Vegetation and landscape dynamics under natural and anthropogenic forcing on the Azores Islands: a 700-year pollen record from the São Miguel Island

Abstract

The Azores archipelago has provided significant clues to the ecological, biogeographic and evolutionary knowledge of oceanic islands. Palaeoecological records are comparatively scarce, but they can provide relevant information on these subjects. We report the palynological reconstruction of the vegetation and landscape dynamics of the São Miguel Island before and after human settlement using the sediments of Lake Azul. The landscape was dominated by dense laurisilvas of Juniperus brevifolia and Morella faya from ca. AD 1280 to the official European establishment (AD 1449). After this date, the original forests were replaced by a complex of Erica azorica/Myrsine africana forests/shrublands and grassy meadows, which remained until ca. AD 1800. Extractive forestry, cereal cultivation (rye, maize, wheat) and animal husbandry progressed until another extensive deforestation (ca. AD 1774), followed by the large-scale introduction (AD 1845) of the exotic forest species Cryptomeria japonica and Pinus pinaster, which shaped the present-day landscape. Fire was a significant driver in these vegetation changes. The lake levels experienced a progressive rise during the time interval studied, reaching a maximum by ca. AD 1778-1852, followed by a hydrological decline likely due to a combination of climatic and anthropogenic drivers. Our pollen record suggests that São Miguel were already settled by humans by ca. AD 1287, approximately one century and a half prior to the official historically documented occupation of the archipelago. The results of this study are compared with the few palynological records available from other Azores islands (Pico and 70 Flores).