Saturday, 15 July 2006

Gradient Distribution of Four Invader Plants in Relation to Soil and Other Factors in CataluÑa (Ne Spain).

E. Sobrino1, Mario Sanz Elorza2, Elias D. Dana Sanchez3, José Miguel Soriano Páez1, and Alberto Gonzalez Moreno4. (1) Departamento de Producción vegetal: Botánica y Protección Vegetal. Univ. Politécnica de Madrid, Ciudad Universitaria sn, Madrid, 28040, Spain, (2) Ministerio de Hacienda, c. Zorrilla, Segovia, Spain, (3) Universidad de Almeria, Las Cañadas, Almeria, Spain, (4) INIA, Carreterad eLa Coruña km. 7,500, Madrid, 28040, Spain

Actually the plants invasion is considered as the second cause of plant decrease biodiversity in our planet. The situation in Mediterranean Basin is the same plant decrease biodiversity picture. Especial influence should be done in areas devastated by man. Spain shows the same scenario as part of a whole in the Mediterranean Basin. Recently in 2004 we have established 12 % of Spanish flora belongs to alien origin and we have related the presence of 123 plant invaders in Spain. In this work we study the plant gradient distribution of four alien invaders species in Catalonia that present at different distributing plant types: Araujia sericifera Brot. (Asclepidacea) from South-America; Carpobrotus edulis, (L.) N.E.Br. (Aizoaceae) from South Africa; Buddlejia davidi, Franchet (Buddlejaeae) from China; Conyza sumatrensis (Retz.) E. Walter (Compositae) from South America. We study the plant gradient distribution considering the following variables: soil type (including the antropic edaphic changes: contamination, existing urban zones, run way nets, etc), the type of basal rock; rainfall; altitude; soil water availability and index of continentally. Catalonia is a relatively small country between the parallels: 40º 30x N and 42º 50x N and the meridians 0º 30x E and 3º 30x E ; even Catalonia shows a big variability on the above mention studied variables. In general it shows basic soils. Nevertheless in the North East area (Gerona) and in a part of the Pyrenees Mountains the acid soils are present. Existing high mountains in the North region, the Pyrenees (Aneto peak 3404 m); steppes in the Ebro river depression, with humidity zones, some salty; and a long rock cost and sandy coast. Special attention has the urban zones like Barcelona, were the antropic pressure is heavy, occupying, modifying and destroying the soil as it is in other Catalonian towns. High way Catalonian net is a dense one, especially on touristic cost zones, which show a high human population density mainly during summer time. About this above mention species, we have already created a Distribution Base List performed by botanic itinerary, bibliographical revision and recording herbarium dry plants. All the localities studied were identified through UTM coordinates and mapped. The distributions of the selected species are in correspondence with the following parameters: Araujia sericifera: is present in all over the cost zone of Catalonia as in some shallow inside coastal localities. Carpobrotus edulis: is a naturalized plant, in sandy and scarp costal localities, invading through the all Catalonian coast, this plant comes in slightly in the valley rivers near to the Mediterranean sea. Buddleja davidii is an invader plant in the North of Catalonia, mainly in humid zones of slopes, ways border, stony river margin. Conyza sumatrensis: invades through a big part of Catalonia country, this plant is not so present in mountain regions, we see them colonizing high way borders, urban and unplugged soils.

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