No abstract

Abstraer. Seleclive principal component s analysis (SPCA) has been appl ied lo highly-a nd/ or liltle-correlated subgroups of bands. It s usefulness \Vas demonst ra ted in t\Vo ways. First, lh e fin al result is a false co lour compositioll based 0 11 lhe first o rd er principa l component of each high ly correlated subgro up of bands, lhe resulting image contain ing more than 95 per cen l of lhe tota l variance of l be six TM ballds lI sed. Seco ndly, Ih e secon d order principal compone nt of pairs of little-correla ted bands will show Ihe informalion Iha1 is unique for eac h bando 80th Iypes of analysis have been a pplied 10 characterizc Ihe geoJl1o rphological un ils al a si te in SW Spain. 80th mCl hodol ogies have demonsl rat ed lO be very useful in a difficult lo access area, wilh high vegela ti on diversily covering quite differenl geomorphic fealures.

A detailed geomorphologica1 srudy has been made of tbe moving dune system in the Doñana National Park and tbe system differentiated into 'morphoedaphic elements'. Tbese are e nsidered me simplest units composing tbe landscape, in which a strong relationship can be observed berween the soils and me characteristic vegetation. Parallel to tbe recognized morphoedaphic elements, tbe soils evolve as a result of two processes: hydromorphy and substratum stabilization. FinaUy, a common evolutionary soil-geomorphology catena is established.

This paper presents the most appropriate image-processing techniques available at the present time to differentiate two different seameadow communities, Posidonia oceanica and Cymodocea nodosa. The pre-processing program is an integral part of the sonar system and, therefore is not discussed in this paper. We propose a methodology based on unsupervised classification to chart and monitor these meadows, so fundamentally important to the mediterranean ecosystem. The images used for discussion were of seabottoms in the Cabrera Archipielago in the Mediterranean Sea.

No abstract

Temporay ponds from Do ñana National Park: a system of natural habitats for the preservation of aquatic ƀora and faunaMediterranean temporary ponds are a priority habitat under the European Union Habitats Directive, but those of natural origin are scarce, as many of them have been destroyed or transformed into permanent waters. The aim of this study is to highlight the conservation value of the system of temporary ponds in Doñana National Park, where more than 3000 water bodies may be ſlled during wet years. They are located on soils of aeolian origin where water persistence is favoured by the presence of an argilic semi permeable horizon and by a relic clay-rich sandy layer. Temporary ponds can be classiſed across a wide hydroperiod gradient. Most ponds ſll with autumnal or winter rains and persist up to late spring or summer, and only a few may persist through summer. Eight of the 11 amphibian species of this area require temporary ponds for breeding. More than 124 taxa of macroinvertebrates have been recorded, coleopterans (56 taxa) and heteropterans (19 taxa) being the richest taxonomic groups. Several zooplankton species are endemic to this kind of habitats, such as the copepod Dussartius baeticus and the rotifer Lecane donyanensis. Regarding vegetation, at least 55 hydrophytes species were identiſed in the ponds sampled, and also some species endemic to SW Iberian Peninsula (Callitriche regis-jubae, Scorzonera ſstulosa, Callitriche lusitanica) and others are in relic situation (Hydrocharis morsus-ranae, Thorella verticillato-inundata, Lemna trisulca). The conservation value of these ponds is highlighted by the large variety of protected and/or rare species of ƀora and fauna, which are favoured by a high pond abundance and connectivity.

The objective of this paper is to present a hypothesis to explain the selective response of Cymodocea nodosa in sonar images taken with frequencies of 100 and 500 kHz, as with the former frequency the communities present a very strong acoustic response, while with the second they appear almost transparent. The morphology and anatomy of the plant is analysed, and it is concluded that the air contained in the channels of leaves, rhizomes and roots, in relationship with the penetration in soft sediments of the frequencies used is the cause for the acoustic signature of the communities.

The influence of geomorphology on the composition of aquatic flora and fauna within a temporary pond network Geomorphological and hydrological features can provide a sound basis for global wetland classification. Temporary ponds located on the sandy area of Doñana can be classified into five different geomorphological areas. We hypothesised that these ponds would differ in soil characteristics, which may also explain differences in the composition of their macroinvertebrate, amphibian, and aquatic plant species assemblages. The study ponds were significantly segregated into southern and northern geomorphological areas based on the depth to the water table. The results of the multivariate ordination of soil variables were consistent with a north-south segregation, which was explained by the carbonate and other main ion concentrations in the pond basins. The ponds located in ecotones (marsh-sand and stable-mobile dunes) were particularly rich in amphibians and macroinvertebrates. This result may be explained because the ponds with the longest permanence of water were located in these areas, which represented the only flooded ponds during droughts. In addition, they also contained a high number of temporary ponds, thus favouring connectivity and environmental heterogeneity in these areas.