Testate Amoeba (Arcellinida,Euglyphida) Ecology along a Poor‐Rich Gradient in Fens of Western Poland

We investigated the relationships between testate amoebae (Arcellinida, Euglyphida), vegetation and water chemistry along environmental gradients in minerotrophic peatlands (fens) in western Poland. We hypothesized that: a) hydrochemistry significantly influences structure of testate amoeba communities, and b) testate amoeba communities are more closely correlated with the hydrochemical variables (environment) than with the vegetation data. Testate amoeba communities and vegetation from 71 sample plots were investigated together with the hydro‐chemistry and hydrology based on 16 environmental variables and vegetation composition. Testate amoeba communities revealed a distinctive poor‐rich gradient in analysed fens. Mineral‐rich habitats, which were dominated by brown mosses, were preferred by a higher number of taxa than acidic habitats, which were dominated by Sphagnum. We recorded a total of 107 testate amoebae taxa. The average species richness of testate amoebae for brown mosses was higher (20) than for Sphagnum (13). We found that testate amoebae communities were similarly correlated with vascular plants, mosses and environmental parameters. Results of direct ordination demonstrate that hydrology, pH, Mg²⁺ and sodium remain the most important environmental control for the entire data set. CCA showed that in case of brown mosses hydrology, sodium and oxygen affect testate amoeba communities significantly whereas in Sphagnum only sodium emerge as most significant determining testate amoeba assemblages. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Biogeography and comparative ecology of testate amoebae inhabiting Sphagnum-dominated peatlands in the Great Lakes and Rocky Mountain regions of North America

Testate amoebae (Protozoa: Rhizopoda) are common inhabitants of peatlands. Strong relationships between community composition and substrate moisture in Sphagnum‐dominated peatlands have made them particularly useful as hydrological proxies in environmental and palaeoenvironmental research. However, stability of these relationships in geographical space is important for widespread applicability. In this study, we compared testate amoeba communities inhabiting Sphagnum‐dominated peatlands of the Great Lakes and Rocky Mountain regions of North America. Our primary objectives were to describe patterns of community composition in the two regions, develop hypotheses to explain differences, and determine if taxa occupy similar ecological niches with respect to substrate moisture in both places. Our results indicated that testate amoeba communities are relatively different in the two regions, and these differences are probably caused by differences in climate and peatland trophic status, although other factors may also play a role. However, many taxa do occur in both regions and these taxa had comparable moisture preferences in each region, suggesting that the ecological niches of taxa with respect to substrate moisture are similar even within communities of relatively different composition.     

Fine-Scale Horizontal and Vertical Micro-distribution Patterns of Testate Amoebae Along a Narrow Fen/Bog Gradient

The ecology of peatland testate amoebae is well studied along broad gradient from very wet (pool) to dry (hummock) micro-sites where testate amoebae are often found to respond primarily to the depth to water table (DWT). Much less is known on their responses to finer-scale gradients, and nothing is known of their possible response to phenolic compounds, which play a key role in carbon storage in peatlands. We studied the vertical (0–3, 3–6, and 6–9 cm sampling depths) micro-distribution patterns of testate amoebae in the same microhabitat (Sphagnum fallax lawn) along a narrow ecological gradient between a poor fen with an almost flat and homogeneous Sphagnum carpet (fen) and a “young bog” (bog) with more marked micro-topography and mosaic of poor fen and bog vegetation. We analyzed the relationships between the testate amoeba data and three sets of variables (1) “chemical” (pH, Eh potential, and conductivity), (2) “physical” (water temperature, altitude, i.e., Sphagnum mat micro-topography, and DWT), and (3) phenolic compounds in/from Sphagnum (water-soluble and primarily bound phenolics) as well as the habitat (fen/bog) and the sampling depth. Testate amoeba Shannon H′ diversity, equitability J of communities, and total density peaked in lower parts of Sphagnum, but the patterns differed between the fen and bog micro-sites. Redundancy analyses revealed that testate amoeba communities differed significantly in relation to Eh, conductivity, water temperature, altitude, water-soluble phenolics, habitat, and sampling depth, but not to DWT, pH, or primarily bound phenolics. The sensitivity of testate amoebae to weak environmental gradients makes them particularly good integrators of micro-environmental variations and has implications for their use in paleoecology and environmental monitoring. The correlation between testate amoeba communities and the concentration of water-soluble phenolic suggests direct (e.g., physiological) and/or indirect (e.g., through impact on prey organisms) effects on testate amoebae, which requires further research.     

