Sandy soil beneath Doñana’s juniper woodland

Environmental conditions

The Mediterranean climate has an oceanic influence: rainfall falls mainly between October and March, while July and August are usually very dry. Variation between years is also important. Terrain and position relative to the water table can add local differences in water availability, even within the same dune landscape.

Distribution and scope

This profile focuses on juniper woodland in Doñana’s stabilised dune system, in south-western Spain. The study describing its soils took place at three nearby localities within an area of about ten square kilometres, roughly three kilometres from the Atlantic. Juniper woodland, shrubland and annual grassland alternate in this landscape; they are not a single type of vegetation cover.

Structure

Sand dominates the soil texture. Its parent material comes from windblown sediments that form stabilised dunes over older deposits. The terrain includes dune tops, slopes and depressions between dunes, with different soil types. Beneath woody cover, the microbial community differs from that in grassland: the study found greater richness of fungal signals in juniper woodland. These DNA fingerprints allow communities to be compared, but do not amount to a catalogue of species.

Ecological processes

Microorganisms decompose fallen leaves and dead branches. This activity recycles nutrients and returns to the atmosphere some of the carbon previously taken up by plants, mainly as carbon dioxide. In juniper woodland, fungi associated with woody roots are part of the connection between vegetation and soil. This is more than just sand: organic matter and the organisms that use it make the substrate a living habitat.

Threats

The 2004–2005 hydrological year combined extreme drought and intense cold, causing defoliation and the death of woody vegetation. In May 2010, damaged plots had still not fully recovered. Soil analyses showed persistent changes in microbial communities: increased bacterial richness and reduced fungal richness in affected juniper woodland. These are results from that episode and sampling period, not an assessment of current conditions. Changes in vegetation and organic remains can affect soil functioning.