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 differentiatio

Unveiling exceptional Baltic bog ecohydrology, autogenic succession and climate change during the last 2000 years in CE Europe using replicate cores, multi-proxy data and functional traits of testate amoebae

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 Europ

The performance of single- and multi-proxy transfer functions (testate amoebae, bryophytes, vascular plants) for reconstructing mire surface wetness and pH

Peatlands are widely exploited archives of paleoenvironmental change. We developed and compared multiple transfer functions to infer peatland depth to the water table (DWT) and pH based on testate amoeba (percentages, or presence/absence), bryophyte presence/absence, and vascular plant presence/absence data from sub-alpine peatlands in the SE Swiss Alps in order to 1) compare the performance of single-proxy vs. multi-proxy models and 2) assess the performance of presence/absence models. Bootstrapping cross-validation showing the best performing single-proxy transfer functions for both DWT and pH were those based on bryophytes. The best performing transfer functions overall for DWT were those based on combined testate amoebae percentages, bryophytes and vascular plants; and, for pH, those based on testate amoebae and bryophytes. The comparison of DWT and pH inferred from testate amoeba percentages and presence/absence data showed similar general patterns but differences in the magnitude and timing of some shifts. These results show new directions for paleoenvironmental research, 1) suggesting that it is possible to build good-performing transfer functions using presence/absence data, although with some loss of accuracy, and 2) supporting the idea that multi-proxy inference models may improve paleoecological reconstruction. The performance of multi-proxy and single-proxy transfer functions should be further compared in paleoecological data

Testing peatland testate amoeba transfer functions: Appropriate methods for clustered training-sets

Transfer functions are widely used in palaeoecology to infer past environmental conditions from fossil remains of many groups of organisms. In contrast to traditional training-set design with one observation per site, some training-sets, including those for peatland testate amoeba-hydrology transfer functions, have a clustered structure with many observations from each site. Here we show that this clustered design causes standard performance statistics to be overly optimistic. Model performance when applied to independent data sets is considerably weaker than suggested by statistical cross-validation. We discuss the reasons for these problems and describe leave-one-site-out cross-validation and the cluster bootstrap as appropriate methods for clustered training-sets. Using these methods we show that the performance of most testate amoeba-hydrology transfer functions is worse than previously assumed and reconstructions are more uncertain

Significance testing testate amoeba water table reconstructions

Transfer functions are valuable tools in palaeoecology, but their output may not always be meaningful. A recently-developed statistical test ('randomTF') offers the potential to distinguish among reconstructions which are more likely to be useful, and those less so. We applied this test to a large number of reconstructions of peatland water table depth based on testate amoebae. Contrary to our expectations, a substantial majority (25 of 30) of these reconstructions gave non-significant results (P > 0.05). The underlying reasons for this outcome are unclear. We found no significant correlation between randomTF P-value and transfer function performance, the properties of the training set and reconstruction, or measures of transfer function fit. These results give cause for concern but we believe it would be extremely premature to discount the results of non-significant reconstructions. We stress the need for more critical assessment of transfer function output, replication of results and ecologically-informed interpretation of palaeoecological data

Widespread drying of European peatlands in recent centuries

This is the author accepted manuscript. The final version is available from Nature Research via the DOI in this record Climate warming and human impacts are thought to be causing peatlands to dry,potentially converting them from sinks to sources of carbon. However, it is unclear whether the hydrological status of peatlands has moved beyond their natural envelope. Here we show that European peatlands have undergone substantial, widespread drying during the last ~300 years. We analyse testate amoeba-derived hydrological reconstructions from 31 peatlands across Britain, Ireland, Scandinavia and continental Europe to examine changes in peatland surface wetness during the last 2000 years. 60% of our study sites were drier during the period CE 1800-2000 than they have been for the last 600 years; 40% of sites were drier than they have been for 1000 years; and 24% of sites were drier than they have been for 2000 years. This marked recent transition in the hydrology of European peatlands is concurrent with compound pressures including climatic drying, warming and direct human impacts on peatlands, although these factors vary between regions and individual sites. Our results suggest that the wetness of many European peatlands may now be moving away from natural baselines. Our findings highlight the need for effective management and restoration of European peatlands.Natural Environment Research Council (NERC

Relationships between testate amoebae assemblages, vegetation and environmental parameters on minerotrophic peatlands of Wielkopolska region

