Ungulate trampling modifies soils and interlinked ecosystem functions across biomes. Until today, most research has focused on temperate ecosystems and mineral soils while trampling effects on cold ...and organic matter‐rich tundra soils remain largely unknown.
We aimed to develop a general model of trampling effects on soil structure, biota, microclimate and biogeochemical processes, with a particular focus on polar tundra soils. To reach this goal, we reviewed literature about the effects of trampling and physical disturbances on soils across biomes and used this to discuss the knowns and unknowns of trampling effects on tundra soils.
We identified the following four pathways through which trampling affects soils: (a) soil compaction; (b) reductions in soil fauna and fungi; (c) rapid losses in vegetation biomass and cover; and (d) longer term shifts in vegetation community composition.
We found that, in polar tundra, soil responses to trampling pathways 1 and 3 could be characterized by nonlinear dynamics and tundra‐specific context dependencies that we formulated into testable hypotheses.
In conclusion, trampling may affect tundra soil significantly but many direct, interacting and cascading responses remain unknown. We call for research to advance the understanding of trampling effects on soils to support informed efforts to manage and predict the functioning of tundra systems under global changes.
A free Plain Language Summary can be found within the Supporting Information of this article.
A free Plain Language Summary can be found within the Supporting Information of this article.
The strontium isotope signature ( 87 Sr/ 86 Sr) of calcite precipitated in rock fractures and faults is a frequently used tool to trace paleofluid flow. However, bedrock fracture networks, such as in ...Precambrian cratons, have often undergone multiple fracture reactivations resulting in complex sequences of fracture mineral infillings. This includes numerous discrete calcite crystal overgrowths. Conventional 87 Sr/ 86 Sr analysis of dissolved bulk samples of such crystals is not feasible as they will result in mixed signatures of several growth zonations. In addition, the zonations are too fine-grained for sub-sampling using micro-drilling. Here, we apply high spatial resolution 87 Sr/ 86 Sr spot analysis (80 µm) in transects through zoned calcite crystals in deep Paleoproterozoic granitoid fractures using laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) to trace discrete signs of paleofluid flow events. We compare the outermost calcite growth zone with 87 Sr/ 86 Sr values of the present-day groundwater sampled in the same boreholes to distinguish potential modern precipitates. We then connect our results to previously reported radiometric dating and C and O isotope signatures to understand the temporal history and physicochemical evolution of fluid flow within the fractures. Comparisons of modern calcite precipitated in a borehole over a period of 17 years with modern waters prove the concept of using 87 Sr/ 86 Sr as a marker for fluid origin in this environment and for how 87 Sr/ 86 Sr changed during marine water infiltration. Intermittent calcite precipitation over very long time spans is indicated in calcite of the currently open fractures, showing an evolution of 87 Sr/ 86 Sr from ~0.705–0.707—a population dated to ~1.43 billion years—to crystal overgrowth values at ~0.715–0.717 that overlap with the present-day groundwater values. This shows that high spatial resolution Sr isotope analysis of fine-scaled growth zonation within single calcite crystals is applicable for tracing episodic fluid flow in fracture networks
Since the last Arctic Monitoring and Assessment Programme (AMAP) effort to review biological effects of the exposure to organohalogen compounds (OHCs) in Arctic biota, there has been a considerable ...number of new Arctic effect studies. Here, we provide an update on the state of the knowledge of OHC, and also include mercury, exposure and/or associated effects in key Arctic marine and terrestrial mammal and bird species as well as in fish by reviewing the literature published since the last AMAP assessment in 2010. We aimed at updating the knowledge of how single but also combined health effects are or can be associated to the exposure to single compounds or mixtures of OHCs. We also focussed on assessing both potential individual as well as population health impacts using population-specific exposure data post 2000. We have identified quantifiable effects on vitamin metabolism, immune functioning, thyroid and steroid hormone balances, oxidative stress, tissue pathology, and reproduction. As with the previous assessment, a wealth of documentation is available for biological effects in marine mammals and seabirds, and sentinel species such as the sledge dog and Arctic fox, but information for terrestrial vertebrates and fish remain scarce. While hormones and vitamins are thoroughly studied, oxidative stress, immunotoxic and reproductive effects need further investigation. Depending on the species and population, some OHCs and mercury tissue contaminant burdens post 2000 were observed to be high enough to exceed putative risk threshold levels that have been previously estimated for non-target species or populations outside the Arctic. In this assessment, we made use of risk quotient calculations to summarize the cumulative effects of different OHC classes and mercury for which critical body burdens can be estimated for wildlife across the Arctic. As our ultimate goal is to better predict or estimate the effects of OHCs and mercury in Arctic wildlife at the individual, population and ecosystem level, there remain numerous knowledge gaps on the biological effects of exposure in Arctic biota. These knowledge gaps include the establishment of concentration thresholds for individual compounds as well as for realistic cocktail mixtures that in fact indicate biologically relevant, and not statistically determined, health effects for specific species and subpopulations. Finally, we provide future perspectives on understanding Arctic wildlife health using new in vivo, in vitro, and in silico techniques, and provide case studies on multiple stressors to show that future assessments would benefit from significant efforts to integrate human health, wildlife ecology and retrospective and forecasting aspects into assessing the biological effects of OHC and mercury exposure in Arctic wildlife and fish.
