1,721,161 research outputs found
SoilTemp: A global database of near-surface temperature
No full textCurrent analyses and predictions of spatially explicit patterns and processes in ecology most often rely on climate data interpolated from standardized weather stations. This interpolated climate data represents long-term average thermal conditions at coarse spatial resolutions only. Hence, many climate-forcing factors that operate at fine spatiotemporal resolutions are overlooked. This is particularly important in relation to effects of observation height (e.g. vegetation, snow and soil characteristics) and in habitats varying in their exposure to radiation, moisture and wind (e.g. topography, radiative forcing or cold-air pooling). Since organisms living close to the ground relate more strongly to these microclimatic conditions than to free-air temperatures, microclimatic ground and near-surface data are needed to provide realistic forecasts of the fate of such organisms under anthropogenic climate change, as well as of the functioning of the ecosystems they live in. To fill this critical gap, we highlight a call for temperature time series submissions to SoilTemp, a geospatial database initiative compiling soil and near-surface temperature data from all over the world. Currently, this database contains time series from 7,538 temperature sensors from 51 countries across all key biomes. The database will pave the way toward an improved global understanding of microclimate and bridge the gap between the available climate data and the climate at fine spatiotemporal resolutions relevant to most organisms and ecosystem processes
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Highways up the mountains: Trails as facilitators for redistribution of plant species in mountain areas.
Get PDFTo protect mountain ecosystems, their biodiversity, ecosystem services, and other contributions to people, it is necessary to understand how climate and disturbances affect them. Trails may change seed dispersal and disrupt biotic interactions between plants, thereby creating opportunities for recruitment in locations where seeds did not arrive or competition prevented establishment. This could change plant distributions in mountain areas. Colonization opportunities may also allow species that are non-native in a particular mountain ecosystem to establish. Such changes in species distributions can influence ecosystem functions, services, and benefits. The aim of this thesis is to improve our understanding of trails' impacts on species’ distributions in the Scandes and to improve knowledge on the impact of invasive species in mountain ranges as they are perceived by stakeholders.
I conducted systematic observational surveys along hiking trails in Norway and Sweden and examined the effect of hiking trails on seed rain, seed bank abundance, seedling recruitment, and species’ realized climatic niches. For further insights in establishment and persistence of species, I investigated the importance of positive and negative neighbour interactions on different species and life stages in a field experiment manipulating environmental stress and distance to neighbouring vegetation. Using a global survey, I evaluated stakeholder perceptions of invasive species’ impacts on ecosystem functions and services in mountains.
Seed rain, seed bank, and seedling recruitment were strongly elevated along trails and trail disturbances reached far into the vegetation. Along trails, alpine species shifted their warm climatic niche edges and optima towards warmer locations, leading to an increased overlap in species' climatic niches. This was reflected by a greater species richness in trailside vegetation than in the vegetation far from trails. Recipient community and distance to anthropogenic structures modulated this increase in species richness in trailsides.
Gap size influenced the microclimate within vegetation gaps. Increased seedling establishment in small gaps appeared to be a result of reduced competition for light, which masked the amelioration of climate by neighbouring vegetation that becomes apparent when including larger gaps sizes. Facilitation by neighbouring vegetation was important throughout the life cycle under stressful conditions. Stress type mattered for the importance of facilitation, with seedlings more susceptible to acute stress.
Stakeholders across regions ranked impacts of invasive species on biodiversity and ecosystem functions predominantly negative, while the ranking of impacts on ecosystem functions and benefits also included positive perceptions. Stakeholder groups varied in their perception of impacts, with on-the-ground stakeholders more frequently reporting positive impacts. Conflicting views on impacts may be a reason for the large proportion of species that currently have no management plan.
