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).     

Technological solutions and operational measures to prevent escapes of Atlantic cod (Gadus morhua) from sea cages

Escapes of cod (Gadus morhua) from sea cages represent an economic problem for farmers and a potential environmental problem. We estimate that 0–6% of cod held in sea‐cage farms in Norway were reported to have escaped each year from 2000 to 2005, which is a high proportion compared with salmon. We interviewed employees at 19 coastal sea‐cage cod farms in Norway to investigate both how and why cultured cod escape and to document cage handling and management strategies that were effective in minimizing escapes. Based on the interviews, we describe five working hypotheses that may explain why a greater proportion of cod than salmon escape: (1) cod are more willing to escape than salmon; (2) cod bite the net cage and create wear and tear; (3) net cages have insufficient technical standards for cod culture; (4) cod are placed in sea cages at considerably smaller sizes than salmon; and (5) cod are more popular feed for predators. Preliminary testing of the hypothesis that cod bite netting and create holes was done by placing pre‐damaged net panels with cut twines and control panels inside sea cages. Holes in the pre‐damaged net panels increased in size over a period of 3 months. The type of damage indicated that biting of netting twines was the likely cause.     

Retention of aspen (Populus tremulae) at final cuttings - The effect of dead wood characteristics on saproxylic beetles

To preserve biodiversity in managed forest landscapes dead and living trees are retained at final cuttings. In the present study we evaluated the effect of these practices for saproxylic (wood-dependent) beetles inhabiting dead aspen trees (Populus tremulae). For saproxylic beetles, tree retention at final cuttings can be expected to be especially valuable for species adapted to sun-exposed dead wood, a substrate that only rarely occurs in well managed forest stands. Therefore, the current evaluation was conducted as a comparison of species richness, species density (number of species per sample), assemblage composition and occurrence of individual species between clear-cuts, where aspen trees were retained, and closed forest stands with aspen trees. The study was conducted in central Sweden and the beetles were sampled by sieving of bark from CWD (coarse woody debris) of aspen. There was no significant difference in rarefied species richness between forest and clear-cut sites. Species composition differed significantly between the two stand types. Generalized linear mixed-effects models predicted the species density to be 34% lower in CWD objects in forest sites than on clear-cuts. This pattern could partly be explained by differences in CWD diameter, decay class and bark types between the two stand types (clear-cut/forest). Stand type was a significant predictor of occurrence in individual CWD objects for 30% of analysed individual beetle species. For all species except one, the variable stand type predicted higher occurrence on clear-cuts than in forest stands. To conclude, our results demonstrate that retention of aspen on clear-cuts contributes to population recruitment of a different assemblage of species than CWD within stands.     

Changes in soil ph over a 50-year period under different forest canopies in SW Sweden

Reinvestigation of soil profiles, down to 70 cm depth in mineral soil, sampled for measurements in 1927 revealed a general decrease in pH for spruce and hardwood stands with 0.3 to 0.9 units. The pH-changes in the top soil can partly be explained by biological acidification, increasing with stand age. Stand age and species composition have less influence in deeper soil horizons and much of the acidification there is ascribed to acid deposition.     

Antioxidant properties of carnosine re-evaluated in a ferrylmyoglobin model system and in cooked pork patties

The antioxidative effect of purified carnosine (i.e., separated from the common contaminant hydrazine) has been evaluated in two systems: (i) Carnosine was found to possess poor reducing properties toward the prooxidant ferrylmyoglobin; at pH approximately 5 the presence of carnosine did not increase the rate of reduction of MbFe(IV)=O compared to autoreduction, whereas at pH 7.4 the rate constant for reduction by carnosine was 0.010 +/- 0.002 M(-1).s(-1) (I = 0.16; 25.0 degrees C). (ii) In cooked pork patties prepared from meat (longissimus dorsi and masseter) with purified or nonpurified carnosine added, the effect of purified carnosine was insignificant when compared to control patties, whereas patties with carnosine contaminated with hydrazine had a lower oxidation level than patties with purified carnosine. Carnosine is concluded not to deactivate the prooxidant ferrylmyoglobin and not to have any antioxidative effect in cooked pork.     

