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71.
Sensitivity of CO<Subscript>2</Subscript> Exchange of Fen Ecosystem Components to Water Level Variation 总被引:1,自引:0,他引:1
Abstract
Climate change is predicted to bring about a water level (WL) draw-down in boreal peatlands. This study aimed to assess the
effect of WL on the carbon dioxide (CO2) dynamics of a boreal oligotrophic fen ecosystem and its components; Sphagnum mosses, sedges, dwarf shrubs and the underlying peat. We measured CO2 exchange with closed chambers during four growing seasons in a study site that comprised different vegetation treatments.
WL gradient in the site was broadened by surrounding half of the site with a shallow ditch that lowered the WL by 10–25 cm.
We modeled gross photosynthesis (P
G) and ecosystem respiration (R
ECO) and simulated the CO2 exchange in three WL conditions: prevailing and WL draw-down scenarios of 14 and 22 cm. WL draw-down both reduced the P
G and increased the R
ECO, thus leading to a smaller net CO2 uptake in the ecosystem. Of the different components, Sphagnum mosses were most sensitive to WL draw-down and their physiological activities almost ceased. Vascular plant CO2 exchange, en bloc, hardly changed but whereas sedges contributed twice as much to the CO2 exchange as shrubs in the prevailing conditions, the situation was reversed in the WL draw-down scenarios. Peat respiration
was the biggest component in R
ECO in all WL conditions and the increase in R
ECO following the WL draw-down was due to the increase in peat respiration. The results imply that functional diversity buffers
the ecosystem against environmental variability and that in the long term, WL draw-down changes the vegetation composition
of boreal fens. 相似文献
72.
Ana P. Tedim Patricia Ruiz-Garbajosa Jukka Corander Concepción M. Rodríguez Rafael Cantón Rob J. Willems Fernando Baquero Teresa M. Coque 《Applied and environmental microbiology》2015,81(5):1820-1831
The diversity of enterococcal populations from fecal samples from hospitalized (n = 133) and nonhospitalized individuals (n = 173) of different age groups (group I, ages 0 to 19 years; group II, ages 20 to 59 years; group III, ages ≥60 years) was analyzed. Enterococci were recovered at similar rates from hospitalized and nonhospitalized persons (77.44% to 79.77%) of all age groups (75.0% to 82.61%). Enterococcus faecalis and Enterococcus faecium were predominant, although seven other Enterococcus species were identified. E. faecalis and E. faecium (including ampicillin-resistant E. faecium) colonization rates in nonhospitalized persons were age independent. For inpatients, E. faecalis colonization rates were age independent, but E. faecium colonization rates (particularly the rates of ampicillin-resistant E. faecium colonization) significantly increased with age. The population structure of E. faecium and E. faecalis was determined by superimposing goeBURST and Bayesian analysis of the population structure (BAPS). Most E. faecium sequence types (STs; 150 isolates belonging to 75 STs) were linked to BAPS groups 1 (22.0%), 2 (31.3%), and 3 (36.7%). A positive association between hospital isolates and BAPS subgroups 2.1a and 3.3a (which included major ampicillin-resistant E. faecium human lineages) and between community-based ampicillin-resistant E. faecium isolates and BAPS subgroups 1.2 and 3.3b was found. Most E. faecalis isolates (130 isolates belonging to 58 STs) were grouped into 3 BAPS groups, BAPS groups 1 (36.9%), 2 (40.0%), and 3 (23.1%), with each one comprising widespread lineages. No positive associations with age or hospitalization were established. The diversity and dynamics of enterococcal populations in the fecal microbiota of healthy humans are largely unexplored, with the available knowledge being fragmented and contradictory. The study offers a novel and comprehensive analysis of enterococcal population landscapes and suggests that E. faecium populations from hospitalized patients and from community-based individuals differ, with a predominance of certain clonal lineages, often in association with elderly individuals, occurring in the hospital setting. 相似文献
73.
