Atmospheric phenanthrene pollution modulates carbon allocation in red clover (Trifolium pratense L.)

The influence of atmospheric phenanthrene (PHE) exposure (160 μg m⁻³) during one month on carbon allocation in clover was investigated by integrative (plant growth analysis) and instantaneous ¹³CO₂ pulse-labelling approaches. PHE exposure diminished plant growth parameters (relative growth rate and net assimilation rate) and disturbed photosynthesis (carbon assimilation rate and chlorophyll content), leading to a 25% decrease in clover biomass. The root-shoot ratio was significantly enhanced (from 0.32 to 0.44). Photosynthates were identically allocated to leaves while less allocated to stems and roots. PHE exposure had a significant overall effect on the ¹³C partitioning among clover organs as more carbon was retained in leaves at the expense of roots and stems. The findings indicate that PHE decreases root exudation or transfer to symbionts and in leaves, retains carbon in a non-structural form diverting photosynthates away from growth and respiration (emergence of an additional C loss process).     

Zn isotope study of atmospheric emissions and dry depositions within a 5 km radius of a Pb–Zn refinery

The present paper examines the use of zinc isotopes as tracers of atmospheric sources and focuses on the potential fractionation of Zn isotopes through anthropogenic processes. In order to do so, Zn isotopic ratios are measured in enriched ores and airborne particles associated with pyrometallurgical activities of one of the major Pb–Zn refineries in France. Supporting the isotopic investigation, this paper also compares morphological and chemical characteristics of Zn particles collected on dry deposition plates (“environmental samples”) placed within a 5 km radius of the smelter, with those of Zn particles collected inside the plant (“process samples”), i.e. dust collected from the main exhaust system of the plant. To ensure a constant isotopic “supply”, the refinery processed a specific set of ores during the sampling campaigns, as agreed with the executive staff of the plant. Enriched ores and dust produced by the successive Zn extraction steps show strong isotope fractionation (from ?0.66 to +0.22‰) mainly related to evaporation processes within the blast furnaces. Dust from the main chimney displays a δ⁶⁶Zn value of ?0.67‰. Application of the Rayleigh equation to evaluate the fractionation factor associated with the Zn vapor produced after a free evaporation gives a range of α_ore/vapor from 1.0004 to 1.0008. The dry deposits, collected on plates downwind of the refinery, display δ⁶⁶Zn variations of up to +0.7‰. However, it is to be noted that between 190 and 1250 m from the main chimney of the refinery, the dry deposits show a high level of large (>10 μm) Zn, S, Fe and O bearing aggregates characterized by positive δ⁶⁶Zn values (+0.02 to +0.19‰). These airborne particles probably derive from the re-suspension of slag heaps and local emissions from the working-units. In contrast, from 1720 to 4560 m, the dry deposits are comprised of small (PM10) particles, including spherical Zn-bearing aggregates, showing negative δ⁶⁶Zn values (?0.52 to ?0.02‰). Our results suggest that the source of the distal dry fallouts is the main chimney plume, whose light Zn isotopic signature they preserve. Based on Zn isotopic analysis in combination with morphological and chemical characteristics of airborne particles, the present study suggests the traceability of smelter dusts by Zn isotopes.     

‘Wannabe Toxic-Free?’ From precautionary consumption to corporeal citizenship

Ecological citizens are increasingly encouraged to adopt ‘precautionary consumption’ – a set of practices aimed at shielding them from the potential health harms of exposures to everyday toxics. The utility and the effects of precautionary consumption in relation to common chemical exposures are investigated. Precautionary consumption is not only of questionable utility, but is fundamentally misguided as an approach for inspiring antitoxics organizing. The failure of this approach is in part due to its assumption of a naturally bounded, autonomous individual who is able to maintain an impermeable boundary between herself and the environment. Drawing on the work of material feminist theorists, it is argued that Gabrielson and Parady’s notion of corporeal citizenship, an approach that places bodies into a complex web of material, ecological relations entangled with the social, offers several strategic advantages for framing resistance strategies.     

Importance of Moisture on Stomatal Behavior Of Plants Subjected to Ozone

The stomatal resistance, measured with a ventilated diffusion porometer at various times before, during, and after exposure to 20–25 pphm ozone, was followed in water-stressed or well-watered beans, beans exposed at either low (37%) or high (73%) atmospheric humidity, and two tobacco cultivars exposed at the same two humidities. The two tobacco cultivars that were compared were the 0₃-susceptible Bel W-3 and the 0₃-resistant Consolidated L. The stomata of the water-stressed but unwilted bean plants closed quickly from a resistance of 2.9 ± 0.3 sec/cm to 8.4 ± 1.0 sec/cm when exposed to O₃ whereas those in the unstressed plants closed slowly from a resistance of 2.5 ± 0.6 sec/cm to 5.2 ± 0.8 sec/cm after exposure to O3 for 10 min. Exposure to 0₃ for 30 min in the moist atmosphere caused no change in stomatal resistance of the bean plants whereas in the dry atmosphere the stomata closed from a resistance of 3.7 ± 0.4 sec/cm to 6.7 ± 0.6 sec/cm, but opened again when ozonation was terminated. With tobacco exposed to O₃ in a dry atmosphere the stomata of the 0₃-resistant cultivar closed more rapidly than the 0₃-susceptible variety, whereas in a moist atmosphere the stomata of both cultivars closed slowly and equally during the 60 min of ozonation.     

