Compositional Dissimilarity Research Articles

Biological surrogates: A word of caution

The value of biological surrogates has been tested for many ecosystems and biological groups. Biological surrogates are biological groups whose biodiversity patterns (e.g. abundance, species richness or assemblage composition) correlate strongly with those of other biological groups. They should thus be cost-effective proxies for overall diversity variation in biodiversity assessment and biomonitoring projects. We assessed whether the available evidence support the use of surrogate groups in biodiversity assessment and biomonitoring studies considering aquatic and terrestrial ecosystems. To achieve this goal, we carried out a meta-analysis of studies testing the strength of different surrogacy approaches (relationship between species richness, ordination patterns and compositional (dis)similarity matrices of different biological groups). The strengths of relationships between species richness of biological groups were higher for plants and microorganisms than for animals, were similar for terrestrial and aquatic ecosystems and for different types of data. The variation in the strength of relationships between compositional dissimilarity matrices was not explained by the explanatory variables ‘taxa’, ‘realms’ or ‘types of data’. However, as main results, we found that the weighted effect sizes, measuring the value of surrogates, were low, highly variable and mostly unpredictable (at least considering our explanatory variables). Therefore, the available evidence suggests caution in the use of surrogate groups and that biodiversity assessment and biomonitoring programs should be based on multiple taxonomic groups, whenever possible.

Correction: DNA extraction replicates improve diversity and compositional dissimilarity in metabarcoding of eukaryotes in marine sediments.

[This corrects the article DOI: 10.1371/journal.pone.0179443.].

Polypore Communities and Their Substrate Characteristics in Atlantic Forest Fragments in Southeast Brazil

Anthropogenic environmental changes have resulted in biodiversity crisis. Although tropical rainforests are one of the global biodiversity hotspots, their biodiversity is still poorly known. Especially fungi are poorly represented in national Red Lists and conservation plans, despite their important role in ecosystem functioning. We studied wood-inhabiting fungi (polypores) in four areas within two Atlantic rainforest fragments in Southeast Brazil. Our aim was to investigate fungal substrate characteristics and community composition. Deadwood amount ranged from 27 to 82 m3/ha among the four study areas and altogether we recorded 53 polypore species. More species were observed in intermediate and late decay stages than in early decay stages, but other deadwood variables did not explain the occurrence of polypores. Similarity in polypore community composition within and among the areas was low. Dissimilarity originated mostly from species turnover from a transect and area to another, and no nestedness in species occurrence pattern was detected. Hence, the observed dissimilarity in community composition was probably a result of heterogeneity in forest composition and structure, instead of environmental gradients or substrate limitations. These results corroborate previous polypore studies from the Atlantic forest in that tropical polypores are specialists toward particular decay stages. To develop ecologically effective conservation program for tropical polypores, more studies are needed on their distribution and abundance globally.

Environmental heterogeneity explains species turnover but not nestedness in fish assemblages of a Neotropical basin

Abstract Aim: Heterogenous environments can contribute to maintain biodiversity. Traditionally beta diversity studies have focused on determining the effect of environmental variables on the total dissimilarity of species composition. However, decomposing beta diversity in species replacement and nestedness could give new insights on mechanisms affecting spatial patterns of biodiversity. We aimed to answer two main questions about spatial patterns of fish diversity in a Neotropical basin: 1) whether some regions contribute differently to fish diversity, and 2) whether species turnover and nestedness are explained by environmental gradients. Methods Sampling sites in the main channel and tributaries of the Upper Paraná River were sampled between 2013 and 2015. We partitioned beta diversity and tested the relationship of turnover and nestedness with environmental variables. Results 74 species were captured. Some of these species were restricted to different sites, contributing to variation in species composition. Hill numbers showed a trend for higher diversity in the tributaries than in Paraná River sampling sites, and the partition of beta diversity revealed that species replacement drove dissimilarity in species composition. Only total beta diversity and turnover were related to environmental variables, mainly conductivity and turbidity. Conclusions Species diversity and composition of fish assemblages in the Upper Paraná River could be related to environmental gradients. Overall, our results suggest that Paraná River tributaries contribute to increase environmental heterogeneity, and hence to maintain a high diversity and variation in species composition. For that reason, we strongly recommend preserving highly heterogeneous habitats in the region.

