Vegetation changes in the southern Pyrenean flank during the last millennium in relation to climate and human activities: the Montcortès lacustrine record

Abstract

We report vegetation changes of the last millennium inferred from palynological analysis of a sediment core from Lake Montcortès, situated at ∼1,000 m elevation in the southern pre-Pyrenean flank. The record begins in the Middle Ages (∼AD 800) and ends around AD1920, with an average resolution of ∼30 years. The reconstructed vegetation sequence is complex and shows the influence of both climate and humans in shaping the landscape. Pre-feudal times were characterized by the presence of well developed conifer forests, which were intensely burned at the beginning of feudal times (AD 1000) and were replaced by cereal (rye) and hemp cultivation, as well as meadows and pastures. In the thirteenth century, a relatively short period of warming, likely corresponding to the Medieval Warm Period, was inferred from the presence of a low Mediterranean scrub community that is today restricted to <800 m elevation. This community disappeared during Little Ice Age cooling in the fifteenth century, coinciding with a decline in human activities around the lake. Forest recovery began around AD 1500, at the beginning of the Modern period, coinciding with wetter climate. Forests, however, declined again during the seventeenth century, coinciding with maximum olive and hemp cultivation. This situation was reversed in post-Modern times (nineteenth century), characterized by an intense agricultural crisis and a significant decline in population that favored forest re-expansion. Correlations with nearby Estanya Lake, situated about 350 m below, provide a regional picture of environmental change. Besides some climate forcing evident in both sequences, human activities seem to have been the main drivers of landscape and vegetation change in the southern Pyrenean flank, in agreement with conclusions from other studies in high-mountain environments.