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Abstract Compared to boreal or Mediterranean biomes, the influence of fire on peatlands in Central Europe is not well studied. We aim to provide first analysis of statistically significant charcoal-inferred fire events from a peatland from central European lowlands, spanning the period of the last 650 years, and define peatland vegetation and microbial trait-related responses to local fire events. Here, we reconstructed regional and local fire activity from Bagno Kusowo bog (Poland) using high-resolution microscopic charcoal and macroscopic charcoal and its morphotypes, inferring past fire regimes using numeric analyses. We compared fire data with extra-local (pollen) and local (plant macrofossils, testate amoebae (TA) and their trait composition) proxies. Our data show that within the chronological uncertainties, regional fires recorded in the peat core coincide with historically-documented fires. Macroscopic charcoal analysis suggests 3–8 local fire events, while fire frequency varied between 0 and 2 events/1000 years. Wood charcoal was dominant throughout the profile, pointing to forest fires in close proximity to the peatland. Local fire activity was the most intensive in the 17th century, when the water table was at its lowest. The abundance of Sphagnum spp. declined, whereas vascular plants, mixotrophs and TA with proteinaceous shells were significantly positively correlated to fire. Xenosomes were significantly negatively correlated to fires, and they responded to water table lowering. We show that the peatlands' vegetation recovered from low-intensity and short-lasting disturbances and, to some extent, maintained "pristine" local vegetation cover with Sphagnum as the dominant taxon. TA traits common before disturbances, mainly mixotrophs and TA with proteinaceous shells, temporarily re-appeared after fire. We conclude that TA communities in peatlands are good bioindicators of disturbances. Highlights • We used high-resolution sampling and numeric analyses to infer past fire activity. • We define peatland vegetation and microbial trait-related responses to fire events. • Higher abundance of vascular plants was significantly positively correlated to fire. • Mixotrophic testate amoebae were significantly positively correlated to fire. • Shell types of testate amoebae responded to fire events. [ABSTRACT FROM AUTHOR]

Abstract: Sound taxonomy is a major requirement for quantitative environmental reconstruction using biological data. Transfer function performance should theoretically be expected to decrease with reduced taxonomic resolution. However for many groups of organisms taxonomy is imperfect and species level identification not always possible. We conducted numerical experiments on five testate amoeba water table (DWT) transfer function data sets. We sequentially reduced the number of taxonomic groups by successively merging morphologically similar species and removing inconspicuous species. We then assessed how these changes affected model performance and palaeoenvironmental reconstruction using two fossil data sets. Model performance decreased with decreasing taxonomic resolution, but this had only limited effects on patterns of inferred DWT, at least to detect major dry/wet shifts. Higher-resolution taxonomy may however still be useful to detect more subtle changes, or for reconstructed shifts to be significant. [Copyright &y& Elsevier]

Phototrophic microbes, also known as micro‐algae, display a high abundance in many terrestrial surface soils. They contribute to atmospheric carbon dioxide fluxes through their photosynthesis, and thus regulate climate similar to plants. However, microbial photosynthesis remains overlooked in most terrestrial ecosystems. Here, we hypothesise that phototrophic microbes significantly contribute to peatland C uptake, unless environmental conditions limit their development and their photosynthetic activity.To test our hypothesis, we studied phototrophic microbial communities in five peatlands distributed along a latitudinal gradient in Europe. By means of metabarcoding, microscopy and cytometry analyses, as well as measures of photosynthesis, we investigated the diversity, absolute abundance and photosynthetic rates of the phototrophic microbial communities.We identified 351 photosynthetic prokaryotic and eukaryotic operational taxonomic units (OTUs) across the five peatlands. We found that water availability and plant composition were important determinants of the composition and the structure of phototrophic microbial communities. Despite environmental shifts in community structure and composition, we showed that microbial C fixation rates remained similar along the latitudinal gradient. Our results further revealed that phototrophic microbes accounted for approximately 10% of peatland C uptake.Synthesis. Our findings show that phototrophic microbes are extremely diverse and abundant in peatlands. While species turnover with environmental conditions, microbial photosynthesis similarly contributed to peatland C uptake at all latitudes. We estimate that phototrophic microbes take up around 75 MT CO2 per year in northern peatlands. This amount roughly equals the magnitude of projected peatland C loss due to climate warming and highlights the importance of phototrophic microbes for the peatland C cycle. [ABSTRACT FROM AUTHOR]

