water Article Birch Bog on Anthropogenically Transformed Raised Bogs. A Case Study from Pomerania (Poland) Zofia Sotek 1,*, Małgorzata Stasi ´nska 1, Ryszard Malinowski 2, Renata Gamrat 3 and Małgorzata Gałczy ´nska 4 1 Department of Botany and Natural Conservation, Faculty of Biology, University of Szczecin, Felczaka 3c, PL-71-412 Szczecin, Poland; [email protected] 2 Department of Soil Science, Grassland and Environmental Chemistry, West Pomeranian University of Technology Szczecin, Słowackiego 17, PL-71-434 Szczecin, Poland; [email protected] 3 Department of Ecology, Environmental Protection and Management, West Pomeranian University of Technology Szczecin, Słowackiego 17, PL-71-434 Szczecin, Poland; [email protected] 4 Department of Chemistry, Microbiology and Environmental Biotechnology, West Pomeranian University of Technology Szczecin, Słowackiego 17, PL-71-434 Szczecin, Poland; [email protected] * Correspondence: [email protected] Received: 1 April 2019; Accepted: 31 May 2019; Published: 12 June 2019 Abstract: Birch bog is formed on the margins of or within raised bogs, on secondary habitats. The study aim was to understand the vegetation and mycological diversity of birch bog on the background of habitat conditions on raised bogs subject to anthropogenic changes, including 15 areas located on seven bogs. Two of the analyzed areas were located on a peat bog not subject to human impact. Phytosociological and mycosociological relevés were taken and substrate analyses were carried out (pH, humidity, N-NH4, N-NO2, N-NO3 and P-PO4). Based on habitat predictors, two area groups were distinguished, differing primarily in humidity. More humid habitats were present on the margins of bogs, and were characterized by lower acidity and higher N-NH4 and P-PO4 abundance. Despite the fact they were enriched by runoffs from the neighboring arable fields, this was not always reflected in the plant and fungi species richness. Quercus robur appeared on less humid habitats, which may be a symptom of unfavorable changes toward habitat drying. In the majority of cases, changes in the habitat independent of the birch patches located and the human impact type are not yet reflected in the vegetation. However, they may be indicated by the fungal diversity, highest in former peat extraction pits, and lowest in pristine peat. Keywords: Vaccinio uliginosi-Betuletum pubescentis; peat bog plants; macrofungi; former peat extraction pits; Betula pubescens; habitat predictors 1. Introduction Bogs are among the most valuable ecosystems, not only due to the rare and valuable species found therein, but also due to the fact that they are natural retention basins. They contain 10% of the freshwater volume of the Earth [1]. Moreover, they are of key importance for the long-term sequestration of atmospheric carbon [2]. It is estimated that peat contains circa 26% of all the terrestrial carbon accumulated since the Last Glacial Maximum [3] thus they are among the largest terrestrial carbon reservoirs. Close to 95% of all peat bogs around the world are located in the northern hemisphere in a cold and at the same time humid temperate climate [4]. It is also here where the majority of raised bogs are present, supplied solely by rainwater. Such ecosystems are highly susceptible not only to natural factors, such as unfavourable climatic changes but above all hydrological disturbances resulting from human activity [5]. Water 2019, 11, 1224; doi:10.3390/w11061224 www.mdpi.com/journal/water Water 2019, 11, 1224 2 of 18 Globally, the human impact on wetlands has intensified in the last 200 years, and particularly in the first half of the 20th century [1,6]. This phenomenon occurred at a high rate and extensively primarily in industrialised countries, where the bog areas have been drastically reduced [7]. Wetlands, including raised bogs, were frequently drained in order to use them in agriculture, forestry and to obtain peat [8,9]. In Europe, almost all bog areas have been disturbed [6], whereas in Poland, close to 80% of bog ecosystems have been subject to human interference [10]. In the majority of cases this has led to a loss or degradation of those valuable habitats and, as a consequence, to changes or loss of vegetation typical of bog ecosystems [11–13]. Plant species of raised bog communities are typically stenobionts; thus, they are among the ecosystem elements that are most sensitive to habitat changes, including rapidly expanding anthropogenic amendments, including drying and eutrophication [12,14]. Drying may trigger peat decomposition processes, leading to C and CO2 loss, as well as to increased mineralisation of nutrients, leading to internal eutrophication [15,16]. Processes occurring as a result of human impact may lead to a rapid invasion of trees on open areas and development of forest communities. This is an unfavourable phenomenon for raised bogs, as it leads to additional water drainage, increasing their degradation [17,18]. However, in the case of undisturbed bogs, tree invasion is