Decomposer biomass in the rhizosphere to assess rhizodposition

Quantification of the organic carbon released from plant roots is a challenge. These compounds of rhizodeposition are quickly transformed into CO2 and eventually bacterial biomass to be consumed by bacterivores (protozoa and nematodes). Microbes stimulate rhizodeposition several-fold so assays under sterile conditions give an unrealistic value. Quantifying bacterial production from H-3-thymidine incorporation falls short in the rhizosphere and the use of isotopes does not allow clear distinction between labeled CO2 released from roots or microbes. We reduced rhizodeposition in 3-5 week old barley with a 2 week leaf aphid attack and found that biomass of bacterivores but not bacteria in the rhizosphere correlated with plant-induced respiration activity belowground. This indicated top-down control of the bacteria. Moreover, at increasing density of aphids, bacterivore biomass in the rhizosphere decreased to the level in soil unaffected by roots. This suggests that difference in bacterivore biomass directly reflects variations in rhizodeposition. Rhizodeposition is estimated from plant-induced increases in bacterial and bacterivore biomass, and yield factors, maintenance requirements, and turnover rates from the literature. We use literature values that maximize requirements for organic carbon and still estimate the total organic rhizodeposition to be as little as 4-6% of the plant-induced respiration belowground

Nematode migration and nutrient diffusion between vetch and barley material in soil

This paper deals with migration of nematodes along nutrient gradients in soil. Portions of barley straw and green vetch leaves were mixed with soil and buried at 6, 12, 18, and 50mm distance from each other in soil. During the following 12 weeks respiration activity, microbial (SIR) biomass, nitrogen limitation of respiration activity in soil slurries all indicated that nitrogen was transferred in the soil from the nutrient rich vetch to the nutrient poor barley at least during the first 3 weeks of the experiment. Twelve out of 39 taxonomic groups of nematodes showed different growth in the two plant material-soil mixtures. Only one of these taxonomic groups (long rhabditid larvae) suggested that migration could have contributed to population development; for three other groups (short rhabditid larvae, Aphelenchoides, and Bursilla) nutrient transport through the soil was the likely mechanism for a distance-dependant population development. We suggest that for most microbivorous nematodes, except larvae of fast growing bacterivores, migration over distances exceeding one centimetre does not contribute markedly to population development even when cues such as nutrient gradients to stimulate the activity exis

Above-belowground interactions govern the course and impact of biological invasions

Introduction of exotic organisms that subsequently become invasive is considered a serious threat to global biodiversity, and both scientists and nature-conservationists attempt to find explanations and means to meet this challenge. This requires a thorough analysis of the invasion phenomenon in an evolutionary and ecological context; in the case of invasive plants, we must have a major focus on above–belowground interactions. Thus, we discuss different theories that have been proposed to explain the course of invasions through interactions between plants and soil organisms. Further, a thorough analysis of invasion must include a temporal context. Invasions will typically include an initial acute phase, where the invader expands its territory and a later chronic phase where equilibrium is re-established. Many studies fail to make this distinction, which is unfortunate as it makes it impossible to thoroughly understand the invasion of focus. Thus, we claim that invasions fall into two broad categories. Some invasions irreversibly change pools and pathways of matter and energy in the invaded system; even if the abundance of the invader is reduced or it is completely removed, the system will not return to its former state. We use earthworm invasion in North America as a particular conspicuous example of invasive species that irreversibly change ecosystems. However, invasions may also be reversible, where the exotic organism dominates the system for a period, but in the longer term it either disappears, declines or its negative impact decreases. If the fundamental ecosystem structure and flows of energy and matter have not been changed, the system will return to a state not principally different from the original

Nye tider og nye mål - et essay om Dansk Idrætshistorisk Forening og Idrætshistorisk Årbog - dengang og i fremtiden

Nyere tider og nye mål er et essay om Dansk Idrætshistorisk Forening og Idrætshistorisk Årbog udvikling til Forum for Idræt, Historie og Samfund og en tidskrift med et nyt navn. Essayet beskriver udviklingen i den humanistiske og samfundsvidenskabelige idrætsforskning og formidlingen af den.

Håndbold i kristendommens tegn

Handball in the name of ChristianityIn the further development of industrial society that took place during the 20th century, a need soon made itself felt for cultural activity other than that provided by religion. One result was that sport became popular among young people. In the Christian KFUM-associations they began discussing the advantages of offering sport as part of their program. Sport could be used to capture youth and thereby make converts to Christianity. On the other hand, there was the dangerous possibility of sport leading youth away from Jesus. In Fredericia members of KFUM began playing handball in 1926. It soon turned out that the sceptics were right. KFUM gained more new members, but they did not come from Christian societies, and they didn’t allow themselves to bee converted to Christianity. In fact they would rather play handball than spend their time with the Bible. This lead to internal difficulties within Fredericia KFUM, where Christian leaders of the sports sectionn tried to put a stop to this »unfortunate« development. First they forbade members to join non-Christian clubs as long they were members of KFUM, then they forbade the teams to join »non« KFUM tournaments and finally they placed a missionary on the board of directors of the sports section to »keep an eye on people.« In the meantime KFUM’s sports section was hit by the phenomenon of secularisation, – in popular terms, a process whereby the impact of Christianity on society in general was gradually decreasing. Secularisation hit Fredericia KFUM so forcefully that during the 1950’s and 60’s members and leaders chose to spent all their time on handball at the expense of proclaiming the Christian message. When in the 1960’s the number of handball players had risen to the point that it was necessary to play matches on Sunday, the church suddenly began to block handball activities. The handball players of KFUM were prepared to play during times intended for church services but a number of leaders were of a different opinion. In the end the handball players had it their way and the church service lost its sacred status