Highlights • The change in vegetation may result into interference with stored carbon in peatland. • A short-term climate manipulation resulted in the change of plant abundance and its physiology in Rzecin peatland. • The simple remote sensing indices can be used for the assessment of the chlorophyll content of peatland vegetation. • Photosynthesis of peatland vegetation can be assessed by simple remote sensing indices. Abstract Global warming is an important issue which is leading to considerable changes in biomes. Environmental biologists are continuously assessing how global warming is going to impact the current population. Peatlands are one of the most important component of the terrestrial ecosystems which makes only 3% of them but contain around 40% of soil organic carbon. The composition of peatland vegetation impacts a range of ecosystem functions, therefore, with a change in composition, the behavior and structure of peatland plant communities are predicted to change. This work is focused on the response of Sphagnum peatland (in Poland), to the manipulated environmental conditions. The experimental design consisted of four treatments (control, warming, reduced precipitation, and a combination of warming & reduced precipitation), three replicates of each. Active warming with infrared heaters (˜1.0–1.4 °C peat temperature increase) and an automatic curtain to reduce precipitation (˜30% reduction in the rain) was applied continuously since 2015. The warming and reduced precipitation caused a significant variation in the vegetation indices such as Normalized Difference Vegetation Index (NDVI), Photochemical Reflectance Index (PRI), Water Band Index (WBI), and Chlorophyll Green Index (CI green) between manipulated sites. The abundance of major plant species was recorded between manipulated sites. The prompt chlorophyll fluorescence measurement was performed in the peak of the vegetation season of August 2017 which had shown a significant variation in photosynthetic induction curve and different photosynthetic parameters from the same plant species in between the manipulated sites. The data clearly indicate that a short-term climate manipulation resulted in the change of plant abundance and its physiology, which varied for different plant species. Our study indicates that the different plant species respond differently to climate change. The study also proposes the significance of simple vegetation indices for peatland vegetation observation. [ABSTRACT FROM AUTHOR]

The Central European area has been extensively studied using qualitative reconstruction techniques focusing on the development of peatlands in the past; however, research based on quantitative techniques is still lacking, especially in relation to highlands and mountainous areas. In this study, we focused on the hydrological changes and human-induced disturbances that affected two raised bogs from the Orawa-Nowy Targ Basin (Carpathian region): Puścizna Krauszowska and Puścizna Mała. We aimed to reconstruct the development of peatlands and changes in water table under different intensities of human activities. Two peat sequences from two different bogs, both possessing absolute chronologies based on high-resolution 14C dating, were examined in terms of pollen, non-pollen palynomorphs, plant macrofossils and testate amoeba records. We detected an asynchronous decrease in the water table level on the bogs that took place between the 4th and the 7th century ad, which occurred simultaneously with a global cold period ad 300–600 (Migration Period) in case of the Puścizna Mała bog. A concurrent but insignificant human impact on bogs was recorded. A distinct wet shift corresponding to the Wolf solar minimum (ca. ad 1280–1340) in Puścizna Mała was detected during ca. ad 1300–1350. The effect of this climatic event on bog hydrology is difficult to estimate because of the simultaneous human-induced deforestation. Drainage and substantial acceleration of peat extraction in the 19th and the 20th century ad led to the significant disturbances in peatland; however, these bogs were still susceptible to dry climatic events. [ABSTRACT FROM AUTHOR]

We present the results of high-resolution, multi-proxy palaeoecological investigations of two parallel peat cores from the Baltic raised bog Mechacz Wielki in NE Poland. We aim to evaluate the role of regional climate and autogenic processes of the raised bog itself in driving the vegetation and hydrology dynamics. Based on partly synchronous changes in Sphagnum communities in the two study cores we suggest that extrinsic factors (climate) played an important role as a driver in mire development during the bog stage (500–2012 CE). Using a testate amoebae transfer function, we found exceptionally stable hydrological conditions during the last 2000 years with a relatively high water table and lack of local fire events that allowed for rapid peat accumulation (2.75 mm/year) in the bog. Further, the strong correlation between pH and community-weighted mean of testate amoeba traits suggests that other variables than water-table depth play a role in driving microbial properties under stable hydrological conditions. There is a difference in hydrological dynamics in bogs between NW and NE Poland until ca 1500 CE, after which the water table reconstructions show more similarities. Our results illustrate how various functional traits relate to different environmental variables in a range of trophic and hydrological scenarios on long time scales. Moreover, our data suggest a common regional climatic forcing in Mechacz Wielki, Gązwa and Kontolanrahka. Though it may still be too early to attempt a regional summary of wetness change in the southern Baltic region, this study is a next step to better understand the long-term peatland palaeohydrology in NE Europe. [ABSTRACT FROM AUTHOR]