Comparative ecology of vascular plant,bryophyte and testate amoeba communities in four Sphagnum peatlands along an altitudinal gradient in Switzerland

Monitoring tools are needed to assess changes in peatland biotic communities and ecosystem functions in response to on-going climate and other environmental changes. Although the responses of soil organisms and plants to ecological gradients and perturbations do not always correlate, peatland monitoring is mainly based on vegetation surveys. Testate amoebae, a group of protists, are important contributors to carbon and nitrogen cycling in organic soils and are useful bioindicators in peatland ecology and paleoecology. There is however little comparative data on the value of testate amoebae, vascular plants and bryophytes as bioindicators of micro-environmental gradients in peatlands.We compared the relationships of testate amoebae, bryophytes, and vascular plants with soil temperature, water table depth, micro-habitats and the carbon and nitrogen content of Sphagnum mosses in four peatlands along a 1300 m altitudinal gradient in Switzerland. We used the full diversity of vascular plants and bryophyte but only a selection of ten easily identifiable testate amoeba morpho-taxa (i.e. species or species-complexes).Indirect and direct gradient ordinations, multiple factor analysis (MFA) and transfer function models for inferring water table depth showed that a selection of ten testate amoeba taxa are more powerful (% variance explained in RDA) and accurate (discrimination among habitats) indicators of local conditions (micro-habitat type, water table depth and Sphagnum C/N ratio) than the vegetation (vascular plants and bryophytes either individually or combined and considering the full diversity).Our study showed that a limited list of ten easily identifiable testate amoeba taxa have higher bioindication value than the full bryophytes and vascular plants. Furthermore, testate amoebae can be analyzed on samples collected at any season (accessibility allowing and if precise sampling sites are well marked) – a clear advantage for biomonitoring and can be used to infer past changes from the peat record at the same taxonomic resolution. This simple approach could therefore be very useful for biomonitoring of peatlands.     

Testate amoebae response and vegetation composition after plantation removal on a former raised bog

Extensive drainage of peatlands in north-west Europe for the purposes of afforestation for timber production and harvesting has altered the carbon balance and biodiversity value. Large-scale restoration projects aim to reinstate hydrological conditions to keep carbon locked up in the peat and to restart active peat growth. Testate amoebae are an informal grouping of well-studied protists in peatland environments and as microbial consumers play an important role in nutrient and carbon cycling. Using a space for time substitution approach, this study investigated the response of testate amoebae assemblages and vegetation composition after tree removal on a drained raised bog. There was a clear difference in microbial assemblages between open and a chronosequence of restoration areas. Results suggest microbial recovery after rewetting is a slow process with plant composition showing a faster response than the microbial assemblage. Mixotrophic testate amoebae had not recovered seventeen years following plantation removal and the establishment of Sphagnum mosses in the wetter microforms. These results suggest that vegetation composition and Testate amoeba assemblages respond differently to environmental drivers at forest-to-bog restoration areas. Local physicochemical peat properties were a stronger driver of the testate assemblage compared with vegetation. Complete recovery of microbial assemblages may take place over decadal timescales.     

