Rare earth and other trace and major elemental distribution in a pedogenic calcrete profile (Slimene,NE Tunisia)

A calcrete profile developed on the top of a calcareous consolidated dune located in a coastal area of NE Tunisia (semi-arid climate) was studied with the aim to investigate the behavior of the chemical elements (rare earth elements—REE—and other trace and major elements) during the processes associated with calcrete formation, particularly dissolution and precipitation of carbonates in the vadose zone. The profile shows a vertical sequence, with clear zonations from the surface downwards: a reddish soil at the land surface, a nodular horizon, a laminar-structured level, and the consolidated old dune. Chemical and mineralogical analyses of samples from all levels were performed by neutron activation analysis and X-ray diffraction (bulk samples and < 2 μm fraction). Detailed studies of iron speciation and iron minerals were done by Mössbauer spectroscopy. Microfauna, mineralogical and chemical variations in the Slimene weathering profile point to a long term aerial exposure of the old dune in a semi-arid carbonated environment leading to the development of a pedogenic calcrete profile. The mineralogical variations with depth indicate carbonate dissolution at the surface and downward leaching of calcium. Secondary carbonates overgrow primary ones and precipitate as coating or concretions below. Minerals found in the upper levels correspond to original materials of the old dune and also weathering phases and atmospheric inputs. Phyllosilicates decrease while calcite and K-feldspars increase with depth. Kaolinite was the only clay mineral found in the old dune. Illite and chlorite were also found in all samples with calcrete. Authigenic smectite formation occurs above the laminar-structured calcrete due to restricted drainage conditions. The most significant chemical variations associated with the calcrete formation are (i) enrichment of Co, U, Br, and REE in calcrete; (ii) depletion of middle REE in the upper levels, particularly Eu, and enrichment of middle REE and heavy REE in calcrete; and (iii) Hf, Zr, Cr, Th, Cs, Ta, Ga, Rb, and K appear to be retained in the upper levels, where calcite has been dissolved. Here iron is more reduced. Fe³⁺ occurs in iron oxides (goethite and hematite), and clay minerals. The ratio goethite/hematite appears to increase down the profile; and Fe²⁺ is mainly present in clay minerals.     

The efect of Zinc (Zn) application on the available Iron (Fe) contents of calcareous soils in thrace region

This research was carried out in order to determine the effect of zinc (Zn) application on the available iron (Fe) contents of calcareous soils in Thrace Region. For this purpose, an experiment was carried out in greenhouse conditions by maize growing. The effect of increasing rates of Zn application on the biological indices of maize plant was determined. Fe concentration of maize plant decreased with Zn application and dry matter yield and Fe uptake of maize plant increased with Zn application. These decreases and increases were determined to be statistically significant (P&lt;0.01).     

Factors controlling the erosion rates in a semi-arid zone (Bardenas Reales,NE Spain)

Bardenas Reales is an erosive depression 415 km² in area located in the central-western part of the Ebro Depression. Tertiary sediments crop out in the margin of the basin whereas Quaternary sediments, Holocene in age, occur only in its centre. These Holocene sediments (clays and silts) are the result of the erosion and weathering of the Tertiary clays and are made up of 3 different stratigraphic units. Erosion is clearly the dominant process in the centre of the depression, generating gullies up to 10 km in long and 8 m deep. In order to analyse and quantify the erosion rates of the studied area, erosion was measured on two Soil Erosion Plots with volumetric and instrumental techniques that have been supplied for the last 12 years. The results show that the estimated erosion rates depend extrinsically on the used method and intrinsically on the time of the year in which they are measured. The most accurate values are those obtained by means of collector devices. The values obtained by the microtopographic profile gauge are overestimated, while the results of the measurement with erosion pins are clearly lower. The study area is located in a semi-arid environment, with two pluviometric maximums, in spring and autumn, associated with convective storms. In summer and winter, rainfall is related to Atlantic cyclonal fronts. Soil loss is significant during the pluviometric maximums when rainfall quantity and intensity are higher. During cyclonal periods, in contrast, water erosion is null or scarce and soil loss is related to mudflows. In addition, the erosion rates of each Holocene unit are different. The C2 Holocene unit has undergone greater erosion because of its physico-chemical properties. All the stratigraphic units have similar characteristics regarding Tertiary materials. Since 1993 the average erosion rate measured by the collector device on the Tertiary materials is 32 Mg ha^− 1 year^− 1 and 77 Mg ha^− 1 year^− 1 in the Holocene.     

