A legacy of human-induced ecosystem changes: spatial processes drive the taxonomic and functional diversities of testate amoebae in Sphagnum peatlands of the Galápagos

Aim Our aims were to compare the composition of testate amoeba (TA) communities from Santa Cruz Island, Galápagos Archipelago, which are likely in existence only as a result of anthropogenic habitat transformation, with similar naturally occurring communities from northern and southern continental peatlands. Additionally, we aimed at assessing the importance of niche-based and dispersal-based processes in determining community composition and taxonomic and functional diversity. Location The humid highlands of the central island of Santa Cruz, Galápagos Archipelago. Methods We survey the alpha, beta and gamma taxonomic and functional diversities of TA, and the changes in functional traits along a gradient of wet to dry habitats. We compare the TA community composition, abundance and frequency recorded in the insular peatlands with that recorded in continental peatlands of Northern and Southern Hemispheres. We use generalized linear models to determine how environmental conditions influence taxonomic and functional diversity as well as the mean values of functional traits within communities. We finally apply variance partitioning to assess the relative importance of niche- and dispersal-based processes in determining community composition. Results TA communities in Santa Cruz Island were different from their Northern Hemisphere and South American counterparts with most genera considered as characteristic for Northern Hemisphere and South American Sphagnum peatlands missing or very rare in the Galápagos. Functional traits were most correlated with elevation and site topography and alpha functional diversity to the type of material sampled and site topography. Community composition was more strongly correlated with spatial variables than with environmental ones. Main conclusions TA communities of the Sphagnum peatlands of Santa Cruz Island and the mechanisms shaping these communities contrast with Northern Hemisphere and South American peatlands. Soil moisture was not a strong predictor of community composition most likely because rainfall and clouds provide sufficient moisture. Dispersal limitation was more important than environmental filtering because of the isolation of the insular peatlands from continental ones and the young ecological history of these ecosystems.

A 700-year paleoecological record of boreal ecosystem responses to climatic variation from Alaska

Recent observations and model simulations have highlighted the sensitivity of the forest - tundra ecotone to climatic forcing. In contrast, paleoecological studies have not provided evidence of tree-line fluctuations in response to Holocene climatic changes in Alaska, suggesting that the forest - tundra boundary in certain areas may be relatively stable at multicentennial to millennial time scales. We conducted a multiproxy study of sediment cores from an Alaskan lake near the altitudinal limits of key boreal-forest species. Paleoecological data were compared with independent climatic reconstructions to assess ecosystem responses of the forest - tundra boundary to Little Ice Age (LIA) climatic. uctuations. Pollen, diatom, charcoal, macrofossil, and magnetic analyses provide the first continuous record of vegetation -. re - climate interactions at decadal to centennial time scales during the past 700 years from southern Alaska. Boreal-forest diebacks characterized by declines of Picea mariana, P. glauca, and tree Betula occurred during the LIA ( AD 1500 - 1800), whereas shrubs ( Alnus viridis, Betula glandulosa/nana) and herbaceous taxa (Epilobium, Aconitum) expanded. Marked increases in charcoal abundance and changes in magnetic properties suggest increases in. re importance and soil erosion during the same period. In addition, the conspicuous reduction or disappearance of certain aquatic ( e. g., Isoetes, Nuphar, Pediastrum) and wetland ( Sphagnum) plants and major shifts in diatom assemblages suggest pronounced lake-level. uctuations and rapid ecosystem reorganization in response to LIA climatic deterioration. Our results imply that temperature shifts of 1 - 2 degrees C, when accompanied by major changes in moisture balance, can greatly alter high-altitudinal terrestrial, wetland, and aquatic ecosystems, including conversion between boreal-forest tree line and tundra. The climatic and ecosystem variations in our study area appear to be coherent with changes in solar irradiance, suggesting that changes in solar activity contributed to the environmental instability of the past 700 years.

Palaeohydrology, fires and vegetation succession in the southern Baltic during the last 7500 years reconstructed from a raised bog based on multi-proxy data

We present the first 7500 yr long multi-proxy record from a raised bog located at the southern Baltic coast, Poland. Testate amoebae, plant macrofossils, pollen and microscopic charcoal were used to reconstruct environmental changes in Pomerania (northern Poland, Kaszuby Lakeland) from a 7-m thick peat archive of Stążki bog dated 5500 BC–AD 1250. We obtained a record of proxies representing different spatial scales: regional vegetation changed simultaneously with local vegetation, and testate amoebae showed a pattern of change similar to that of pollen and plant macrofossils. On the basis of the combined proxies, we distinguished three hydroclimatic stages: moist conditions 5500–3450 BC, drier conditions with regionally increased fires up to 600 BC, and again moist conditions from 600 BC onward. During the drier interval, a first climatic shift to wetter conditions at 1700 BC is indicated by regional pollen as the replacement of Corylus by Carpinus, and locally by, e.g., the increase of Hyalosphenia elegans and mire plants such as Sphagnum sec. Cuspidata. Furthermore, we observed a correlation since 600 BC among the re-expansion of Carpinus (after a sudden decline ca. 950 BC), increased peat accumulation, increase of Hyalosphenia species, and fewer fires, suggesting lower evapotranspiration and a stable high water table in the bog. Fagus started to expand after AD 810 gradually replacing Carpinus, which was possibly due to a gradually more oceanic climate, though we cannot exclude human impact on the forests. Peat accumulation, determined by radiocarbon dating, varied with bog surface wetness. The hydroclimatic phases found in Stążki peatland are similar to moisture changes recorded in other sites from Poland and Europe. This is the first detailed record of hydroclimatic change during the Holocene in the southern Baltic region, so it forms a reference site for further studies on other southern Baltic bogs that are in progress.

