High-resolution (sub-decadal) pollen analysis of varved sediments from Lake Montcortès (southern Pyrenean flank): A fine-tuned record of landscape dynamics and human impact during the last 500 years

Abstract

A high-resolution (6 years/sample) palaeoenvironmental reconstruction using pollen, charcoal and non-pollen palynomorphs was carried out on annually laminated sediments of Lake Montcortès (South-Central Pre-Pyrenean flank). The results were combined with historical data to better understand landscape evolution and human interaction during the last 500 years. Our results show that human activities (cropping, livestock breeding and hemp cultivation and retting) have been the most important factors responsible for vegetation changes with highest intensity between 1530 and 1900 CE. By means of a sub-decadal study we have been able to evaluate short-lasting events at local and regional scales related to climate (heavy rainfall events and, highland forest fluctuations) or to historical and well-dated and documented socioeconomic events (i.e., crop promotions (hemp) or land abandonment-population emigration). The temporal extent (400 years) and continuity of Cannabis pollen peaks have been confirmed, and new evidence of water quality changes, likely as a consequence of hemp retting practices between the mid 17 th to late 19 th century, are provided. This is the first high-resolution palaeoenvironmental study carried out in a varved lake on the Iberian Peninsula so far. With these data we hope to contribute to filling the gap in high-resolution palaeoenvironmental data.

Modern Analogue Approach Applied to High-Resolution Varved Sediments—A Synthesis for Lake Montcortès (Central Pyrenees)

“…In summary, pollen analysis was able to identify two well differentiated modern assemblages, one corresponding to spring/summer and the other representing fall/winter. This matches well to the seasonal pattern identified in sedimentological (varve) studies [41]. Thus, utilising appropriate transfer functions supports the hypothesis that the combination of pollen data from sediment traps, varved lake sediments and modern meteorological data may produce long and high-resolution ecological time series.…”

Bronze Age “pristinity”, Iron Age anthropization and Medieval intensification of human impact around Lake Montcortès (southern-central Pyrenees): a possible mid-elevation pattern and its significance for the definition of the Anthropocene

“…A further study increased the resolution of the last ca. 500 years (1420 CE to 2013 CE) to the subdecadal scale and added the last century, which was absent in previous studies (Trapote et al, 2018b). These time intervals were characterized by a dominant anthropogenic forcing, mainly by burning, cultivation and grazing, from 780 CE onwards (Rull & Vegas-Vilarrúbia, 2015;Montoya et al, 2018).…”

“…Locally, the lake is surrounded by an almost continuous belt of aquatic and semiaquatic vegetation dominated by Phragmites australis, with Typha domingensis and Cladium mariscus also found. The local and regional ora and vegetation around Lake Montcortès have been described and mapped in detail elsewhere (Rull et al, 2011;Mercadé et al, 2013;Trapote et al, 2018b). The forest stands around the lake are dominated by deciduous Quercus (Fig.…”

“…Among them, Lake Montcortès holds the longest and a more continuous varved sequence, which encompasses approximately the last three millennia (Corella et al, 2016(Corella et al, , 2019, and has been the most studied of these lakes from paleoclimatic and paleoecological perspectives. These studies have shown that human activities have been the main driver of vegetation and landscape change and have signi cantly in uenced the sedimentary patterns during the last millennium (Corella et al, 2011a(Corella et al, , 2012(Corella et al, , 2014Rull et al, 2011;Scussolini et al, 2011;Rull & Vegas-Vilarrúbia, 2014, 2015Trapote et al, 2018b;Vegas-Vilarrúbia et al, 2018). However, the eventual anthropogenic in uence that occurred during the former ca.…”

On the Usefulness of the Modern Analog Approach to Interpret High Resolution Records: The Case of Varved Sediments from Lake Montcortès (Central Pyrenees)

“…The formation of annually laminated lake sediments relies on seasonal events linked to To empirically support this hypothesis, this study is primarily intended to identify seasonal pollen sedimentation patterns in a trap deployed in varved LM that would be useful for interpreting past records from the same lake. Hence, the interpretation of past pollen records was beyond the scope of this work and has been addressed in another paper [31]. Canonical correspondence analysis (CCA) was applied and showed the first two axes accounting for 70.74% of the total variance.…”