandoah River. Analysis of the THg concentration and Hg isotopic composition of these environmental samples indicates that the regional background Hg source is isotopically distinct in both Δ199Hg and δ202Hg from Hg derived from the original source of contamination, allowing the tracing of contamination-sourced Hg throughout the study reach. Three distinct end-members are required to explain the Hg isotopic and concentration variation observed in the South River. A consistent negative offset in δ202Hg values (∼0.28‰) was observed between Hg in the suspended particulate and dissolved phases, and this fractionation provides insight into the processes governing partitioning and transport of Hg in this contaminated river system.

Aspectos bioecológicos de la ostra de agua dulce Acostaea rivoli (Mollusca, Etheriidae) en el río Opia, Tolima, Colombia

La ostra de agua dulce Acostaea rivoli es una especie endémica de Colombia, que desempeña un papel ecológico relevante en el ecosistema acuático. El presente estudio se realizó en la cuenca del río Opia departamento del Tolima en los meses de septiembre y octubre de 2009, donde se establecieron 18 estaciones de muestreo, en cada una de las estaciones fueron empleados cuadrantes de 1m2 distribuidos en diez transectos longitudinales. Adicionalmente, fue evaluada la distribución vertical entre 1 y 3 m de profundidad. Paralelamente se evaluaron variables fisicoquímicas in situ y se tomaron muestras de agua para la determinación de 12 variables fisicoquímicas. Para evaluar la relación entre la especie y las variables fisicoquímicas se realizó un análisis de componentes principales y una correlación de Spearman. Fueron observados 303 organismos, donde la mayor densidad se presentó en la estación Lorencito con 6,67 ind/m2 y la menor densidad en las estaciones puente Doima, molino federal y quebrada Opia en donde no se registró ningún individuo. Con relación al perfil vertical la mayor densidad se presentó en el primer metro con 29,62 ind/m2 y la menor en el tercer metro con 4,50 ind/m2. Las variables fisicoquímicas que influyeron de forma significativa en la distribución y densidad de la población fueron la alcalinidad (r=0,698; p=0,001), dureza (r=0,650; p=0,004), pH (r=0,714; p=0,001), cloruros (r= -0,530; p=0,024), fosfatos (r= -0,603; p=0,008), nitratos (r= -0,490; p=0,039) y coliformes totales (r= -0,540; p=0,021). Estas variables podrían estar relacionados con los procesos de mineralización de la cuenca, que junto con un alto porcentaje de calcio, una buena oxigenación del agua y un sustrato adecuado estarían relacionados con la presencia de esta especie en la zona de estudio. © 2017. Acad. Colomb. Cienc. Ex. Fis. Nat.

Distribution and fractionation of rare earth elements and Yttrium in suspended and bottom sediments of the Kali estuary, western India

Concentrations of rare earth elements (REE) and yttrium (Y), and major metals (Al, Fe and Mn) were measured in suspended particulate matter (SPM) and bottom sediments of the Kali estuary, western India, for their distribution and fractionation. The contents of SPM and metals in it were more uniform along the longitudinal transect during the monsoon. During the post- and pre-monsoons, low SPM in the upper/middle estuary coincided with high Fe and Mn and total REE (∑REE). But in the lower estuary SPM and its ∑REE content increased seaward, while Fe and Mn decreased. The Y/Ho ratios decreased seaward during the monsoon but increased during the post-monsoon. Sm/Nd ratios were more uniform along the transect during monsoon but decreased marginally seaward in other seasons. The Post-Archean Average Australian Shale (PAAS)-normalized REE patterns exhibited middle REE and heavy REE enrichment with positive Ce ($${\text{Ce}}/{\text{Ce}}^{*}$$ ), Eu ($${\text{Eu}}/{\text{Eu}}^{*}$$ ) and Y anomalies. The $${\text{Ce}}/{\text{Ce}}^{*}$$ increased but $${\text{Eu}}/{\text{Eu}}^{*}$$ decreased marginally seaward. The fine-grained sediments showed higher ∑REE and lower Y/Ho ratios than in coarse-grained sediments. The PAAS-normalized REE patterns of sediment were similar to that of SPM. The results revealed two processes, colloidal flocculation and coagulation of metals in the low-salinity zone and an estuarine turbidity maximum in the high salinity zone. Rare earths and yttrium (REY) in SPM and sediments primarily reflected the source rock composition than that of chemical weathering. Apart from physico-chemical processes, the mineralogy and grain size of sediments controlled the distribution and fractionation of REY in the estuary.