Natural and Anthropogenic Variations in the Large Shifting Dune in the Corrubedo Natural Park, NW Iberian Peninsula (1956–2017)

This work analyzes the evolution of the large shifting dune included in the Corrubedo Natural Park from 1956 until the present day. The analysis was carried out using aerial images, orthophotographs, topographic surveys and LiDAR (Light Detection and Ranging) data. Variations were analyzed in terms of four different aspects: evolution of pathways in each period, changes in the position of the mobile dune front and the degree of vegetation cover, all between 1956 and 2017; and variations in elevation and volume of the dune system between 2001 and 2015. To analyze these aspects, geospatial and geostatistical techniques were employed, which revealed that the dune front had undergone two different phases: one until the 1980s, with a mean seaward advance of 32 m and another one between the 1980 s and 2017, when the front prograded to the continent, with an approximate mean advance of 82 m. Loss of volume, related to the expansion of the mobile dune towards the north, was confirmed in this sector. It is evident that these changes are closely linked to anthropic influence, due to sand extraction until the early 1990s and, more recently, due to an increase in the number of visitors to the Natural Park. The results obtained highlight the need to carry out detailed studies to understand the evolution of this system and to prevent further damage in the future. Moreover, based on these analyses, a strategy to improve coastal and environmental management in the Corrubedo Natural Park could be designed.

Increasing status of non-native vascular plants in the Sefton Coast sand-dune system, north Merseyside, UK

Over 460 non-native (alien) taxa were recorded in a Sefton Coast sand-dune vascular plant inventory, their proportion in the flora increasing after 1999. Between 2005/06 and 2018, twice as many non-native as native plants were found. An analysis of occurrences of native and non-native taxa in six major habitat types found that a higher proportion of aliens was present in scrub/woodland and disturbed ground, while native plants had more occurrences in fixed dunes/dune grasslands, dune heath and wetlands. No differences between the two groups were detected for strandline/shingle and embryo/mobile dune habitats. Twenty-four non-native and 14 native taxa showed invasive characteristics in the duneland. The former included especially Hippophae rhamnoides and Rosa rugosa, both constituting major threats to sand-dune biodiversity. Particularly invasive native plants were Arrhenatherum elatius, Betula spp., Salix cinerea, and Ulex europaea. The main findings accord with studies elsewhere in Britain and Europe showing recent increases of neophytes in semi-natural habitats and that both non-native and native species can have invasive traits. The open habitats of coastal dunes seem to be particularly susceptible to plant invasions.

Can Vegetation Removal Successfully Restore Coastal Dune Biodiversity?

Coastal dune habitats have been declining globally over the last several decades due to rapid urbanization. Within remaining dune systems, dune fixation has resulted in further losses of mobile dunes with negative impacts on their associated species. Some studies suggest vegetation removal can initially promote habitat heterogeneity, and increase availability of suitable habitats for psammophile, xeric and endemic mobile dune species, but longer-term responses are generally unknown. We investigated the temporal trends of four taxonomic groups to determine the effect of vegetation removal on dune assemblages over a 12-year period at an LTER site. Three different forms of removal are investigated here—removal in a grid form on fixed dunes, removal of the wind-facing slope vegetation on semi-fixed dunes and opportunistic off-road driving on disturbed dunes. Results were varied across taxa, highlighting the need for multi-taxa monitoring in conservation and restoration management. Overall, fixed dune treatment had very little effect, while a stronger response was found in semi-fixed treatments in particular for mobile dune indicator species, which showed evidence of recolonization within a few years following treatment. Disturbed dunes were most similar to mobile dunes for animal taxa indicating that pulse removal may not be as effective as continuous press disturbance. Nevertheless, a less destructive form of disturbance such as re-introduction of grazing might be preferable and requires further investigation.

