Management implications inferred from the multivariate analysis of vadose zone chemical variables in Las Tablas de Daimiel National Park (Spain)

A multivariate analysis approach has been developed in order to explain the observed variability in soil chemistry at Las Tablas de Daimiel National Park (TDNP). Either natural or anthropogenic alterations of the amount or distribution of these chemicals may have severe consequences not only on the Tablas ecosystem itself, but also downstream the watershed (i.e. eutrophication), given the actual system functioning as recharge area for the Western La Mancha aquifer. The analysis has been carried out over 20 chemical variables measured at different depths in 22 sites along TDNP (n = 111), considering their interaction with 3 environmental factors: soil type, microtopographic variation and position upstream or downstream the central dam. Statistical analysis consisted on bivariate correlation, trend surface analysis, analysis of variance, principal component analysis and redundancy analysis. The results allow defining the vadose zone in TDNP as a highly saline carbonated media, with a large accumulation of solutes in the topsoil (0–20 cm). Recent drainage conditions favor the process of organic matter mineralization and subsequent nutrient release, thus increasing the risk of groundwater pollution. The multivariate model approximately explains 60% of the observed variability, 40% in terms of the environmental factors, and allows distinguishing three main domains: saline, organic and carbonated. This paper discusses the management implications derived from this analysis taking into account that the environmental factors considered are susceptible from being modified by certain managing activities such as reed reaping, construction of ditches and artificial ponding with brackish groundwater.

Research highlights
► The wetland has developed a vadose zone with accumulation of solutes in the topsoil.
► There are three different soil chemical environments: carbonated, organic and saline.
► Only three environmental factors explain variability in soil chemistry.
► Present anthropic management increases the risk of releasing stored nutrients.