Peatlands form important landscape elements in many parts of the world and play significant roles for biodiversity and global carbon balance. This new edition has been revised and updated, ...documenting the latest advances in areas such as microbial processes and relations between biological processes and hydrology. As well as referencing the latest research, this book exposes a rich older literature where an immense repository of natural history has accumulated. It starts with an overview of the main peatland types before examining the entire range of biota present, together with their specific adaptations to peatland habitats. Detailed coverage is devoted to the genus Sphagnum, the most important functional plant group in northern peatlands, although tropical and southern hemisphere peatlands are also covered. Throughout the book the interactions between organisms and environmental conditions (especially wetness, availability of oxygen, and pH) are emphasised, with chapters on the physical and chemical characteristics of peat, the role of peat as an archive of past vegetation and climate, and peatland succession and development. Several other key factors and processes are then discussed, including hydrology and nutrient cycling. The fascinating peatland landforms in different parts of the world are described, together with theories on how they have developed. Human interactions with peatlands are considered in terms of management, conservation, and restoration. A final chapter focuses on the role of peatlands as sources or sinks for the greenhouse gases carbon dioxide and methane, and the influences of climate change on peatlands.
Ancient plant DNA in lake sediments Parducci, Laura; Bennett, Keith D.; Ficetola, Gentile Francesco ...
The New phytologist,
20/May , Letnik:
214, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Recent advances in sequencing technologies now permit the analyses of plant DNA from fossil samples (ancient plant DNA, plant aDNA), and thus enable the molecular reconstruction of ...palaeofloras.Hitherto, ancient frozen soils have proved excellent in preservingDNAmolecules, and have thus been the most commonly used source of plant aDNA. However, DNA from soil mainly represents taxa growing a fewmetres fromthe sampling point. Lakes have larger catchment areas and recent studies have suggested that plant aDNAfromlake sediments is a more powerful tool for palaeofloristic reconstruction. Furthermore, lakes can be found globally in nearly all environments, and are therefore not limited to perennially frozen areas. Here,we review the latest approaches and methods for the study of plant aDNA from lake sediments and discuss the progressmade up to the present.Weargue that aDNAanalyses add newand additional perspectives for the study of ancient plant populations and, in time, will provide higher taxonomic resolution and more precise estimation of abundance. Despite this, key questions and challenges remain for such plant aDNA studies. Finally, we provide guidelines on technical issues, including lake selection, and we suggest directions for future research on plant aDNA studies in lake sediments.
Netrin1 has been proposed to act from the floor plate (FP) as a long-range diffusible chemoattractant for commissural axons in the embryonic spinal cord. However, netrin1 mRNA and protein are also ...present in neural progenitors within the ventricular zone (VZ), raising the question of which source of netrin1 promotes ventrally directed axon growth. Here, we use genetic approaches in mice to selectively remove netrin from different regions of the spinal cord. Our analyses show that the FP is not the source of netrin1 directing axons to the ventral midline, while local VZ-supplied netrin1 is required for this step. Furthermore, rather than being present in a gradient, netrin1 protein accumulates on the pial surface adjacent to the path of commissural axon extension. Thus, netrin1 does not act as a long-range secreted chemoattractant for commissural spinal axons but instead promotes ventrally directed axon outgrowth by haptotaxis, i.e., directed growth along an adhesive surface.
•Netrin1 signaling from the VZ, not the FP, guides spinal commissural axons•Spinal progenitors produce netrin1 and deposit it as a substrate on the pial surface•The VZ-derived netrin1 substrate promotes ventrally directed axonal growth•Dcc is required to interpret the axonal response to VZ-derived netrin1
Varadarajan et al. show that netrin1 supplied by neural progenitors, not floor plate (FP) cells, guides commissural axons in the developing spinal cord. These findings contrast with the long-held model that the FP supplies a long-range axonal chemoattractant. Rather, netrin1 is produced by neural progenitors and deposited on the pial surface, providing a growth substrate that directs ventrally directed axonal growth.
