1,720,979 research outputs found
Rewiring of peatland plant–microbe networks outpaces species turnover
No full textInteractions between plant and microbial communities in peatlands are complex, yet pivotal for the functioning of these carbon-dense ecosystems. Our understanding of how climate change affects important peatland processes such as carbon dynamics is often based on assumed fixed relationships between above-and belowground communities. Our work shows that the turnover in plant–microbial interactions along enviro–climatic gradients is faster than species turnover within both communities, resulting in a mismatch in alpha diversity between plant and microbial communities. Notably, warming and increased nutrient deposition weakens plant–microbe linkages, which may consequentially decrease the overall robustness of peatland ecosystem processes to future anthropogenic pressures.</span
Rewiring of peatland plant–microbe networks outpaces species turnover
No full textInteractions between plant and microbial communities in peatlands are complex, yet pivotal for the functioning of these carbon-dense ecosystems. Our understanding of how climate change affects important peatland processes such as carbon dynamics is often based on assumed fixed relationships between above-and belowground communities. Our work shows that the turnover in plant–microbial interactions along enviro–climatic gradients is faster than species turnover within both communities, resulting in a mismatch in alpha diversity between plant and microbial communities. Notably, warming and increased nutrient deposition weakens plant–microbe linkages, which may consequentially decrease the overall robustness of peatland ecosystem processes to future anthropogenic pressures
Plant functional types define magnitude of drought response in peatland CO2 exchange
No full textPeatlands are important sinks for atmospheric carbon (C), yet the role of plant functional types (PFTs) for C sequestration under climatic perturbations is still unclear. A plant removal experiment was used to study the importance of vascular PFTs for the net ecosystem CO2 exchange (NEE) during (i.e. resistance) and after (i.e. recovery) an experimental drought. The removal of PFTs caused a decrease of NEE, but the rate differed between microhabitats (i.e. hummocks and lawns) and the type of PFTs.
Ericoid removal had a large effect on NEE in hummocks, while in the lawns the graminoids played a major role. The removal of PFTs did not affect the resistance or the recovery after the experimental drought. We argue that the response of Sphagnum mosses (the only PFT present in all treatments) to drought is dominant over that of coexisting PFTs. However, we observed that the moment in time in which the system switched from C sink to C source during the drought was controlled by the vascular PFTs. In the light of climate change, the shifts in species composition or even the loss of certain PFTs are expected to strongly affect the future C dynamics in response to environmental stress
Snow cover manipulation effects on microbial community structure and soil chemistry in a mountain bog
No full textBackground and Aims: Alterations in snow cover driven
by climate change may impact ecosystem functioning,
including biogeochemistry and soil (microbial)
processes. We elucidated the effects of snow cover
manipulation (SCM) on above-and belowground processes
in a temperate peatland.
Methods: In a Swiss mountain-peatland we manipulated
snow cover (addition, removal and control), and
assessed the effects on Andromeda polifolia root enzyme
activity, soil microbial community structure, and
leaf tissue and soil biogeochemistry.
Results: Reduced snow cover produced warmer soils
in our experiment while increased snow cover kept
soil temperatures close-to-freezing. SCM had a major
influence on the microbial community, and prolonged
‘close-to-freezing’ temperatures caused a shift in microbial
communities toward fungal dominance. Soil
temperature largely explained soil microbial structure,
while other descriptors such as root enzyme activity
and pore-water chemistry interacted less with the soil
microbial communities.
Conclusions: We envisage that SCM-driven changes
in the microbial community composition could lead to substantial changes in trophic fluxes and associated
ecosystem processes. Hence, we need to improve our
understanding on the impact of frost and freeze-thaw
cycles on the microbial food web and its implications
for peatland ecosystem processes in a changing climate;
in particular for the fate of the sequestered
carbon
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
Field Simulation of Global Change: Transplanting Northern Bog Mesocosms Southward
Get PDFA large proportion of northern peatlands consists of Sphagnum-dominated ombrotrophic bogs. In these bogs, peat mosses (Sphagnum) and vascular plants occur in an apparent stable equilibrium, thereby sustaining the carbon sink function of the bog ecosystem. How global warming and increased nitrogen (N) deposition will affect the species composition in bog vegetation is still unclear. We performed a transplantation experiment in which mesocosms with intact vegetation were transplanted southward from north Sweden to north-east Germany along a transect of four bog sites, in which both temperature and N deposition increased. In addition, we monitored undisturbed vegetation in control plots at the four sites of the latitudinal gradient. Four growing seasons after transplantation, ericaceous dwarf shrubs had become much more abundant when transplanted to the warmest site which also had highest N deposition. As a result ericoid aboveground biomass in the transplanted mesocosms increased most at the southernmost site, this site also had highest ericoid biomass in the undisturbed vegetation. The two dominant Sphagnum species showed opposing responses when transplanted southward; Sphagnum balticum height increment decreased, whereas S. fuscum height increment increased when transplanted southward. Sphagnum production did not differ significantly among the transplanted mesocosms, but was lowest in the southernmost control plots. The dwarf shrub expansion and increased N concentrations in plant tissues we observed, point in the direction of a positive feedback toward vascular plant-dominance suppressing peat-forming Sphagnum in the long term. However, our data also indicate that precipitation and phosphorus availability influence the competitive balance between Sphagnum, dwarf shrubs and graminoids
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
Microclimatological consequences for plant and microbial composition in Sphagnum-dominated peatlands
No full textIn three Scandinavian peatlands we studied to what extent plant and microbial community composition are governed by local scale microhabitat, with a special interest in the effect of aspect (i.e. exposition of slopes). Despite differences in solar irradiance between south-facing and north-facing slopes, maximum temperature was elevated in the south-facing slopes at the most northern site only. Porewater nutrient concentrations were not affected by aspect, yet dissolved organic carbon concentrations were higher in south-facing microhabitats. This is likely caused by higher vascular plant biomass. Plant and microbial community composition clearly differed between sites. In all three sites, microhabitat (i.e. prevailing water table depth) exerted a large control on the plant and microbial community composition. Aspect, however, did
not affect community composition, even though microclimate significantly differed between the south- and the north‐facing aspect in the northernmost site. Our results highlight the complex link between plant community composition, microbial community and environmental conditions, which deserves much more attention than it currently does in order to fully understand the effects of climate change on peatland ecosystem function
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