Chemical Speciation of Heavy Metals in the Fractionated Rhizosphere Soils of Sunflower Cultivated in a Humic Andosol

Chemical speciation and bioaccumulation factor of iron (Fe), manganese (Mn), and zinc (Zn) were investigated in the fractionated rhizosphere soils and tissues of sunflower plants grown in a humic Andosol. The experiment was conducted for a period of 35 days in the greenhouse, and at harvest the soil system was differentiated into bulk, rhizosphere, and rhizoplane soils based on the collection of root-attaching soil aggregates. The chemical speciations of heavy metals in the soil samples were determined after extraction sequentially into fractions classified as exchangeable, carbonate bound, metal–organic complex bound, easily reducible metal oxide bound, hydrogen peroxide (H₂O₂)–extractable organically bound, amorphous mineral colloid bound, and crystalline Fe oxide bound. Iron and Zn were predominantly crystalline Fe oxide bound in the initial bulk soils whereas Mn was mainly organically bound. Heavy metals in the exchangeable form accumulated in the rhizosphere and rhizoplane soils, comprising <4% of the total content, suggesting their relatively low availability in humic Andosol. Concentrations of organically bound Fe and Mn in soils decreased with the proximity to roots, suggesting that organic fraction is the main source for plant uptake. Concentrations of Mn and Zn in the metal–organic complex also decreased, indicating a greater ability of sunflower to access Mn from more soil pools. Sunflower showed bioaccumulation factors for Zn, Fe, and Mn as large as 0.39, 0.05, and 0.04 respectively, defining the plant as a metal excluder species. This result suggests that access to multiple metal pools in soil is not necessarily a major factor that governs metal accumulation in the plant.     

Morphological analysis and erosion rate evaluation in badlands of Radicofani area (Southern Tuscany — Italy)

Since 1988, geomorphologic research based on field surveys and photo-geological analysis, has been conducted in southern Tuscany (Italy), in areas characterised by very rapid morphological evolution. In the area outcrop Pliocene marine claystones uplifted during the Quaternary up to 750 m above sea level, now undergoing intense erosion processes, leading to considerable badlands formation. Morphodynamic analysis, conduced by direct and indirect measurements in a sample area, were taken in order to quantify the erosion rate in badland areas. The “Torrente Piantrafolla” sample area was chosen as representative of the study area; it was most recently monitored during the period Nov. 2000–Feb. 2004. At this time, morphographic and morphometric analyses carried out in selected measurement stations located on slopes, identified gravity as the main morphogenetic process responsible for slope shaping. The calanchi badland areas are characterised by constant and rapid shrinking of their edges resulting from landslides which occur in autumn and winter as a consequence of intense rainstorms. Selected measurement stations indicate an erosion rate value range from 5 to 7.5 cm/y. The comparison between 1976 and 1994 digital elevation models (DEM), obtained from photogrammetric restitution, indicated a mean erosion rate of about 5 cm/y in a nineteen year period. This value, considerably higher than the values measured in other Italian basins, indicate a very rapid evolution of the slopes, due mainly to small earth flows inside calanchi badlands.     

Ability of the earthworms Aporrectodea rosea and Aporrectodea trapezoides to increase plant growth and the foliar concentration of elements in wheat (Triticum aestivum cv. spear) in a sandy loam soil

In a greenhouse study, the ability of the earthworms Aporrectodea rosea and A. trapezoides to influence the foliar concentration of elements and the growth of wheat plants was assessed 27 days after sowing in a sandy loam soil. The presence of A. rosea and A. trapezoides (at densities equivalent to 314 and 471 m^-2, respectively) caused a significant increase in the shoot dry weight of wheat. The presence of A. rosea and A. trapezoides (at densities equivalent to 314 and 157 m^-2, respectively) was also associated with a significant increase in the root dry weight of wheat. The presence of A. rosea caused a significant increase in the foliar concentration of Ca, Cu, K, Mn, N, Na, and P, but did not influence the foliar concentration of Al, B, Fe, Mo, Mg, S, and Zn. The presence of A. trapezoides was associated with a significant increase in the foliar concentration of Al, Ca, Fe, K, Mn, N, and Na, but did not influence the foliar concentration of B, Cu, Mo, Mg, P, S, and Zn. These results demonstrate the potential of A. rosea and A. trapezoides to increase the growth of wheat in a sandy loam soil and suggest that the mechanism by which they increased plant growth was, in part, through increasing the availability and uptake of nutrients from this soil.     