This paper evaluates how long-term records could and should be utilized in conservation policy and practice. Traditionally, there has been an extremely limited use of long-term ecological records ...(greater than 50 years) in biodiversity conservation. There are a number of reasons why such records tend to be discounted, including a perception of poor scale of resolution in both time and space, and the lack of accessibility of long temporal records to non-specialists. Probably more important, however, is the perception that even if suitable temporal records are available, their roles are purely descriptive, simply demonstrating what has occurred before in Earth's history, and are of little use in the actual practice of conservation. This paper asks why this is the case and whether there is a place for the temporal record in conservation management. Key conservation initiatives related to extinctions, identification of regions of greatest diversity/threat, climate change and biological invasions are addressed. Examples of how a temporal record can add information that is of direct practicable applicability to these issues are highlighted. These include (i) the identification of species at the end of their evolutionary lifespan and therefore most at risk from extinction, (ii) the setting of realistic goals and targets for conservation 'hotspots', and (iii) the identification of various management tools for the maintenance/restoration of a desired biological state. For climate change conservation strategies, the use of long-term ecological records in testing the predictive power of species envelope models is highlighted, along with the potential of fossil records to examine the impact of sea-level rise. It is also argued that a long-term perspective is essential for the management of biological invasions, not least in determining when an invasive is not an invasive. The paper concludes that often inclusion of a long-term ecological perspective can provide a more scientifically defensible basis for conservation decisions than the one based only on contemporary records. The pivotal issue of this paper is not whether long-term records are of interest to conservation biologists, but how they can actually be utilized in conservation practice and policy.
Abstract Background Fish injury and mortality resulting from entrainment and/or impingement during downstream passage over/through hydropower infrastructure has the potential to cause negative ...effects on fish populations. The primary goal of this systematic review was to address two research questions: (1) What are the consequences of hydroelectric dam fish entrainment and impingement on freshwater fish productivity in temperate regions?; (2) To what extent do various factors like site type, intervention type, and life history characteristics influence the consequences of fish entrainment and impingement? Methods The review was conducted using guidelines provided by the Collaboration for Environmental Evidence and examined commercially published and grey literature. All articles found using a systematic search were screened using a priori eligibility criteria at two stages (title and abstract, and full-text, respectively), with consistency checks being performed at each stage. The validity of studies was appraised and data were extracted using tools explicitly designed for this review. A narrative synthesis encompassed all relevant studies and a quantitative synthesis (meta-analysis) was conducted where appropriate. Review findings A total of 264 studies from 87 articles were included for critical appraisal and narrative synthesis. Studies were primarily conducted in the United States (93%) on genera in the Salmonidae family (86%). The evidence base did not allow for an evaluation of the consequences of entrainment/impingement on fish productivity per se; therefore, we evaluated the risk of freshwater fish injury and mortality owing to downstream passage through common hydropower infrastructure. Our quantitative synthesis suggested an overall increased risk of injury and immediate mortality from passage through/over hydropower infrastructure. Injury and immediate mortality risk varied among infrastructure types. Bypasses resulted in decreased injury risk relative to controls, whereas turbines and spillways were associated with the highest injury risks relative to controls. Within turbine studies, those conducted in a lab setting were associated with higher injury risk than field-based studies, and studies with longer assessment time periods (≥ 24–48 h) were associated with higher risk than shorter duration assessment periods (< 24 h). Turbines and sluiceways were associated with the highest immediate mortality risk relative to controls. Within turbine studies, lab-based studies had higher mortality risk ratios than field-based studies. Within field studies, Francis turbines resulted in a higher immediate mortality risk than Kaplan turbines relative to controls, and wild sourced fish had a higher immediate mortality risk than hatchery sourced fish in Kaplan turbines. No other associations between effect size and moderators were identified. Taxonomic analyses revealed a significant increased injury and immediate mortality risk relative to controls for genera Alosa (river herring) and Oncorhynchus (Pacific salmonids), and delayed mortality risk for Anguilla (freshwater eels). Conclusions Our synthesis suggests that hydropower infrastructure in temperate regions increased the overall risk of freshwater fish injury and immediate mortality relative to controls. The evidence base confirmed that turbines and spillways increase the risk of injury and/or mortality for downstream passing fish compared to controls. Differences in lab- and field-based studies were evident, highlighting the need for further studies to understand the sources of variation among lab- and field-based studies. We were unable to examine delayed mortality, likely due to the lack of consistency in monitoring for post-passage delayed injury and mortality. Our synthesis suggests that bypasses are the most “fish friendly” passage option in terms of reducing fish injury and mortality. To address knowledge gaps, studies are needed that focus on systems outside of North America, on non-salmonid or non-sportfish target species, and on population-level consequences of fish entrainment/impingement.
