Liming and fertilization of acid forest soil: Short-term effects on runoff from small catchments

Increased atmospheric deposition of strong acids and deposition of potentially acidifying compounds (e.g. ammonium) has caused a decline in pH and exchangeable base cations in forest soils in Sweden. In recent years, attention has been paid to liming of forest soil as a method to counteract the effects of acid deposition. Experiments with liming, fertilization and woodash treatment of acid forest soils started in 1984. The aim of this study was to determine the effects of low doses of lime (500 to 1500 kg ha^–1) in combination with N fertilizers on tree growth, nutritional status of trees as well as soil, and runoff chemistry. This paper describes the short term effects of liming and fertilization on runoff from ten small catchments in two regions in south Sweden. The effects of liming were small in both areas. In the catchments fertilized with N (NH₄NO₃), a substantial leakage of various N species appeared in runoff after treatment. The increased N output was dominated by nitrate. The excess leakage of N during 2 yr after fertilization was 25 and 13% as an average of the applied N in the two study areas. The mobile nitrate increased the base cations output via runoff with 10 to 100% during 1 yr after N treatment. The runoff of Al increased with 60 to 1009, the first year in the fertilized catchments. Mobilization of cations was also influenced by ammonium, especially K that was exchanged by ammonium on the surface of the soil particles. The effects of woodash-treatment were small, however, sulfate in the ash leaked out following application and about 100% of the added sulfate was found in runoff during the first year.     

Mercury in runoff from drained and undrained peatlands in Sweden

The concentration of Hg was studied in runoff from drained and undrained peatlands in the south and central parts of Sweden, from 1987 to 1989. Mercury was speciated into total Hg, water-soluble Hg (Hg II) including reactive Hg (Hg IIa) and non-reactive Hg (Hg IIb), and methyl Hg. The aim of the study was to investigate if normally low concentrations of different species of Hg in runoff from peatland were elevated at drained mires with peat-harvesting. Five drained mires with different nutrient statuses were studied, and compared with undrained controls. The highest concentration of total Hg (5.3 to 21.3 ng L⁻¹) was found in runoff from an undrained, oligotrophic bog with low pH (3.79 to 4.08). Mires in south Sweden showed in general higher concentrations of all species of Hg in runoff compared to central Sweden. The concentrations of total Hg, Hg IIa and Hg IIb in runoff from peatland showed similar levels as runoff from forested areas. No data showed that the drained peatland leached more total Hg than the undrained areas.     

Standardized method for the Holmen pellet tester (NHP100) as a tool for evaluating the physical quality of fish feed

The fish feed production industry requires reliable methods measuring the physical quality of feed before it is being released to the customer. The Holmen pellet tester (NHP 100) could be adapted for this purpose, but the special characteristics of fish feed require particular care during testing. The aim of the study was to determine the standardized conditions for using the Holmen tester as a tool measuring the durability of fish feed. Screening tests were performed on commercial fish feed samples to assess the effects of temperature, pressure and cleaning the instrument between runs. The operating pressure was found to be the most important factor that can influence the results. The temperature of the operating air can also alter the results; increased temperatures can cause oil to melt and leak from the pellets. Cleaning the instrument between analyses can also affect the results. This study shows that when these factors are maintained at a standardized level, the Holmen pellet tester is a valuable tool for assessing the physical quality of fish feed giving additional information on the quality of feed pellets compared to other durability tests like DORIS.     

Tree recovery during the aftermath of an outbreak episode of the Hungarian spruce scale in southern Sweden

In 2010, the first, and so far only, infestation of the Hungarian spruce scale (Physokermes inopinatus) and accompanying sooty mould occurred in Scania, southernmost Sweden. About 1000?ha of Norway spruce (Picea abies) were affected, and the trees suffered from the sucking of the insects as well as from the dense sooty mould that covered the needles. Salvage cuttings were carried out in many of the massively attacked forest stands, both in response to the fear that the trees otherwise would die, e.g. from secondary bark beetle attacks and to prevent spreading of the infestation. The aim of this study was to provide basic, quantitative knowledge on the aftermath response of trees that were heavily infested, but not exposed to salvage cutting. Growth characteristics, in terms of needle weight, shoot length and tree-ring size were measured on infested and uninfested trees to compare and contrast the spruce growth before, during and after the scale outbreak. The infestation resulted in dwarf annual shoots, stunted needles and thin tree rings. The needle weight returned to normal the following year, whereas shoot length and tree rings required one growing season before full recovery.     

靖远松叶蜂性信息素的初步研究

试验结果表明，靖远松叶蜂雄蜂对处女雌蜂的昼夜趋性反应发生在白天，每天有两个高峰，强峰为９：００～１３：００，弱峰为１７：００～１９：００，晚２０：００～早８：００之间未见趋性反应；雄蜂对不同日龄处女雌蜂的反应不同，随着雌蜂日龄的增加，诱捕器诱到雄蜂的数量逐渐下降，１日龄雌蜂诱到雄蜂的数量最多，其诱捕率为５１．６４％；含有１头处女雌蜂的诱捕器在５０～１５００ｍ之间，均能诱到雄蜂；雄蜂对７种不同的人工合成性信息素反应表明，只有（２Ｓ，３Ｒ，７Ｒ）－３，７－二甲基－２－十三碳醇丙酸酯对雄蜂有引诱作用。     

Determinants of litter mixing effects in a Swedish boreal forest

When the litter of a given species decomposes, it will often break down in the proximity of litters from other species. We investigated the effects of litters of 10 different species in a boreal forest of northern Sweden on each others' decomposition and N release rates; this was done through the use of litterbags containing two compartments separated by single mesh partition. Different litters could be placed on opposite sides of this mesh so that they were in contact with each other. Treatments consisted of all the possible pairwise combinations of the 10 species, with members of each pair placed in different compartments of the same litterbag. Litterbags were harvested after 1, 2 and 4 years in the field. Species differed significantly in their effects on decomposition and N loss rates of associated litters. Generally, litters from feather mosses and lichens showed the greatest promotion of decomposition on associated litters, while some vascular plant species, notably Empetrum hermaphroditum, showed the least. At year four, feather mosses also had the greatest positive effects on N loss from the litters of associated species. There were several instances in which litter of a given species decomposed at different rate when litter from its own species, rather than that of a different species, was placed in the adjacent litterbag compartment. This was particularly apparent in the second year, when across the entire data set, litters decomposed fastest when associated with their own litters. Generally, slowly decomposing litters had the greatest positive effects on decomposition of associated litters. It is proposed that in boreal forests slow decomposing litters (particularly those of feather mosses) may contribute to enhancing moisture attention in the litter layer, which in turn promotes the decomposition and N release of associated litters. Further, while litter mixing effects were clearly demonstrated in our study, they were also shown to be of secondary importance to the effects of species identity on decomposition.     

Coastal river connectivity and the distribution of ascending juvenile European eel (Anguilla anguilla L.): Implications for conservation strategies regarding fish‐passage solutions

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