Lake responses to historical land use changes in northern Spain:: The contribution of non-pollen palynomorphs in a multiproxy study

Environmental changes discussed in an earlier work using pollen, sedimentology, ostracods and charcoal proxies were evaluated with new non-pollen palynomorph data. The limits of non-pollen palynomorph biozones are consistent with the main environmental changes reported earlier in the Pre-Pyrenean Lake Estanya. The non-pollen palynomorph diagram from Lake Estanya Gran shows that changes in human activity during the last 2000 years are reflected in lake responses. Palaeoecological data from non-pollen palynomorphs have helped to determine the causes of these environmental changes, e.g. the lake use for hemp water-retting and its limnological impacts. The main change in the non-pollen palynomorph diagram is the expansion of Desmidiaceae, indicating more acid water conditions between 1220 AD and 1760 AD. The onset of Desmidiaceae in 1220 AD may be attributed to the development of farming and probably to the construction of water channels. Desmidiaceae undergo a considerable decline after 1760 AD, coinciding with the fall in hemp production in the XVIIIth century. Consequently, the lake water recovered the oligotrophic, status that had prevailed before 1220 AD. The perturbation caused by the introduction of hemp retting practices in Lake Estanya led to changes in all the proxies such as sedimentology, non-pollen palynomorphs, pollen and faunal communities. (c) 2006 Elsevier B.V. All rights reserved.