Middle and late Holocene climate change and human impact inferred from diatoms,algae and aquatic macrophyte pollen in sediments from Lake Montcortès (NE Iberian Peninsula) |
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| Authors: | Paolo Scussolini Teresa Vegas-Vilarrúbia Valentí Rull Juan Pablo Corella Blas Valero-Garcés Joan Gomà |
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| Institution: | 1.Faculty of Biology, Department of Ecology,Universitat de Barcelona,Barcelona,Spain;2.Faculty of Earth and Life Sciences, Department of Marine Biogeology,Vrije Universiteit,Amsterdam,The Netherlands;3.Institut Botànic de Barcelona (CSIC-ICUB),Barcelona,Spain;4.Instituto Pirenaico de Ecología (CSIC-IPE),Zaragoza,Spain |
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| Abstract: | During the middle and late Holocene, the Iberian Peninsula underwent large climatic and hydrologic changes, but the temporal
resolution and regional distribution of available palaeoenvironmental records is still insufficient for a comprehensive assessment
of the regional variability. The high sedimentation rate in karstic, meromictic Montcortès Lake (Catalan pre-Pyrenees) allows
for a detailed reconstruction of the regional palaeoecology over the last 5,340 years using diatom analysis, aquatic pollen,
sedimentological data, and historic documentary records. Results show marked fluctuations in diatom species assemblage composition,
mainly between dominant Cyclotella taxa and small Fragilariales. We suggest that the conspicuous alternation between Cyclotella comta and C. cyclopuncta reflects changes in trophic state, while the succession of centric and pennate species most likely reflects changes in the
hydrology of the lake. The diatom assemblages were used to identify six main phases: (1) high productivity and likely lower
lake levels before 2350 BC, (2) lower lake levels and a strong arid phase between 2350 and 1850 BC, (3) lake level increase
between 1850 and 850 BC, (4) relatively high lake level with fluctuating conditions during the Iberian and Roman Epochs (650
BC–350 AD), (5) lower lake levels, unfavourable conditions for diatom preservation, eutrophication and erosion triggered by
increased human activities in the watershed during the Medieval Climate Anomaly (900–1300 AD), and (6) relatively higher lake
levels during the LIA (1380–1850 AD) and afterwards. The combined study of diatoms, algae and pollen provides a detailed reconstruction
of past climate, which refines understanding of regional environmental variability and interactions between climate and socio-economic
conditions in the Pyrenees. |
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