inhibited, and their increasing share takes place only under conditions typical of late stages of natural succession [19]. Among forest communities found on raised bogs, bog coniferous and deciduous forests are distinguished, which are rare and valuable components of those ecosystems. They are included in the Annex 1 to the Habitats Directive of the EU, as 91D0: natural habitats of Community interest whose conservation requires the designation of special areas of conservation [20]. Birch bog (Vaccinio uliginosi-Betuletum pubescentis) is one such community. It is a plant community with Atlantic distribution type, occurring primarily in north-west Europe, including Austria [21], the Czech Republic [22], Denmark [23], Germany [24,25], Hungary [26], Ireland [27], Slovakia [28], and in Ukraine [29]. In Poland, it reaches its eastern boundary of geographic distribution. Patches of birch bog develop typically on drainless terrain depressions with high groundwater level, on rather shallow, mesotrophic, acidic transition peats, on acidic soils with the nature of stagnosol. It is the final stage of succession on transitional bogs, whereas it occurs on the margins of raised bogs, as well as on the habitats with secondary genesis—in the areas where intensive decomposition processes occur [30,31]. In many parts of Ireland, it develops on exploited and drained peatlands, while raised bogs are mainly associated with areas enriched with nutrients, originating from surface runoffs from surrounding areas [32]. Previous studies of swamp birch, both in north-western [23,27,32] and central [21,22] Europe, were mainly focused on understanding the species composition of plants that build this community and its structure. However, in general this aim was not a separate subject of consideration. Usually, it was included in the study on plants colonising the examined bog [33–35]; sometimes, the selected properties of the habitat were also taken into account [36]. Few reports concern the Holocene history of birch bog woodlands [37–41]. They show that phases rich in Betula were already present in the early Holocene or the Late Glacial in Central and Eastern Europe. Apart from plants, fungi are important biotic factors for the formation and functioning of phytocenoses because they are heterotrophic organisms they enter into a range of relationships with plants as well as influence their habitat directly, causing organic matter decomposition. Macromycetes of birch bog are sporadically included in research but they usually are only a single element of wider, more comprehensive studies [42,43]. Certain macromycetes species are strictly associated with peat ecosystems not to be found anywhere else [42,44,45]. Therefore, the condition of the plant community can be reflected not only by plants, their species composition and share, but also the diversity and composition of the mycobiota. These elements remain in a close relationship with the habitat conditions. However, to date these three components were not considered together in the aspect of anthropopression in birch bog. The aim of the study was to investigate the floristic and mycological diversity of birch bog in regard to habitat conditions in raised bogs under anthropogenic transformations. This objective was completed based on the answers to the following research questions: (1) Did the research areas differ significantly in terms of selected physical and chemical Water 2019, 11, 1224 3 of 18 properties of the soil, affecting the trophy of the habitat and, if so, whether this was influenced by the type of anthropopression? (2) Are there any significant differences in composition of fungal biota and plant species depending on the location of the research area and the type of anthropogenic impact? (3) If a lower level of habitat predictors (soil properties) is found, is this reflected in both plants and fungi or only in one of these components of the ecosystem? (4) Does the plant community have a chance to preserve its individuality and biodiversity despite the presence of anthropopression? 2. Materials and Methods The study was conducted in the period 2002–2004 and 2007–2009 in the area of seven raised bogs: Niewiadowo, Roby, Mszar near Stara Dobrzyca, Stramniczka, Torfowisko Toporzyk, Zielone Bagno and Ziemomy´sl,located in north-west Poland. Two of the studied objects are mid-forest bogs, and the other ones are located in the close vicinity of agricultural areas, used as arable fields or meadows. This means that they are exposed to an inflow of biogens as a result of surface runoffs. Only Mszar near Stara Dobrzyca was in the past and, is not exposed currently to any anthropogenic influences. Peat exploitation was performed on five of the examined locations, and it was preceded by the dewatering of deposits through a system of ditches that drained water from the peat bogs. However, the time of excavation of the first drainage ditches and the beginning of exploitation is unknown it may be concluded only on the basis of available historical maps.