An easy and rapid method using microscopy to determine herbicide effects in Poaceae weed species

A new, easy, rapid and relatively inexpensive method using microscopy has been developed for the detection of herbicide effects in leaves of grass weed species displaying no visual signs of damage. The method has potential to be used as a tool to indicate future death of grass species due to herbicide exposure by observing phytochemical effects, i.e. early-warning effects. In the present study, Apera spica-venti (L.) Beauv., Bromus hordeaceus L., Alopecurus myosuroides Huds., Lolium perenne L. and Poa annua L. were exposed to lethal rates of four herbicides with different mode of action. The herbicides investigated were the thiocarbamate: prosulfocarb, the sulfonylurea: iodosulfuron, the aryloxyphenoxypropionate: fenoxaprop-P-ethyl and the organophosphate glyphosate. Autofluorescence of leaves was studied under a microscope using ultraviolet and blue light. The fluorescence of leaves treated to enhance flavonoids was also examined. To confirm the results, microspectrofluorometry was performed. Effects indicating future death of the grasses were observed in visually healthy leaves following treatment with prosulfocarb, glyphosate and iodosulfuron. No changes were detected following treatment with fenoxaprop-P-ethyl. After exposure to glyphosate or iodosulfuron, changes in the content of flavonoids and other compounds with a conjugation system and rigid structure and a decrease in the content of chlorophyll were detected in the leaves. Prosulfocarb treatment resulted in changes in the content of flavonoids and other compounds with a conjugation system and rigid structure and an increase in the content of chlorophyll in the leaves. The results obtained from microspectrofluorometry indicated that exposure to prosulfocarb caused a reduction in the flavonoids quercetin, naringenin and/or naringin.     

Comparative growth,dry matter accumulation and photosynthetic rate of seven species of Eucalypt in response to phosphorus supply

Plantations of eucalypts as short-rotation tree crops are rapidly expanding in tropical and sub-tropical regions, including southern China, where the soils are acidic and available phosphorus(P) is limited. We investigated seedling growth, dry matter accumulation, and the dynamics of photosynthetic rate and chlorophyll content of seven Eucalyptus species/hybrids(E. dunnii, E. grandis, E. grandis × E. camaldulensis, E. urophylla × E. camaldulensis, E. urophylla × E. tereticornis, E. grandis × E. tereticornis, E. urophylla × E. grandis) in response to different levels of P supply(0, 6, 12 and 18 mg?kg-1 KH2PO4). The photosynthetic rate and the chlorophyll content significantly declined as the P supply declined in almost a linear fashion for all species as the P stress period extended. In the absence of P supply, height growth of seedlings of all species was significantly impaired, while root collar diameter growth and whole plant dry matter accumulation was not affected by the level of P supply in most of the species. Significant inter-species variations in growth, dry matter accumulation and photosynthetic rate in response to P supply were detected. Eucalyptus dunnii had the lowest growth performance across all levels of P supply while E. urophylla × E. tereticornis showed superior growth performance. From a practical point of view, E. urophylla × E. tereticornis is suggested as a candidate hybrid for planting on slightly P-deficient sites in southern China while E. dunnii, being a slow-growing species, is not suitable for short-rotation plantation. On plantation sites where severe P deficiency exists, P fertilization needs to be considered to boost rapid growth of seedlings so as to meet the management objectives of short-rotation plantation.     

Carbon footprint including effect of carbon storage for selected wooden facade materials

Abstract

The outer facade constitutes a substantial volume of the total consumption of materials used in a building and the need for maintenance of the facade makes it especially interesting from a life cycle perspective. The range of wooden materials and products used for facades has different impacts over the life cycle, but the analyses so far have not included a time-adjusted global warming potential (GWP). Wooden facade materials were assessed with respect to their life cycle carbon footprint based on the environmental product declarations (EPD) and adjusted according to EN15804. The results showed low impacts of untreated Scots pine heartwood (≈1 kg CO₂-eq. per square meter [m²]), medium for thermally modified Scots pine, coated Norway spruce and oil/copper–organic preservative-treated Scots pine (1–5 kg CO₂-eq. per m²) and high for furfurylated Scots pine and acetylated Radiata pine (5–10 kg CO₂-eq. per m²). The results with time-adjustment showed that these methods have a potential large effect on the carbon footprint of wooden claddings. The inclusion of biogenic carbon flows and timing seems to be more important than the difference between the product when biogenic carbon is not included. This fact highlights the importance time-adjusted GWP would have for wood products EPDs.     

