Holocene vegetation changes in NW Iberia revealed by anthracological and palynological records from a colluvial soil

Abstract

Macroscopic charcoal, pollen and non-pollen palynomorphs were isolated from a colluvial soil located on a small hill in Campo Lameiro (NW Spain) in order to elucidate the vegetation history of the area and its relation to fire and human activities. The presence of macroscopic charcoal throughout the 2.10 m thick soil (42 samples) is evidence of frequent fires during the last c. 6300 years. The charcoal record was dominated by Quercus (probably Q. robur), Ericaceae (probably Arbutus unedo and Erica arborea) and Fabaceae (mainly Genista type). Abrupt changes in the charcoal assemblage are less explicit in the pollen sequence, probably as a result of pollen inflow from the downhill surroundings of the study site. Combined results indicated that the original oak woodland was gradually replaced by pyrophytic shrubs (Ericaceae and Fabaceae) as a result of fire recurrence. Non-pollen palynomorphs strongly suggested that vegetation was deliberately ignited by past human societies to facilitate grazing. No evidence of local agricultural practices was found. Episodes of accelerated shrubland expansion occurred c. 6000—5500 cal. BP, c. 4000—3500 cal. BP and c. 1700 cal. BP, the latter of which caused the definitive settlement of shrublands dominated by Ericaceae and Fabaceae which are nowadays widespread in NW Iberia.

Post-disturbance vegetation dynamics during the Late Pleistocene and the Holocene: An example from NW Iberia

“…The shift to locally drier conditions might suggest that the cause of 475 these changes was climatic -this chronology broadly coincides with the Neoglaciation, as found 476 in other records from NW Iberia (Martínez Cortizas et al, 1999; López-Merino et al, 2010a) -477 but further research, taking into account the information of nearby environmental records and 478 archaeological findings, is necessary to confirm it. In the nearby PRD-2 soil sequence the 479 overall picture is slightly different, as coprophilous fungi are present in the record since ~5500 480 cal yr BP, indicating local grazing (Carrión et al, 2010b). But between ~4000 and 3500 cal yr 481 BP a change in the composition occurred, with increased abundance of Sporormiella-type, 482…”

Causes and Evolutionary Consequences of Population Subdivision of an Iberian Mountain Lizard, Iberolacerta monticola

“…In the NW, the observation of lowland populations associated to relict Atlantic forests of an otherwise montane species is not an exclusive characteristic of I. monticola [88]–[92]. Major woodland declines in NW Iberia occurred during the Galician-Roman Medieval Period [93], [94], often due to recurrent fires produced by past human societies to facilitate grazing [95]. The loss of intervening suitable habitat, and the orientation of the retreating front of the Atlantic forests (from west to east), should have produced a succession of splits of the gene pools of I. monticola populations, which can be traced through the results of all our analyses of microsatellite variation, but particularly of FCA and Mantel tests.…”

Holocene distribution of woody taxa at the westernmost limit of the Circumboreal/Mediterranean boundary: Evidence from wood remains

“…Those studies, combined with macrocharcoal identification, suggest the spread of fire, linked to pastoral activities and local changes in vegetation composition, since ca. 6000 cal yr BP in some lowlands of the Atlantic coastal area (Carrion et al, 2010a).…”

“…In the innermost mountains of northwestern Iberia, a number of pollen diagrams show noticeable changes in the vegetation composition when unequivocal indicators of anthropogenic disturbance appear (i.e., Cerealia, Plantago, Rumex, Asphodelus; Allen et al, 1996;Mufioz Sobrino et al, 2005;Carrion et al, 2010a). Nevertheless, the ambivalent responses of some species may obscure the changes in the forest due to such disturbances, instead indicating a relative resilience to them.…”

“…In this area of southwestern Europe, most of the available information comes from the study of pollen sequences, and few studies have been conducted on macrofossil or megafossil remains (Alcalde et al, 2006;Carrion et al, 2010a). The pollen-derived reconstructions that have been recently developed in the Cantabrian Mountains offer a large body of sequential data (e.g.…”