Ecological study of Las Tablas de Daimiel National Park (Ciudad Real, Central Spain): Differences in water physico-chemistry and vegetation between 1974 and 1989

Las Tablas de Daimiel National Park (TDNP) constitutes a SW-oriented continental wetland within the province of Ciudad Real (Central Spain). During the 1980s, the inundated area of the TDNP markedly decreased as a consequence of the apparent decline in both surface and groundwater resources. A Hydric Regeneration Plan was initiated in 1988 to increase water resources and enlarge the inundated area. This paper reports an ecological study of the water physico-chemistry and vegetation of the TDNP that was carried out in 1988-89. The data obtained are compared with previous data from a 1974-75 study to examine physico-chemical and botanical differences between both periods. Mean values of chloride and chemical oxygen demand were significantly higher in 1988-89 than in 1974-75, the spatial patterns of maximum and minimum values of conductivity tending to change. The number of hydrophyte species decreased in 1988-89 compared with 1974-75, hydrophytes inhabiting permanent waters being much more affected than hydrophytes inhabiting seasonal waters. Owing to the linear relationship between the area of habitats and the numbers of species living within them, it can be concluded that the reduction in inundated area during the 1980s, rather than the alteration in water quality, is the major environmental factor responsible for the decrease in species richness.