In the decade since the first pan-European testate amoeba-based transfer function for peatland palaeohydrological reconstruction was published, a vast amount of additional data collection has been undertaken by the research community. Here, we expand the pan-European dataset from 128 to 1799 samples, spanning 35° of latitude and 55° of longitude. After the development of a new taxonomic scheme to permit compilation of data from a wide range of contributors and the removal of samples with high pH values, we developed ecological transfer functions using a range of model types and a dataset of ∼1300 samples. We rigorously tested the efficacy of these models using both statistical validation and independent test sets with associated instrumental data. Model performance measured by statistical indicators was comparable to other published models. Comparison to test sets showed that taxonomic resolution did not impair model performance and that the new pan-European model can therefore be used as an effective tool for palaeohydrological reconstruction. Our results question the efficacy of relying on statistical validation of transfer functions alone and support a multi-faceted approach to the assessment of new models. We substantiated recent advice that model outputs should be standardised and presented as residual values in order to focus interpretation on secure directional shifts, avoiding potentially inaccurate conclusions relating to specific water-table depths. The extent and diversity of the dataset highlighted that, at the taxonomic resolution applied, a majority of taxa had broad geographic distributions, though some morphotypes appeared to have restricted ranges. [ABSTRACT FROM AUTHOR]

[Display omitted] • All proxies showed a shift towards drier environmental conditions starting from 920 cal. CE. • Human activities and climate change left clear signatures in the Wölflmoor peat bog. • eDNA metabarcoding gave results with similar trends as the other proxies but highlighting some methodological limitations. In the last decades, climate and human activities significantly affected ecosystems, particularly in mountain areas. Whereas the Alps have been extensively studied for palaeoclimatic reconstructions, little information is available about ecological changes, especially in the Southeastern Alps. This study presents a palaeoclimatic and palaeoecological reconstruction from a 1500-years-old mountain peatland record: Wölflmoor, Bozen (Italy). Through Physico-chemical proxies, testate amoeba, pollen, plant macro-fossils, and environmental DNA (eDNA) analyses, we pursued a twofold objective: 1) reconstructing the palaeoenvironmental variations of the peatland and the surrounding environment to identify the main dry/wet periods, and their correlations with climate and human activities; 2) testing the use of eDNA from a peatland in palaeoecological reconstructions. The dating highlighted a distinct change of age at a depth of 55.5–50.5 cm (ca. 800–930 calibrated years), which suggests a depositional gap (hiatus), at least in this section, occurred during the Medieval Warm Period, due to the increase in air temperature. However, the possible exploitation of the peatland by humans cannot be excluded. Indeed, the increase of Poaceae, Cerealia type, and Secale cereale , and the reduction of Fagus sylvatica and Quercus presented a high human pressure starting around 720 cal. CE. Environmental DNA metabarcoding results showed similar trends. However, it gave limitations such as the preferential amplification of the most abundant species, leading to a relatively small number of detected taxa. This is one of the first studies of eDNA metabarcoding from peatland; thus, we argue that ample room for improvement is expected in a short time, making eDNA metabarcoding a valuable complementary approach, primarily when both flora and fauna taxa are targeted. [ABSTRACT FROM AUTHOR]

Climate change is likely to cause increased tree recruitment on open peatlands but we currently have little idea what consequences this vegetation change may have below-ground. Here we use transects across forested to open bog ecotones at three Russian peatland complexes to assess potential changes in the most abundant group of peatland protists – the testate amoebae. We show that the testate amoeba communities of forested and open bog are markedly different with a very abrupt boundary at, or near, the vegetation ecotone. Changes along our transects suggest that tree encroachment may reduce the trophic level of testate amoeba communities and reduce the contribution of mixotrophic testate amoebae to primary production. Our study strongly suggests that increased tree recruitment on open peatlands will have important consequences for both microbial biodiversity and microbially-mediated ecosystem processes. [ABSTRACT FROM AUTHOR]

Sphagnum peatlands in the oceanic-continental transition zone of Poland are currently influenced by climatic and anthropogenic factors that lead to peat desiccation and susceptibility to fire. Little is known about the response of Sphagnum peatland testate amoebae (TA) to the combined effects of drought and fire. To understand the relationships between hydrology and fire dynamics, we used high-resolution multi-proxy palaeoecological data to reconstruct 2000 years of mire history in northern Poland. We employed a new approach for Polish peatlands – joint TA-based water table depth and charcoal-inferred fire activity reconstructions. In addition, the response of most abundant TA hydrological indicators to charcoal-inferred fire activity was assessed. The results show four hydrological stages of peatland development: moderately wet (from ∼35 BC to 800 AD), wet (from ∼800 to 1390 AD), dry (from ∼1390 to 1700 AD) and with an instable water table (from ∼1700 to 2012 AD). Fire activity has increased in the last millennium after constant human presence in the mire surroundings. Higher fire activity caused a rise in the water table, but later an abrupt drought appeared at the onset of the Little Ice Age. This dry phase is characterized by high ash contents and high charcoal-inferred fire activity. Fires preceded hydrological change and the response of TA to fire was indirect. Peatland drying and hydrological instability was connected with TA community changes from wet (dominance of Archerella flavum , Hyalosphenia papilio , Amphitrema wrightianum ) to dry (dominance of Cryptodifflugia oviformis , Euglypha rotunda ); however, no clear fire indicator species was found. Anthropogenic activities can increase peat fires and cause substantial hydrology changes. Our data suggest that increased human fire activity was one of the main factors that influenced peatland hydrology, though the mire response through hydrological changes towards drier conditions was delayed in relation to the surrounding vegetation changes. [ABSTRACT FROM AUTHOR]