This thesis illustrates that trailsides may provide temporary escape routes from strongly competitive lowland plants for pressed alpine species, and locally increase species richness in the Scandes. When examining biotic interactions, the spatial scales on which different stresses act and target species tolerances to them should be considered. Further research on changes in native and non-native species distributions should consider impacts beyond biodiversity.Zusammenfassung
Um Gebirgsökosysteme mit ihrer Artenvielfalt und ihren Ökosystemdienstleistungen zu schützen, ist es notwendig zu verstehen, wie Klima und Störungen diese beeinflussen. Eine häufige Störung in Gebirgen sind Wanderwege. Wanderwege können die Ausbreitung von Samen verändern und die biotischen Interaktionen zwischen Pflanzen stören. Dadurch können Samen an Orte gelangen, die sie sonst nicht erreichen würden und sich so Pflanzen an Orten etablieren, an denen die Konkurrenz dies sonst verhindert hätte. So können Wanderwege die Verbreitung von Pflanzen in Gebirgsregionen verändern. Durch Störungen können sich auch Arten etablieren, die in einem bestimmten Bergökosystem nicht heimisch sind. Veränderungen in der Artenverteilung können wiederum die Ökosystemfunktionen und -dienstleistungen verändern. Ziel dieser Arbeit ist es, die Auswirkungen von Wanderwegen auf die Verbreitung von Arten in den Skanden, dem Gebirge Norwegens und Schwedens, besser zu verstehen und das Wissen darüber, wie verschiedene Interessensgruppen die Auswirkungen invasiver Arten in Gebirgsregionen wahrnehmen zu verbessern.
Mit systematischen Vegetationserhebungen entlang von Wanderwegen in Norwegen und Schweden untersuchte ich die Auswirkungen von Wanderwegen auf die Samenverteilung, die Samenbank, die Rekrutierung von Keimlingen und die realisierten klimatischen Nischen der dort heimischen Arten. Um weitere Erkenntnisse über die Etablierung und das Überleben von Arten zu gewinnen, untersuchte ich die Bedeutung von Interaktionen mit benachbarter Vegetation für ausgewählte Zielarten in verschiedenen Lebensstadien in einem Feldexperiment. Hierzu manipulierte ich Umweltstress und die Entfernung zur benachbarten Vegetation. Mithilfe einer Umfrage unter Interessenvertretern erhob ich deren Wahrnehmung der Auswirkungen invasiver Arten auf Ökosystemfunktionen und -dienstleistungen.
Samenregen, Samenbank und Keimlingsrekrutierung waren entlang von Wegen stark erhöht, und die Störungen durch Wege reichten weit in die Vegetation hinein. Entlang von Wanderwegen konnten alpine Arten weiter unten vorkommen, ihre warmen klimatischen Nischenränder und Optima in wärmere Gebiete verschieben), was zu einer stärkeren Überlappung der klimatischen Nischen mit Flachlandarten führte. Dies spiegelte sich in einem größeren Artenreichtum an Wegrändern als in der Vegetation abseits der Wege wider. Die ursprünglichen Planzengemeinschaft am Rande desWanderwegs und die Entfernung zu anthropogenen Strukturen, wie Hütten, beeinflussten, wie stark der Artenreichtum an Wegrändern zunahm. Die Größe der Vegetationslücken beeinflusste ihr Mikroklima. Die verstärkte Ansiedlung von Keimlingen in kleinen Vegetationslücken scheint das Ergebnis einer geringeren Konkurrenz um Licht zu sein. Bei kleinen Vegetationslücken scheint das einen größeren Effekt zu haben als die Verbesserung des Klimas durch die benachbarte Vegetation, die bei größeren Lücken fehlt. Die positiven Klimaeffekte durch die benachbarte Vegetation sind unter Stressbedingungen während des gesamten Lebenszyklus wichtig, doch besonders Keimlinge sind anfällig für akuten Stress. Je nach Art des Stresses ist die Unterstützung durch benachbarte Vegetation wichtiger oder unwichtige. Die Umfrage hat ergeben, dass die Auswirkungen invasiver Arten auf die biologische Vielfalt und die Ökosystemfunktionen von den Interessengruppen in allen Regionen überwiegend als negativ eingestuft wurde. Die Auswirkungen auf die Ökosystemdienstleistungen und -vorteile wurden hingegen auch positiv wahrgenommen. Verschiedene Interessentengruppen nahmen die Auswirkungen unterschiedlich wahr, wobei die Interessentengruppen vor Ort, wie z.B.Bauern oder Förster häufiger von positiven Auswirkungen berichteten. Die widersprüchlichen Auffassungen über die Auswirkungen könnten ein Grund für den großen Anteil der invasiven Arten sein, für die derzeit kein Managementplan vorliegt.
