Linnebjer—a south swedish oak forest and meadow area—revisited after half a century

An oak forest and three wet meadows/fens were reinvestigated after 50 years concerning tree vitality,biomass and productivity, and soil chemistry. Sulphur and nitrogen deposition has changeddramatically during these years, and the aim was to analyse the differences in both the oak forestand the open field ecosystems. Trees were re-measured and soil profiles were resampled. Importantvisible changes in the oak forest were stated concerning the vitality of oaks. Abovegroundthere was a decrease in tree biomass, production and litter fall, but a huge increase in standingdead logs. During the years, the deposition of sulphur had decreased drastically, but nitrogendeposition was still high. Soil acidification in the forest had decreased, reflected in an increasedbase saturation in the forest, in spite of slightly lowered pH-values. Strongly increased amounts ofexchangeable Ca and Mg now appeared in the forest soil, and a substantial transport of calciumand magnesium had obviously taken place from the forest soil to the meadow and fens during theyears. However, the most important soil change was the accumulation of organic matter. The increasedaccumulation of organic matter in turn meant increased amounts of colloid particles andmicrosites for ion exchange in the soil. This favoured 2-valence base cations, and especially Ca andMg that increased very much in all the studied ecosystems. Carbon as well as nitrogen had stronglyincreased in the forest, meadow and fen soils. This was interpreted as a natural result of increasedvegetation growth due to high nitrogen deposition, increased global annual temperature and increasedcarbon dioxide concentration in air. It was concluded that the decreased deposition ofsulphur had have a positive effect on soil chemistry, and that the deposition of nitrogen probablyhad stimulated vegetation growth in general, and contributed to increased amount of organicmatter in the soils. However, in this studied oak forest, the decreased vitality and many killedtrees were also suspected to be a result of high nitrogen deposition. Obviously increased treegrowth was counteracted by decreased stress resistance, and increased appearance of pathogensin the oak trees

Pathogenicity of Swedish isolates of Phytophthora quercina to Quercus robur in two different soils

Several studies have demonstrated the involvement of soil-borne Phytophthora species, especially Phytophthora quercina , in European oak decline. However, knowledge about the pathogenicity of P. quercina in natural forest soils is limited. The short-term effects of two south-Swedish isolates of P. quercina on root vitality of Quercus robur seedlings grown in two different soils, one high pH, nutrient-rich peat-sand mixture and one acid, nitrogen-rich but otherwise nutrient-poor forest soil are described. Pathogenicity of P. quercina was tested using a soil infestation method under a restricted mesic water regime without prolonged flooding of the seedlings. There was a significant difference in dead fine-root length between control seedlings and seedlings grown in soil infested with P. quercina . Trends were similar for both soil types and isolates, but there was a higher percentage of fine-root die-back and more severe damage on coarse roots in the acid forest soil. No effects on above-ground growth or leaf nutrient concentration between control seedlings and infected seedlings were found. The results confirm the pathogenicity of south-Swedish isolates of P. quercina in acid forest soils under restricted water availability. Stress-induced susceptibility of the seedlings and/or increased aggressiveness of the pathogen in the forest soil are discussed as key factors to explain the difference in root die-back between soil types

Alkaline air: changing perspectives on nitrogen and air pollution in an ammonia-rich world

Ammonia and ammonium have received less attention than other forms of air pollution, with limited progress in controlling emissions at UK, European and global scales. By contrast, these compounds have been of significant past interest to science and society, the recollection of which can inform future strategies. Sal ammoniac (nūshādir, nao sha) is found to have been extremely valuable in long-distance trade (ca AD 600–1150) from Egypt and China, where 6–8 kg N could purchase a human life, while air pollution associated with nūshādir collection was attributed to this nitrogen form. Ammonia was one of the keys to alchemy—seen as an early experimental mesocosm to understand the world—and later became of interest as ‘alkaline air’ within the eighteenth century development of pneumatic chemistry. The same economic, chemical and environmental properties are found to make ammonia and ammonium of huge relevance today. Successful control of acidifying SO2 and NOx emissions leaves atmospheric NH3 in excess in many areas, contributing to particulate matter (PM2.5) formation, while leading to a new significance of alkaline air, with adverse impacts on natural ecosystems. Investigations of epiphytic lichens and bog ecosystems show how the alkalinity effect of NH3 may explain its having three to five times the adverse effect of ammonium and nitrate, respectively. It is concluded that future air pollution policy should no longer neglect ammonia. Progress is likely to be mobilized by emphasizing the lost economic value of global N emissions ($200 billion yr−1), as part of developing the circular economy for sustainable nitrogen management

