A Comparison of Temporal Patterns in Trace Metal Concentration in Tree Rings of Four Common European Tree Species Adjacent to a Cu-Cd Refinery

Metal processing at a Cu-Cd refinery at Prescot in N.W. England has led to severe contamination of the surrounding soils and vegetation, although Cu and Cd in bulk deposition declined dramatically between 1975 and 1990. Despite high spatial and temporal variability in metal deposition, mean Cd concentrations in annual tree rings of sycamore (Acer pseudoplatanus L.), lime (Tilia europaea L.) and beech (Fagus sylvatica L.) at Prescot were correlated with annual bulk Cd deposition. In contrast, mean Cd concentrations in ash (Fraxinus excelsior L.) were unrelated to Cd deposition and there was no significant relationship between mean Cu concentrations in tree rings and Cu deposition in any species. Mean Pb concentrations in sycamore, lime and beech at Prescot and the reference site also decreased over time. At Prescot however, Cd concentrations in tree rings formed in the mid 1990s were up to 10-fold higher than the reference site despite Cd deposition values during this period that were typical of levels expected for urban areas in the UK. The high Cd concentrations in wood during this period indicate that the majority of Cd in tree rings at Prescot is derived from soil, limiting the usefulness of dendrochemistry for monitoring temporal changes in metal deposition. It appears that trees are not simply passive recorders of metal deposition and other possibilities, in addition to decreasing atmospheric deposition, may explain the patterns of Cd and Pb found in sycamore, lime and beech. More research on the physiology of metal cycling in trees is required before dendrochemical techniques can be applied with confidence in environmental monitoring programs.     

Changes to soil physical properties after grazing exclusion

Abstract. The potential for degraded physical properties of soil to regenerate naturally after exclusion of grazing animals was examined at a long-term stocking rate trial near Armidale, New South Wales, Australia. Unsaturated hydraulic conductivity was measured before grazing was excluded, and after 7 months and 2.5 years' grazing exclusion. These data were compared with controls grazed at 10,15 and 20 sheep/ha. After 2.5 years, there were significant increases in unsaturated hydraulic conductivity at 5 and 15 mm tension in the ungrazed treatments compared with the grazed controls. The unsaturated hydraulic conductivities and bulk density of surface soils under pasture which had been ungrazed for 2.5 years were comparable to those where the pasture had been ungrazed for 27 years. We speculate that the natural amelioration of soil physical properties in these soils was due to biological activity and wetting and drying cycles, in the absence of the compactive effect of animal treading.     

Fonofos toxicosis in dairy cows: an accidental poisoning (1977)

An accidental poisoning (in 1977) of 28 Holstein cows occurred when approximately 0.9 kg of 25% active ingredient fonofos, O-ethyl S-phenyl ethylphosphonothiolothionate, was spilled onto bulk feed in a delivery truck. Eight cows died within 2 days; the remaining 20 were necropsied 29 days later. Of the 8 fatally poisoned, 7 were being fed a high-grain diet and 1 was fed a medium-grain diet. Fonofos concentrations in feed cart and storage bin samples were 100 micrograms/g and 61 micrograms/g, respectively. Tissues from 6 animals were analyzed extensively for fonofos concentrations: 2 had died immediately; the other 4 were in the recovery state when they were necropsied. Rumen contents and liver, kidney, brain, heart, and milk samples were analyzed. Fonofos concentrations in these samples were significantly higher in the cows fatally affected than in the cows necropsied 3 weeks later. The oral acute LD50 and LD1 of fonofos in Holstein cows were calculated by the Litchfield and Wilcoxon method to be 1.30 and 0.84 mg/kg, respectively, with a 95% confidence range of +/- 0.20 mg/kg.     

Azole fungicides – understanding resistance mechanisms in agricultural fungal pathogens

Plant fungal pathogens can have devastating effects on a wide range of crops, including cereals and fruit (such as wheat and grapes), causing losses in crop yield, which are costly to the agricultural economy and threaten food security. Azole antifungals are the treatment of choice; however, resistance has arisen against these compounds, which could lead to devastating consequences. Therefore, it is important to understand how these fungicides are used and how the resistance arises in order to tackle the problem fully. Here, we give an overview of the problem and discuss the mechanisms that mediate azole resistance in agriculture (point mutations in the CYP51 amino acid sequence, overexpression of the CYP51 enzyme and overexpression of genes encoding efflux pump proteins). © 2015 Society of Chemical Industry     

Interactions between elevated atmospheric CO2 and defoliation on North American rangeland plant species at low and high N availability

Although common disturbances of grazing lands like plant defoliation are expected to affect their sensitivity to increasing atmospheric CO₂ concentration, almost no research has been conducted to evaluate how important such effects might be on the direct responses of rangelands to CO₂. This growth chamber experiment subjected intact plant–soil cylinders from a Wyoming, USA, prairie to a 3‐way factorial of CO₂ (370 vs. 720 μL L^?1), defoliation (non‐clipped vs. clipped) and soil nitrogen (control vs. 10 g m^?2 added N) under simulated natural climatic conditions. Above‐ and below‐ground biomass and N dynamics of the functional groups C₃ grasses, C₄ grasses and forbs were investigated. CO₂ and defoliation had independent influences on biomass and N parameters of these rangeland plants. Growth under CO₂‐enriched conditions enhanced above‐ground biomass 50% in C₃ grasses alone, while shoot N concentration declined 16% in both C₃ and C₄ grasses. Plant‐soil ¹⁵N uptake was unaffected by CO₂ treatment. In contrast, defoliation had no effect on biomass, but increased tissue N concentration 29% across all functional groups. Without additional N, forage quality, which is in direct relation to N concentration, will decline under increasing atmospheric CO₂. Increased dominance of C₃ grasses plus reduced forage quality may necessitate changes in grazing management practices in mixed‐species rangelands.