Identification of uncultured bacteria tightly associated with the intestine of the earthworm Lumbricus rubellus (Lumbricidae; Oligochaeta)

The bacteria associated with the intestine and casts of the earthworm Lumbricus rubellus Hoffmeister, 1843, were examined by direct counts, culturability studies, 16S rRNA gene clone libraries, and fluorescent in situ hybridization (FISH). A significant fraction, 24-47%, of the total numbers of prokaryotes remaining in the intestine after casting were tightly associated with the intestinal wall. Bacterial 16S rRNA gene clone libraries constructed from washed earthworm intestinal tissue suggested that the bacterial community was dominated by a few phylotypes that were either absent from, or in low abundance, in the casts. The specific phylotypes present depended on the date of sampling and included representatives of the Acidobacteria, Firmicutes, β-Proteobacteria, and one phylogenetically deep, unclassified group. Juvenile earthworms subsequently collected contained three of the four phylotypes observed in the intestine clone libraries. The Firmicutes phylotype was examined by FISH and was found to be a short rod that represented only a small fraction of the total population of the juvenile samples. These results suggested that the microbial community tightly associated with the intestine was dominated by a small number of phylotypes and that this association was opportunistic rather than obligate.     

Effectiveness and geomorphological impacts of check dams for soil erosion control in a semiarid Mediterranean catchment: El Cárcavo (Murcia, Spain)

The construction of transverse structures (check dams) is a widely used method in Spanish Mediterranean areas to stabilise gullies and ephemeral streams, to reduce channel incision and to prevent sediment deposition downstream. The effectiveness of check dams and their effects on the morphology of ephemeral channels (ramblas) were investigated in a semiarid, highly degraded catchment. In the study area, 36 dams were surveyed, of which 29 were filled up with sediments, 2 had been destroyed and only 5 had still not completely filled with sediments. The streams above the dams held sediments, which resulted in a decrease in the longitudinal gradient. Field observations of changes in the cross-sectional shape of the stream channel, the composition of channel bed material, and bankfull stage measurements indicated that the dams cause erosion downstream. The amount of sediments stored by the dams was found to be higher than the amount of eroded material in the downstream reaches of the dam.     

Ethnobotanical,morphological, phytochemical and molecular evidence for the incipient domestication of Epazote (<Emphasis Type="Italic">Chenopodium ambrosioides</Emphasis> L.: Chenopodiaceae) in a semi-arid region of Mexico

Use and management of wild and weedy species may involve artificial selection, which can determine morphological, physiological, reproductive, and genetic divergences between wild and managed populations, resulting in the initial or incipient phases of plant domestication. In this study we combined ethnobotanical, morphological, phytochemical and genetic information for analyzing differences between managed and unmanaged populations of the Mexican edible weed, Epazote (Chenopodium ambrosioides L.), in Santa María Tecomavaca, Oaxaca, a rural community within the Tehuacán-Cuicatlán Biosphere Reserve, Mexico. Our hypothesis was that differences in morphology (e.g. leave dimensions and density of pubescence), phytochemistry (e.g. flavor, odor, and amount of strong scented and toxic compounds) and/or molecular genetic markers, between managed and wild populations of Epazote in Santa María Tecomavaca, would indicate that managed populations have been and/or are under a process of incipient domestication. Our results revealed the existence in the study area of morphological variants associated with a gradient of management intensity, which involved apparent improved palatability correlated with a lowering of chemical defense. Most remarkably, we found agreement in the groupings defined by the cluster analyses of morphological and genetic data. Although Epazote is considered a weed or, at best, a minor crop, the results from four lines of evidence (cultural differentiation patterns, gigantism, reduction in chemical defenses, toxic compounds and inheritance of adaptive traits) suggest the existence of an incipient domestication process in the study zone.     