Biomass burning in eastern Europe during spring 2006 caused high deposition of ammonium in northern Fennoscandia

High air concentrations of ammonium were detected at low and high altitude sites in Sweden, Finland and Norway during the spring 2006, coinciding with polluted air from biomass burning in eastern Europe passing over central and northern Fennoscandia. Unusually high values for throughfall deposition of ammonium were detected at one low altitude site and several high altitude sites in north Sweden. The occurrence of the high ammonium in throughfall differed between the summer months 2006, most likely related to the timing of precipitation events. The ammonia dry deposition may have contributed to unusual visible injuries on the tree vegetation in northern Fennoscandia that occurred during 2006, in combination with high ozone concentrations. It is concluded that long-range transport of ammonium from large-scale biomass burning may contribute substantially to the nitrogen load at northern latitudes. (C) 2013 Elsevier Ltd. All rights reserved

Ecosystem Carbon Stock Influenced by Plantation Practice: Implications for Planting Forests as a Measure of Climate Change Mitigation

Uncertainties remain in the potential of forest plantations to sequestrate carbon (C). We synthesized 86 experimental studies with paired-site design, using a meta-analysis approach, to quantify the differences in ecosystem C pools between plantations and their corresponding adjacent primary and secondary forests (natural forests). Totaled ecosystem C stock in plant and soil pools was 284 Mg C ha−1 in natural forests and decreased by 28% in plantations. In comparison with natural forests, plantations decreased aboveground net primary production, litterfall, and rate of soil respiration by 11, 34, and 32%, respectively. Fine root biomass, soil C concentration, and soil microbial C concentration decreased respectively by 66, 32, and 29% in plantations relative to natural forests. Soil available N, P and K concentrations were lower by 22, 20 and 26%, respectively, in plantations than in natural forests. The general pattern of decreased ecosystem C pools did not change between two different groups in relation to various factors: stand age (<25 years vs. ≥25 years), stand types (broadleaved vs. coniferous and deciduous vs. evergreen), tree species origin (native vs. exotic) of plantations, land-use history (afforestation vs. reforestation) and site preparation for plantations (unburnt vs. burnt), and study regions (tropic vs. temperate). The pattern also held true across geographic regions. Our findings argued against the replacement of natural forests by the plantations as a measure of climate change mitigation

Growth response of spruce saplings in relation to climatic conditions along a gradient of gap size

To evaluate the relative importance of climatic factors and the level of natural canopy disturbance on sapling growth rates, terminal shoot increment of Norway spruce (Picea abies (L.) Karst.) saplings was analyzed in old-growth Sphagnum-Myrtillus forests of the European southern boreal zone (Tver Region, Russia). For a 5-year period, terminal increments were retrospectively measured in 225 saplings in a range of naturally created canopy gaps. Climatic variability was estimated by Seljaninov hydrothermal coefficient. Variation in the growth rate was partitioned as (i) annual variation observed within a particular sapling over a 5-year period ("within-stem variation," WSV) and (ii) variation of 5-year cumulative height increments within a particular location ("within-location variation," WLV). Sapling growth was positively related to gap size and, except when under canopy location, with the height of the saplings. For the growth, differences in sapling location along a gradient of gap sizes were more important than annual dynamics of water availability. Impact of the annual climatic variability was less pronounced in large gap, compared with other locations. Absolute values of WSV and WLV were similar under an intact canopy. WSV had a tendency to decrease in greater gaps, whereas WLV variation increased

Distribuera mera - Spark och Hadoop utan Big Data

Distribution as a concept means that a task (for example, data storage or code execution) is parallelized on multiple computers. It goes hand in hand with the concept of big data – extreme amounts of data that can’t be processed by a single computer. Because of this, the most established tools for distributed parallelization is tools that are designed to handle big data. This thesis explores whether two such tools, Spark (distributed code execution) and Hadoop Distributed File System (distributed data storage), are also suited for handling smaller amounts of data. Distribution is a potentially cheap and scalable way of working even for small amounts of data. The primary method of the report is performance tests. As a side track, an abstraction layer that allows for code to be executed either distributed or locally is implemented by using Java streams as a local equivalent of Spark. With this abstraction layer small tasks that are only sometimes suited for distribution can choose the best alternative at run time. It is concluded that these tools can be useful even for small amounts of data, and even when the execution time for a non-distributed solution is very short (under a minute)