Seasonal Influences on the Ecology of Testate Amoebae (Protozoa) in a Small <Emphasis Type="Italic">Sphagnum</Emphasis> peatland in Southern Ontario,Canada

Testate amoebae (Protozoa) were studied in spring, summer, and fall from the same microhabitats in a small Sphagnum-dominated peatland in southern Ontario, Canada. A total of 32 sampling stations were established in two wetland plant communities, 19 in an open Ericaceae low-shrub community and 13 in a closed Picea mariana and Larix laricina swamp community. Sphagnum was collected in each station for analysis of testate amoebae and measurement of soil water content parameters and water table depth in May, August, and October 2001. pH and dissolved oxygen of the groundwater under the Sphagnum were measured also. A total of 52 taxa including the rotifer, Habrotrocha angusticollis, were identified. Soil water content and water table variables emerged as the primary factors separating testate amoebae between the open bog/fen community and swamp community. Testate amoebae in the open bog/fen community showed a clear separation between the May sampling period and the August and October sampling periods. Sampling stations in May had much higher water table and were wetter than those in August and October. Conversely, testate amoebae in the swamp community did not show a clear difference between sampling periods. Soil moisture and water tables appear to be more constant in the swamp communities. Biological factors or other microscale environmental factors may need to be considered to explain seasonal changes in testate amoebae. A greater understanding of relationships between testate amoebae and microenvironmental factors is necessary to track seasonality in testate amoebae distributions.     

Relationships among testate amoebae (Protozoa), vegetation and water chemistry in five Sphagnum-dominated peatlands in Europe

To study the relationships between groups of organisms and the degree to which these relationships are consistent across major climatic gradients, we analysed the testate amoeba ( Protozoa ) communities, vegetation and water chemistry of one peatland in five countries: Switzerland, The Netherlands, Great Britain, Sweden and Finland, as part of the BERI (Bog Ecosystem Research Initiative) project. The relationships between the different data sets and subsets were investigated by means of detrended correspondence analysis, canonical correspondence analysis and Mantel permutation tests. The comparison of data on vegetation and testate amoebae showed that inter-site differences are more pronounced for the vegetation than for the testate amoebae species assemblage. Testate amoebae are a useful tool in multi-site studies and in environmental monitoring of peatlands because: (1) the number of species in Sphagnum -dominated peatlands is much higher than for mosses or vascular plants; (2) most peatland species are cosmopolitan in their distributions and therefore less affected than plants by biogeographical distribution patterns, thus differences in testate amoeba assemblages can be interpreted primarily in terms of ecology; (3) they are closely related to the ecological characteristics of the exact spot where they live, therefore they can be used to analyse small-scale gradients that play a major role in the functioning of peatland ecosystems. This study revealed the existence of small-scale vertical gradients within the vegetation and life-form niche separation in response to water chemistry. The deep-rooted plants such as Carex spp. and Eriophorum spp. are related to the chemistry of water sampled at or near the ground water table, whereas the mosses are not. Testate amoebae were shown to be ecologically more closely related to the chemistry of water sampled at or near the water table level and to the mosses than to the deep-rooted plants.     

Seasonal changes in Sphagnum peatland testate amoeba communities along a hydrological gradient

Testate amoebae are an abundant and functionally important group of protists in peatlands, but little is known about the seasonal patterns of their communities. We investigated the relationships between testate amoeba diversity and community structure and water table depth and light conditions (shading vs. insolation) in a Sphagnum peatland in Northern Poland (Linje mire) in spring and summer 2010. We monitored the water table at five sites across the peatland and collected Sphagnum samples in lawn and hummock micro-sites around each piezometer, in spring (3 May) and mid-summer (6 August) 2010. Water table differed significantly between micro-sites and seasons (Kruskal–Wallis test, p = 0.001). The community structure of testate amoebae differed significantly between spring and summer in both hummock and lawn micro-sites. We recorded a small, but significant drop in Shannon diversity, between spring and summer (1.76 vs. 1.72). Strongest correlations were found between testate amoeba communities and water table lowering and light conditions. The relative abundance of mixotrophic species Hyalosphenia papilio, Archerella flavum and of Euglypha ciliata was higher in the summer.     