Wydział Biologii: Instytut Biologii Środowiska/Zakład HydrobiologiiGłównym celem pracy było określenie relacji pomiędzy roślinnością torfowiskową, parametrami fizyczno-chemicznymi wody a strukturą zgrupowań ameb skorupkowych na torfowiskach minerotroficznych Wielkopolski. Badaniom poddano 9 torfowisk. W sumie do analiz pobrano 147 prób powierzchniowych, w skład których wchodziły różnorodne gatunki mchów torfowców oraz mchów brunatnych i ramienic. Ameby skorupkowe oraz roślinność rozmieszczone były na torfowiskach głównie wzdłuż gradientu żyzności, natomiast gradient wilgotnościowy oraz troficzny miały znaczenie drugorzędne. W sumie zarejestrowano 141 gatunków ameb skorupkowych. Analiza MFA wskazała na najwyższą korelację pomiędzy zgrupowaniami ameb skorupkowych a mchami brunatnymi. Wśród czynników fizyczno-chemicznych do najważniejszych, wpływających na strukturę ameb skorupkowych na torfowiskach minerotroficznych należą: pH, poziom wody gruntowej (DWT), przewodność elektrolityczna, magnez (Mg2+), sód (Na+), potas (K+), siarczany (SO4), jony fosforanowe (PO42-) oraz barwa wody. Zmienne te tłumaczyły 23,5% wariancji. Ameby skorupkowe wykazały również korelację z poszczególnymi gatunkami mchów. Dane uzyskane z powyższych badań wskazują na duże znaczenie ameb skorupkowych w kontekście monitoringu środowiska jak również możliwości wykorzystania tej wiedzy w badaniach paleoekologicznych torfowisk.The main aim of this study was to determine the relationship between the peatland vegetation, physical-chemical parameters of water and the structure of testate amoeba assemblages in minerotrophic fens of Wielkopolska region. The study involved 9 fens. In total, 147 samples were collected from the peatland surface, part of which consisted of various species of Sphagnum, brown mosses and charophytes. Testate amoebae and vegetation were located mainly along the poor-rich gradient, while the moisture and trophic gradients were of secondary importance. In total 141 taxa of testate amoebae were recorded. MFA analysis indicated the highest correlation between the assemblages of testate amoebae and mosses. Among the most important physical and chemical factors, influencing the structure of testate amoebae on fens belong: pH, ground water level (DWT), conductivity, magnesium (Mg2+), sodium (Na+), potassium (K+), sulphate (SO4), phosphate ions (PO42-) and the color of water. These variables explained 23,5% of variance. Testate amoebae also showed a correlation with the particular moss species found in minerotrophic fens. Data obtained from these studies indicate the importance of testate amoebae in the context of environmental monitoring as well as the possibility to use this knowledge in the palaeoecological studies

Climate change and human impact in the southern Baltic during the last millennium reconstructed from an ombrotrophic bog archive

We pres ent the last mil len nium of his tory of a peatland lo cated in north ern Po land. Our re sults are based on two rep li - cate mono liths taken from a Bal tic raised bog. We ap plied a high-res o lu tion ap proach and ra dio car bon dat ing to the peat ma te rial to ob tain a de tailed palaeoenvironmental re con struc tion. To re con struct past peatland mois ture, we used three prox ies: tes tate amoe bae, plant macrofossils and pol len. De spite dif fer ent peat ac cu mu la tion and ex ten sive hi a tus in the for merly stud ied core, both mono liths show a sim i lar pat tern of changes. How ever, the core from this study pro - vides us with more de tailed data on S. fuscum dis ap pear ance which cor re lates well with the data from the other Bal tic bog, S³owiñskie B³oto. Our re search shows that pris tine Bal tic bogs can be dated to AD 1350. S³owiñskie B³oto palaeohydrology con firms AD 1300 as the be gin ning of the hy dro log i cal dis tur bance. In the case of the St¹¿ki and S³owiñskie B³oto bogs, the Lit tle Ice Age (LIA) is re corded be tween AD 1500 and AD 1800. How ever, this cli ma tic change might have been blurred by hu man im pact. In the case of the Bal tic bogs, their ref er ence vir gin state can be dated to AD 1200. Af ter this date, we ob served in creas ing hu man im pact and cli ma tic in sta bil ity con nected with the LIA. How ever, be tween AD 1800 and 1900, bogs were wet, most pos si bly due to cli ma tic forc ing. This fact sug gests that de spite hu man im pact, re cent peat de pos its can still re flect cli mate. Our re search pro vided in for ma tion re lated to the time of ex is tence, lo ca tion and char ac ter is tics of the nat u ral/pris tine state. High-res o lu tion peatland palaeo ec ol ogy is cru cial for res to ra tion ac tiv i ties, e.g., rewetting and en vi ron men tal man age ment. The palaeohydrological con text (sup ported by other prox ies) of the last 1000 years pro vides a re li able an swer to the ques tion: ‘To rewet or not to rewet?

Plant functional diversity drives niche-size-structure of dominant microbial consumers along a poor to extremely rich fen gradient

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