The cultural background of the sustainability of the traditional farming system in the Ghouta the oasis of Damascus, Syria

This paper discusses thepractical impact of a non-materialistic cultureon sustainable farm management.Two elements are discussed: first, how deeplyrooted religion is in this culture; second,the feasibility of using both human knowledgeand experience, so-called tradition and divineguidance in management. Finally, theimplications of the fusion of these twoelements are drawn. The outcome is thecapability of man to integrate ethical valuesinto decisions and actions. This integration,when applied by skilled farmers, leads to amanagement of natural resources in analtruistic fashion and not merely to economicends. Moreover, it makes agriculture meaningfuland sustainable.     

A 10,000-year record of Arctic Ocean sea-ice variability--view from the beach

We present a sea-ice record from northern Greenland covering the past 10,000 years. Multiyear sea ice reached a minimum between ~8500 and 6000 years ago, when the limit of year-round sea ice at the coast of Greenland was located ~1000 kilometers to the north of its present position. The subsequent increase in multiyear sea ice culminated during the past 2500 years and is linked to an increase in ice export from the western Arctic and higher variability of ice-drift routes. When the ice was at its minimum in northern Greenland, it greatly increased at Ellesmere Island to the west. The lack of uniformity in past sea-ice changes, which is probably related to large-scale atmospheric anomalies such as the Arctic Oscillation, is not well reproduced in models. This needs to be further explored, as it is likely to have an impact on predictions of future sea-ice distribution.     

Mitigation of subsoil recompaction by light traffic and on-land ploughing: I. Soil response

Mechanically loosened subsoil has been shown to be prone to recompaction. We addressed a sandy loam that had been mechanically loosened by a subsoiler to a depth of 35 cm in 1997 and again in 1998. Perennial grass/clover was grown with limited traffic intensity in 1999 and 2000. A recompaction experiment was conducted in 2001 and 2002 when the soil was grown with oat and winter wheat, respectively. Using the formerly loosened plots, on-land ploughing was compared with traditional mouldboard ploughing with the tractor wheels in the furrow. In addition, the loosened plots were either light-trafficked (<6 Mg axle load and <100 kPa inflation pressure) or heavy-trafficked (10–18 Mg axle load and 200 kPa inflation pressure), respectively. Finally, the soil loosened by non-inversion deep tillage was referenced with a conventional ploughing–harrowing tillage system that never received the subsoil treatment. The conventional treatment was also grown with the grass/clover in 1999 and 2000. On-land ploughing and light traffic was applied in 2001 and 2002 instead of traditional ploughing and traffic for the conventional treatment. Penetration resistance and bulk density was recorded in the field. Undisturbed soil cores were taken in 1998, 1999 and 2002 from the 7–14, 18–27 and 25–30 cm layer and used for measuring total porosity, pores >30 μm and air permeability at −100 hPa matric potential. The results showed that on-land ploughing mitigated recompaction of the upper part of the formerly loosened subsoil. In contrast, only small differences in recompaction between heavy and light traffic were observed. The mitigation of subsoil recompaction was needed for the loosened soil to provide an upper subsoil with similar—not better—pore characteristics than the non-loosened soil in the conventional treatment. The structural conditions in the plough pan improved for the conventional treatment from 1998 to 2002 as indicated by an almost doubling in air permeability. This was interpreted as being related to the growing of grass/clover ley in 1999 and 2000 combined with a shift from traditional tillage and traffic to on-land ploughing and light traffic when growing cereals in 2001 and 2002. Results on root growth and crop yield are reported in an adjoining paper.     