Contrasting Species—Environment Relationships in Communities of Testate Amoebae, Bryophytes and Vascular Plants Along the Fen–Bog Gradient

We studied the vegetation, testate amoebae and abiotic variables (depth of the water table, pH, electrical conductivity, Ca and Mg concentrations of water extracted from mosses) along the bog to extremely rich fen gradient in sub-alpine peatlands of the Upper Engadine (Swiss Alps). Testate amoeba diversity was correlated to that of mosses but not of vascular plants. Diversity peaked in rich fen for testate amoebae and in extremely rich fen for mosses, while for testate amoebae and mosses it was lowest in bog but for vascular plants in extremely rich fen. Multiple factor and redundancy analyses (RDA) revealed a stronger correlation of testate amoebae than of vegetation to water table and hydrochemical variables and relatively strong correlation between testate amoeba and moss community data. In RDA, hydrochemical variables explained a higher proportion of the testate amoeba and moss data than water table depth. Abiotic variables explained a higher percentage of the species data for testate amoebae (30.3% or 19.5% for binary data) than for mosses (13.4%) and vascular plants (10%). These results show that (1) vascular plant, moss and testate amoeba communities respond differently to ecological gradients in peatlands and (2) testate amoebae are more strongly related than vascular plants to the abiotic factors at the mire surface. These differences are related to vertical trophic gradients and associated niche differentiation.     

Evaluating the use of dominant microbial consumers (testate amoebae) as indicators of blanket peatland restoration

Peatlands represent globally-important ecosystems and carbon stores. However, large areas of peatland have been drained for agriculture, or peat has been harvested for use as fuel or in horticulture. Increasingly, these landscapes are being restored through ditch blocking and rewetting primarily to improve biodiversity and promote peat accumulation. To date we have little knowledge of how these interventions influence the microbial communities in peatlands. We compared the responses of dominant microbial consumers (testate amoebae) to drainage ditch restoration relative to unblocked ditches in a UK upland blanket peatland (Migneint, North Wales). Two techniques were used for restoration: (i) dammed ditches with re-profiling; and (ii) dammed ditches with pools of open water behind each dam. Testate communities in the inter-ditch areas changed markedly over time and between treatments illustrating the potential of this group of organisms as indicators of blanket peatland restoration status. However, the responses of testate amoebae to peat rewetting associated with restoration were partially obscured by inter-annual variability in weather conditions through the course of the experiment. Although there was considerable variability in the response of testate amoebae communities to peatland drain blocking, there were clearly more pronounced changes in samples from the dammed and reprofiled treatments including an increase in diversity, and the appearance of unambiguous wet-indicator species in relatively high abundances (including Amphitrema stenostoma, Archerella flavum, Arcella discoides type, Difflugia bacillifera and Difflugia bacillarium). This reflects a shift towards overall wetter conditions across the site and the creation of new habitats. However, water-table was not a significant control on testate amoebae in this case, suggesting a poor relationship between water table and surface moisture in this sloping blanket peatland. Our findings highlight the potential of testate amoebae as bioindicators of peatland restoration success; however, there is a need for caution as mechanisms driving change in the microbial communities may be more complex than first assumed. Several factors need to be taken into account when implementing biomonitoring studies in peatlands including: (i) the natural variability of the peatland ecosystem under changing weather conditions; (ii) any disturbance connected with the restoration procedures; and (iii) the timescales over which the ecosystem responds to the management intervention. Our results also suggest an indicator species approach based on population dynamics may be more appropriate for biomonitoring peatland restoration than examining changes at the community level.     

Testate amoeba records indicate regional 20th‐century lowering of water tables in ombrotrophic peatlands in central‐northern Alberta,Canada

