The influence of abiotic factors on the bloom-forming alga Ulva flexuosa (Ulvaceae, Chlorophyta): possibilities for the control of the green tides in freshwater ecosystems

Ulva species are characterised by the capacity to achieve rapid biomass increase, which results in the formation of “green tides”, particularly in nutrient-rich seawaters. Over the last decade, formation of large-scale Ulva mats has been increasingly observed in freshwater systems in Central Europe. Mass development of Ulva in freshwater ecosystems presents a growing burden in spite of its economic benefits. This study explores the formation dynamics of Ulva flexuosa mats with respect to habitat conditions, using the examples of a number of water systems located in Poland. Elevated water temperature, pH and high concentration of sulphates are among the most important factors affecting biometric parameters of Ulva blooms. An evident disparity was observed between lotic water ecosystems and lentic water ecosystems, which differed in terms of chemical characteristics of the habitat and mat structure properties. In flowing water, U. flexuosa displays a definitely higher potential for blooms. On the other hand, mass occurrence of U. flexuosa in freshwaters is caused by the inflow of fecund waters, especially following intense precipitation in summertime, as well as by periodic increases in salinity, pH and sulphate levels. The study suggests that potential U. flexuosa blooms in landlocked ecosystems may be controlled by means of reducing the inflow of particularly sulphate-rich waters.This research was partially supported by the project S/P – B/028: “Interrelation among abiotic and biotic factors in aquatic ecosystems: environmental and experimental research”

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

Fruit yield of european cranberry (Oxycoccus palustris Pers.) in different plant communities of peatlands (northern Wielkopolska, Poland)

The aim of this study was to determine fruit yield of Oxycoccus palustris under the climatic and habitat conditions of northern Wielkopolska (the Greater Poland region), depending on the type of occupied plant community. Total fruit number and fruit weight as well as average cranberry leaf size were determined on 33 plots with an area of 1 m2, located on 7 peatlands. On the study areas, European cranberry produced crops from 9.2 up to 242.0 g ���� m-2, which gives 92-2420 kg ����ha-1. It has been demonstrated that on the peatlands of northern Wielkopolska O. palustris reaches its generative and vegetative optimum in the communities of the class Scheuchzerio- Caricetea fuscae, in particular in the community Sphagno recurvi-Eriophoretum angustifolii

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

Checklist, Red List, and Distribution Pattern of Charophytes (Charophyceae, Charales) in Slovakia Based on Critical Revision of Herbarium Specimens

A critical revision of charophytes collected in Slovakia from 1887 up to present, based on herbaria specimens, provided us with the opportunity to compile an updated checklist and to revaluate their threat status in order to obtain the current red list of charophytes of Slovakia. The data obtained will fill the gap in knowledge about these macroscopic algae in Central Europe. The revised list of charophytes includes 19 representatives of three genera: Chara (11), Nitella (7), and Nitellopsis (1). Following the latest IUCN red-list categories and criteria (version 3.1) and using the modified category regionally extinct (RE), derived from the category extinct (EX), 36.8% of charophytes are classified as RE (Chara connivens, C. subspinosa (=rudis), Nitella capillaris, N. confervacea, N. flexilis, N. gracilis, and N. opaca); 21% as EN (endangered; Chara braunii, Nitella mucronata, N. syncarpa, and Nitellopsis obtusa); 21% as VU (vulnerable; Chara contraria, C. gymnophylla, C. hispida, and C. virgata); 10.6% as NT (near-threatened; Chara globularis, C. vulgaris); and 5.3% as CR (critically endangered; Chara canescens) species; finally, 5.3% species could not be assessed (DD; Chara aspera)

Checklist, Red List, and Distribution Pattern of Charophytes (Charophyceae, Charales) in Slovakia Based on Critical Revision of Herbarium Specimens

A critical revision of charophytes collected in Slovakia from 1887 up to present, based on herbaria specimens, provided us with the opportunity to compile an updated checklist and to revaluate their threat status in order to obtain the current red list of charophytes of Slovakia. The data obtained will fill the gap in knowledge about these macroscopic algae in Central Europe. The revised list of charophytes includes 19 representatives of three genera: Chara (11), Nitella (7), and Nitellopsis (1). Following the latest IUCN red-list categories and criteria (version 3.1) and using the modified category regionally extinct (RE), derived from the category extinct (EX), 36.8% of charophytes are classified as RE (Chara connivens, C. subspinosa (=rudis), Nitella capillaris, N. confervacea, N. flexilis, N. gracilis, and N. opaca); 21% as EN (endangered; Chara braunii, Nitella mucronata, N. syncarpa, and Nitellopsis obtusa); 21% as VU (vulnerable; Chara contraria, C. gymnophylla, C. hispida, and C. virgata); 10.6% as NT (near-threatened; Chara globularis, C. vulgaris); and 5.3% as CR (critically endangered; Chara canescens) species; finally, 5.3% species could not be assessed (DD; Chara aspera)

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

Can Vegetation Indices Serve as Proxies for Potential Sun-Induced Fluorescence (SIF)? A Fuzzy Simulation Approach on Airborne Imaging Spectroscopy Data

In this study, we are testing a proxy for red and far-red Sun-induced fluorescence (SIF) using an integrated fuzzy logic modelling approach, termed as SIFfuzzy and SIFfuzzy-APAR. The SIF emitted from the core of the photosynthesis and observed at the top-of-canopy is regulated by three major controlling factors: (1) light interception and absorption by canopy plant cover; (2) escape fraction of SIF photons (fesc); (3) light use efficiency and non-photochemical quenching (NPQ) processes. In our study, we proposed and validated a fuzzy logic modelling approach that uses different combinations of spectral vegetation indices (SVIs) reflecting such controlling factors to approximate the potential SIF signals at 760 nm and 687 nm. The HyPlant derived and field validated SVIs (i.e., SR, NDVI, EVI, NDVIre, PRI) have been processed through the membership transformation in the first stage, and in the next stage the membership transformed maps have been processed through the Fuzzy Gamma simulation to calculate the SIFfuzzy. To test whether the inclusion of absorbed photosynthetic active radiation (APAR) increases the accuracy of the model, the SIFfuzzy was multiplied by APAR (SIFfuzzy-APAR). The agreement between the modelled SIFfuzzy and actual SIF airborne retrievals expressed by R2 ranged from 0.38 to 0.69 for SIF760 and from 0.85 to 0.92 for SIF687. The inclusion of APAR improved the R2 value between SIFfuzzy-APAR and actual SIF. This study showed, for the first time, that a diverse set of SVIs considered as proxies of different vegetation traits, such as biochemical, structural, and functional, can be successfully combined to work as a first-order proxy of SIF. The previous studies mainly included the far-red SIF whereas, in this study, we have also focused on red SIF along with far-red SIF. The analysis carried out at 1 m spatial resolution permits to better infer SIF behaviour at an ecosystem-relevant scal