Phytoavailability of lead altered by two Pelargonium cultivars grown on contrasting lead-spiked soils

Purpose

This study assesses the potential of two contrasted fragrant Pelargonium cultivars to induce pH and dissolved organic carbon (DOC) changes in the soil solution, Pb speciation, and their subsequent effects on rhizosphere phytoavailable Pb.

Materials and methods

Rooted plantlets were grown in special devices, floating on aerated nutrient solution in PVC tanks. This setup allows roots to be physically separated, through a mesh, from a 3-mm soil matrix layer that can be considered as rhizosphere soil. Two contrasted soils, each spiked with Pb-rich particles, emitted from a battery recycling industry, were used at total burdens of 500 and 1500 mg Pb kg^?1 in addition to a control unspiked soil. Soil solution pH, phytoavailable Pb, DOC, Pb adsorption, precipitation on roots, and Pb phases in soil and plant were investigated.

Results and discussion

Attar of Roses (Attar) cultivar acidified its rhizosphere by 0.4 pH units in both spiked soils. Concolor Lace (Concolor) was unable to change soil solution pH on soil-1 and increased it by 0.7 units on soil 2. Concentrations of Pb in soil solution from Attar plants were always higher than those of Concolor ones. DOC contents of both unspiked soil-1 and soil-2 without plants were not significantly different. In the case of spiked samples, DOC contents in the rhizosphere soil were increased by three and two times for Attar and Concolor, respectively, compared to the unspiked soil without plant. Both cultivars were able to increase DOC contents, independent of soil type and level of contamination. Accumulation of Pb in shoots and roots was higher in Attar as compared to Concolor due to enhanced available Pb as a result of pH and DOC modifications of the rhizosphere soil. Significant amounts of Pb were adsorbed on roots of both cultivars. X-ray elemental analysis of precipitates on roots revealed the association of Pb with P in cylinder-like structures. Extended X-ray absorption fine structure (EXAFS) spectroscopy revealed that Pb was present, to a major extent in the inorganic form, mainly as PbSO₄ in the soil, whereas it was complexed with organic species within plant tissues. The conversion of Pb into organic species could decrease toxicity, may enhance plant tolerance, and could increase translocation.

Conclusions

Plant-induced changes were responsible for the modification of lead phases within the soil. Immobile forms present in the source leaded particles as well as in the soils were converted into soluble species, ultimately improving the phytoavailable or soil solubilized Pb.

     

Evaluation of Methods to Determine Sperm Density for the European eel,Anguilla anguilla

European eel, Anguilla anguilla, is a target species for future captive breeding, yet best methodology to estimate sperm density for application in in vitro fertilization is not established. Thus, our objectives were to evaluate methods to estimate European eel sperm density including spermatocrit, computer‐assisted sperm analysis (CASA) and flow cytometry (FCM), using Neubauer Improved haemocytometer as benchmark. Initially, relationships between spermatocrit, haemocytometer counts and sperm motility were analysed, as well as the effect of sperm dilution on haemocytometer counts. Furthermore, accuracy and precision of spermatocrit, applying a range of G‐forces, were tested and the best G‐force used in method comparisons. We found no effect of dilution on haemocytometer sperm density estimates, whereas motility associated positively with haemocytometer counts, but not with spermatocrit. Results from all techniques, spermatocrit, CASA and FCM, showed significant positive correlations with haemocytometer counts. The best correlation between spermatocrit and haemocytometer counts was obtained at 6000 ×  g (r = 0.68). Of two CASA variants, one or three photographic fields (CASA‐1 and CASA‐2), CASA‐2 showed a very high accuracy to haemocytometer counts (r  =  0.93), but low precision (CV: CASA‐2 = 28.4%). FCM was tested with and without microfluorospheres (FCM‐1 and FCM‐2), and relationships to haemocytometer counts were highly accurate (FCM‐1: r  =  0.94; FCM‐2: r  =  0.88) and precise (CV: FCM‐1 = 2.5; FCM‐2 = 2.7%). Overall, CASA‐2 and FCM‐1 feature reliable methods for quantification of European eel sperm, but FCM‐1 has a clear advantage featuring highest precision and accuracy. Together, these results provide a useful basis for gamete management in fertilization protocols.     

Considering neighborhood effects improves individual dbh growth models for natural mixed-species forests in Mexico

Key message

More accurate diameter at breast height (dbh)-growth models are needed for developing management tools for mixed-species forests in Mexico. Individual distance-dependent dbh growth models that quantify local neighborhood effects have been developed for four species groups in such forests. The performance of the models is improved by distinguishing between inter- and intraspecific group competitions.

Context

The management of mixed-species forests in the northwest of Durango, Mexico, is mainly based on the selection method. Understanding the interspecific and intraspecific competition is critical to developing management tools for such mixed-species forests.