Diese Arbeit veranschaulicht, dassWegränder für bedrängte alpine Arten temporäre Fluchtwege vor konkurrenzstarken Flachlandpflanzen darstellen und den Artenreichtum in den Skanden lokal erhöhen können. Bei der Untersuchung biotischer Interaktionen sollten die räumlichen Skalen, auf denen die verschiedenen Umweltstressoren wirken, und die Toleranz der Zielarten gegenüber diesen Belastungen berücksichtigt werden. Weitere Forschungsarbeiten zu Veränderungen in der Verbreitung einheimischer und invasiver Arten sollten Auswirkungen berücksichtigen, die über die biologische Vielfalt hinausgehen.Sammendrag
For å beskytte fjelløkosystemer, deres biologiske mangfold og andre økosystemtjenester, må vi også forstå hvordan de påvirkes av klima og forstyrrelser. Menneskeskapte stier finnes det mange av i fjellområder, og dette er forstyrrelser som kan bidra til frøspredning og endre biotiske interaksjoner mellom planter, og potensielt tilrettelegge for rekruttering på steder hvor frø tidligere ikke kom frem, eller hvor etablering var hindret av konkurranse. Slik kan stier være med på å endre utbredelsen av hjemlige planter og bidra til spredning av fremmedarter i fjellområder, som igjen vil kunne påvirke økosystemfunksjoner, -tjenester og-goder. Målet med denne avhandlingen er å øke vår forståelse av hvordan stier påvirker arters utbredelse i den skandinaviske fjellkjeden og å øke kunnskapen vår om hvordan ulike aktører oppfatter påvirkningen av invaderende arter i fjellet.
Jeg utførte systematiske observasjonsundersøkelser langs turstier i Norge og Sverige og undersøkte hvilken effekt stiene hadde på frøregn, frøbanksammensetning, rekruttering fra frø og arters realiserte klimatiske nisjer. For å finne ut enda mer om de ulike artenes evne til å etablere seg og overleve, undersøkte jeg positive og negative interaksjoner mellom arter i forskjellige livsstadier. Det gjorde jeg i et felteksperiment ved å manipulere miljøstress og plantenes avstand til nabovegetasjonen. For å evaluere ulike aktørers oppfatning av påvirkningen fremmede skadelige arter/invaderende arter har på økosystemtjenester og -funksjoner utførte jeg en global spørreundersøkelse.
Langs stiene var det både økt frøregn, større frøbank og flere frøplanter, og forstyrrelser fra stiene nådde langt inn i vegetasjonen. Langs stier skiftet alpine arter sine varme klimatiske nisjekanter og optima mot varmere steder, noe som førte til økt overlapping av artens klimatiske nisjer. Dette gjenspeiles i at artsrikdommen var større i vegetasjonen langs stiene enn i vegetasjonen langt fra stien. Hvor mye artsrikdommen økte var avhengig av vegetasjonstype og avstand til menneskeskapte strukturer. Størrelsen på forstyrrelsen påvirket mikroklimaet i de forstyrrede åpningene i vegetasjonen. Økt etablering i små forstyrrelser ser ut til å være et resultat av redusert konkurranse om lys, noe som maskerer klimaforbedring av nabovegetasjon som blir tydeligere når man inkluderer større forstyrrelser. Under stressende forhold var fasilitering fra nabovegetasjonen viktig gjennom hele livssyklusen. Hvor viktig denne fasiliteringen var, kom an på type miljøstress. Spirer var mer utsatt for alvorlig stress enn voksne planter.
Aktører på tvers av regioner rangerte i hovedsak virkningene av invaderende arter/fremmede skadelige arter på biologisk mangfold og økosystemfunksjoner til å være negative, men det var også noen som rangerte virkningene på økosystemfunksjoner og -goder til å være positive. Aktørgruppene hadde ulik oppfatning av virkningene, og det var oftere rapporter om positve effekter fra aktører med en praktisk tilnærming. Motstridende syn på invaderende arters innvirkninger kan være grunnen til den store andelen av arter som i dag mangler en forvaltningsplan.