Mid to high latitude forest ecosystems have undergone several major compositional changes during the Holocene. The temporal and spatial patterns of these vegetation changes hold potential information ...to their causes and triggers. Here we test the hypothesis that the timing of vegetation change was synchronous on a sub-continental scale, which implies a common trigger or a step-like change in climate parameters. Pollen diagrams from selected European regions were statistically divided into assemblage zones and the temporal pattern of the zone boundaries analysed. The results show that the temporal pattern of vegetation change was significantly different from random. Times of change cluster around 8.2, 4.8, 3.7, and 1.2 ka, while times of higher than average stability were found around 2.1 and 5.1 ka. Compositional changes linked to the expansion of
Corylus avellana and
Alnus glutinosa centre around 10.6 and 9.5 ka, respectively. A climatic trigger initiating these changes may have occurred 0.5 to 1 ka earlier, respectively. The synchronous expansion of
C. avellana and
A. glutinosa exemplify that dispersal is not necessarily followed by population expansion. The partly synchronous, partly random expansion of
A. glutinosa in adjacent European regions exemplifies that sudden synchronous population expansions are not species specific traits but vary regionally.
► Statistical division of 59 pollen diagrams from European regions into assemblage zones. ► The timing of zone boundaries is different from random. ► Times of vegetation change and stability can be distinguished. ► The expansion of hazel and black alder populations was triggered by climate. ► The two species may have been widespread long before their populations expanded.
Objective Early in our experience with endovascular aortic aneurysm repair (EVAR) we performed both serial computed tomography scans and duplex ultrasound (DU) imaging in our post-EVAR surveillance ...regimen. Later we conducted a prospective study with DU imaging as the sole surveillance study and determined cost savings and outcome using this strategy. Methods From September 21, 1998, to May 30, 2008, 250 patients underwent EVAR at our hospital. Before July 1, 2004, EVAR patients underwent CT and DU imaging performed every 6 months during the first year and then annually if no problems were identified (group 1). We compared aneurysm sac size, presence of endoleak, and graft patency between the two scanning modalities. After July 1, 2004, patients underwent surveillance using DU imaging as the sole surveillance study unless a problem was detected (group 2). CT and DU imaging charges for each regimen were compared using our 2008 health system pricing and Medicare reimbursements. All DU examinations were performed in our accredited noninvasive vascular laboratory by experienced technologists. Statistical analysis was performed using Pearson correlation coefficient. Results DU and CT scans were equivalent in determining aneurysm sac diameter after EVAR ( P < .001). DU and CT were each as likely to falsely suggest an endoleak when none existed and were as likely to miss an endoleak. Using DU imaging alone would have reduced cost of EVAR surveillance by 29% ($534,356) in group 1. Cost savings of $1595 per patient per year were realized in group 2 by eliminating CT scan surveillance. None of the group 2 patients sustained an adverse event such as rupture, graft migration, or limb occlusion as a result of having DU imaging performed as the sole follow-up modality. Conclusion Surveillance of EVAR patients can be performed accurately, safely, and cost-effectively with DU as the sole imaging study.
Altering the natural flow regime, an essential component of healthy fluvial systems, through hydropower operations has the potential to negatively impact freshwater fish populations. Establishing ...improved management of flow regimes requires better understanding of how fish respond to altered flow components, such as flow magnitude. Based on the results of a recent systematic map on the impacts of flow regime changes on direct outcomes of freshwater or estuarine fish productivity, evidence clusters on fish abundance and biomass responses were identified for full systematic review. The primary goal of this systematic review is to address one of those evidence clusters, with the following research question: how do changes in flow magnitude due to hydropower operations affect fish abundance and biomass?
This review follows the guidelines of the Collaboration for Environmental Evidence. It examined commercially published and grey literature originally identified during the systematic map process and a systematic search update. All articles were screened using an a priori eligibility criteria at two stages (title and abstract, and full-text) and consistency checks were performed at all stages. All eligible articles were assessed for study validity and specifically designed data extraction and study validity tools were used. A narrative synthesis included all available evidence and meta-analysis using the standardized mean difference (Hedges'
) was conducted where appropriate.
A total of 133 studies from 103 articles were included in this systematic review for data extraction and critical appraisal. Most studies were from North America (60%) and were conducted at 146 different hydropower dams/facilities. Meta-analysis included 268 datasets from 58 studies, separated into three analyses based on replication type temporal (within or between year replication) or spatial. Fish abundance (226 datasets) and biomass (30 datasets) had variable responses to changes in flow magnitude with estimated overall mean effect sizes ranging from positive to negative and varying by study design and taxa. In studies with temporal replication, we found a detectable effect of alterations to the direction of flow magnitude, the presence of other flow components, sampling methods, season, and fish life stage. However, we found no detectable effect of these moderators for studies with spatial replication. Taxonomic analyses indicated variable responses to changes in flow magnitude and a bias towards salmonid species.