Aims

An individual-based distance-dependent modeling approach was used to model the growth of dbh and to evaluate neighborhood effects for four species groups in Mexican mixed-species stands.

Methods

Twenty-two species were classified into four groups: Pinus (seven species), other conifers (three species), other broadleaves (four species), and Quercus (eight species). Four methods were used to select neighboring trees and 12 competition indices (CIs) were calculated. Comparisons of the neighboring trees selection methods and CIs and tests of assumptions about neighborhood effects were conducted.

Results

Intra-species-group competition significantly reduced diameter growth for all species groups, except for the Quercus group. The Pinus, other conifers, and Quercus groups had significant and negative neighborhood effects on the other broadleaves species group, and not vice versa. The Quercus group also had negative neighborhood effect on the Pinus and other conifers species groups, and not vice versa. The Pinus and other conifers species groups had negative neighborhood effects on each other. All fitted age-independent dbh growth models showed a good of fit to the data (adjusted coefficient of determination larger than 0.977).

Conclusion

The growth models can be used to predict dbh growth for species groups and competition in mixed-species stand from Durango, Mexico.

     

Seasonal and temporal changes in species use of the landscape: how do they impact the inferences from multi-scale habitat modeling?

Context

Multi-scale approaches to habitat modeling have been shown to provide more accurate understanding and predictions of species-habitat associations. It remains however unexplored how spatial and temporal variations in habitat use may affect multi-scale habitat modeling.

Objectives

We aimed at assessing how seasonal and temporal differences in species habitat use and distribution impact operational scales, variable influence, habitat suitability spatial patterns, and performance of multi-scale models.

Methods

We evaluated the environmental factors driving brown bear habitat relationships in the Cantabrian Range (Spain) based on species presence records (ground observations) for the period 2000–2010, LiDAR data on forest structure, and seasonal estimates of foraging resources. We separately developed multi-scale habitat models for (i) each season (spring, summer, fall and winter) (ii) two sub-periods with different population status: 2000–2004 (with brown bear distribution restricted to the main population nuclei) and 2005–2010 (with expanding bear population and range); and (iii) the entire 2000–2010 period.

Results

Scales of effect remained considerably stable across seasonal and temporal variations, but not the influence of certain environmental variables. The predictive ability of multi-scale models was lower in the seasons or periods in which populations used larger areas and a broader variety of environmental conditions. Seasonal estimates of foraging resources, together with LiDAR data, appeared to improve the performance of multi-scale habitat models.

Conclusions

We highlight that the understanding of multi-scale behavioral responses of species to spatial patterns that continually shift over time may be essential to unravel habitat relationships and produce reliable estimates of species distributions.

     

Weeds,aphids, and specialist parasitoids and predators benefit differently from organic and conventional cropping of winter cereals

The aphid–natural enemy interaction in winter wheat fields constitutes a complex system that has been frequently studied because of its implication for biological control. However, not all of the aphids living in cereal fields are crop pests, as there are also aphids living on weeds that may serve as alternative hosts or prey for aphid parasitoids or predators. In this context, a concomitant survey of the plant and insect communities was conducted to understand how different plant communities affect the abundance and richness of aphids and the interactions with their natural enemies. The plant community was split into functional groups (grasses, legumes and forbs), and the aphid community was divided into feeding groups according to their host preferences (specialists in grasses or forbs). The grass aphids, which dominated the total aphid catches, responded positively to grass cover, which was particularly enhanced in the conventional fields. Conversely, the forb aphids, which mainly conditioned the total species richness of the aphids, were closely correlated with the local abundance of legumes. The system of cereal aphid-parasitoids was enhanced in the conventional fields, where the abundance of grasses was higher, whereas the legumes of the organic fields indirectly played a key role in enhancing the richness of the parasitoids and the abundance of predators. Our findings indicate that a bottom-up effect exists throughout the plant community, aphids, and aphidophagous insects and that plant community characteristics should be considered to better understand cereal aphid control.     

A NMR study of water distribution in hardwoods at several equilibrium moisture contents

The water state of one tropical (Robinia coccinea) and two temperate (Acer saccharum and Fagus grandifolia) hardwoods was determined at different equilibrium moisture contents (EMC) during desorption at 25°C. NMR technique was used to separate different components of water in wood. The species studied presented different structures, which were apparent on the spin–spin relaxation T₂ values. Three different water components were separated: slow T₂ (liquid water in vessel elements), medium T₂ (liquid water in fiber and parenchyma elements) and fast T₂ (bound or cell wall water). The NMR results showed that even at equilibrated conditions a region exists where loss of liquid water and bound water takes place simultaneously. This region will vary according to the wood structure. Finally, liquid water was present at EMC lower than the fiber saturation point, which contradicts the concept of this point when considered as a bulk property of wood.     