Fungal communities associated with the decomposition of a common leaf litter (Quercus leucotrichophora A. Camus) along an elevational transect in the Central Himalaya

Summary We studied the fungal communities associated with decomposing common leaf litter (Quercus leucotrichophora A. Camus) placed in five forests of Central Himalaya between the elevations of 330 and 2150 m. During the initial period of decay, conciding with the rainy season, a progressive increase in fungal counts and species diversity was observed in all forest sites. The sal forest site had a greater weight loss and supported the largest fungal densities, whereas the pine forest had a lower weight loss and the smallest fungal densities. Deuteromycetes were the dominant group in all the forest sites. Most of the species isolated during the annual cycle of the forest sites were of the accidental type. Species diversity and fungal counts on the common leaf litter were markedly affected by the environmental changes brought about by the native leaf litter. This effect was most obvious in the chir pine forest site where the leaf litter of the native dominant species was distinctly more resistant to decay than those of the other sites, making the soil environment of the site markedly different from that of other sites. The pattern of fungal-species changes with progressive decay of the substrate was similar to that suggested by the tolerance model of Connel and Slatyer.     

Impact of the heatwave in 2003 on the summer CH4 budget of a spruce forest with large variation in soil drainage: A four‐year comparison (2001–2004)

Well‐aerated soils are sinks for atmospheric methane (CH₄) whereas hydromorphic soils act as sources. Both CH₄ oxidation and production are highly sensitive to variation in soil moisture. Significant changes of net CH₄ fluxes from soils can therefore be expected to accompany redistribution of precipitation in the course of climate change where more extreme events are predicted for the future. The extreme summer drought in 2003 offered the opportunity to study the impact of such events on methane fluxes under field conditions. The objective was to evaluate the impact of the summer drought in 2003 on net methane budget of a spruce‐forest ecosystem. We studied net CH₄ flux (bi‐)weekly during the summers of 2000–2004 using a closed‐chamber technique on six different soil types ranging from well‐aerated Cambisols, to poorly drained Gleysols and a wet Histosol in a cool‐humid spruce forest.     

Extinction of a shark population in the Archipelago of Saint Paul’s Rocks (equatorial Atlantic) inferred from the historical record

Detecting and determining the validity of local extinctions is an important conservation measure in order to uncover management failures. There are quantitative and qualitative methods that estimate extinction probability based on past sighting records. However, because current baselines about species’ abundances and distributions in the sea were mostly established after humans had started affecting marine populations, researchers must often rely on historical data to elucidate past environmental conditions. We review early historical records from the Archipelago of Saint Paul’s Rocks, together with data from recent expeditions, with the aim of testing the hypothesis that reef sharks (Carcharhinus spp.) have become extinct there. Our analyses are based on non-parametric probabilistic tests for extinction and on a qualitative framework to examine and judge as objectively as possible the likelihood of local extinction. Until the mid-20th century, visitors to St. Paul’s Rocks invariably commented on the remarkable number of sharks around the Archipelago. These observations contrast with those of expeditions carried out during the last decade, which report no carcharhinid reef sharks while scuba diving in the archipelago, despite many more hours of underwater fieldwork than previous expeditions. All quantitative and qualitative methods conclude that the reef shark Carcharhinus galapagensis is locally extinct at St. Paul’s Rocks after a sharp decrease in abundance that took place following the commencement of fishing. However, the persistence of occasional individuals of the once locally common Carcharhinus falciformis in the vicinity of the Archipelago, as a result of constant immigration of this oceanic species from outside the area, suggest that the population might recover if the present fishing pressure was removed.     

CAST基因5'调控区的多态性与鸡肉质性状的关联性分析

为探讨钙蛋白酶抑制蛋白(Calpastatin,CAST)基因5'调控区的多态性与鸡肉质性状的关系,本研究以中国农业科学院家禽研究所选育的F、D、Y、B和S3等5个优质肉鸡(Gallus gallus)品系为试验素材,利用聚合酶链式反应限制性片段长度多态性(polymerase chain reaction-restriction fragment length polymorphism,PCR-RFLP)技术检测CAST基因的SNPs,并分析其多态性与肌肉pH值、维生素B1、肉色、系水力、肌内脂肪和肌纤维密度之间的关系.结果显示,在距CDS-198位点发现1个突变位点(G→A),G-198A位点检测到3种基因型GG、GA和AA,相关分析显示,AA基因型个体的肌内脂肪和肌纤维密度显著高于GG型和GA型个体(P＜0.05),而其他肉质性状无显著差异(P＞0.05).由此可见,对于肉质性状而言,AA是最有利基因型,本研究结果初步表明CAST基因G-198A多态位点的A等位基因是提高鸡肉质性状的一个潜在的DNA标记.     

