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

Abstract

Macrofossils and megafossils of different genera, which were found in twelve localities in the mountains of northwest Iberia, provide spatially precise evidence of their distribution in the region during the Holocene. Macrofossils were recovered from mires, eroded peat bogs and lakes, identified by their wood anatomy and dated using radiocarbon methods. Conifers (Pinus), deciduous trees (Betula, Salix, Quercus) and shrubs (Erica, Fabaceae) were identified. The findings of Pinus gr. sylvestris/nigra have special biogeographical significance. The available palaeoecological data from the Cantabrian Range and nearby mountains (Ancares and Courel) indicate that pines have grown during the Holocene over the highlands of the western part of the Cantabrian Range area as a natural vegetation element. Nevertheless, Pinus sylvestris is the only pine species that is currently present in the Cantabrian Mountains, and its natural distribution area is now limited to a few enclaves. In this study, we provide a number of conclusive findings demonstrating that the past distribution of Pinus gr. sylvestris/nigra in this region suffered an important range contraction during the last two millennia. Historical data also support this idea, as they strongly suggest that this species survived well into the historical period.

8000 years of vegetation history in the northern Iberian Peninsula inferred from the palaeoenvironmental study of the Zalama ombrotrophic bog (Basque‐Cantabrian Mountains, Spain)

“…The reasons for this phenomenon are probably climatic. The increased precipitation and temperature in the early middle Holocene, as detected in lake, bog, marine sediment and speleothem records in the northern Iberian Peninsula (Santos et al 2000;Roucoux et al 2001;Moreno et al 2011;Stoll et al 2013), which resulted in tree recolonization, caused an early decline of pine forests across Rubiales et al (2008Rubiales et al ( , 2011Rubiales et al ( , 2012. Deciduous taxa, especially Quercus, Corylus and sometimes Betula, in this temperate and humid climate had certain advantages that allowed them to compete successfully against coniferous formations, which survived in other areas.…”

“…In this area, the 19th‐century authors Willkomm & Lange (), following the works of Planelles () and Olazabal (), suggested the nature of relict Scots pine forests in the Cantabrian Mountains (Rubiales et al . , ). Similarly, Catón‐Santaren & Uribe‐Etxebarria (), Ruiz‐Urrestarazu () and Aseginolaza et al .…”

“…() and Rubiales et al . (, , ). Deciduous taxa, especially Quercus , Corylus and sometimes Betula , in this temperate and humid climate had certain advantages that allowed them to compete successfully against coniferous formations, which survived in other areas.…”

“…Although we could not distinguish between them and we retrieved no macro-remains, we suggest that the vast majority of pine pollen in the core originated from Pinus sylvestris because it is the only species remaining today in the area surrounding the peat bog (Aseginolaza et al 1996). In this area, the 19th-century authors Willkomm & Lange (1861), following the works of Planelles (1852) and Olazabal (1856), suggested the nature of relict Scots pine forests in the Cantabrian Mountains (Rubiales et al 2010(Rubiales et al , 2012. Similarly, Cat on-Santaren & Uribe-Etxebarria (1980), Ruiz-Urrestarazu (1989) and Aseginolaza et al (1996) pointed to the presence of relict Pinus sylvestris forests in the Basque Country, hardly altered by anthropogenic activities in the last millennium.…”

Seis mil años de gestión y dinámica antrópica en el entorno del Parque Natural de los Collados del Asón (Cordillera Cantábrica Oriental)

“…La presencia de estos bosques en zonas elevadas de la Cordillera Cantábrica es un tema largamente discutido. Desde el Tardiglaciar y los inicios del Holoceno, la mayoría de los estudios paleobotánicos del norte de la Península Ibérica indican que los pinos jugaron un papel importante en la recuperación postglacial de los bosques (Menéndez Amor y Florschütz, 1963;Hannon, 1985;Watts, 1986;Muñoz Sobrino et al, 2007, López Merino, 2009Rubiales et al, 2010Rubiales et al, , 2012. En el caso concreto de la Cordillera Cantábrica, son numerosísimas las evidencias palinológicas que demuestran la importancia de los pinares durante el Holoceno inicial y medio (Menéndez Amor y Florschütz, 1963;Menéndez Amor, 1968;Peñalba, 1989;Belet, 1993;Allen et al, 1996;Muñoz Sobrino et al, 1996, 1997Santos et al, 2000;Iriarte et al, 2001Iriarte et al, , 2003García Rovés et al, 2001;García Rovés, 2007;Moreno et al, 2011;Pérez Díaz et al, 2016), en las mismas fechas que en el registro paleoambiental de Sotombo.…”