Intra-annual variation in planktonic ciliate species composition (Protista: Ciliophora) in different strata in a shallow floodplain lake

Abstract Aim: We aimed to evaluate the variation in planktonic ciliate species composition in different strata of the Guaraná Lake, encompassing high and low water periods, at the Upper Paraná River floodplain. Methods Samplings were collected monthly between March 2007 and February 2008, from the epilimnion, metalimnion and hypolimnion. Ciliates samples were filtered using a plankton net of 10µm mesh size and identified in vivo under an optical microscope. Results Among 112 species identified, 13 were found exclusively during the high water periods and 39 during the low water period. Results of nonparametric extrapolation indices evidenced that the observed richness represented between 70% and 90% of the estimated richness. Regarding the variation in species composition, Beta1 index showed that the alteration in composition between strata during the low water period was slightly greater than that registered during high waters. Cluster analysis evidenced a higher dissimilarity in ciliate species composition between periods than among the different strata. The greatest variation in species composition was verified during the distinct hydrological periods, whereas no significant differences were observed for the different strata analysed. Conclusions We found that in the pelagic compartment, ciliate species composition changed significantly between hydrological periods, and a higher similarity in species composition among strata was observed during the high water period. Therefore, alterations in the vertical distribution seem to be related to the homogenizing effect of the floods in the water column stability.

Synergistic effects of the components of global change: Increased vegetation dynamics in open, forest-steppe grasslands driven by wildfires and year-to-year precipitation differences.

Climate change and land use change are two major elements of human-induced global environmental change. In temperate grasslands and woodlands, increasing frequency of extreme weather events like droughts and increasing severity of wildfires has altered the structure and dynamics of vegetation. In this paper, we studied the impact of wildfires and the year-to-year differences in precipitation on species composition changes in semi-arid grasslands of a forest-steppe complex ecosystem which has been partially disturbed by wildfires. Particularly, we investigated both how long-term compositional dissimilarity changes and species richness are affected by year-to-year precipitation differences on burnt and unburnt areas. Study sites were located in central Hungary, in protected areas characterized by partially-burnt, juniper-poplar forest-steppe complexes of high biodiversity. Data were used from two long-term monitoring sites in the Kiskunság National Park, both characterized by the same habitat complex. We investigated the variation in species composition as a function of time using distance decay methodology. In each sampling area, compositional dissimilarity increased with the time elapsed between the sampling events, and species richness differences increased with increasing precipitation differences between consecutive years. We found that both the long-term compositional dissimilarity, and the year-to-year changes in species richness were higher in the burnt areas than in the unburnt ones. The long-term compositional dissimilarities were mostly caused by perennial species, while the year-to-year changes of species richness were driven by annual and biennial species. As the effect of the year-to-year variation in precipitation was more pronounced in the burnt areas, we conclude that canopy removal by wildfires and extreme inter-annual variability of precipitation, two components of global environmental change, act in a synergistic way. They enhance the effect of one another, resulting in greater long-term and year-to-year changes in the composition of grasslands.

Forest floor mesofauna communities respond to a gradient of biomass removal and soil disturbance in a boreal jack pine (Pinus banksiana) stand of northeastern Ontario (Canada)

Abstract Woody biomass is increasingly harvested in Canadian boreal forests as a source of bioenergy. However, there is concern over the environmental sustainability of harvesting practices. Our study assessed how forest floor mesofauna communities responded to an increasing intensity gradient of biomass removal and soil disturbance in a jack pine (Pinus banksiana) forest in northeastern Ontario, and whether any modification in community structure could be related to environmental change. Five experimental treatments were established that included a mature jack pine control stand (no recent harvesting) and harvesting of stem-only, whole-tree (stem, top and branches), whole-tree with stump removal and whole-tree with stump and forest floor (organic layer) removal. Two years after treatment application, we compared the structure of Collembola and Oribatida communities in moss, organic and mineral soil samples along this gradient. Despite both taxa showing somewhat contrasting responses, in general, each community had significantly lower density and species richness (α-diversity) and more compositional dissimilarities in response to biomass removal compared to uncut mature stands. These differences were especially marked in the two most intense removal treatments (whole-tree harvesting with stump removal and that with the additional forest floor removal). We attributed this result to the major loss of surface-dwelling species after harvesting and along the biomass removal gradient, especially in Oribatida communities, likely due to the loss of favourable microhabitats provided by moss and woody debris. Environmental changes observed along the gradient, beyond the loss of these microhabitats, were driven by the removal of forest floor decreasing soil nutrient richness and acidity and increasing soil temperature. Forest floor mesofaunal communities were clearly modified by more intensive biomass removal practices as compared to stem-only and whole-tree biomass harvesting. Long-term studies will be needed to investigate to what extent these patterns vary through time in order to inform sustainable management of woody biomass removal in this ecosystem.

