A unique Pyrenean varved record provides a detailed reconstruction of Mediterranean vegetation and land-use dynamics over the last three millennia

V. Rull, T. Vegas-Vilarrúbia, J.P. Corella, M.C. Trapote, E. Montoya, B. Valero-Garcés

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Abstract

The Pyrenean Lake Montcortès sediments hold the longest continuous and absolutely varve-dated record of the Mediterranean region, encompassing the last three millennia, from the Late Bronze Age to the present. The reconstruction of vegetation and landscape dynamics during this time period has advanced gradually, following the progress of absolute dating by varve counting, and has been progressively published and updated in a number of papers dealing with specific time intervals at different temporal resolutions. This paper synthesizes all these studies in a single composite paleoecological sequence constrained by a single age-depth varve model. The final resolution of this reconstruction is bidecadal, on average, but some periods have been resolved at quasidecadal (Middle Ages) and subdecadal (Modern Age to present) resolutions. The study is focused on the timing of anthropization and the further development of vegetation under climatic and anthropogenic drivers until the shaping of present landscapes. An additional advantage of Montcortès is that the local history of the Pallars region, where the lake is located, is well documented and can be easily correlated with the paleoecological record. Contrary to former interpretations of general landscape anthropization of the Pyrenees during the Middle Ages, the Montcortès catchment was irreversibly transformed by anthropic activities at the beginning of the Iron Age (ca. 750-650 BCE). From this point, the catchment underwent successive transformations due to varied human uses (fire, grazing, cereal cultivation, weed/ruderal plant expansions, hemp cultivation/retting), which have been related to the different cultural phases and sociopolitical changes documented in the local historical records. The regional forests, dominated by Pinus and Quercus, experienced four main clearance events (RD) during the Iron Age (RD1; ca. 300 BCE), the Roman Period (RD2; ca. 300 CE), the Middle Ages (RD3; ca. 1000 CE) and the Modern Age (RD4; ca. 1800 CE). The detailed trends of the last two deforestation events and their causes could be studied at a decadal resolution, which significantly improved interpretation quality in ecological terms. The potential effects of climatic changes and the eventual interactions with human activities on catchment vegetation and regional forests throughout the record have also been discussed. The Montcortès record has been compared with other records at local (Pyrenees), regional (Iberian Peninsula) and biome (Mediterranean) scales. Locally and regionally, anthropization times and further ecological trends showed significant heterogeneity according to elevation, biogeographical patterns and cultural trends. The most significant coincidence is an intensification of human pressure, as noted in forest clearing and extensive land use, during several phases of the Middle Ages. At the Mediterranean level, the Montcortès record emerges as a unique sequence for the western sector of this biome that should be complemented with similar archives from the central and eastern Mediterranean. The most promising candidates for such sequences are discussed on the basis of available Mediterranean varved records. © 2021 The Author(s)
Original languageEnglish (US)
Article number107128
Number of pages23
JournalQuaternary Science Reviews
Volume268
DOIs
StatePublished - Sep 15 2021