Laura Morley Alan McNally Konrad Paszkiewicz Jukka Corander Guillaume Méric Samuel K. Sheppard Jochen Blom Georgina Manning 《Applied and environmental microbiology》2015,81(11):3641-3647
Campylobacter jejuni is a highly diverse species of bacteria commonly associated with infectious intestinal disease of humans and zoonotic carriage in poultry, cattle, pigs, and other animals. The species contains a large number of distinct clonal complexes that vary from host generalist lineages commonly found in poultry, livestock, and human disease cases to host-adapted specialized lineages primarily associated with livestock or poultry. Here, we present novel data on the ST403 clonal complex of C. jejuni, a lineage that has not been reported in avian hosts. Our data show that the lineage exhibits a distinctive pattern of intralineage recombination that is accompanied by the presence of lineage-specific restriction-modification systems. Furthermore, we show that the ST403 complex has undergone gene decay at a number of loci. Our data provide a putative link between the lack of association with avian hosts of C. jejuni ST403 and both gene gain and gene loss through nonsense mutations in coding sequences of genes, resulting in pseudogene formation. 相似文献
74.
Hui Sun Minna Santalahti Jukka Pumpanen Kajar K?ster Frank Berninger Tommaso Raffaello Ari Jumpponen Fred O. Asiegbu Jussi Heinonsalo 《Applied and environmental microbiology》2015,81(22):7869-7880
Forest fires are a common natural disturbance in forested ecosystems and have a large impact on the microbial communities in forest soils. The response of soil fungal communities to forest fire is poorly documented. Here, we investigated fungal community structure and function across a 152-year boreal forest fire chronosequence using high-throughput sequencing of the internal transcribed spacer 2 (ITS2) region and a functional gene array (GeoChip). Our results demonstrate that the boreal forest soil fungal community was most diverse soon after a fire disturbance and declined over time. The differences in the fungal communities were explained by changes in the abundance of basidiomycetes and ascomycetes. Ectomycorrhizal (ECM) fungi contributed to the increase in basidiomycete abundance over time, with the operational taxonomic units (OTUs) representing the genera Cortinarius and Piloderma dominating in abundance. Hierarchical cluster analysis by using gene signal intensity revealed that the sites with different fire histories formed separate clusters, suggesting differences in the potential to maintain essential biogeochemical soil processes. The site with the greatest biological diversity had also the most diverse genes. The genes involved in organic matter degradation in the mature forest, in which ECM fungi were the most abundant, were as common in the youngest site, in which saprotrophic fungi had a relatively higher abundance. This study provides insight into the impact of fire disturbance on soil fungal community dynamics. 相似文献
75.
Fecundity selection does not vary along a large geographical cline of trait means in a passerine bird
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Päivi M. Sirkiä Peter Adamík Alexandr V. Artemyev Eugen Belskii Christiaan Both Stanislav Bureš Malcolm Burgess Andrey V. Bushuev Jukka T. Forsman Vladimir Grinkov Dieter Hoffmann Antero Järvinen Miroslav Král Indrikis Krams Helene M. Lampe Juan Moreno Marko Mägi Andreas Nord Jaime Potti Pierre‐Alain Ravussin Leonid Sokolov Toni Laaksonen 《Biological journal of the Linnean Society. Linnean Society of London》2015,114(4):808-827
Local environmental and ecological conditions are commonly expected to result in local adaptation, although there are few examples of variation in phenotypic selection across continent‐wide spatial scales. We collected standardized data on selection with respect to the highly variable plumage coloration of pied flycatcher (Ficedula hypoleuca Pall.) males from 17 populations across the species' breeding range. The observed selection on multiple male coloration traits via the annual number of fledged young was generally relatively weak. The main aim of the present study, however, was to examine whether the current directional selection estimates are associated with distance to the sympatric area with the collared flycatcher (Ficedula albicollis Temminck), a sister species with which the pied flycatcher is showing character displacement. This pattern was expected because plumage traits in male pied flycatchers are changing with the distance to these areas of sympatry. However, we did not find such a pattern in current selection on coloration. There were no associations between current directional selection on ornamentation and latitude or longitude either. Interestingly, current selection on coloration traits was not associated with the observed mean plumage traits of the populations. Thus, there do not appear to be geographical gradients in current directional fecundity selection on male plumage ornamentation. The results of the present study do not support the idea that constant patterns in directional fecundity selection would play a major role in the maintenance of coloration among populations in this species. By contrast, the tendency for relatively weak mosaic‐like variation in selection among populations could reflect just a snapshot of temporally variable, potentially environment‐dependent, selection, as suggested by other studies in this system. Such fine‐grained variable selection coupled with gene flow could maintain extensive phenotypic variation across populations. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 808–827. 相似文献
76.