Is environmental legislation conserving tropical stream faunas? A large-scale assessment of local, riparian and catchment-scale influences on Amazonian fish.

Agricultural expansion and intensification are major threats to tropical biodiversity. In addition to the direct removal of native vegetation, agricultural expansion often elicits other human-induced disturbances, many of which are poorly addressed by existing environmental legislation and conservation programmes. This is particularly true for tropical freshwater systems, where there is considerable uncertainty about whether a legislative focus on protecting riparian vegetation is sufficient to conserve stream fauna.To assess the extent to which stream fish are being effectively conserved in agricultural landscapes, we examined the spatial distribution of assemblages in river basins to identify the relative importance of human impacts at instream, riparian and catchment scales, in shaping observed patterns. We used an extensive dataset on the ecological condition of 83 low-order streams distributed in three river basins in the eastern Brazilian Amazon.We collected and identified 24,420 individual fish from 134 species. Multiplicative diversity partitioning revealed high levels of compositional dissimilarity (DS) among stream sites (DS = 0.74 to 0.83) and river basins (DS = 0.82), due mainly to turnover (77.8% to 81.8%) rather than nestedness. The highly heterogeneous fish faunas in small Amazonian streams underscore the vital importance of enacting measures to protect forests on private lands outside of public protected areas.Instream habitat features explained more variability in fish assemblages (15%-19%) than riparian (2%-12%), catchment (4%-13%) or natural covariates (4%-11%). Although grouping species into functional guilds allowed us to explain up to 31% of their abundance (i.e. for nektonic herbivores), individual riparian - and catchment - scale predictor variables that are commonly a focus of environmental legislation explained very little of the observed variation (partial R2 values mostly <5%).Policy implications. Current rates of agricultural intensification and mechanization in tropical landscapes are unprecedented, yet the existing legislative frameworks focusing on protecting riparian vegetation seem insufficient to conserve stream environments and their fish assemblages. To safeguard the species-rich freshwater biota of small Amazonian streams, conservation actions must shift towards managing whole basins and drainage networks, as well as agricultural practices in already-cleared land.

Plant diversity is coupled with beta not alpha diversity of soil fungal communities following N enrichment in a semi-arid grassland

Soil fungi and plants are tightly linked in pathogenic, commensal, and mutualistic ways. These interactions play a critical role in terrestrial ecosystem decomposition, nutrient cycling, and maintenance of plant productivity and diversity. A comprehensive understanding whether this fundamental plant-fungi relationship persists in ecosystems with increased N input is, however, still lacking. In this study, we investigated the relationships between plant and soil fungal diversity in a 6-year multi-level nitrogen addition experiment in a semi-arid grassland in northern China, using Illumina Miseq sequencing of the ITS1 barcode region for fungal identification. We hypothesized that N-induced changes in plant communities would be positively associated with those in soil fungal communities, and that the corresponding changes in both communities can be explained by the direct functional associations between plant and soil fungal communities and their shared environmental drivers. Our results showed that N-induced changes in plant alpha diversity, i.e., Shannon diversity, showed no significant relationship with those in soil fungal alpha diversity. The lack in significance of the relationship was primarily due to their contrasting correlates with N-induced soil physicochemical variables (i.e., soil available P (AP), inorganic N (NH4+_N and NO3−_N) and organic C content), and weakened plant-fungi functional associations. In contrast to the lack of relationship between plant and soil alpha diversity, we did find a significant positive relationship between plant and fungal beta diversity (compositional dissimilarity between plots) under N enrichment. Our results reveal that the same soil physicochemical variables, including soil AP, inorganic N, moisture, pH, and associated extractable cations, correlated with compositional changes in plant and fungi following N enrichment. The strong coupling of plant and fungal beta diversity could largely be driven by their consistent responses to these shared edaphic factors. As such, our results suggest that information on N-induced changes in plant diversity can be used to predict beta, but not alpha diversity of soil fungal communities in semi-arid grassland ecosystems.