Testate amoebae are abundant in the surface layers of northern peatlands. Analysis of their fossilized shell (test) assemblages allows for reconstructions of local water‐table depths (WTD). We have reconstructed WTD dynamics for five peat cores from peatlands ranging in distance from the Athabasca bituminous sands (ABS) region in western Canada. Amoeba assemblages were combined with plant macrofossil records, acid‐insoluble ash (AIA) fluxes and instrumental climate data to identify drivers for environmental change. Two functional traits of testate amoebae, mixotrophy and the tendency to integrate xenogenic mineral matter in test construction, were quantified to infer possible effects of AIA flux on testate amoeba presence. Age–depth models showed the cores each covered at least the last ~315 years, with some spanning the last millennium. Testate amoeba assemblages were likely affected by permafrost development in two of the peatlands, yet the most important shift in assemblages was detected after 1960 CE. This shift represents a significant apparent lowering of water tables in four out of five cores, with a mean drop of ~15 cm. Over the last 50 years, assemblages shifted towards more xerophilous taxa, a trend which was best explained by increasing Sphagnum s. Acutifolia and, to a lesser extent, mean summer temperature. This trend was most evident in the two cores from the sites located farthest away from the ABS region. AIA flux variations did not show a clear effect on mineral‐agglutinating taxa, nor on S. s. Acutifolia presence. We therefore suggest the drying trend was forced by the establishment of S. s. Acutifolia, driven by enhanced productivity following regional warming. Such recent apparent drying of peatlands, which may only be reconstructed by appropriate indicators combined with high chronological control, may affect vulnerability to future burning and promote emissions of CO₂.     

The Ecology of Testate Amoebae (Protists) in Sphagnum in North-western Poland in Relation to Peatland Ecology

We studied the relationship between testate amoebae (Protozoa) communities and the depth to the water table (DWT), pH, conductivity, and microhabitat type in Sphagnum dominated peatlands of north-western Poland and built predictive (transfer function) models for inferring DWT and pH based on the testate amoebae community structure. Such models can be used for peatland monitoring and paleoecology. A total of 52 testate amoebae taxa were recorded. In a redundancy analysis, DWT and pH explained 20.1% of the variation in the species data and allowed us to identify three groups of taxa: species that are associated with (1) high DWT and low pH, (2) low DWT and low pH, and (3) high pH and mid-range DWT. Our transfer function models allow DWT and pH to be estimated with mean errors of 9.89 cm and 0.71 pH units. The prediction error of the DWT model and the tolerance of the species both increase with increasing dryness. This pattern mirrors the ecology of Sphagnum mosses: Species growing in wet habitats are more sensitive to change in water table depth than the species growing in drier microhabitats. Our results are consistent with studies of testate amoeba ecology in other regions, and they provide additional support for the use of these organisms in paleoecological and biomonitoring contexts.     

Ecology of testate amoebae from mires in the Central Rhodope Mountains, Greece and development of a transfer function for palaeohydrological reconstruction

Testate amoebae are useful environmental indicators in ecological and palaeoecological studies from peatlands. Previous quantitative studies have focused on the peatlands of Northern and Central Europe, North America, and New Zealand and have considered a relatively restricted variety of peatland types, mostly ombrotrophic or Sphagnum-dominated while more minerotrophic fens have been less studied. Here we present the first quantitative ecological study of testate amoebae from four small mesotrophic fens (pH 5.5-8.1) in the Elatia Forest, northern Macedonia province, Greece. Relationships with the environmental data were investigated using redundancy analysis and mantel tests. Transfer function models were derived using a variety of techniques. Results demonstrate that as for Sphagnum-dominated mires hydrology is the most important control on amoebae community composition. Transfer function models should enable water tables to be predicted within 2.5 cm, when data selection is used this is reduced to less than 2 cm. pH is also an important environmental control on testate amoebae communities, a transfer function model enables pH prediction within 0.4 pH units. The hydrological transfer function is the best performing such model yet produced in terms of prediction error. This study provides new data on the ecology of testate amoebae in fens, and the transfer function models should allow quantitative palaeohydrological reconstruction.     

To What Extent Do Food Preferences Explain the Trophic Position of Heterotrophic and Mixotrophic Microbial Consumers in a Sphagnum Peatland?