Helle Gotved 1912-2006

Artiklen tegner et billede af Helle Gotveds liv og virke i gymnastik- og bevægelseskulturen i Danmark

Håndbold i kristendommens tegn

Handball in the name of ChristianityIn the further development of industrial society that took place during the 20th century, a need soon made itself felt for cultural activity other than that provided by religion. One result was that sport became popular among young people. In the Christian KFUM-associations they began discussing the advantages of offering sport as part of their program. Sport could be used to capture youth and thereby make converts to Christianity. On the other hand, there was the dangerous possibility of sport leading youth away from Jesus. In Fredericia members of KFUM began playing handball in 1926. It soon turned out that the sceptics were right. KFUM gained more new members, but they did not come from Christian societies, and they didn’t allow themselves to bee converted to Christianity. In fact they would rather play handball than spend their time with the Bible. This lead to internal difficulties within Fredericia KFUM, where Christian leaders of the sports sectionn tried to put a stop to this »unfortunate« development. First they forbade members to join non-Christian clubs as long they were members of KFUM, then they forbade the teams to join »non« KFUM tournaments and finally they placed a missionary on the board of directors of the sports section to »keep an eye on people.« In the meantime KFUM’s sports section was hit by the phenomenon of secularisation, – in popular terms, a process whereby the impact of Christianity on society in general was gradually decreasing. Secularisation hit Fredericia KFUM so forcefully that during the 1950’s and 60’s members and leaders chose to spent all their time on handball at the expense of proclaiming the Christian message. When in the 1960’s the number of handball players had risen to the point that it was necessary to play matches on Sunday, the church suddenly began to block handball activities. The handball players of KFUM were prepared to play during times intended for church services but a number of leaders were of a different opinion. In the end the handball players had it their way and the church service lost its sacred status

I virkeligheden startede historien… - om NFI

Artiklen kaster et tilbageblik på NFI's (Netværk for Folkelig Idrætshistorie) undfangelse omkring år 2000. NFI blev sat i verden for at styrke netværket mellem arkivforsamlinger, folkelige foreninger og forskningsinstitutioner

Extent and effects of microplastic pollution in soil with focus on recycling of sewage sludge and composted household waste and experiences from the long-term field experiment CRUCIAL

Microplastics (MP) occur in household waste products, which can be recycled as fertilizers in agricultural fields. Recycling of waste products has many benefits but concerns of the effects of MP on soil health limit recycling. MP are present in composted household waste and sewage sludge. Sewage sludge contains many small particles (primarily fibers and fragments), whereas compost mainly contains larger fragments (flakes from packaging and bags). Here, we review the extent and possible consequences of MP pollution in soil with focus on waste product recycling. We summarize the results from studies that have measured MP concentration in soil and waste products. We review the possible hazards of MP on soil invertebrates, plant growth and microbial communities based on published studies. We discuss these results in relation to MP quantities measured in agricultural fields and generally find that MP contents in fields are below the MP levels that cause negative effects in most current effects studies. Finally, we present results from the long-term field experiment CRUCIAL, which have received composted household waste and sewage sludge in dosages corresponding to more than 100 years of legal amendment. Experiments with earthworms and quantification of various soil organisms do not indicate that household waste and sewage sludge, including the inherent contaminants, affect soil health negatively. In fact, growth of earthworms and abundances of organisms were often higher in these treatments compared to NPK-fertilized or unfertilized plots, probable due to the content of organic matter in the waste product. Based on these assessments, we conclude that the potential risk of current levels of microplastics in terrestrial environments is low for agricultural soils, but more studies are needed to perform a robust risk assessment

DATADELING I MEDGANG OG MODGANG: Refleksioner over et kollektivt feltarbejde

Vi argumenterer for, at det kollektive feltarbejde påvirker forståelsen og genereringen af data og herved den etnografiske analyse. Samarbejde medvirker til, at data får et eksplicit udtryk, og giver mulighed for at udarbejde analyser med forskellige perspektiver og en stor mængde data på kort tid. Vi fremhæver vigtigheden af kritisk stillingtagen til, hvordan samspillet mellem data, metode og analyse bliver påvirket af at være to i felten. Artiklen tager afsæt i vores erfaringer fra et fem måneders feltarbejde i slummen i Nairobi, Kenya