Oil palm monoculture induces drastic erosion of an Amazonian forest mammal fauna.

Oil palm monoculture comprises one of the most financially attractive land-use options in tropical forests, but cropland suitability overlaps the distribution of many highly threatened vertebrate species. We investigated how forest mammals respond to a landscape mosaic, including mature oil palm plantations and primary forest patches in Eastern Amazonia. Using both line-transect censuses (LTC) and camera-trapping (CT), we quantified the general patterns of mammal community structure and attempted to identify both species life-history traits and the environmental and spatial covariates that govern species intolerance to oil palm monoculture. Considering mammal species richness, abundance, and species composition, oil palm plantations were consistently depauperate compared to the adjacent primary forest, but responses differed between functional groups. The degree of forest habitat dependency was a leading trait, determining compositional dissimilarities across habitats. Considering both the LTC and CT data, distance from the forest-plantation interface had a significant effect on mammal assemblages within each habitat type. Approximately 87% of all species detected within oil palm were never farther than 1300 m from the forest edge. Our study clearly reinforces the notion that conventional oil palm plantations are extremely hostile to native tropical forest biodiversity, which does not bode well given prospects for oil palm expansion in both aging and new Amazonian deforestation frontiers.

Deposition of a saline giant in the Mississippian Windsor Group, Nova Scotia, and the nascent Late Paleozoic Ice Age

Saline giants are vast marine evaporite deposits that currently have no modern analogues and remain one of the most enigmatic of chemical sedimentary rocks. The Mississippian Windsor Group (ca. 345Ma), Maritimes Basin, Atlantic Canada is a saline giant that consists of two evaporite-rich sedimentary sequences that are subdivided into five subzones. Sequence 1 is composed almost entirely of thick halite belonging to Subzone A (Osagean). Sequence 2 is in unconformable contact and comprised of stacked carbonate-evaporite peritidal cycles of Subzones B through E (Meramecian). Subzone B, the focus of research herein, documents the transition from wholly evaporitic to open marine conditions and thus, preserves an exceptional window into the processes forming saline giants.Lithofacies stacking patterns in Subzone B reveal that higher-order fluctuations in relative sea level produced nine stacked parasequences interpreted to reflect high frequency glacioeustatic oscillations during the onset of the Late Paleozoic Ice Age. Each parasequence reflects progradation of intertidal and sabkha sediments over subtidal carbonate and evaporite deposits. Dissimilarities in cycle composition between sub-basins imply the development of contrasting brine chemistries from differing recharge rates with the open ocean.What the Windsor Group shows is that evaporite type is ostensibly linked to the amplitude and frequency of sea level rise and fall during deposition. True saline giants, like the basinwide evaporites of Sequence 1, apparently require low amplitude, long frequency changes in sea level to promote the development of stable brine pools that are only periodically recharged with seawater. By contrast, the high amplitude, short frequency glacioeustatic variability in sea level that controlled the accumulation of peritidal evaporites in Subzone B produce smaller, subeconomic deposits with more complex facies relationships.

Herbivory and presence of a dominant competitor interactively affect salt marsh plant diversity

AbstractQuestionDo herbivory and the presence of a dominant grass competitor interactively affect herbaceous communities and assembly rules in a SW Atlantic salt marsh?LocationUpper salt marsh, Mar Chiquita coastal lagoon, Argentina.MethodsWe performed a field factorial experiment over 4 yr to evaluate the separate and interactive effects of (1) herbivory and (2) competition with the dominant grass species (i.e. Spartina densiflora) on the salt marsh subordinate plant community. The factorial design includes dominant grass removal and herbivory manipulation.ResultsOur results show that herbivory and presence of the dominant competitor interactively affect subordinate plant cover and diversity. Results further indicate that, in the presence of the dominant competitor, patch‐to‐patch variation in subordinate species composition is lower than expected at random, a result consistent with the expected outcomes of deterministic exclusion following light competition. Removal of the dominant grass nevertheless led to patch‐to‐patch dissimilarity in subordinate species composition, far from the dissimilarity expected at random, indicating increased importance of deterministic processes that drive communities to diverge.ConclusionOur results show that the conditional effect of herbivory on plant diversity can be determined by the presence of a single plant species. Dominant plant species, in addition, may not only affect plant species diversity by determining the number and identity of subordinate species in a given patch (i.e. α‐diversity) but also by affecting spatial variability through habitat homogenization.