Although microorganisms are the primary drivers of biogeochemical cycles, the structure and functioning of microbial food webs are poorly studied. This is the case in Sphagnum peatlands, where microbial communities play a key role in the global carbon cycle. Here, we explored the structure of the microbial food web from a Sphagnum peatland by analyzing (1) the density and biomass of different microbial functional groups, (2) the natural stable isotope (δ ¹³C and δ ¹⁵N) signatures of key microbial consumers (testate amoebae), and (3) the digestive vacuole contents of Hyalosphenia papilio, the dominant testate amoeba species in our system. Our results showed that the feeding type of testate amoeba species (bacterivory, algivory, or both) translates into their trophic position as assessed by isotopic signatures. Our study further demonstrates, for H. papilio, the energetic benefits of mixotrophy when the density of its preferential prey is low. Overall, our results show that testate amoebae occupy different trophic levels within the microbial food web, depending on their feeding behavior, the density of their food resources, and their metabolism (i.e., mixotrophy vs. heterotrophy). Combined analyses of predation, community structure, and stable isotopes now allow the structure of microbial food webs to be more completely described, which should lead to improved models of microbial community function.     

Testate amoebae taxonomy and trait diversity are coupled along an openness and wetness gradient in pine-dominated Baltic bogs

Sphagnum peatlands host a high abundance of protists, especially testate amoebae. Here, we designed a study to investigate the functional diversity of testate amoebae in relation to wetness and forest cover in Baltic bogs. We provided new data on the influence of openness/wetness gradient on testate amoebae communities, showing significant differences in selected testate amoebae (TA) traits. Three key messages emerged from our investigations: 1) we recorded an effect of peatland surface openness on testate amoebae functional traits that led us to accept the hypothesis that TA traits differ according to light intensity and hydrology. Mixotrophic species were recorded in high relative abundance in open plots, whereas they were nearly absent in forested sites; 2) we revealed a hydrological threshold for the occurrence of mixotrophic testate amoebae that might be very important in terms of peatland functioning and carbon sink vs. source context; and 3) mixotrophic species with organic tests were nearly absent in forested sites that were dominated by heterotrophic species with agglutinated or idiosomic tests. An important message from this study is that taxonomy of TA rather indicates the hydrological gradient whereas traits of mixotrophs the openness gradient.     

Light variability and mixotrophy: Responses of testate amoeba communities and shell δ13C values to a peatland shading experiment

Paleoecological records suggest that growing season length and/or cloudiness may affect peatland carbon accumulation and testate amoeba-based environmental reconstructions, highlighting a need to understand how light intensity affects microbial communities. We shaded plots on two peatlands for two years to examine effects on testate amoeba communities, the relative abundance of mixotrophic and heterotrophic testate amoebae, transfer-function performance, and δ¹³C values of two species of mixotrophic testate amoebae. Surprisingly, relative abundance of mixotrophic species increased in shade, although compositional changes did not affect transfer-function performance. Shading did not affect δ¹³C values of Hyalosphenia papilio and Heleopera sphagni, which ranged from −23.5 to −19.6‰ and −23.2 to −19.2‰, respectively. These δ¹³C values were higher than those of potential food sources and lower than literature-derived values for Chlorella, the zoochlorellae inhabiting mixotrophic testate amoebae. δ¹³C values thus suggest that these mixotrophic species obtain some carbon from Chlorella, although coupled dietary and isotope studies are needed to quantify this contribution. More research is needed to assess impacts of light variability on peatland microbial communities; however, carbon sources are recorded by δ¹³C values of testate amoebae, indicating potential for studies of carbon cycling and how mixotrophy varies temporally and spatially.     

Palaeoecology of testate amoebae in a tropical peatland

We present the first detailed analysis of subfossil testate amoebae from a tropical peatland. Testate amoebae were analysed in a 4-m peat core from western Amazonia (Peru) and a transfer function developed from the site was applied to reconstruct changes in water table over the past ca. 8,000 years. Testate amoebae were in very low abundance in the core, especially in the lower 125 cm, due to a combination of poor preservation and obscuration by other organic matter. A modified preparation method enabled at least 50 testate amoebae to be counted in each core sample. The most abundant taxa preserved include Centropyxis aculeata, Hyalosphenia subflava, Phryganella acropodia and Trigonopyxis arcula. Centropyxis aculeata, an unambiguous wet indicator, is variably present and indicates several phases of near-surface water table. Our work shows that even degraded, low-abundance assemblages of testate amoebae can provide useful information regarding the long-term ecohydrological developmental history of tropical peatlands.     