Denne avhandlingen viser at stikantvegetasjon kan fungere som midlertidige rømningsveier for fjellplanter fra konkurransedyktige lavlandsplanter, og at stier kan føre til lokalt høyere artsrikdom i den skandinaviske fjellkjeden. Avhandlingen understreker også viktigheten av å vurdere på hvilke skala ulikt miljøstress opererer, samt stresstoleranse hos fokusarten, når man undersøker biotiske interaksjoner. Videre forskning på endringer i utbredelsen av hjemlige og fremmede arter bør også ta hensyn til påvirkninger utover biologisk mangfold
Plant-mycorrhizal interactions and their role in plant invasions in mountains
No full textAbstract: Non-native species invasions are one of the most impactful drivers of biodiversity and ecosystem services loss worldwide. One aspect of plant species invasion, which is only recently starting to be recognized as a determinant of invasion success, is the symbiosis between plant and mycorrhizal fungi. Here, I focus on anthropogenic disturbance in mountain ecosystems and its impact on plant communities and mycorrhizal fungi to answer how these communities are impacted by disturbance and whether non-native plants can benefit to establish and spread. To this end I used a combination of different approaches: 1) repeated surveys of plants and arbuscular mycorrhizal fungi along disturbed roadsides in the mountains of Norway, 2) combining a global dataset of native and non-native plants along mountain roads with a database associating plants with their mycorrhizal types, and 3) an in-situ experiment measuring non-native plant success and changes in fungal community following different types of disturbances. Through these methods, I could assess the effects of anthropogenic disturbance on mycorrhizal symbiosis and non-native plant species at multiple scales and resolutions. We found that road disturbance has a globally consistent effect on mycorrhizal types in mountain systems, as plants associated with arbuscular mycorrhizal (AM) fungi were more abundant following disturbance. Conversely, vegetation associated with either ectomycorrhizal (EcM) or ericoid mycorrhizal (ErM) fungi was less abundant in disturbed sites. In the regional study, AM fungi were most abundant and diverse in the roots of plant communities affected by road disturbance. Non-native plants were also restricted to these disturbed sites. The experimental results showed that physical disturbance and nutrient addition have negative effects on EcM fungi and positive effects on fungal pathogens, and facilitate non-native plant success. Our results show that anthropogenic disturbance does have an effect on mycorrhizal fungi that in turn impacts the distribution of plant species in disturbed mountain systems. The resulting shift in mycorrhizal fungi benefiting AM fungi and AM plant species could have implications for non-native plant invasions. Indeed, we know that non-native plants predominantly form associations with AM fungi. Therefore, anthropogenic disturbance can facilitate non-native plant success through disruption of the native fungal communities, and especially so in high elevation and cold climate regions which are naturally less dominated by AM plants. I believe this highlights the importance of mycorrhizal symbiosis in understanding plant invasions and emphasizes the importance of monitoring sources of anthropogenic disturbance in mountains to prevent future establishment of non-native plants
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Hiking trails as conduits for the spread of non-native species into mountain areas
No full textRoadsides are major pathways of plant invasions in mountain regions. However, the increasing importance of tourism may also turn hiking trails into conduits of non-native plant spread to remote mountain landscapes. Here, we evaluated the importance of such trails for plant invasion in five protected mountain areas of southern central Chile. We therefore sampled native and non-native species along 17 trails and in the adjacent undisturbed vegetation. We analyzed whether the number and cover of non-native species in local plant assemblages is related to distance to trail and a number of additional variables that characterize the abiotic and biotic environment as well as the usage of the trail. We found that non-native species at higher elevations are a subset of the lowland source pool and that their number and cover decreases with increasing elevation and with distance to trails, although this latter variable only explained 4–8% of the variation in the data. In addition, non-native richness and cover were positively correlated with signs of livestock presence but negatively with the presence of intact forest vegetation. These results suggest that, at least in the region studied, hiking trails have indeed fostered non-native species spread to higher elevations, although less efficiently than roadsides. As a corollary, appropriate planning and management of trails could become increasingly important to control plant invasions into mountains in a world which is warming and where visitation and recreational use of mountainous areas is expected to increase.Fil: Liedtke, Rebecca. Universidad de Viena; AustriaFil: Barros, Ana Agustina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Essl, Franz. Universidad de Viena; AustriaFil: Lembrechts, Jonas J.. Universiteit Antwerp; BélgicaFil: Wedegärtner, Ronja E. M.. Universiteit Antwerp; BélgicaFil: Pauchard, Aníbal. Universidad de Concepción; ChileFil: Stefan Dullinger. Universidad de Viena; Austri
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