Is microbial terroir related to geographic distance between vineyards?

While there are substantial studies suggesting that characteristics of wine are related to regional microbial community composition (microbial terroir), there has been little discussion about what factors affect variation in regional microbial community composition. In this study, we compared the microbial community composition of leaves and berries of a grape variety (Carmenere) from six different Chilean vineyards within 35 km of each other. In order to determine relationships between spatial proximity and microbial compositional dissimilarity, we sequenced amplicons of the internal transcribed spacer (ITS) region for fungi and 16S rRNA gene for bacteria. Results showed that both the fungal and the bacterial community compositions of the studied vineyards differed, but this difference was much clearer in fungi than in bacteria. In addition, while bacterial community dissimilarity was not correlated with geographic distance, the leaf and berry fungal community dissimilarities between locations increased with geographic distance. This indicates that spatial processes play an important role in structuring the biogeographic pattern of grape-associated fungal communities at local scales, which might in turn contribute to the local identity of wine.

Two decades of change in a field margin vegetation metacommunity as a result of field margin structure and management practice changes

Field margins have considerable ecological significance in agricultural landscapes by providing habitat and resources for farmland biodiversity. Few attempts have been made to examine the long term dynamics of multiple vegetation communities in field margins, at the landscape scale. In addition, drivers and processes governing such long term vegetation dynamics are poorly investigated. The aim of the study was to assess whether the diversity and composition of a field margin metacommunity have changed over the last two decades as a result of changes in both structural condition and management of field margins. In total, 309 field margins in north-western France, first surveyed in 1994, were resurveyed in 2015 by using the same protocol. Total species richness (gamma diversity) was stable over time while mean species richness per field margin (alpha diversity) increased. No difference in species composition dissimilarity (beta diversity) was recorded indicating that no biotic homogenization had occurred between 1994 and 2015. Species composition has shifted over time, with a decline of hemicryptophytes and an increase of shade-tolerant species. No change in Ellenberg nitrogen value was observed. Analysis of drivers revealed a significant influence of changes in the structural condition of field margins, i.e. the development of the tree layer, on vegetation diversity. Dominant height of vegetation and tree cover were highest in 2015 compared with 1994. This has likely been driven by a decline in intensity of field margin management. Despite changes in alpha diversity, the field margin metacommunity had a stable Clementsian structure over time, suggesting grouped distribution of species along environmental gradients. This study provides a rare example of the long term vegetation change in field margins in relation with margin structure and management changes, using permanent plots and diachronic data. Results highlight the need to maintain a variety of differently structured and managed field margins to preserve high plant diversity. They underline the need to place conservation strategies in the context of regional-scale processes to ensure the long-term conservation of field margin metacommunities.

Eficiencia de trampas pitlight con led para el muestreo de coleoptera nocturnos (insecta) en selvas tropicales

RESUMEN. Se evaluó el uso de trampas de caída con luz portables (pitlight) con diodos emisores de luz (LED) para la captura de Coleoptera nocturnos en una selva tropical, con la finalidad de proveer herramientas eficientes para el monitoreo de insectos. Se comparó la diversidad de familias y morfoespecies recolectada con trampas de caída pasivas (pitfall) y con trampas de caída con luz (pitlight) de tresdistintas longitudes de onda (azul, blanca y amarilla), bajo la hipótesis de que las trampas pitlight son más eficientes, y que los insectos serán más atraídos por las longitudes de onda más cortas y de alta frecuencia. Además, el muestreo se dividió en dos períodos nocturnos de cinco horas, con el objetivo de analizar el tiempo necesario para obtener una colecta significativa. Las recolectas con trampas pitlight fueron notablemente superiores a las pitfall pasivas, y aunque no se encontraron diferencias significativas entre los valores de riqueza, abundancia y diversidad de coleópteros obtenidos con tres colores de LED (azul, blanco, amarillo), ni entre los horarios nocturnos de recolecta, sí se observó una alta disimilitud en la composición de morfoespecies entre los distintos tratamientos. Las trampas pitlight con LED son un método sencillo, portátil y económico que es capaz de obtener una captura eficiente y representativa en periodos de tiempo muy cortos, por lo quese recomienda su uso para el inventario de comunidades de insectos.