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•We review current knowledge of contaminant exposure and effects in Arctic biota.•Effects were found on vitamin metabolism, immune functioning and hormones.•Other effects included oxidative stress, pathology and reproduction.•Marine mammals and seabirds well studied, terrestrial wildlife and fish much less.•Methods exist to model contaminant population effects, but more work is needed.
Genome sequences from over 200 plant species have already been published, with this number expected to increase rapidly due to advances in sequencing technologies. Once a new genome has been ...assembled and the genes identified, the functional annotation of their putative translational products, proteins, using ontologies is of key importance as it places the sequencing data in a biological context. Furthermore, to keep pace with rapid production of genome sequences, this functional annotation process must be fully automated. Here we present a redesigned and significantly enhanced MapMan4 framework, together with a revised version of the associated online Mercator annotation tool. Compared with the original MapMan, the new ontology has been expanded almost threefold and enforces stricter assignment rules. This framework was then incorporated into Mercator4, which has been upgraded to reflect current knowledge across the land plant group, providing protein annotations for all embryophytes with a comparably high quality. The annotation process has been optimized to allow a plant genome to be annotated in a matter of minutes. The output results continue to be compatible with the established MapMan desktop application.
MapMan4 is a substantial redesign of the MapMan framework incorporating the latest literature knowledge to provide greatly enhanced protein family granularity. The online Mercator4 tool uses this framework to rapidly functionally annotate protein sequences from any land plant species.
The PREDICTS project—Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)—has collated from published studies a large, reasonably representative database ...of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.
The collation of biodiversity datasets with broad taxonomic, biogeographic, and spatial extents is necessary to understand historical declines and to project—and hopefully avert—future declines. We describe and make freely available a database of more than 3.2 million biodiversity measurements from 94 countries representing over 47,000 species, collated from 480 existing spatial comparisons of local‐scale biodiversity exposed to different intensities and pressures relating to land use, from terrestrial sites around the world.
A large number of organic pollutants (OPs) emitted from vehicles and traffic-related activities exhibit environmental persistence and a tendency to bioaccumulate, and may have detrimental long-term ...effects on aquatic life. The aim of the study was to establish a list of significant sources of OPs occurring in road runoff, identify the OPs emitted from these sources, select a number of priority pollutants (PP), and estimate the quantity of PPs emitted in a road environment case study using substance flow analysis (SFA). The priority pollutants included in the SFA were selected from a list of approximately 1100 compounds found after comprehensive screening, including literature and database searches, expert judgments, the Ranking and Identification of Chemical Hazards method, and chemical analysis of sediments. The results showed the following priority order: polycyclic aromatic hydrocarbons (PAHs)>alkanes C20–C40>alkylphenols>phthalates>aldehydes>phenolic antioxidants>bisphenol A>oxygenated-PAHs>naphtha C5–C12>amides>amines. Among these, PAHs were chosen for a SFA, which was performed for a highway case study area in Gothenburg (Sweden). The SFA showed that the main sources of PAHs emitted in the area were vehicle exhaust gases, followed by tyre wear, motor lubricant oils, road surface wear, and brake linings. Only 2–6% of the total 5.8–29kg annually emitted PAHs/ha ended up in the stormwater sewer system. The measured PAH loads were found in much smaller amounts than the calculated loads and the outflow to stormwater contained much more of the hazardous PAHs than the total loads emitted in the catchment area.
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•Methodology to select organic priority pollutants for stormwater treatment•Sources of organic pollutant emissions in a traffic environment were identified.•The loads of PAH emitted in the road catchment area were estimated by means of SFA.•2–6% of the total PAHs emitted reached road runoff.•Calculated quantities and measured PAH and oxy-PAH loads show large differences.
