Lichen specific thallus mass and secondary compounds change across a retrogressive fire-driven chronosequence

In the long-term absence of major disturbances ecosystems enter a state of retrogression, which involves declining soil fertility and consequently a reduction in decomposition rates. Recent studies have looked at how plant traits such as specific leaf mass and amounts of secondary compounds respond to declining soil fertility during retrogression, but there are no comparable studies for lichen traits despite increasing recognition of the role that lichens can play in ecosystem processes. We studied a group of 30 forested islands in northern Sweden differing greatly in fire history, and collectively representing a retrogressive chronosequence, spanning 5000 years. We used this system to explore how specific thallus mass (STM) and carbon based secondary compounds (CBSCs) change in three common epiphytic lichen species (Hypogymnia phsyodes, Melanohalea olivacea and Parmelia sulcata) as soil fertility declines during this retrogression. We found that STMs of lichens increased sharply during retrogression, and for all species soil N to P ratio (which increased during retrogression) was a strong predictor of STM. When expressed per unit area, medullary CBSCs in all species and cortical CBSCs in P. sulcata increased during retrogression. Meanwhile, when expressed per unit mass, only cortical CBSCs in H. physodes responded to retrogression, and in the opposite direction. Given that lichen functional traits are likely to be important in driving ecological processes that drive nutrient and carbon cycling in the way that plant functional traits are, the changes that they undergo during retrogression could potentially be significant for the functioning of the ecosystem

Contrasting changes in palatability following senescence of the lichenized fungi Lobaria pulmonaria and L. scrobiculata

Epiphytic lichens can contribute significantly to ecosystem nutrient input because they efficiently accumulate atmospheric mineral nutrients and, in the case of cyanolichens, also fix nitrogen. The rate at which carbon and other nutrients gained by lichens enters the ecosystem is determined by lichen litter decomposability and by invertebrate consumption of lichen litter. In turn, these processes are driven by the secondary compounds present in senesced lichens. Therefore, we explored how lichen palatability and concentrations of secondary compounds change with tissue senescence for Lobaria pulmonaria, a green algal lichen with cyanobacterial cephalodia, and L. scrobiculata, a cyanobacterial lichen. During senescence both lichens lost 38-48% of their stictic acid chemosyndrome, while m-scrobiculin and usnic acid in L. scrobiculata remained unchanged. Snails preferred senesced rather than fresh L. pulmonaria, while senesced L. scrobiculata were avoided. This provides evidence that species with labile secondary compounds will have higher turnover rates, through consumption and decomposition, than those producing more stable secondary compounds

Strategic management - An online collaboration between two class groups separated by a "small pond" and six time zones

An undergraduate course in Strategic Management seemingly provides similar basic content to students including the infamous SWOT (strengths, weaknesses, opportunities and threat) analysis along with the identification of functional level, business level, and generic strategies to enhance an organization’s competitiveness. One of the most common resources for this type of course is the article outlining a theoretical framework “How Competitive Forces Shape Strategy” by Michael Porter [Porter, 1979]. This paper discusses the differences and similarities of teaching an undergraduate Strategic Management course for two different institutions located in different countries. Secondly, the paper addresses the logistics of connecting the two separate student groups for a collaboration project using an on-line platform. Additionally, the paper shares the experiences learned when students work in multi-culturally mixed groups to analyze an industry around Michael Porter’s framework [Porter, 1979]

Simulated global warming increases usnic acid but reduces perlatolic acid in the mat-forming terricolous lichen Cladonia stellaris

Lichens as sessile and slow-growing symbiotic associations have evolved various carbon-based secondary compounds (CBSCs) to mitigate the effects of some stressors in the extreme environments in which they often grow. The mat-forming lichen Cladonia stellaris, an important fodder for reindeer, produces usnic acid in the outermost layer and perlatolic acid in the medulla. Here, we studied effects of simulated global warming on these CBSCs in C. stellaris cultivated in climate chambers with: 1) ambient conditions as control or 2) ambient conditions +4°C. The chambers simulated, at an hourly resolution, an averaged 10-year growing season dynamic from a long-term monitored boreal mire in northern Sweden. After two months of acclimation, +4°C warming in one simulated growing season increased the concentration of usnic acid by 31% compared with ambient conditions, whereas the warming decreased the concentration of perlatolic acid by 14%. Since lichen CBSCs play important roles in ecosystem processes such as lichenivory and decomposition, these changes may profoundly affect lichen-dominated ecosystems.acceptedVersio

Performance Comparison Analysis of ArangoDB, MySQL, and Neo4j: An Experimental Study of Querying Connected Data

Choosing and developing performant database solutions helps organizations optimize their operational practices and decision-making. Since graph data is becoming more common, it is crucial to develop and use them in big data with complex relationships with high and consistent performance. However, legacy database technologies such as MySQL are tailored to store relational databases and need to perform more complex queries to retrieve graph data. Previous research has dealt with performance aspects such as CPU and memory usage. In contrast, energy usage and temperature of the servers are lacking. Thus, this paper evaluates and compares state-of-the-art graphs and relational databases from the performance aspects to allow a more informed selection of technologies. Graph-based big data applications benefit from informed selection database technologies for data retrieval and analytics problems. The results show that Neo4j performs faster in querying connected data than MySQL and ArangoDB, and energy, CPU, and memory usage performances are reported in this paper

Performance Comparison Analysis of ArangoDB, MySQL, and Neo4j: An Experimental Study of Querying Connected Data