What is the optimum sample size for the study of peatland testate amoeba assemblages?

Testate amoebae are widely used in ecological and palaeoecological studies of peatlands, particularly as indicators of surface wetness. To ensure data are robust and comparable it is important to consider methodological factors which may affect results. One significant question which has not been directly addressed in previous studies is how sample size (expressed here as number of Sphagnum stems) affects data quality. In three contrasting locations in a Russian peatland we extracted samples of differing size, analysed testate amoebae and calculated a number of widely-used indices: species richness, Simpson diversity, compositional dissimilarity from the largest sample and transfer function predictions of water table depth. We found that there was a trend for larger samples to contain more species across the range of commonly-used sample sizes in ecological studies. Smaller samples sometimes failed to produce counts of testate amoebae often considered minimally adequate. It seems likely that analyses based on samples of different sizes may not produce consistent data. Decisions about sample size need to reflect trade-offs between logistics, data quality, spatial resolution and the disturbance involved in sample extraction. For most common ecological applications we suggest that samples of more than eight Sphagnum stems are likely to be desirable.

Bridging the gap between climate science and regional-scale biodiversity conservation in south-eastern Australia

Recognition of a trajectory of climate change has raised concerns over implications for the conservation of biodiversity. Quantifying the severity of the issue and informing adaptation measures presents a challenge to ecological modelling.We undertook a study of biodiversity impacts and adaptation using spatial modelling across south-eastern Australia. The study aimed to (1) forecast future impacts on biodiversity arising from 18 plausible climate futures, and (2) identify places where land management actions including revegetation will maximise expected improvements to projected biodiversity persistence. This work augments well-tested regional-scale biodiversity assessment by considering an uncertain future climate.Generalised Dissimilarity Models (GDMs) were developed at two baselines (1990 and 2000) to characterise the continuous nature of compositional turnover of vascular plants varying with climate, soils and landform across the region. The classified outputs of the GDM, representing a vegetation-based biodiversity surrogate, were projected using kernel regression to simulate changing distributions for the future epochs 2020, 2030, 2050 and 2070, referred to as Bio-climatic Classes (BCC). BCC distributions were combined with a model of current ecosystem condition and applied to a range of biodiversity assessment methodologies, including the Biodiversity Forecasting Tool, the Spatial Links Tool and a new coupled time-series metapopulation occupancy model.The BFT evaluation of the BCC distributions and their respective ecosystem conditions, forecasts a reduction in biodiversity persistence across the region of between 3 and 20 percent by 2070 (due to climate change only) adding to a past loss of 20 percent since European settlement (due to land use change only, not other factors such as weeds and pests). Maps of compositional dissimilarity change in vascular plants point to varying degrees of expected change in biodiversity across south-eastern Australia. Conservation benefit analysis indicates a general increase and re-distribution of the relative benefits of undertaking conservation to sustain or enhance biodiversity across the region. Results have been incorporated into novel visualisations, to assist environmental managers and others to interpret the complex concepts and issues associated with the work, and support regional adaptation planning.

Macrofaunal community structure in Bahía Concepción (Chile) before and after the 8.8 Mw Maule mega-earthquake and tsunami

Faunal assemblages of subtidal sedimentary environments are key components of coastal ecosystems. Benthic communities inhabiting the coastal zone near urban centers in Concepción Bay (Chile) have been described as highly disturbed (i.e. impoverished in diversity and species richness). This is due to the frequent presence of hypoxic conditions at the bottom due to the intrusion of low oxygen Equatorial Subsurface Water, high natural productivity and the high load of organic matter generated by several anthropogenic activities. A mega-earthquake (8.8 Mw) and subsequent tsunami occurred on the coast of south-central Chile on February 27, 2010 (27F), heavily impacting Concepción Bay, which is located 30 km south of the epicenter. The objectives of the present study are: (i) to evaluate the effect produced by the mega-earthquake and tsunami on the benthic community, and (ii) to assess dissimilarity in macrofauna composition and abundance in Concepción Bay at an inter-decadal time scale based on a comparison between our sampling conducted between 2010 and 2013 and information published since 1969. Our results show that the benthic macrofauna of Concepción Bay was disturbed by the 27F (i.e. high community dissimilarity in 2010). Changes in community structure were observed at an inter-annual scale (i.e. diminished community dissimilarity in 2013), suggesting a recovery post-27F. At an inter-decadal scale, community structure post-27F was dissimilar to the structure described for the 1980's and 1990's but more similar to that reported for 1969. The reducing conditions of the sediments due to the high input of organic matter that took place in the 1980's and 1990's may explain this dissimilarity.