Effects of past and present livestock grazing on herpetofauna in a landscape‐scale experiment

Livestock grazing is the most widespread land use on Earth and can have negative effects on biodiversity. Yet, many of the mechanisms by which grazing leads to changes in biodiversity remain unresolved. One reason is that conventional grazing studies often target broad treatments rather than specific parameters of grazing (e.g., intensity, duration, and frequency) or fail to account for historical grazing effects. We conducted a landscape‐scale replicated grazing experiment (15,000 km², 97 sites) to examine the impact of past grazing management and current grazing regimes (intensity, duration, and frequency) on a community of ground‐dwelling herpetofauna (39 species). We analyzed community variables (species richness and composition) for all species and built multiseason patch‐occupancy models to predict local colonization and extinction for the 7 most abundant species. Past grazing practices did not influence community richness but did affect community composition and patch colonization and extinction for 4 of 7 species. Present grazing parameters did not influence community richness or composition, but 6 of the 7 target species were affected by at least one grazing parameter. Grazing frequency had the most consistent influence, positively affecting 3 of 7 species (increased colonization or decreased extinction). Past grazing practice affected community composition and population dynamics in some species in different ways, which suggests that conservation planners should examine the different grazing histories of an area. Species responded differently to specific current grazing practices; thus, incentive programs that apply a diversity of approaches rather than focusing on a change such as reduced grazing intensity should be considered. Based on our findings, we suggest that determining fine‐scale grazing attributes is essential for advancing grazing as a conservation strategy.     

Relationships between diversity of grassland vegetation, field characteristics and land use management practices assessed at the farm level

In order to assess the impact of policies to encourage extensification in less favoured areas and improve our knowledge of extensive livestock systems, we analyzed relationships between the diversity of grassland vegetation and land use management practices and field characteristics. This study, conducted on a mountainous area in the centre of France, was based on 149 fields, mainly of natural grasslands belonging to 7 farmers. Regression analyses were performed to analyze the relations between the grassland vegetation types (five types established from the list of dominant species), management practices (cutting versus grazing and fertilization) and the topographic (altitude and aspect) and topologic (slope, distance and surface area) characteristics of the fields. The land use management rules used by the farmers were studied by specifying the grazing management rules of the herd (dairy cows), as well as those for conserved forage (mainly hay or silage) and were identified from observations mentioned on the “grazing schedules”, as well as from interviews at the beginning, in the middle and at the end of the study period. The statistical analysis showed that neither the topographic characteristics of the fields nor the distance from the cowshed or surface area were correlated with the grassland vegetation types. It was the management practices used, largely determined by the field slope, which determined the grassland vegetation type. On the other hand, farmers’ statements showed that the grazing and cutting management rules were mostly determined by the slope of the fields and the distance from the cowshed and, to a lesser extent, by the altitude and aspect. These results showed that the farmers take into consideration environmental differences when choosing fields to allocate for grazing and cutting at different seasons, particularly when they are constrained by these features. Nevertheless, when the constraints were minimal, a wide diversity of grassland vegetation types was also observed. This diversity was a result of attributing different functions to the fields which led to different management practices (defoliation methods and fertilization) and, thus, to different grassland vegetation types. Consequently, for farms where animal feed requirements vary according to the time of the year and the type of animal, we suggest that diversity in the grassland vegetation types is a sound component of these livestock systems.     

Recovery of the Kakerori: An Endangered Forest Bird of the Cook Islands

The Kakerori, or Rarotonga Flycatcher (Pomarea dimidiata) , is an endangered monarch flycatcher endemic to the island of Rarotonga, Cook Islands. This bird was reported to be common until the middle of the nineteenth century, but it declined before 1885 and was thought to be extinct early this century. A small population persisted in the rugged interior of Rarotonga; in 1987 the population stood at 38 birds but was in decline. We determined that introduced predators, especially ship rats (Rattus rattus) , were affecting breeding success. Through a program of experimental management, aimed mainly at rodent control, the population increased from a low of 29 birds in Spring 1989 to 60 birds in Spring 1993. The recovery can be attributed to both improved breeding success and increased adult survivorship.     

RESERVOIR WATER QUALITY SAMPLING DESIGN1

ABSTRACT: The design of monitoring programs often serves as one of the major sources of error or uncertainty in water quality data. Properly designed programs should minimize uncertainty or at least provide a means by which variability can be partitioned into recognizable components. While the design of sampling programs has received recent attention, commonly employed strategies for limnological sampling of lakes may not be completely appropriate for many reservoirs. Based on NES data, reservoirs are generally larger, deeper, and morphologically more complex than natural lakes. Reservoirs also receive a majority of their inflow from a single tributary located a considerable distance from the point of outflow. The result is the establishment of marked physical, biological, and chemical gradients from headwater to dam. The existence of horizontal as well as vertical gradients, and their importance in water quality sampling design were the subject of intensive transect sampling efforts at DeGray Lake, a U.S. Army Corps of Engineers reservoir in southern Arkansas. Data collected were used to partition Variance, identify areas of similarity, and demonstrate how an equitable sampling program might be designed.