Palaeoecologial development of the Quiaios–Mira dunes, northern-central littoral Portugal

Abstract

Pollen and non-pollen palynomorph data are presented from two lakes and two adjacent areas in the Quiaios–Mira dunes of northern-central littoral Portugal. The region consists of a large sand plain afforested in the early 20th Century in response to the threat of sand dunes advancing towards settlements and agricultural fields. The lakes are situated in the border zone between the sand plain to the west and the agricultural fields to the east. The investigated sediments cover a period of deposition of ca. 1600 years. Initially the sites were wetland areas with changes in humidity revealed by variations in local hygrophilous vegetation and non-pollen palynomorphs. Lakes developed first in the period 1723–1866 AD seemingly as a direct result of sand dunes moving in from the west and interfering with the hydrological drainage system. Vegetation in the region was an open heathland from 1630 BP (420 AD) until around 1720 AD when reforestation, in the form of pine plantations, occurred. Anthropogenic influence on the vegetation (grazing and agriculture) is detected early in some of the diagrams but is more prevalent in the upper part following the reforestation 200–300 years ago. Various periods of strong aeolian activity are reflected through sand layers, suggesting multiple sand invasions and dune generations.