Ecology of testate amoebae in moorland with a complex fire history: implications for ecosystem monitoring and sustainable land management

Testate amoebae represent a crucial component of soil microfauna and have been studied extensively in ombrotrophic peatlands. However, little is known about their ecology in moorlands which are important habitats in terms of biodiversity and carbon storage potential. Moorlands are under threat from a range of factors such as drainage, burning, over grazing, pollution and climate change. In this study we investigate testate amoebae communities within three zones of a UK moorland characterised by contrasting fire histories, and use these data to examine the potential of testate amoebae as environmental bioindicators in moorlands. Although several factors control testate amoebae communities in moorlands, it is clear that there are marked differences in testate amoebae communities between the zones which primarily relate to hydrological status, influenced by fire regime. The taxon Hyalosphenia subflava is a clear indicator of severe disturbance as it was found to be abundant in mosses which colonised a hydrophobic peat surface following a severe wild-fire event. Testate amoebae have much potential for ecosystem monitoring of moorlands which can inform sustainable land management practices.     

Decreased carbon accumulation feedback driven by climate‐induced drying of two southern boreal bogs over recent centuries

Northern boreal peatlands are important ecosystems in modulating global biogeochemical cycles, yet their biological communities and related carbon dynamics are highly sensitive to changes in climate. Despite this, the strength and recent direction of these feedbacks are still unclear. The response of boreal peatlands to climate warming has received relatively little attention compared with other northern peatland types, despite forming a large northern hemisphere‐wide ecosystem. Here, we studied the response of two ombrotrophic boreal peatlands to climate variability over the last c. 200 years for which local meteorological data are available. We used remains from plants and testate amoebae to study historical changes in peatland biological communities. These data were supplemented by peat property (bulk density, carbon and nitrogen content), ¹⁴C, ²¹⁰Pb and ¹³⁷Cs analyses and were used to infer changes in peatland hydrology and carbon dynamics. In total, six peat cores, three per study site, were studied that represent different microhabitats: low hummock (LH), high lawn and low lawn. The data show a consistent drying trend over recent centuries, represented mainly as a change from wet habitat Sphagnum spp. to dry habitat S. fuscum. Summer temperature and precipitation appeared to be important drivers shaping peatland community and surface moisture conditions. Data from the driest microhabitat studied, LH, revealed a clear and strong negative linear correlation (R² = .5031; p < .001) between carbon accumulation rate and peat surface moisture conditions: under dry conditions, less carbon was accumulated. This suggests that at the dry end of the moisture gradient, availability of water regulates carbon accumulation. It can be further linked to the decreased abundance of mixotrophic testate amoebae under drier conditions (R² = .4207; p < .001). Our study implies that if effective precipitation decreases in the future, the carbon uptake capacity of boreal bogs may be threatened.     

Abrupt ecological changes in the last 800 years inferred from a mountainous bog using testate amoebae traits and multi-proxy data

Mountainous peatlands of Western Sudetes are considered a unique habitat in Central Europe. The region contains one of the largest raised bog complexes in temperate Europe and is thus of great importance for biodiversity conservation. In this first high-resolution study from this region we use long-term ecological data to assess how these mountain wetland ecosystems responded to anthropogenic impacts and climate change. We used testate amoebae morphological traits, micro- and macroscopic charcoal, pollen and plant macrofossils to reconstruct the history of peatland development over 800 years, illustrating shifts in its development and fire dynamics. Five hydrological stages of peatland development were recognized. Testate amoebae morphological traits reflected several abrupt ecological changes linked to anthropogenic modifications of landscape openness. A shift towards mixotrophic taxa, linked to hydrological change or shrubs expansion and shading, preceded aperture position change, which was associated to dust input through surrounding deforestation and simultaneous water-table increase. Fire reconstruction revealed increasing burning together with intensifying human activity, including the expansion of a nearby settlement. This study confirms the potential of testate amoeba communities and the use of morpho-functional traits as indicators of ecological effects of land-use change over long-temporal scales.