Pollen and plant macrofossil analyses of radiocarbon dated mid-Holocene                 profiles from two subalpine lakes in the Rila Mountains, Bulgaria

Climate change has increased the temperature and altered the mixing regime of high-value lakes in the subalpine region of Northern Italy. Remote sensing of chlorophyll-a can help provide a time series to allow an assessment of the ecological implications of this. Non-parametric multiplicative regression (NPMR) was used to visualize and understand the changes that have occurred between 2003–2018 in Lakes Garda, Como, Iseo, and Maggiore. In all four deep subalpine lakes, there has been a disruption from a traditional pattern of a significant spring chlorophyll-a peak followed by a clear water phase and summer/autumn peaks. This was replaced after 2010–2012, with lower spring peaks and a tendency for annual maxima to occur in summer. There was a tendency for this switch to be interspersed by a two-year period of low chlorophyll-a. Variables that were significant in NPMR included time, air temperature, total phosphorus, winter temperature, and winter values for the North Atlantic Oscillation. The change from spring to summer chlorophyll-a maxima, relatively sudden in an ecological context, could be interpreted as a regime shift. The cause was probably cascading effects from increased winter temperatures, reduced winter mixing, and altered nutrient dynamics. Future trends will depend on climate change and inter-decadal climate drivers.

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Impacts of vegetation and palaeohydrological changes on the n-alkane composition of a Holocene peat sequence from the Upper Vistula Valley (southern Poland)

Journal of Soils and Sediments ◽

10.1007/s11368-021-02981-4 ◽

2021 ◽

Author(s):

Sylwia Skreczko ◽

Artur Szymczyk ◽

Weronika Nadłonek

Keyword(s):

Vegetation Change ◽

Higher Plants ◽

Large River ◽

Gas Chromatography Mass Spectrometry ◽

Botanical Composition ◽

Central European ◽

Plant Macrofossil ◽

Southern Poland ◽

River Valleys ◽

Palaeoenvironmental Conditions

Abstract Purpose The analysis of n-alkanes in palaeoenvironmental studies of peatlands is mainly limited to ombrogenous peatlands which are a rare feature in the environment. Using n-alkane and plant macrofossil analysis, we have tracked changes in the environment in the valley of a large Central European river. We tested the possibilities for applying such studies to low-moor bogs which are the most commonly occurring type of bog in the world. Materials and methods Representative peat samples were taken from two profiles in a peatland located in the Vistula Valley (southern Poland), and they were analysed for the occurrence and distribution of biomarkers. The distribution of n-alkanes was determined using gas chromatography-mass spectrometry (GC–MS). The botanical composition of the samples was determined by analysis of plant macrofossil remains, and the degree of peat decomposition was also determined. Results and discussion Samples of low-moor peat were characterised by a prevalence of medium- and long-chain n-alkane homologues, which is typical for higher plants. The variable values of the CPI, CPI (25–31), and the C23/C25 ratio have provided information on the stages of formation of the Zapadź bog. The source of n-alkane differentiation is vegetation change related to palaeohydrological dynamics and palaeoenvironmental conditions within the peatland. Conclusions We have shown that analysis of n-alkanes can be successfully used in low-moor bogs as a complement to palaeobotanical and palaeozoological methods. The bringing together of these types of research enables changes in the ecosystems of large river valleys to be tracked.

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Geochemical Trends in Sediments From 13 Italian Subalpine Lakes

Sediments and Water Interactions ◽

10.1007/978-1-4612-4932-0_14 ◽

1986 ◽

pp. 157-165 ◽

Cited By ~ 5

Author(s):

G. Premazzi ◽

A. Provini ◽

G. F. Gaggino ◽

G. Parise

Keyword(s):

Subalpine Lakes

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Identification of a population of Ranunculus achenes extracted from Middle Pleistocene sediments exposed at Belhus Park, Essex, UK

Acta Palaeobotanica ◽

10.2478/acpa-2013-0011 ◽

2013 ◽

Vol 53 (2) ◽

pp. 181-189

Author(s):

Michael H. Field

Keyword(s):

Morphological Characteristics ◽

Middle Pleistocene ◽

Fluvial Sediments ◽

Flowing Water ◽

Dry Grassland ◽

River Catchment ◽

Plant Macrofossil ◽

Organic Sediments

ABSTRACT A plant macrofossil assemblage extracted from Middle Pleistocene fluvial organic sediments collected from Belhus Park, Aveley, Essex, UK contained a number of tuberculate (verrucose) achenes attributed to the genus Ranunculus, one of which had two short spines preserved on its surface. The identification of these achenes is discussed here. This is worthy of note because Ranunculus tuberculate or spinose fossil achenes can be difficult to determine to species as they can have similar features, some Ranunculus species produce achenes in several morphological forms, and during fossilization delicate structures maybe destroyed (e.g. spines). After careful morphological consideration it is concluded that the fossil achenes from Belhus Park are Ranunculus parviflorus L., indicating that dry grassland or disturbed ground existed in the river catchment. The plant macrofossil assemblages that included the Ranunculus parviflorus achenes were dominated by waterside, damp ground, and aquatic taxa. It is probable that flowing water transported the achenes from further afield before their incorporation into the fluvial sediments. The identification of these fossils illustrates the importance of considering the morphological characteristics of the achene only and not to make a determination on the nature of the predominant palaeoenvironmental signal from an assemblage.

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Midge-inferred Holocene climate history of two subalpine lakes in southern British Columbia, Canada

The Holocene ◽

10.1191/0959683604hl703rp ◽

2004 ◽

Vol 14 (2) ◽

pp. 258-271 ◽

Cited By ~ 46

Author(s):

Sandra M. Rosenberg ◽

Ian R. Walker ◽

Rolf W. Mathewes ◽

Douglas J. Hallett

Keyword(s):

British Columbia ◽

Holocene Climate ◽

Climate History ◽

Subalpine Lakes ◽

History Of

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Excavations at an Iron Age Defended Enclosure at Tattershall Thorpe, Lincolnshire.

Proceedings of the Prehistoric Society ◽

10.1017/s0079497x00006642 ◽

1986 ◽

Vol 52 ◽

pp. 159-188 ◽

Cited By ~ 14

Author(s):

Peter Chowne ◽

Maureen Girling ◽

James Greig

Keyword(s):

Human Activity ◽

Iron Age ◽

Human Activities ◽

Organic Material ◽

Plant Macrofossil ◽

Late Iron Age

Excavation of a late Iron Age enclosure at Tattershall Thorpe, Lincolnshire, produced substantial quantities of organic material preserved in the ditch filling. Insect, pollen and plant macrofossil remains allowed reconstruction of the environment and human activity in the area. Evidence for cultivation, grassland and human activities in the enclosure is discussed.

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