Bibliographical note

Funding Information:
Inside the catchment, the vegetation was mostly herbaceous and dominated by grass meadows and weeds (Artemisia, Plantago). Cereal cultivation had been abandoned during the prefeudal phase. Grazing was less intense than in former periods, probably due to the development of extensive horizontal transhumance (Fig. S4; Supplementary Material), which relaxed the local grazing pressure. The dominance of open landscapes and the increase in runoff, as expressed in the frequency of HREs and the appearance of Glomus, led to a significant increase in SY to the lake. In addition to grazing, the main human activity inside the catchment seems to have been hemp cultivation/retting, although the relatively low abundance of this pollen type suggests that the hemp industry was intended only for local consumption. The possibility of hemp cultivation around the lake would be supported by the coeval in situ occurrence of lowland wild and cultivated plants migrating upwards thanks to the warmer climates of the MCA (950?1250 CE) (Fig. 6). Indeed, previous analyses (Rull et al., 2011) recorded the occurrence, in the Montcort?s catchment, of a low scrub community dominated by Rosmarinus and Helianthemum, which is characteristic of present Mediterranean dry lowlands situated below 800 m elevation (de Bol?s, 2001). In addition, historical documents report that during the same epoch, warmer climates allowed extension of lowland crops such as vineyards and olive groves to elevations above 1000 m, which include the Lake Montcort?s catchment (Fig. S4; Supplementary Material). Under these climatic conditions, hemp cultivation for local subsistence purposes around the lake would have been likely and is supported by the pollen record (Fig. 5).This work was funded by the Spanish Ministry of Science and Technology, projects RyC2003 to Valent? Rull, LIMNOCLIBER (REN 2003-09130-C02-02) and MEDLANT (CGL 2016-7215-R) to Blas Valero-Garc?s; and the Spanish Ministry of Economy and Competitiveness, project MONT-500 (CGL 2012-3665 and CGL 2017-85682-R) to Teresa Vegas-Vilarr?bia. Fieldwork was conducted with the aid of Doug Shnurrenberger, Mark Shapley and Anders Noren (Limnological Research Center, USA); Pen?lope Gonz?lez-Samp?riz and Ana Moreno (Pyrenean Institute of Ecology, Spain); Santiago Giralt and N?ria Ca?ellas (Institute of Earth Sciences Jaume Almera, Spain), and Elisabet Safont and Sandra Garc?s (University of Barcelona, Spain). Fieldwork permits were granted by the Territorial Service of the Department of Agriculture, Livestock, Fishing and Natural Environment of Catalonia (Barcelona). Samples were processed by N?ria Ca?ellas (Laboratory of Paleoecology, Institute of Earth Sciences Jaume Almera). Climatic data were provided by Javier Sigr? (University Rovira I Virgili). The collaboration of local entities and persons, notably the Council of Baix Pallars (Gerri de la Sal) and Xavier Figuera (Montcort?s), was crucial for fieldwork development. Historical documentation was provided by the Pallars Sobir? District Archive (Sort). The authors acknowledge the comments of three anonymous reviewers.

Funding Information:
This work was funded by the Spanish Ministry of Science and Technology , projects RyC2003 to Valentí Rull, LIMNOCLIBER ( REN 2003-09130-C02-02 ) and MEDLANT ( CGL 2016-7215-R ) to Blas Valero-Garcés; and the Spanish Ministry of Economy and Competitiveness , project MONT-500 ( CGL 2012-3665 and CGL 2017-85682-R ) to Teresa Vegas-Vilarrúbia. Fieldwork was conducted with the aid of Doug Shnurrenberger, Mark Shapley and Anders Noren (Limnological Research Center, USA); Penélope González-Sampériz and Ana Moreno (Pyrenean Institute of Ecology, Spain); Santiago Giralt and Núria Cañellas (Institute of Earth Sciences Jaume Almera, Spain), and Elisabet Safont and Sandra Garcés (University of Barcelona, Spain). Fieldwork permits were granted by the Territorial Service of the Department of Agriculture, Livestock, Fishing and Natural Environment of Catalonia (Barcelona). Samples were processed by Núria Cañellas (Laboratory of Paleoecology, Institute of Earth Sciences Jaume Almera). Climatic data were provided by Javier Sigró (University Rovira I Virgili). The collaboration of local entities and persons, notably the Council of Baix Pallars (Gerri de la Sal) and Xavier Figuera (Montcortès), was crucial for fieldwork development. Historical documentation was provided by the Pallars Sobirà District Archive (Sort). The authors acknowledge the comments of three anonymous reviewers.

Publisher Copyright:
© 2021 The Author(s)

Keywords

  • Anthropization
  • Iberian peninsula
  • Landscape transformations
  • Late Holocene
  • Palynology
  • Pyrenees
  • Varved lake sediments
  • Vegetation dynamics
  • Western Mediterranean

Continental Scientific Drilling Facility tags

  • ESP

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