1,721,031 research outputs found
Wetter winters amplify temperature effects on fine root growth and increase tree growth in north-eastern European beech forests
No full texthttp://dx.doi.org/10.13039/501100001659 German Research Foundatio
Forest understory vegetation is more related to soil than to climate towards the cold distribution margin of European beech
No full textQuestion It is debated whether forest understory communities will be sensitive to projected climate change or inert due to the regulating effect of local site conditions and soil parameters. A distinction between the relative importance of climate or soil is often hardly possible because both factors usually change at different spatial scales in forests. Here, we compare the relative influence of climate and soil on the forest understory vegetation in lowland beech forest ecosystems (Fagus sylvatica), which were selected for their ecological homogeneity. Location Nine sites along a strong temperature gradient (ΔT = 4 K from east to west in winter, south to north in summer) between Rostock (Germany) and Gdańsk (Poland) in a Baltic Quaternary ground moraine landscape. Methods We conducted a vegetation survey in 55 vegetation plots (80 m2 each) across nine forest sites mono‐dominated by European beech and analysed how much variation in understory plant composition is explained by climate and soil parameters. Results Soil explained 32% of the compositional variation of understory vegetation across sites, climate 22%, and their interaction 14%. Topsoil pH, subsoil organic matter content, and subsoil C/N ratio were the most important soil variables; growing season temperature and annual water availability were the most important climatic variables. Conclusion The strong dependence on soil properties could moderate the response of the forest understory vegetation to projected climate change. Forest soil properties, however, also depend on the dominant tree species and the macroclimate. To predict climate change impacts on forest understory vegetation, climate change assessments should consider indirect climate change effects as well as interactions between climate and soil
15N tracer enrichment in response to winter soil temperature manipulation differs between canopy trees and juveniles
No full textSeasonal dynamics of fine root length in European beech: unveiling unexpected winter peaks and summer declines
Full text linkAbstract Fine roots play a crucial role in many ecological and biogeochemical processes in temperate forests. Generally, fine root biomass is expected to increase during the growing season, when water and nutrient demands are high, but information on seasonal variability is still scarce. Here, seasonal differences in root length of European beech ( Fagus sylvatica L.) were analysed at eight sites within its north-eastern distribution range. Fine roots of mature trees were monitored using minirhizotrons. Scans were taken for three different depths at the beginning of winter, the end of winter and over the summer for two consecutive years, and analysed automatically by an AI-algorithm (RootDetector). An additional experiment was carried out to show that the RootDetector was unaffected by changes in soil moisture. Root-length density was 40% higher at the beginning of winter and 51% higher at the end of winter than in summer. Our results indicate a net root loss during adverse conditions in early summer, but no trend towards deeper root growth over these drier periods. Interestingly, the root loss was compensated afterwards during more favourable conditions in autumn. We could show that fine root length in temperate forests is seasonally more variable and, so far, less predictable than previously assumed. A profound understanding of this seasonal variability is important for modelling terrestrial biogeochemical processes and global carbon fluxes.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659Universität Greifswald 50110001893
Winter matters: Sensitivity to winter climate and cold events increases towards the cold distribution margin of European beech (Fagus sylvatica L.)
No full textAim The dominant forest tree in Europe, European beech (Fagus sylvatica L.), covers large areas of continental Europe and thus experiences diverse climatic conditions. In the face of predicted climate change and shifts of distribution ranges, it is important to understand the diverse climate–growth relationships towards distribution margins. Beech is generally reported to be sensitive to summer drought towards dry and continental regions; yet, few studies have investigated climate sensitivity towards the cold distribution margin of beech. We hypothesized that at colder sites (a) growth of beech is more sensitive to winter cold, (b) growth is less influenced by summer drought, and (c) stand‐wide growth reductions (negative pointer years) are related to extreme winter cold events. Taxon European beech (Fagus sylvatica L.). Location A large gradient of decreasing winter temperature (ΔT >4 K along 500 km) from Rostock (Germany) to Gdańsk (Poland). Methods We analysed climate–growth relationships and the nature of growth reductions of 11 beech stands from more central to cold marginal beech populations. Results Towards the cold marginal populations, growth became increasingly sensitive to winter cold (February temperature) and less sensitive to summer water availability (June precipitation). Likewise, negative pointer years coincided with winter cold anomalies at the colder sites and with summer drought anomalies at the warmer sites. Thus, over the studied gradient, the general sensitivity of beech to summer drought transitions into sensitivity to winter cold. Main conclusions A range shift of beech across the current cold distribution margin is often assumed to compensate for habitat and productivity losses of drought‐prone southern and central populations. With respect to the winter cold sensitivity found in our study, such assumptions should be taken with caution. Since winter cold events are predicted to persist with similar frequency and magnitude even during predicted climate warming, beech populations in the newly colonized habitat might be significantly sensitive to winter cold
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Assessing the national red lists of European vascular plants: Disparities and implications
Full text linkThe diversity of vascular plant taxa in Europe is threatened. National red lists are valuable biodiversity conservation tools that provide us with information on the proximity of a taxon to extinction. However, there are still differences in the methods and implementation of these assessments across European countries, indicating gaps in conservation efforts at national and regional levels. To address these disparities, we conducted a study in which we compiled data from the most recent national red lists of vascular plants in European countries, including some countries from the eastern part of the Mediterranean biodiversity hotspot. Our results confirm concerns that the conservation status of European vascular flora is not fully mapped. We also found that this knowledge is not evenly distributed across European regions. There were differences in the availability of red lists, the regularity of updates, and the implementation of assessment methods. Countries that assessed their entire flora had a higher proportion of threatened taxa than countries that assessed only a portion of the flora.
This highlights the risk of overlooking the conservation status of less known taxa when
assessments are limited to specific taxa. Financial capacity was found to be a critical factor influencing the extent of these shortcomings.
Our study has shown that countries that assess their entire flora have, on average, higher national spending on environmental protection within their overall economies. This information is critical for developing effective biodiversity conservation strategies across Europe and for addressing the threats faced by vascular plants in the region
Variations on the Author
Full text link“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
Full text linkWe 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
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