Choosing and developing performant database solutions helps organizations optimize their operational practices and decision-making. Since graph data is becoming more common, it is crucial to develop and use them in big data with complex relationships with high and consistent performance. However, legacy database technologies such as MySQL are tailored to store relational databases and need to perform more complex queries to retrieve graph data. Previous research has dealt with performance aspects such as CPU and memory usage. In contrast, energy usage and temperature of the servers are lacking. Thus, this paper evaluates and compares state-of-the-art graphs and relational databases from the performance aspects to allow a more informed selection of technologies. Graph-based big data applications benefit from informed selection database technologies for data retrieval and analytics problems. The results show that Neo4j performs faster in querying connected data than MySQL and ArangoDB, and energy, CPU, and memory usage performances are reported in this paper.Comment: https://hdl.handle.net/10125/10731

Microclimatic comparison of lichen heaths and shrubs: Shrubification generates atmospheric heating but subsurface cooling during the growing season

Lichen heaths are declining in abundance in alpine and Arctic areas partly due to an increasing competition with shrubs. This shift in vegetation types might have important consequences for the microclimate and climate on a larger scale. The aim of our study is to measure the difference in microclimatic conditions between lichen heaths and shrub vegetation during the growing season. With a paired plot design, we measured the net radiation, soil heat flux, soil temperature and soil moisture on an alpine mountain area in southern Norway during the summer of 2018 and 2019. We determined that the daily net radiation of lichens was on average 3.15 MJ (26 %) lower than for shrubs during the growing season. This was mainly due to a higher albedo of the lichen heaths but also due to a larger longwave radiation loss. Subsequently, we estimate that a shift from a lichen heath to shrub vegetation leads to an average increase in atmospheric heating of 3.35 MJ d−1 during the growing season. Surprisingly, the soil heat flux and soil temperature were higher below lichens than below shrubs during days with high air temperatures. This implies that the relatively high albedo of lichens does not lead to a cooler soil compared to shrubs during the growing season. We predict that the thicker litter layer, the presence of soil shading and a higher evapotranspiration rate at shrub vegetation are far more important factors in explaining the variation in soil temperature between lichens and shrubs. Our study shows that a shift from lichen heaths to shrub vegetation in alpine and Arctic areas will lead to atmospheric heating, but it has a cooling effect on the subsurface during the growing season, especially when air temperatures are relatively high.publishedVersio

Організаційна структура управління маркетингом на підприємстві

Som en avslutande del i kandidatarbetet inom mekatronik år 2013 gavs uppgiften att konstruera en robot åt pop-artisten Robyn. Arbetet är ett grupparbete där fem teknologer med specialiseringar inom olika områden samarbetar för att konstruera ett mera komplext, sammansatt system. De krav som ställdes var att roboten skulle kunna interagera, antingen med Robyn själv eller hennes publik. De begränsningar som fanns var tidsmässiga så väl som ekonomiska. I en förstudie identifierades viktiga nyckelord baserat på Robyn och hennes musik. Nyckelorden lades som grund för den efterföljande konceptgenereringen. Exempel på nyckelord var självständighet, folkkär, egensinnig och oväntad. Arbetet resulterade i en robot som kan kommunicera via Twitter, dansa i takt till omgivande musik samt skapa olika ljuseffekter. Hela roboten är byggd i ett hölje lånat från en gammal radio från 60-talet. Roboten är inte tänkt att vara en fulländad konstruktion utan illustrerar ett koncept med stor utvecklingspotential.As a final part of the bachelor thesis in mechatronics 2013 the students were given the task to design a robot to pop artist Robyn. The work is a group project in which five students with specializations in different fields collaborate to construct a more complex, composite system. The requirements were that the robot would be able to interact either with Robyn herself or her audience. The project was limited by time as well as economics. In a preliminary study important keywords based on Robyn and her music were established. The key words became the basis for the subsequent concept generation. Examples of keywords are independence, publicly loved, headstrong and unpredictable. The work resulted in a robot that can communicate via Twitter, dancing to the beat of the music, and create different lighting effects. The entire robot is built in a housing from an old radio from the 60's. The robot is by no means a perfect design, but illustrate a concept with great potential

Spatial variation of surface soil carbon in a boreal forest – the role of historical fires, contemporary vegetation, and hydro-topography

Knowledge about the spatial variation of boreal forest soil carbon (C) stocks is limited, but crucial for establishing management practices that prevent losses of soil C. Here, we quantified the surface soil C stocks across small spatial scales, and aim to contribute to an improved understanding of the drivers involved in boreal forest soil C accumulation. Our study is based on C analyses of 192 soil cores, positioned and recorded systematically within a forest area of 11 ha. The study area is a south-central Norwegian boreal forest landscape, where the fire history for the past 650 years has been reconstructed. Soil C stocks ranged from 1.3 to 96.7 kg m−2 and were related to fire frequency, ecosystem productivity, vegetation attributes, and hydro-topography. Soil C stocks increased with soil nitrogen concentration, soil water content, Sphagnum- and litter-dominated forest floor vegetation, and proportion of silt in the mineral soil, and decreased with fire frequency in site 1, feathermoss- and lichen-dominated forest floor vegetation and increasing slope. Our results emphasize that boreal forest surface soil C stocks are highly variable in size across fine spatial scales, shaped by an interplay between historical forest fires, ecosystem productivity, forest floor vegetation, and hydro-topography.Spatial variation of surface soil carbon in a boreal forest – the role of historical fires, contemporary vegetation, and hydro-topographyacceptedVersio