THE IMPACT OF BURNING AND GRAZING OF HEATHLAND PLANTS AND INVERTEBRATES IN COUNTRY ANTRIM

The impact of burning and grazing on plant, ground beetle and spider species was investigated experimentally in stands of varying ages (burnt in 1982 and 1988 and unburnt plots) on an area of heather moorland in County Antrim, north-east Ireland. Burning initiated complex succession pathways which appear to have characteristic plant and invertebrate species associations. Removal of Calluna dominance initiated a period of high plant species diversity. Investigation of initial post-fire regeneration suggested that the frequency of occurrence of plant species changed over time and was affected by grazing. Grouping of species by the position of their renewal bud, i.e. their life-form, did not account for all observed interspecific variation. The dominant species after burning were Eriophorum vaginatum, E. angustifolium and Vaccinium myrtillus. Studies of vegetation canopy structure showed that, even with the exclusion of the main grazing herbivores, Calluna will not re-establish itself as the dominant species until several years after burning. The ground beetle Nebria salina was trapped more often on plots burnt in 1988 than on unburnt plots or those burnt in 1982. In comparison, Pterostichus niger and Carabus granulatus were trapped in greater numbers on plots burnt in 1982 than on unburnt plots and plots burnt in 1988. The large species Carabus problematicus and Carabus glabratus were trapped in greater numbers on unburnt plots. Similarly, more of the spiders Ceratinella brevipes and Centromerita concinna were trapped on the plots burnt in 1982. In comparison, Lepthyphantes zimmermanni and Robertus lividus were trapped more often on unburnt plots than on plots burnt in 1982 and 1988. Results are discussed with respect to the importance of the continuation of traditional heathland management practices.

Job Strain and Tobacco Smoking:An Individual-Participant Data Meta-Analysis of 166 130 Adults in 15 European Studies

BACKGROUND: Tobacco smoking is a major contributor to the public health burden and healthcare costs worldwide, but the determinants of smoking behaviours are poorly understood. We conducted a large individual-participant meta-analysis to examine the extent to which work-related stress, operationalised as job strain, is associated with tobacco smoking in working adults. METHODOLOGY AND PRINCIPAL FINDINGS: We analysed cross-sectional data from 15 European studies comprising 166 130 participants. Longitudinal data from six studies were used. Job strain and smoking were self-reported. Smoking was harmonised into three categories never, ex- and current. We modelled the cross-sectional associations using logistic regression and the results pooled in random effects meta-analyses. Mixed effects logistic regression was used to examine longitudinal associations. Of the 166 130 participants, 17% reported job strain, 42% were never smokers, 33% ex-smokers and 25% current smokers. In the analyses of the cross-sectional data, current smokers had higher odds of job strain than never-smokers (age, sex and socioeconomic position-adjusted odds ratio: 1.11, 95% confidence interval: 1.03, 1.18). Current smokers with job strain smoked, on average, three cigarettes per week more than current smokers without job strain. In the analyses of longitudinal data (1 to 9 years of follow-up), there was no clear evidence for longitudinal associations between job strain and taking up or quitting smoking. CONCLUSIONS: Our findings show that smokers are slightly more likely than non-smokers to report work-related stress. In addition, smokers who reported work stress smoked, on average, slightly more cigarettes than stress-free smokers.

Uptake and translocation of inorganic and methylated arsenic species by plants

The uptake and translocation into shoots of arsenate, methylarsonate (MA), and dimethylarsinate (DMA) by 46 different plant species were studied. The plants (n = 3 per As species) were exposed for 24 h to 1 mg of As per litre under identical conditions. Total arsenic was measured in the roots and the shoots by acid digestion and inductively coupled plasma mass spectrometry from which, besides total As values, root absorption factors and shoot-to-root transfer factors were calculated. As uptake into the root for the different plant species ranged from 1.2 to 95 (mu g of As per g of dry weight) for As-V, from 0.9 to 44 for MA(V) and from 0.8 to 13 for DMA(V), whereas in shoots the As concentration ranged from 0.10 to 17 for As-V, 0.1 to 13 for MA(V), and 0.2 to 17 for DMA(V). The mean root absorption factor for As-V (1.2 to 95%) was five times higher than for DMA(V) (0.8 to 13%) and 2.5 times higher than for MA(V) (0.9 to 44%). Although the uptake of arsenic in the form of As-V was significantly higher than that of MA(V) and DMA(V), the translocation of the methylated species was more efficient in most plant species studied. Thus, an exposure of plants to DMA(V) or MA(V) can result in higher arsenic concentrations in the shoots than when exposed to As-V. Shoot-to-root transfer factors (TFs) for all plants varied with plant and arsenic species. While As-V had a median TF of 0.09, the TF of DMA(V) was nearly a factor of 10 higher (0.81). The median TF for MA(V) was in between (0.30). Although the TF for MA(V) correlates well with the TF for DMA(V), the plants can be separated into two groups according to their TF of DMA(V) in relation to their TF of As-V. One group can immobilise DMA(V) in the roots, while the other group translocates DMA(V) very efficiently into the shoot. The reason for this is as yet unknown.

Levels of cadmium and zinc in soil and plants following the toxic spill from a pyrite mine, Aznalcollar, Spain

On 25 April 1998, a breach of the tailings dam of the Los Frailes pyrite mine in southwestern Spain resulted in the release of 6 million m(3) of acidic water and toxic sludge high in heavy metals. Contaminated material extended 40 km downstream, affecting agricultural land and parts of the wildlife-rich Donana Natural and National Parks, including the Entremuros, a very important area for birds. We report on the concentrations, distributions and bioavailability of zinc and cadmium in soil and vegetation from the Entremuros in November 1998 and October 1999, following 2 'cleanup' operations. Levels of Zn and Cd in soil increased significantly over this period, although this was not reflected consistently in metal concentrations in emergent macrophytes. We recommend monitoring of further cleanup attempts in order to develop means of minimizing potential impacts to wildlife in the area.

Selenium in higher plants: understanding mechanisms for biofortification and phytoremediation:understanding mechanisms for biofortification and phytoremediation

Selenium (Se) is an essential micronutrient for many organisms, including plants, animals and humans. As plants are the main source of dietary Se, plant Se metabolism is therefore important for Se nutrition of humans and other animals. However, the concentration of Se in plant foods varies between areas, and too much Se can lead to toxicity. As we discuss here, plant Se uptake and metabolism can be exploited for the purposes of developing high-Se crop cultivars and for plant-mediated removal of excess Se from soil or water. Here, we review key developments in the current understanding of Se in higher plants. We also discuss recent advances in the genetic engineering of Se metabolism, particularly for biofortification and phytoremediation of Se-contaminated environments.