This synthesis did not find consistent patterns in fish abundance or biomass responses to alterations or changes in flow magnitude. Fish responses to flow magnitude alterations or changes were highly variable and context dependent. Our synthesis suggests that biotic responses may not be generalizable across systems impacted by hydroelectric power production and operations, where specific features of the system may be highly influential. Site-specific and adaptive management may be necessary. To improve study validity and interpretability, studies with long-term continuous monitoring, and both temporal and spatial replication are needed. When this gold standard is unfeasible, studies should strive, at minimum, to maximize replication within both intervention and comparator groups for either temporal or spatial designs. To further address knowledge gaps, studies are needed that focus on non-salmonids, multiple seasons, and systems outside of North America.
The online version contains supplementary material available at 10.1186/s13750-021-00254-8.
Objective While the significance of type II endoleaks (T2ELs) on the long-term outcome of endovascular abdominal aneurysm repair (EVAR) to repair abdominal aortic aneurysms (AAAs) is debatable, ...duplex ultrasonography (DU) parameters have been suggested to be predictive of their closure or persistence. The purpose of this study was to determine which, if any, of these variables was associated with persistent T2EL or increased AAA sac diameter. Methods Between 1998 and 2009, 278 patients underwent EVAR and post-operative DU surveillance during long-term follow-up (1-11 years) in our accredited non-invasive vascular laboratory by one of three experienced technologists. DU measured intra-sac flow velocity (IFV), spectral doppler waveform (SDW) patterns, post-EVAR sac diameter, and number of T2ELs. Results T2ELs developed in 14% (38/278) of patients post-EVAR. Fourteen patients had T2ELs that resolved, and sac diameter decreased or remained the same: the average IFV was 42 cm/second; SDW patterns were monophasic in five, biphasic in seven and bidirectional in two; and multiple T2ELs were not present (0%) in any patient. Twelve patients had T2ELs that persisted, but sac diameter decreased or remained the same: the average IFV was 47 cm/second; SDW patterns were monophasic in one, biphasic in five, bidirectional in five, and undetermined in one; and multiple T2ELs were found in 17% (2) of patients. Twelve patients had T2ELs that persisted and were associated with increased sac diameter: the average IFV was 43 cm/second, SDW patterns were monophasic in one, biphasic in two, and bidirectional in nine; and multiple T2ELs were identified in 75% (9) of patients. None of the 38 patients with T2ELs treated with selective surgical or endovascular intervention for enlarging sac diameters (11/12) experienced a ruptured aneurysm. Conclusion Contrary to previous smaller reports of T2ELs and DU surveillance, parameters such as IFV did not correlate with increased post-EVAR sac diameter. The presence of multiple T2ELs and bidirectional SDW may be the strongest factors predictive of increased sac diameter.
•A multiplex assay for the bovine inflammatory cytokines IL-1b, IL-6, and TNF-a was developed using the MSD U-PLEX platform.•“Do-It-Yourself” ELISA kits can be adapted to work in this platform.
...Commercially available bovine-specific assays are limited in number, and multiplex assays for this species are rare. Our objective was to develop a multiplex assay for the bovine inflammatory cytokines IL-1β, IL-6, and TNF-α using the Meso Scale Discovery U-PLEX platform. "Do-It-Yourself" ELISA kits that contained polyclonal antibodies, both unlabeled and biotinylated, and the specific recombinant bovine cytokine standard, were purchased for each of these three cytokines. The biotinylated antibodies were coupled to linkers that bind to specific locations within each well of the U-PLEX plate. Unique linkers were used for each of the cytokines. The unlabeled antibodies were conjugated with electrochemiluminescent labels to serve as detection antibodies. Each cytokine assay was optimized individually prior to performing an optimization on the multiplex assay containing reagents for all three cytokines. To calculate cytokine concentrations, standard curves were developed using the recombinant cytokines and were run concurrently on each plate. Standard curves for IL-1β and TNF-α were run at concentrations ranging from 0 to 50,000 pg/mL, and for IL-6 from 0 to 10,000 pg/mL. The average lowest level of detection concentration measured by the standard curves were 5.3 pg/mL, 0.92 pg/mL, and 22.34 pg/mL for IL-1β, IL-6, and TNF-α respectively, as determined by data from seven plates containing bovine plasma samples from a combination of healthy and diseased cattle. The U-PLEX platform was a viable means to develop custom analyte- and species-specific multiplex assays using privately developed or purchased sets of commercially available reagents.
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