Kristian?SpillingEmail author Jukka?Sepp?l? Timo?Tamminen 《Journal of applied phycology》2011,23(6):959-966
The effect of pH on flocculation was studied using the diatom Phaeodactylum tricornutum and the green algae Scenedesmus cf. obliquus as surrogate species. There was a distinct, species-specific threshold of pH where flocculation started. P. tricornutum started to flocculate at pH 10.5 and S. cf. obliquus at pH 11.3. Above this threshold, settling rates up to 360 cm h−1 were observed for P. tricornutum and the concentrating factor was up to 60-fold. The combined effect of pH, turbulence, and cell density on flocculation of
P. tricornutum was additionally studied in a factorial 53-design experiment. pH was the most important factor affecting flocculation, but at the pH threshold (pH 10.5), the concentrating
factor was increased by increasing cell density and turbulence. Algae increases the pH during photosynthesis, and the P. tricornutum and S. cf. obliquus cultures increased the pH to a maximum of 10.8 and 9.5, respectively, after discontinuing the CO2 supply. For P. tricornutum, this was above the flocculation threshold, and rapid settling of this species due to increased pH was observed in a matter
of hours after the CO2 supply was turned off. This could be used as a simple, low-cost, initial dewatering step for this species. 相似文献
77.
78.
Marco Pautasso Katrin Böhning‐Gaese Philippe Clergeau Victor R. Cueto Marco Dinetti Esteban Fernández‐Juricic Marja‐Liisa Kaisanlahti‐Jokimäki Jukka Jokimäki Michael L. McKinney Navjot S. Sodhi David Storch Ludwik Tomialojc Peter J. Weisberg John Woinarski Richard A. Fuller Elena Cantarello 《Global Ecology and Biogeography》2011,20(3):426-436
Aim Despite the increasing pace of urbanization, little is known about how this process affects biodiversity globally. We investigate macroecological patterns of bird assemblages in urbanized areas relative to semi‐natural ecosystems. Location World‐wide. Methods We use a database of quantitative bird surveys to compare key assemblage structure parameters for plots in urbanized and semi‐natural ecosystems controlling for spatial autocorrelation and survey methodology. We use the term ‘urbanized’ instead of ‘urban’ ecosystems as many of the plots were not located in the centre of towns but in remnant habitat patches within conurbations. Results Some macroecological relationships were conserved in urbanized landscapes. Species–area, species–abundance and species–biomass relationships did not differ significantly between urbanized and non‐urbanized environments. However, there were differences in the relationships between productivity and assemblage structure. In forests, species richness increased with productivity; in both forests and open habitats, the evenness of species abundances declined as productivity increased. Among urbanized plots, instead, both species richness and the evenness of species abundances were independent of variation in productivity. Main conclusions Remnant habitats within urbanized areas are subject to many ecological alterations, yet key macroecological patterns differ remarkably little in urbanized versus non‐urbanized plots. Our results support the need for increased conservation activities in urbanized landscapes, particularly given the additional benefits of local experiences of biodiversity for the human population. With increasing urbanization world‐wide, broad‐scale efforts are needed to understand and manage the effects of this driver of change on biodiversity. 相似文献
79.
80.
Vibhor Kumar Sarah J. Butcher Katariina ??rni Peter Engelhardt Jukka Heikkonen Kimmo Kaski Mika Ala-Korpela Petri T. Kovanen 《PloS one》2011,6(5)