Transport of polychlorinated biphenyls (PCBs) in freshwater mesocosms from sediment to water and air

With sediment as a source the flux of PCBs to water and air was followed in mesocosms with and without fish for two vegetation seasons. The fish represented the largest lipid pool in the mesocosm, and their presence increased the flux of PCBs across the sediment/water interface. The flow of PCBs from sediment to water followed a seasonal pattern with higher rates during summer than in the winter. The rates were governed by the turbation activity of benthic invertebrates, the extent of gas production in the sediment, the amount and quality of the lipid pools in the water column, and the solubility of the PCBs. The greatest amount of PCBs among the lipid pools was found in the dissolved extractable lipids, which also showed the highest concentration of PCBs calculated on a lipid basis. After about 1.5 yr, >90% of the PCBs added was still in the sediment. The remainder was distributed within the mesocosms to various extents depending on the amount and quality of the lipid pools, or transferred into the air. Transfer into the air was governed by PCB concentrations in the water, and by water temperature. The flow was highest during summer, when the surface microlayer renewed its load of PCBs every 8th day.     

Regional assessment of the temporal trends in soil acidification in Southern Sweden,using the safe model

The dynamic soil acidification model SAFE was applied to 44 forested sites in Skåne, southern Sweden, using available Swedish databases on present soil status, vegetation and deposition. Time series of deposition were derived for each site from present deposition in a generalized fashion by dividing deposition into different classes and scaling with deposition trends from the literature. This study connects the current status of the soil and the soil development with critical load maps calculated with the steady-state model PROFILE.The model was calibrated against measurements of present base saturation from the Swedish Forest Inventory. Model output was compared with available measurements of soil water chemistry.     

Inhibitory effect of low partial pressures of acetylene on nitrification

The inhibiting effect of C₂H₂ on nitrification was investigated in two agricultural soils. Nitrification was totally inhibited at 10 Pa partial pressure of C₂H₂ which is lower than previously reported for soils. There were no differences in rates of nitrate production between flasks without C₂H₂ and flasks with C₂H₂ at 0.01 Pa, while there was an effect on nitrification at 0.1 PaC₂H₂. At 0.1 Pa no inhibition was noted during the first 3 days; after this period nitrification was partially inhibited. The inhibiting effect did not cease until 7 days after removal of C₂H₂. The sensitivity of nitrification to low concentrations of C₂H₂ should be noted when denitrification rates are determined by the use of the acetylene inhibition method (usually C₂H₂ at 10kPa).     

Nitrogen turnover rates in a riparian fen determined by 15N dilution

Summary Gross rates of N mineralization, assimilation, nitrification, and NO _in3 ^sup- reduction were determined in soil from a wet riparian fen by 1-day incubations of soil cores and slurries with ¹⁵N-labelled substrates. N mineralization transformed 0.1% of the total organic N pool daily in the soil cores, of which 25% was oxidized through autotrophic nitrification and 53%–70% was incorporated into microorganisms. N mineralization and nitrification were markedly inhibited below 5 cm in soil depth. At least 80% of the NO _in3 ^sup- reduction in aerated cores occurred through dissimilatory processes. Dissimilatory reduction to NH _in4 ^sup+ (DNRA) occurred only below 5 cm in depth. The results show that NH _in4 ^sup+ oxidation was limited by available substrate and was itself a strong regulator of NO _in3 ^sup- -reducing activity. NO _in3 ^sup- reduction was significantly increased when the soil was suspended under anaerobiosis; adding glucose to the soil slurries increased NO _in3 ^sup- reduction by 2.4–3.7 times. Between 3% and 9% (net) of the added NO _in3 ^sup- was reduced through DNRA in the soil slurries. The highest percentage was observed in soil samples from deeper layers that were pre-incubated anaerobically.