Łukasz Lamentowicz

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.

Testate amoebae ecology and a local transfer function from a peatland in western Poland

In Chlebowo mire (Wielkopolska region), we investigated testate amoebae in relation to 10 environmental parameters in the semi-natural floating vegetation of flooded peat workings. The measured parameters included: depth to water table (DWT), ground-water pH, color, conductivity, PO4, NO3, NH4, SO4, Ca, and Mg. Detrended correspondence analysis and canonical correspondence analysis (CCA) were used to analyze relations between the composition of testate amoebae communities and those variables. In canonical correspondence analysis, DWT, pH, and Mg remained after forwardselection as the main factors characterizing the changes in testate amoebae communities along the moisture and nutrient gradients. Characteristic species of testate amoebae for the various stages of floating-mat development in the flooded peat workings were distinguished. Communities of testate amoebae along with present-day vegetation reflect the process of progressive acidification, driven mainly by Sphagnum fallax. We consider this as secondary succession, since preliminary investigations of peat stratigraphy revealed sedge peat below no more than 5–40 cm of Sphagnum peat in undisturbed parts of the mire. This study increases our understanding of relationships between testate amoebae and their habitat, which is valuable for palaeoenvironmental studies. A local transfer function was developed with the use of six models: partial least squares, maximum likelihood, modern analogue technique, weighted averaging, tolerance down-weighted averaging, and weighted averaging-partial least squares. The weighted averaging model performed the best for depth to water table (root mean square error of prediction RMSEP = 6.99) and pH (RMSEP = 0.8). Results will be used as part of a regional training set to improve palaeoenvironmental reconstructions of Sphagnum peatlands.

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.

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.

Palaeoecology of Sphagnum obtusum in NE Poland

Abstract This paper describes a fossil record from northeastern Poland of Sphagnum obtusum Warnst., a plant that has rarely been found in Holocene sediments. This species occurred circa 1710–1570 cal. BP on Mechacz Wielki peatland and was present in the transitional phase between a fen that developed on lake sediments and a bog. Sphagnum obtusum was a dominant species and was accompanied by such vascular plants such as Scheuchzeria palustris, Carex rostrata, Comarum palustre and Oxycoccus palustris. Using testate amoebae, we reconstructed the past habitat (water table and pH), with S. obtusum occurring in a moderately wet habitat (mean depth to the water table or DWT  =  9.5, SD  =  0.5) and under slightly acid conditions (mean pH  =  5, SD  =  0.1). A clear correlation was found between the distributions of the subfossil S. obtusum and those of the indicator testate amoebae Hyalosphenia papilio and Cyclopyxis arcelloides. The disappearance of S. obtusum is assumed to have been caused by a trophic shift and succession of a more acidophilic species, Sphagnum angustifolium.

Towards quantitative reconstruction of peatland nutrient status from fens

In rich fens, unlike bogs, the key drivers structuring testate amoeba communities are related to nutrient status, suggesting the potential for transfer functions to quantitatively reconstruct changing nutrient status from palaeoecological records. Such records could be useful tools to investigate the long-term impacts of pollution and landscape change. Here, we derive and test transfer functions for pH, water-table depth, conductivity and Ca and Mg concentrations using a data set from Polish fens. Results show that transfer functions for Ca and conductivity have apparent predictive power for surface samples; these models will require further validation and testing with palaeoecological data. Testate amoeba transfer functions for fen nutrient status may be a valuable addition to the peatland palaeoecologist’s tool-kit, although further work will be required to demonstrate their usefulness in practice.