Using ecosystem engineers as tools in habitat restoration and rewilding: beaver and wetlands

Potential for habitat restoration is increasingly used as an argument for reintroducing ecosystem engineers. Beaver have well known effects on hydromorphology through dam construction, but their scope to restore wetland biodiversity in areas degraded by agriculture is largely inferred. Our study presents the first formal monitoring of a planned beaver-assisted restoration, focussing on changes in vegetation over 12years within an agriculturally-degraded fen following beaver release, based on repeated sampling of fixed plots. Effects are compared to ungrazed exclosures which allowed the wider influence of waterlogging to be separated from disturbance through tree felling and herbivory. After 12years of beaver presence mean plant species richness had increased on average by 46% per plot, whilst the cumulative number of species recorded increased on average by 148%. Heterogeneity, measured by dissimilarity of plot composition, increased on average by 71%. Plants associated with high moisture and light conditions increased significantly in coverage, whereas species indicative of high nitrogen decreased. Areas exposed to both grazing and waterlogging generally showed the most pronounced change in composition, with effects of grazing seemingly additive, but secondary, to those of waterlogging.Our study illustrates that a well-known ecosystem engineer, the beaver, can with time transform agricultural land into a comparatively species-rich and heterogeneous wetland environment, thus meeting common restoration objectives. This offers a passive but innovative solution to the problems of wetland habitat loss that complements the value of beavers for water or sediment storage and flow attenuation. The role of larger herbivores has been significantly overlooked in our understanding of freshwater ecosystem function; the use of such species may yet emerge as the missing ingredient in successful restoration.

Phase and compositional analysis of a Sèvres soft paste porcelain plate from 1781, with a review of early porcelain techniques

Optical microscopy, X-ray diffraction, X-ray fluorescence and scanning electron microscopy analyses were carried out on a typical Sevres soft (frit) porcelain plate from 1781 in order to determine the chemical and mineralogical composition as well as the microstructure of its ceramic body, glaze, overglaze decoration and gilding. The body is rich in SiO 2 (73 mass%), CaO (16) and alkali oxide (8) and shows acicular wollastonite and tridymite crystals embedded in a glassy matrix consisting of SiO 2 (75), K 2 O (12) and CaO (9). The 50–90 µm thick, transparent lead glaze (40.9 PbO) contains 47.6 SiO 2 , 6.5 K 2 O and 3.5 CaO and shows a 35–75 µm thick reaction zone (50 SiO 2 , 30 PbO, 14 CaO) towards the body. The maximum thickness of the different paints is 50 µm, with 15 µm as mean thickness of the individual paint stroke. Two blue colours, for the dentil comb and the flower painting, are chemically distinct (colouring CoO in the dental rim 7, in the flower’s blue 2 mass%) and contain many As- and Pb-rich globules and dendrites. Pseudohexagonal shaped platelets of Pb–Sb–Sn triple oxide crystals, embedded in a colourless glassy matrix, generate the opacity and the colour of the yellow paints. Opaque olive green colours are created by the combination of such yellow crystals with a bluish, Cu and Co bearing glassy matrix. The opaque red overglaze enamel is a mechanical mix of yellow Pb–Sb oxide crystals with an iron-rich (16 Fe 2 O 3 ) Pb–silica glass. Purple is very homogeneous and shows tiny drops of pure gold (max. diam. 0.5 µm) in a glassy matrix (47 PbO, 46 SiO 2 , 5 K 2 O). Violet is a mechanical blend of flower’s blue and purple. The pure (99.5 Au, 0.5 Fe 2 O 3 ) gilt consists of several folded gold particles. The results of this study are only broadly consistent with the archival documented 18 th century technologies. The compositional dissimilarities of the studied enamels suggest that each colour was independently fritted. Consequently, the original colour recipes written down by Hellot in 1753 must have been modified in the 30 years since then.