MORFOGÊNESE E GEODINÂMICA DAS DUNAS COSTEIRAS DE CANOA QUEBRADA, CEARÁ, BRAZIL

Este trabalho apresenta uma análise da geodinâmica e morfogênese do campo de dunas na região de Canoa Quebrada, localizada no município do Aracati, inserido no Estado do Ceará. Abrange a área formada pela planície flúvio-marinha, faixa de praia e campo de dunas localizados na margem direita da foz do rio Jaguaribe. O recorte temporal avaliado corresponde à análise da dinâmica do campo de dunas com base nas taxas de migração no período de 1988 a 2013. Os objetivos dessa pesquisa foram analisar a dinâmica ambiental do campo de dunas móveis em direção ao ecossistema manguezal localizado na foz do rio Jaguaribe. Associado à abordagem metodológica, realizou-se geoprocessamento de fotografias aéreas da década de 80 na escala de 1:25.000 e imagens de satélites Quickbird dos anos de 2004, 2010 e 2013. Foram identificadas dunas móveis do tipo longitudinais, barcanóides e lençóis de areias. Do ponto de vista de cobertura vegetal, foram identificadas dunas semi-fixas no contato com o ecossistema manguezal. Quanto às gerações dunares, domina a geração D1, caracterizada pela ocorrência de dunas atuais, móveis. No contato com o ecossistema manguezal, as dunas semi-fixas se combinam com a geração de dunas anteriores às atuais, do tipo sub-atuais, definindo a existência de dunas de geração D2. A taxa média de migração no campo de dunas durante todo esse período de 40 anos foi de 7m/ano. Nos anos de 2010 a 2013 praticamente não ocorreu migração, mas as dunas continuam se deslocando em direção ao ecossistema manguezal.Palavras chaves: Dunas costeiras, geodinâmica; morfogênese de dunas.ABSTRACTThis paper presents an analysis of geodynamic and morphogenesis of the dune field in the Canoa Quebrada region, located in the municipality of Aracati, inserted in the state of Ceará. It covers the area formed by fluvial-marine plain, the strip of beach and dune field located on the right bank of the mouth of the river Jaguaribe. The estimated period corresponds to the dynamic analysis of the dune field based on migration rates from 1988 to 2013. The objectives are to analyze the environmental dynamics of the mobile dune field towards the mangrove ecosystem located at the mouth of the river Jaguaribe. Associated with the methodological approach, we analyzed through GIS aerial photographs of the 80 on the scale of 1: 25,000 and 2004, 2010 and 2013 years of Quickbird satellite images. We find mobile dunes of the longitudinal type, barcanoids and sand sheets. Semi-fixed dunes were identified in the contact with the mangrove ecosystem. As for dune generations, we can say that dominates the generation D1, characterized by the occurrence of present-day dunes. In the contact with the mangrove ecosystem, the semi-fixed dunes combine with older dunes to define the existence of D2 generation. The average migration of the dune field during that period of 40 years was 7m / year. In the years 2010-2013, virtually no migration occurred, but the dunes continue to move towards the mangrove ecosystem.Keywords: Coastal dunes, geodynamics; dune morphogenesis.

The impact of Acacia saligna and the loss of mobile dunes on rodent populations: a case study in the Ashdod-Nizzanim sands in Israel

The Mediterranean coastal dune habitat of Israel is diminishing rapidly, mostly due to massive urbanization, changes in habitat characteristics caused by dune stabilization and the presence of Acacia saligna, an invasive species brought to Israel for the purpose of dune stabilization. In this study we document the effect of sand stabilization on the composition of small mammal communities in the Ashdod-Nizzanim sands, Israel. We analyzed differences in species diversity and abundance for species of rodents in four types of habitat: unstable (mobile) sand dune, semi-stabilized dune, inter-dune depression and a plot of the invasive Acacia saligna. Rodent communities were found to undergo gradual changes concurrently with the stabilization of the sands. The mobile dune was the only habitat in which the strict psammophiles Jaculus jaculus and Gerbillus pyramidum were captured in abundance. No species commensal with human were captured neither in the mobile nor in the semi-stabilized dunes. However, in the inter-dune depression there was quite a large representation of Mus musculus, a rodent commensal with humans. The Acacia saligna plot had the lowest number of captures and the lowest rodent biomass calculated, with Mus musculus composing nearly half of the captures. The results of this study demonstrate that stabilization of the sands in Ashdod-Nizzanim area is associated with the disappearance of psammophile rodents and the appearance of species commensal with humans. In order to preserve the habitat for psammophile rodents, measures should be taken to halt the spread of acacia and the continuing stabilization of the sands.

Causes of Ground Settlements in Upper Reservoir of Hydro-Wind Plant of El Hierro and Method Implemented for Soil Improvement

This article exposes one of the main engineering problems in the design and construction of the upper reservoir of El Hierro hydro-wind plant, relative to the high settlement of the bottom in the southeast area. The high settlements measured during the construction phase are consequence of the geological-geotechnical settings of the site, a natural depression of a volcanic crater occupied by highly deformable soils derived from the weathering of volcanic materials. Ground improvement was carried out by partial preloading (mobile dune), preceded by the execution of a trial embankment in the southeast area of the reservoir, where the greatest thickness of deformable soils was identified.