GEOCHEMICAL RELATIONSHIPS BETWEEN GROUNDWATER AND WETLAND SOILS AND THEIR EFFECTS ON VEGETATION IN CENTRAL SPAIN

Groundwater hydrochemistry and topography are the main factors affecting wetland soils and the vegetation in the semi-arid area under study. Groundwater flow systems are responsible for transport and dispersion of the soluble materials concentrated in discharge areas. Groundwater chemical and hydrodynamic characteristics and the chemical composition of soluble salts in the soils are closely correlated. Factor analysis reveals two major trends in the chemical evolution of groundwater: (1) increasing salinity with ''flow length'', and (2) alkalinization, with consequent effects on the chemical characteristics of soils. The distribution of plant species is correlated with the patterns of salinity and alkalinity in soils and justifies use of some plant species as biological indicators.