Landscape changes influence the reproductive behaviour of a key ‘capital breeder’ snake (Boa constrictor occidentalis) in the Gran Chaco region, Argentina

Many wild reptile species are threatened by habitat loss. However, the way in which changes in landscape patterns influence intraspecific ecological processes is not completely understood. Boa constrictor occidentalis is an endangered species and has a special conservation value since it is endemic of dry forests in the Gran Chaco region. Because the Gran Chaco is largely threatened due to habitat loss it is necessary to know how landscape changes influence this species. Therefore, we evaluated the effects of forest loss and landscape composition on the reproductive life-history parameters. Landscape changes were assessed by analyzing satellite imagery and reproductive parameters were determined by ultrasound images of the reproductive structures. The obtained results indicate that habitat loss may affect body condition, clutch size and testicular volume of the Argentine boa constrictor. We also found that the spatial pattern of vegetation influences the distribution of females and males in the landscape. Matting aggregations are scarce in shrublands. Therefore, our study shows that forest loss could enhance vulnerability to extirpation through constraints placed on reproduction. We encourage resource managers to evaluate sensitive reproductive life-history parameters as well as habitat deterioration to asses the conservation status of the populations of the Argentine boa constrictor. Since the Gran Chaco forest, a key habitat to the species’ reproduction, is largely threatened, strong conservation action is needed to halt and reverse forest loss in this region.     

Analysis of genetic diversity in Indian robusta coffee genepool (<Emphasis Type="Italic">Coffea canephora</Emphasis>) in comparison with a representative core collection using SSRs and AFLPs

Genetic diversity among 40 accessions (Coffea canephora) of robusta coffee genepool available in India was determined in comparison with 14 representative samples from a C. canephora core collection and three accessions of C. congensis, using amplified fragment length polymorphism (AFLP) and simple sequence repeats (SSR) markers. Both these molecular approaches were able to generate unique fingerprints for each of the accessions analysed. All the 12 SSR primers used in the present study were found polymorphic, with an average of six alleles per primer pair. Comparative analysis revealed the higher amount of diversity in representatives from a core collection than in the Indian genepool. Moreover, a total of 205 polymorphic AFLP bands were scored in all the 57 accessions analysed. The genetic relationship among 57 accessions was compared on the basis of SSR and AFLP polymorphisms. Genetic similarity dendrograms showed high correlation between the two marker systems. This study clearly established the high amount of diversity present in core samples, which is not represented in Indian genepool. Furthermore, the three accessions of C. congensis did not exhibit any significant diversity from other robusta accessions supporting the school of thought that C. congensis forms a biotype of C. canephora. The potential use of SSRs and AFLP markers in genetic diversity analysis for better ex situ management and also for exploitation of diversity in breeding programmes is discussed.     

Microcalorimetric study of changes in the microbial activity in a humic Cambisol after reforestation with eucalyptus in Galicia (NW Spain)

The microcalorimetric technique was used to analyse the influence of successive reforestations with Eucalyptus globulus Labill, a fast growing species, on the microbial activity in soil. With this aim, samples of similar origin soils, humic-eutrophic Cambisol, were collected from two adjacent land plots. One of the plots, to be taken as the reference, was not subjected to man activities for the last 100 years. The other plot was subjected to two reforestations in the last 20 years. For collection of the two samples, 100 m² homogeneous and perfectly defined zones were chosen in each of the adjacent land plots to obtain final representative bulk samples of 400 g each.The study was carried out using the microbial population as a bioindicator of the productive potential in soil. The experiments were carried out using 1 g soil samples that were treated with 1.25 mg glucose and stored at 4 °C for 3 months. The analysis was complemented by the determination of physical, chemical, and biological properties and environmental parameters.The study was performed over 1 year and samples were seasonally collected (spring, summer, autumn and winter) in the same zone situated in Viveiro (Galicia, NW Spain) with the objective of checking the influence of environmental conditions on the microbial activity in the two soils studied.From the measured results, it can be observed that soils subjected to reforestations suffer not only important changes in physical structure, such as an increase in bulk density, from 600 to 660 kg m⁻³, a reduction in hydraulic conductivity, from 8.85×10⁻³ to 4.4×10⁻³ m s⁻¹, or a decrease in the C-to-N ratio, from 13 to 8, but also they have lower microbial activity, for example 2.84 J g⁻¹ in the reforested soil versus 6.14 J g⁻¹ in the reference soil, in spring, thus presenting a lower productive potential that suggests the use of both amendments and adequate management techniques to ensure a sustainable exploitation, thus avoiding future degradation of soil.