The study explored the techniques and a model that could be used to incorporate Indigenous Knowledge Systems (IKS) into the Natural Science (NS) curriculum. An interpretivist research philosophy and ...a qualitative research approach guided the collection of in-depth data from participants in their natural settings in schools. Data was collected from Headmasters through face-to-face interviews using an interview guide, and from NS Heads of Departments (HODs) and NS teachers through a focus group discussion guide. In each of the five selected schools in Pongola, three NS teachers, one Headmaster and one NS HOD participated in the study. This gave a total of twenty-five participants. Findings revealed that though NS Curriculum and Policy Statements (CAPS) 2012 curriculum documents instructs teachers to use IKS in class, these documents do not state which IKS content should be taught. Discretion is left to individual teachers. This poses challenges to teachers as IKS differ across different cultures in the country, and schools did not have IKS study material for teachers and learners. The study recommended that the Department of Basic Education should review its policy and clearly state the content of IKS that should be taught in NS, broaden the scope of parental involvement to include participation in IKS topics and activities, develop a standardised IKS knowledge strand, involve researchers and publishers to produce IKS study material, and adopt the Madlela model as a guiding Framework to incorporate IKS into the NS curriculum as a full knowledge strand.
This study aims to determine the effectiveness of the use of Powtoon video learning media in an effort to improve science learning outcomes at SDN Cibuk Lor Seyegan, Sleman Yogyakarta in class VI ...students in the 2020/2021 academic year. This research used Classroom Action Research method with 2 cycles with 2 meetings in each cycle. The data collection instrument used an observation sheet on the implementation of learning and tests to determine the improvement of student learning outcomes. The results showed that the mastery of learning from cycle 1 to cycle 2 reached 75%. In addition, student learning outcomes also increased with the acquisition of test results from an average of 67.65 to 74.12. The use of powtoon video learning media can improve student learning outcomes at SD Negeri Cibuk Lor on plant vegetative propagation materials.
In (st)age-structured populations, the long-run population growth rate is negatively affected by temporal variation in vital rates. In most cases, natural selection should minimize temporal variation ...in the vital rates to which the long-run population growth is most sensitive, resulting in demographic buffering. By reviewing empirical studies on demographic buffering in wild populations, we found overall support for this hypothesis. However, we also identified issues when testing for demographic buffering. In particular, solving scaling problems for decomposing, measuring, and comparing stochastic variation in vital rates and accounting for density dependence are required in future tests of demographic buffering. In the current context of climate change, demographic buffering may mitigate the negative impact of environmental variation and help populations to persist in an increasingly variable environment.
Climate change is expected to increase the environmental variation of ecosystems on Earth, highlighting the need to understand how populations will respond to these new environmental conditions.The demographic buffering hypothesis is derived from classical models of population dynamics. It predicts selection for a reduction in variance of the vital rates with the strongest influence on population growth and individual fitness.We review current knowledge about demographic buffering and critically assess the various methods and results published so far.A pattern of reduced variation in the most influential vital rates emerges from the review.Differences in methodology highlight the need for further studies with standardized methods to reveal whether the observed pattern is a direct result of selection for lower variation of the most influential vital rates.Modern statistical methods that allow decomposing variation in population growth rate into environmental variation, density dependence, and demographic stochasticity can stimulate the search for improved models to predict the effect of increasing environmental variation on population dynamics and life-history evolution.
Iridium chemistry is versatile and widespread, with superior performance for reaction types such as enantioselective hydrogenation and C–H activation. In order to gain insight into the mechanistic ...details of such systems, density functional theory (DFT) studies are often employed. But how accurate is DFT for modeling iridium-mediated transformations in solution? We have evaluated how well DFT reproduces the energies and reactivities of 11 iridium-mediated transformations, which were carefully chosen to correspond to elementary steps typically encountered in iridium-catalyzed chemistry (bond formation, isomerization, ligand substitution, and ligand association). Five DFT functionals, B3LYP, PBE, PBE0, M06L, and M11L, were evaluated as-is or in combination with an empirical dispersion correction (D2, D3, or D3BJ), leading to 13 combinations. Different solvent models (IEFPCM and SMD) were evaluated, alongside various correction terms such as big basis set effects, counterpoise corrections, frequency scaling, and different entropy modifications. PBE-D type functionals are clearly superior, with PBE-D2,IEFPCM providing average absolute errors for uncorrected Gibbs free energies of 0.9 kcal/mol for the nine reactions with a constant number of moles (1.2 kcal/mol for all 11 reactions). This provides a straightforward and accurate computational protocol for computing free energies of iridium-mediated transformations in solution. However, because the good results may originate from favorable error cancellations of larger and oppositely signed enthalpy and entropy errors, this protocol is recommended for free energies only.
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