Plant community composition is recognized more and more for playing an important role in ecosystem processes, such as C cycling. In particular, plant functional type ( PFT) composition seems to have a key regulatory role, yet the underlying mechanisms in the interaction between PFTs and ecosystem processes are still to be identified., Here, we assess the link between PFTs and dominant microbial consumers along a calcareous poor to extremely rich fen gradient in western Poland. We particularly focussed on dominant microbial consumers (testate amoebae), which can exert large effects on the functioning of peatlands. Using moving-window analyses and path-relation networks subjected to structural equation modelling ( SEM), we investigated linkages among abiotic factors, PFTs and testate amoebae., We show that along the poor to extremely rich fen gradient, the dependence of testate amoebae to PFTs is higher than their dependence to abiotic factors. We also found that the link between testate amoebae and PFTs differs between size assemblages of testate amoebae. While large testate amoeba species (i.e. high trophic level) were highly linked to Sphagnum mosses cover, small species (i.e. low trophic level) were linked to brown mosses. Distinction between shallow-rooted and deep-rooted vascular plants also showed that shallow-rooted plants play a role on testate amoeba community structure at the 'poor' side of the gradient., Our results further show a dominant role for calcium content and the structure of the bryophyte community on testate amoeba size assemblages at the poor to extremely rich fen scale, both for diversity and abundance of testate amoebae., Synthesis. Variations in plant functional type composition drive niche-size-structure of testate amoebae along the (calcareous) poor to extremely rich fen gradient. Furthermore, strong relationships between moss types and testate amoeba size-structure suggest that mosses specifically influence testate amoeba development through autogenic effects. Therefore, moss cover composition is key to microbial consumers and may be the driving factor determining microbial network structure and associated ecosystem processes, such as carbon cycling. [ABSTRACT FROM AUTHOR]

Although the contribution of current summer warming to the widespread drying of European peatlands is undeniable, summer temperature fluctuations alone are unable to explain all the hydrological shifts of these ecosystems. We aim to determine whether the current coupling of high summer temperatures and low water tables of peatlands in northern Poland is recent or has been stable over long timescales, and to infer the climatic context driving past relationships between temperature and peatland hydrology. We compare the previously published 4000-year long paleohydrological record from Kusowo bog with a new chironomid-based summer temperature record covering the last 4.5 ka from nearby (~7 km) Lake Spore. Although several simultaneous shifts in our hydrological and temperature reconstructions are evident on multi-decadal to centennial timescales, for instance during the peak cooling of the Migration Period or Little Ice Age (~1.4 and 0.4 cal ka, respectively), the records reveal mostly independent fluctuations. However, the relatively high uncertainty of our quantitative estimates suggests caution is warranted when inferring the strength of the relationship between the reconstructed variables at this temporal resolution. However, at centennial to millennial timescales, the relationship between the records is surprisingly strong. Overall, warmer summers (mean July temperature = 18.7 °C) before ~2.3 cal. ka corresponded well with lower ground water tables at Kusowo bog (mean = 11.2 cm), whereas cooler summers in the following period (mean = 17.4 °C) were accompanied by higher water tables (mean = 7.9 cm). Particularly wet bog conditions during the last ~0.7 ka were also the coldest. The finding that on long timescales the drying of Kusowo bog coincided with warming suggests a persistent regional climate pattern in which drought conditions change along with summer temperatures. If this millennial-scale pattern holds for the projected warming, further peatland drying can be expected in northern Poland. • We compare paleohydrological record from a bog with a summer temperature reconstruction • On millennial timescales, dry conditions at the bog were concurrent with high temperatures • Conditions at the bog were generally drier before 2.3 cal. ka BP and wetter thereafter • Temperature rise above the late-Holocene maximum can result in unprecedented drying [ABSTRACT FROM AUTHOR]