Climate- and human-induced hydrological change since AD 800 in an ombrotrophic mire in Pomerania (N Poland) tracked by testate amoebae, macro-fossils, pollen, and tree-rings of pine

This high-resolution, multiproxy, palaeoenvironmental study of the Slowinskie Blota raised bog in N Poland, 10km from the Baltic Sea, covering the last 1200 years reveals different aspects of environmental change in a range of spatial scales from local to regional. Testate amoebae allowed quantitative reconstruction of the local water table using a transfer function based on a training set from N and W Poland. Special attention is paid to the testate amoeba Arcella discoides, which responds to rapid water-table fluctuations more than to average surface wetness. Macrofossils supported by local pollen tracked the local vegetation dynamics caused by local human impact and disturbance, including nutrients. Regional pollen showed human-induced landscape change outside the bog. Tree rings of Pinus sylvestris reflected the history of tree establishment and desiccation of the bog. Strong correlations between DCA axes 1 of regional pollen, of macrofossils and of testate amoebae, and a testate-amoebae-based water-table reconstruction that excludes A. discoides, indicate that changes on all spatial scales are linked, which is explained by a strong hydrologic connection between bog and surroundings. The combination of proxies shows that groundwater levels were modified by both human impact and climate change.

Palaeoecological evidence for anthropogenic acidification of a kettle-hole peatland in northern Poland

Mariusz Lamentowicz, Edward Mitchell

We studied the Holocene developmental history of a small kettle-hole peatland in northern Poland using radiocarbon dating and analyses of pollen, plant macrofossils, and testate amoebae with the aim to sort out the influences of climate change, autogenic succession, and human impact. The mire followed the classical succession from lake to a Sphagnum-dominated peatland, but peat accumulation only started about 3000 years before present. A rapid shift to wetter conditions, lower pH, and higher peat accumulation rate took place about 110-150 years before present, when the vegetation shifted to a Sphagnum-dominated poor fen with some bog plants. While the first shift to a peat-accumulating system was most likely driven by climate, the second one was probably caused by forest clearance around the mire. This shift towards a Sphagnum-dominated vegetation mirrors both in pattern and timing the changes observed in similar situations in North America and New-Zealand. While human activities have overall caused the loss of vast expanses of peatlands worldwide in recent centuries, locally they may have also allowed the development of communities that are now ironically considered to have a high conservation value. However, in the case of the site studied and possibly elsewhere the likely anthropogenic shift to bog vegetation was at the expense of a species-rich poor fen, which today has even higher conservation value than ombrotrophic bogs. Thus this study also illustrates the value of palaeoecology for peatland management and biodiversity conservation.

2007

Last millennium palaeoenvironmental changes from a Baltic bog (Poland) inferred from stable isotopes, pollen, plant macrofossils and testate amoebae

Mariusz Lamentowicz, Edward Mitchell

The Baltic coast of Northern Poland is a region of considerable potential interest for paleoclimatic studies because this region is under the influence of both oceanic and continental climates and that these two influences have likely changed through time. Also unlike many more intensively studied regions of Europe human impact was more limited until the 19th century. We present a multiproxy high-resolution record from Stążki mire, an ombrotrophic mire located in northern Poland 35 km from the Baltic sea coast. We combined four proxies from the peat: testate amoebae, stable isotopes (δ13C) of Sphagnum stems, pollen, and plant macrofossils supported by dendroecological data to assess the palaeoenvironmental changes that took place during the last millennium. The general aim of this study was to test if a range of proxies (testate amoebae, pollen, plant macrofossils and tree rings) could allow inferring a climatic signal from a peat monolith despite the considerable anthropogenic impact on the Pomerania landscape since the Early Medieval period. Combining internal (e.g. macrofossils and testate amoebae) and external (pollen) signals is key to distinguishing human from climatic signals in palaeoenvironmental studies of peatlands. Our more specific aims were to: a) reconstruct the last millennium palaeoenvironment in a Baltic raised bog and its surroundings, b) identify the major wet-dry shifts and correlate those events with climate change and human impact, c) assess the resilience of the Baltic bog ecosystem following human impact. We noted two disturbance periods in the history of the mire. The two major disturbances in the history of the mire were dry periods [(I) 1100-1500 AD and (II) 1650-1900 (2005) AD]. These are reflected in all indicators and can be interpreted as the mixture of climate impact and human activities. However, the pollen record shows little evidence of human indicators during the first dry shift. The second disturbance can be related to local peat exploitation of the mire and then in the 20th century with limited artificial drainage. From 1500 AD all proxies show that the water table abruptly rose in the mire. The beginning of this shift occurred during the Little Ice Age and therefore it is likely a climatic signal. Alternatively, this wet shift could have been interpreted as a re-wetting mire surface after peat burning, but this interpretation is rejected because there is no evidence of major local fire in the macrofossil record. The macrofossil data shows that Sphagnum fuscum dominated the pristine mire vegetation but then declined and finally disappeared. This pattern is comparable with the timing of extinction of Sphagnum austinii in Western Europe. This study illustrated the value of palynological analysis of peat archives (especially for last millennium) to assess the magnitude of anthropogenic land-use changes. For example the comparison of Fagus (beech) and Carpinus (hornbeam) history with the palaeohydrological record allowed us to exclude climate change as the most important factor for the decline and expansion of these tree species. This study is the first direct comparison of testate amoeba and stable isotope data.

2008

Climate change and Arctic ecosystems: 2. Modeling, paleodata-model comparisons, and future projections

Jed Oliver Kaplan

Large variations in the composition, structure, and function of Arctic ecosystems are determined by climatic gradients, especially of growing-season warmth, soil moisture, and snow cover. A unified circumpolar classification recognizing five types of tundra was developed. The geographic distributions of vegetation types north of 55degreesN, including the position of the forest limit and the distributions of the tundra types, could be predicted from climatology using a small set of plant functional types embedded in the biogeochemistry-biogeography model BIOME4. Several palaeoclimate simulations for the last glacial maximum (LGM) and mid-Holocene were used to explore the possibility of simulating past vegetation patterns, which are independently known based on pollen data. The broad outlines of observed changes in vegetation were captured. LGM simulations showed the major reduction of forest, the great extension of graminoid and forb tundra, and the restriction of low- and high-shrub tundra (although not all models produced sufficiently dry conditions to mimic the full observed change). Mid-Holocene simulations reproduced the contrast between northward forest extension in western and central Siberia and stability of the forest limit in Beringia. Projection of the effect of a continued exponential increase in atmospheric CO2 concentration, based on a transient ocean-atmosphere simulation including sulfate aerosol effects, suggests a potential for larger changes in Arctic ecosystems during the 21st century than have occurred between mid-Holocene and present. Simulated physiological effects of the CO2 increase (to >700 ppm) at high latitudes were slight compared with the effects of the change in climate.

2003

Last millennium palaeoenvironmental changes from a Baltic bog (Poland) inferred from stable isotopes, pollen, plant macrofossils and testate amoebae

Mariusz Lamentowicz, Edward Mitchell

2008