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Las Palmas de Gran Canaria, Spain

Lopez-Merino L.,Brunel University | Moreno A.,CSIC - Pyrenean Institute of Ecology | Leira M.,University of La Coruna | Sigro J.,Rovira i Virgili University | And 6 more authors.
Journal of Paleolimnology | Year: 2011

We present a study of two short sediment cores recovered from Lago Enol, in the Picos de Europa National Park, Cantabrian Mountains, northern Iberia. We inferred past climate conditions and anthropogenic impacts using geochemical and biological (pollen and diatoms) variables in the dated sequences, in conjunction with temperature and precipitation data collected since 1871 at meteorological stations in the region. The record provides evidence of environmental changes during the last 200 years. At the end of the Little Ice Age (~1800-1875 AD) the region was characterized by an open landscape. Long-term use of the area for mixed livestock grazing in the mountains, and cultivation of rye during the nineteenth century, contributed to the expansion of grassland at the expense of forest. Warmer temperatures since the end of the nineteenth century are inferred from a change in diatom assemblages and development of the local forest. Socioeconomic transformation during the twentieth century, such as livestock changes related to dairy specialization, planting of non-native trees, mining activities, and management of the national park since its creation in 1918, caused profound changes in the catchment and in the lake ecology. The last several decades (~1970-2007 AD) of the Lago Enol sediment record are strikingly different from previous periods, indicating lower runoff and increasing lake productivity, particularly since AD 2000. Today, the large number of tourists who visit the area cause substantial impacts on this ecosystem. © 2011 Springer Science+Business Media B.V. Source

Lopez-Merino L.,Brunel University | Silva Sanchez N.,University of Santiago de Compostela | Kaal J.,Institute Ciencias del Patrimonio Incipit | Lopez-Saez J.A.,Institute Historia CCHS | Martinez Cortizas A.,University of Santiago de Compostela
Global and Planetary Change | Year: 2012

There is a wealth of studies dealing with the reconstruction of past environmental changes and their effects on vegetation composition in NW Iberia, but none of them have focused specifically on the post-disturbance dynamics (i.e. the type of response) of the vegetation at different space and time scales. To fill this gap, we analysed the record of pollen and non-pollen palynomorphs (NPP) of a 235-cm thick colluvial sequence spanning the last ~13,900years. The aims were to detect the changes in vegetation, identify the responsible drivers and determine the type of responses to disturbance. To extract this information we applied multivariate statistical techniques (constrained cluster analysis and principal components analysis on transposed matrices, PCA tr) to the local (hydro-hygrophytes and NPP) and regional (land pollen) datasets separately. In both cases the cluster analysis resulted in eight local and regional assemblage zones, while five (local types) and four (regional types) principal components were obtained by PCA tr to explain 94.1% and 96.6% of the total variance, respectively. The main drivers identified were climate change, grazing pressure, fire events and cultivation. The vegetation showed gradual, threshold and elastic responses to these drivers, at different space (local vs. regional) and time scales, revealing a complex ecological history. Regional responses to perturbations were sometimes delayed with respect to the local response. The results also showed an ecosystem resilience, such as the persistence of open Betula-dominated vegetation community for ~1700years after the onset of the Holocene, and elastic responses, such as the oak woodland to the 8200calyr BP dry/cold event. Our results support the notion that palaeoecological research is a valuable tool to investigate ecosystem history, their responses to perturbations and their ability to buffer them. This knowledge is critical for modelling the impact of future environmental change and to help to manage the landscape more sustainably. © 2012 Elsevier B.V. Source

Moreno A.,University of Minnesota | Moreno A.,CSIC - Pyrenean Institute of Ecology | Lopez-Merino L.,Institute Historia CCHS | Leira M.,University of La Coruna | And 7 more authors.
Journal of Paleolimnology | Year: 2011

We present the Holocene sequence from Lago Enol (43°16′N, 4°59′W, 1,070 m a. s. l.), Cantabrian Mountains, northern Spain. A multiproxy analysis provided comprehensive information about regional humidity and temperature changes. The analysis included sedimentological descriptions, physical properties, organic carbon and carbonate content, mineralogy and geochemical composition together with biological proxies including diatom and ostracod assemblages. A detailed pollen study enabled reconstruction of variations in vegetation cover, which were interpreted in the context of climate changes and human impact. Four distinct stages were recognized for the last 13,500 years: (1) a cold and dry episode that includes the Younger Dryas event (13,500-11,600 cal. year BP); (2) a humid and warmer period characterizing the onset of the Holocene (11,600-8,700 cal. year BP); (3) a tendency toward a drier climate during the middle Holocene (8,700-4,650 cal. year BP); and (4) a return to humid conditions following landscape modification by human activity (pastoral activities, deforestation) in the late Holocene (4,650-2,200 cal. year BP). Superimposed on relatively stable landscape conditions (e. g. maintenance of well established forests), the typical environmental variability of the southern European region is observed at this site. © 2009 Springer Science+Business Media B.V. Source

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