Greenhouse gas emissions from farmed organic soils: a review

Abstract. The large boreal peatland ecosystems sequester carbon and nitrogen from the atmosphere due to a low oxygen pressure in waterlogged peat. Consequently they are sinks for CO₂ and strong emitters of CH₄. Drainage and cultivation of peatlands allows oxygen to enter the soil, which initiates decomposition of the stored organic material, and in turn CO₂ and N₂O emissions increase while CH₄ emissions decrease. Compared to undrained peat, draining of organic soils for agricultural purposes increases the emissions of greenhouse gases (CO₂, CH₄, and N₂O) by roughly 1t CO₂ equivalents/ha per year. Although farmed organic soils in most European countries represent a minor part of the total agricultural area, these soils contribute significantly to national greenhouse gas budgets. Consequently, farmed organic soils are potential targets for policy makers in search of socially acceptable and economically cost-efficient measures to mitigate climate gas emissions from agriculture. Despite a scarcity of knowledge about greenhouse gas emissions from these soils, this paper addresses the emissions and possible control of the three greenhouse gases by different managements of organic soils. More precise information is needed regarding the present trace gas fluxes from these soils, as well as predictions of future emissions under alternative management regimes, before any definite policies can be devised.     

Antioxidant properties of green tea extract protect reduced fat soft cheese against oxidation induced by light exposure

The effect of two different antioxidants, EDTA and green tea extract (GTE), used individually or in combination, on the light-induced oxidation of reduced fat soft cheeses (0.2 and 6% fat) was investigated. In samples with 0.2% fat, lipid hydroperoxides as primary lipid oxidation products were not detected, but their interference was suggested from the formation of secondary lipid oxidation products such as hexanal and heptanal. The occurrence of these oxidation markers was inhibited by spiking with 50 ppm EDTA or 750 ppm GTE, or a combination of the two prior to irradiation. In contrast, addition of 50 ppm EDTA to samples with 6% fat was ineffective, but 750 ppm GTE (alone or in combination with EDTA) strongly reduced levels of hexanal and heptanal. Accumulation of primary lipid hydroperoxides was not affected by GTE, hence antioxidative activity was ascribed to scavenging of hexanal and heptanal precursors. These radical intermediates result from hydroperoxide disintegration, and subsequent scavenging by GTE, which acts as a radical sink, corroborates the intense signal observed by electron paramagnetic resonance (EPR) spectroscopy.     

Effect of long-term field exposure of soil to acetylene on nitrification,denitrification, and acetylene consumption

Coated CaC₂ is a newly developed product which can supply nitrification-inhibiting quantities of C₂H₂ (1–10 Pa) to the soil, throughout a cropping season. This method of applying C₂H₂ to the soil maintains C₂H₂ in the soil continuously for several months. It is not know whether these low C₂H₂ concentrations alter soil microbial processes. A field study was initiated to determine the effect of supplying C₂H₂ to a clay soil, using coated CaC₂, on soil respiration, denitrification, nitrification, and C₂H₂ consumption. The C₂H₂ consumption rate increased with length of soil exposure to C₂H₂ (r ²=0.59). The rates of CO₂ production (r ²=0.88) and denitrification (r ²=0.86) were both highly correlated with the C₂H₂ consumption rates. The nitrifier potential decreased to a minimum of 21% of the control after 3 months of C₂H₂ treatment. After this time, nitrifier activity increased to 41% of the control after 11 months of treatment. This increase was due to increased C₂H₂ consumption in the soil. After 3 months of continuous application of C₂H₂ to the soil, the C₂H₂ concentrations were generally below that necessary to inhibit nitrification. No adaptation to the C₂H₂ by nitrifiers was found. Repeating these measurements 1 year later showed that soils previously exposed to C₂H₂ retained their enhanced C₂H₂ oxidation capacity and the capacity to use C₂H₂ to increase denitrification. Nitrification potentials remained about 50% lower in soils exposed to C₂H₂ a year earlier compared to soils not previously exposed to C₂H₂.     

Plant-derived CO2 flux from cultivated peat soils

Abstract

Methods used to estimate the CO₂ emission from soil commonly measure the total CO₂ flux. To be able to quantify the net CO₂ emission from cultivated peat soils there is a need to distinguish between soil organic matter-derived CO₂ respiration and plant-derived respiration. In this investigation we used the root exclusion method to separate the plant-derived respiration from total CO₂ emission. The plant-derived contribution was estimated to be between 27 and 63% of total CO₂ emission depending on soil type and season. We also found a relationship between soil temperature, biomass growth and CO₂ efflux, which can be used to estimate plant-derived respiration. Due to the priming effect the root exclusion method is less reliable late in the season.