Heavy metal, total arsenic, and inorganic arsenic contents of algae food products

The total arsenic, inorganic arsenic, lead, cadmium, and mercury contents of 18 algae food products currently on sale in Spain were determined. The suitability of the analytical methodologies for this type of matrix was confirmed by evaluating their analytical characteristics. The concentration ranges found for each contaminant, expressed in milligrams per kilogram of dry weight, were as follows: total arsenic, 2.3-141; inorganic arsenic, 0.15-88; lead, < 0.05-1.33; cadmium, 0.03-1.9; and mercury, 0.004-0.04. There is currently no legislation in Spain regarding contaminants in algae food products, but some of the samples analyzed revealed Cd and inorganic As levels higher than those permitted by legislation in other countries. Given the high concentrations of inorganic As found in Hizikia fusiforme, a daily consumption of 1.7 g of the product would reach the Provisional Tolerable Weekly Intake recommended by the WHO for an average body weight of 68 kg. A more comprehensive study of the contents and toxicological implications of the inorganic As present in the algae food products currently sold in Spain may be necessary, which might then be the basis for the introduction of specific sales restrictions.     

Species proportions by area in mixtures of Scots pine (<Emphasis Type="Italic">Pinus sylvestris</Emphasis> L.) and European beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis> L.)

Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) dominate many of the European forest stands. Also, mixtures of European beech and Scots pine more or less occur over all European countries, but have been scarcely investigated. The area occupied by each species is of high relevance, especially for growth evaluation and comparison of different species in mixed and monospecific stands. Thus, we studied different methods to describe species proportions and their definition as proportion by area. 25 triplets consisting of mixed and monospecific stands were established across Europe ranging from Lithuania to Spain in northern to southern direction and from Bulgaria to Belgium in eastern to western direction. On stand level, the conclusive method for estimating the species proportion as a fraction of the stand area relates the observed density (tree number or basal area) to its potential. This stand-level estimation makes use of the potential from comparable neighboring monospecific stands or from maximum density lines derived from other data, e.g. forest inventories or permanent observations plots. At tree level, the fraction of the stand area occupied by a species can be derived from the proportions of their crown projection area or of their leaf area. The estimates of the potentials obtained from neighboring monospecific stands, especially in older stands, were poorer than those from the maximum density line depending on the Martonne aridity index. Therefore, the stand-level method in combination with the Martonne aridity index for potential densities can be highly recommended. The species’ proportions estimated with this method are best approximated by the proportions of the species’ leaf areas. In forest practice, the most commonly applied method is an ocular estimation of the proportions by crown projection area. Even though the proportions of pine were calculated here by measuring crown projection areas in the field, we found this method to underestimate the proportion by 25% compared to the stand-level approach.     

Genetic diversity of the myrtle rust pathogen (Austropuccinia psidii) in the Americas and Hawaii: Global implications for invasive threat assessments

Since the myrtle rust pathogen (Austropuccinia psidii) was first reported (as Puccinia psidii) in Brazil on guava (Psidium guajava) in 1884, it has been found infecting diverse myrtaceous species. Because A. psidii has recently spread rapidly worldwide with an extensive host range, genetic and genotypic diversities were evaluated within and among A. psidii populations in its putative native range and other areas of myrtle rust emergence in the Americas and Hawaii. Microsatellite markers revealed several unique multilocus genotypes (MLGs), which grouped isolates into nine distinct genetic clusters [C1–C9 comprising C1: from diverse hosts from Costa Rica, Jamaica, Mexico, Puerto Rico, and USA‐Hawaii, and USA‐California; C2: from eucalypts (Eucalyptus spp.) in Brazil/Uruguay and rose apple (Syzygium jambos) in Brazil; C3: from eucalypts in Brazil; C4: from diverse hosts in USA‐Florida; C5: from Java plum (Syzygium cumini) in Brazil; C6: from guava and Brazilian guava (Psidium guineense) in Brazil; C7: from pitanga (Eugenia uniflora) in Brazil; C8: from allspice (Pimenta dioica) in Jamaica and sweet flower (Myrrhinium atropurpureum) in Uruguay; C9: from jabuticaba (Myrciaria cauliflora) in Brazil]. The C1 cluster, which included a single MLG infecting diverse host in many geographic regions, and the closely related C4 cluster are considered as a “Pandemic biotype,” associated with myrtle rust emergence in Central America, the Caribbean, USA‐Florida, USA‐Hawaii, Australia, China‐Hainan, New Caledonia, Indonesia and Colombia. Based on 19 bioclimatic variables and documented occurrences of A. psidii contrasted with reduced sets of specific genetic clusters (subnetworks, considered as biotypes), maximum entropy bioclimatic modelling was used to predict geographic locations with suitable climate for A. psidii which are at risk from invasion. The genetic diversity of A. psidii throughout the Americas and Hawaii demonstrates the importance of recognizing biotypes when assessing the invasive threats posed by A. psidii around the globe.