The ecological consequences of megafaunal loss: giant tortoises and wetland biodiversity

The giant tortoises of the Galapagos have become greatly depleted since European discovery of the islands in the 16th Century, with populations declining from an estimated 250000 to between 8000 and 14000 in the 1970s. Successful tortoise conservation efforts have focused on species recovery, but ecosystem conservation and restoration requires a better understanding of the wider ecological consequences of this drastic reduction in the archipelago's only large native herbivore. We report the first evidence from palaeoecological records of coprophilous fungal spores of the formerly more extensive geographical range of giant tortoises in the highlands of Santa Cruz Island. Upland tortoise populations on Santa Cruz declined 500-700years ago, likely the result of human impact or possible climatic change. Former freshwater wetlands, a now limited habitat-type, were found to have converted to Sphagnum bogs concomitant with tortoise loss, subsequently leading to the decline of several now-rare or extinct plant species.

Palaeoenvironmental changes in Central Europe (NE Poland) during the last 6200 years reconstructed from a high-resolution multi-proxy peat archive

Peat deposits from an ombrotrophic bog (north-eastern Poland) were analysed to reconstruct peatland development and environmental changes. This paper presents reconstructions of hydrological changes and plant succession over the last 6000 years. The methods included the high-resolution analysis of plant macrofossils, pollen and testate amoebae, supported by radiocarbon dating. Three main phases were identified in the history of the bog and surrounding woodland vegetation: 4000–400 BC, 400 BC–AD 1700 and AD 1700–2011. Except for terrestrialisation and the fen-to-bog transition phase, the development of bog vegetation was mainly dependent on the climate until approximately AD 1700. The dominant taxon in Gązwa bog was Sphagnum fuscum/rubellum. Woodland development was significantly affected by human activity at several time periods. The most visible human activity, manifested by the decline of deciduous species, occurred ca. 350 BC, ca. AD 250, ca. AD 1350 and after AD 1700. These events correspond to phases of human settlement in the area. During 400–300 BC, the decline of deciduous trees, primarily Carpinus, coincided with an increase in indicators of human activity and fire frequency. At ca. AD 200, Carpinus and Tilia abundance decreased, corresponding to an increased importance of cereals (Secale and Triticum). Since ca. AD 1350, the impact of Teutonic settlement is apparent, and after AD 1700, deciduous forests largely disappeared.

Long-term hydrological dynamics and fire history over the last 2000 years in CE Europe reconstructed from a high-resolution peat archive

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.

Human and climatic impact on mires: a case study of Les Amburnex mire, Swiss Jura Mountains

Modern period long-term human and climatic impacts on a small mire in the Jura Mountains were assessed using testate amoebae, macrofossils and pollen. This multiproxy data analysis permitted detailed interpretations of local and regional environmental change and thus a partial disentanglement of the different variables that influence long-term mire development. From the Middle Ages until a.d. 1700 the mire vegetation was characterised by ferns, Caltha and Vaccinium, but then abruptly changed into the modern vegetation characterised by Cyperaceae, Potentilla and Sphagnum. The cause for this change was most probably deforestation, possibly enhanced by climatic cooling. A decrease in trampling intensity by domestic animals from a.d. 1950 onwards allowed Sphagnum growth and climatic warming in the a.d. 1980s and 1990s may have been responsible for considerable changes in the species composition. The mire investigated is an example of the rapid changes in mire vegetation and peat development that occurred throughout the central European mountain region during the past centuries as a result of changing climate and land-use practice. These processes are still active today and will determine the future development of high-altitude mires.

Present-day vegetation and the Holocene and recent development of Egelsee-Moor, Salzburg province, Austria

This paper describes the present-day vegetation, stratigraphy and developmental history of the mire of Egelsee-Moor (Salzburg, Austria; 45°45′N, 13°8.5′E, 700 m a.s.l., 15 ha in area) since the early Late Glacial on the basis of 4 transects with 14 trial borings across the peatland. We present a vegetation map of the mire, a longitudinal section through the peat body based on six cores showing the peat types, overview macrofossil diagrams of six cores showing the local mire development and two pollen diagrams covering the Late Glacial and Holocene. The chronology of the diagrams depends on biostratigraphic dating for the Late Glacial and early Holocene and radiocarbon dating for the remaining Holocene. The northern part of the mire originated through terrestrialisation of nutrient-rich, mostly inundated fen and the southern part through paludification of wet soils. The very small lake of today was a reservoir until recently for providing water-power for timber rafting (‘Holztrift’). The mire vegetation today is a complex of forested parts (mainly planted Pinus sylvestris and Thuja occidentalis, but also spontaneous Picea abies, Betula pubescens and Frangula alnus), reed-lands (Phragmites) and litter meadows (Molinietum, Schoenetum, etc.). The central part has hummock-hollow complexes with regionally rare species of transitional mires (Drosera anglica, D. intermedia, Lycopodiella inundata, Scorpidium scorpioides, Sphagnum platyphyllum, S. subnitens). The results indicate that some of the mid-Holocene sediments may have been removed by the timber-rafting practices, and that water extraction from the hydrological catchment since 1967 has resulted in a partial shift of transitional mire to ombrotrophic bog. The latter potentially endangers the regionally rare species and was used as an argument to stop further water extraction.