JBCLM | 2010-2025

Approximately 6 million years ago, during the so-called Messinian Salinity Crisis, the Mediterranean Sea became isolated from the Atlantic Ocean due to tectonic uplift of the Betic Mountains (southern Iberia) and the Rif Mountains (northern Morocco). This event caused the desiccation of large areas of water. The new azonal* habitats that emerged posed a significant challenge for the local flora, which gradually managed to colonize the exposed seabed. At the same time, naturally colonizing Asian species spread westward across Europe as the sea retreated. New species evolved that were capable of surviving in hypersaline soils—halophytes—or in gypsum-rich soils—gypsophytes—both of which are highly challenging substrates for life. Descendants of this ancient flora now populate the salt flats and gypsum steppes of inland Iberia, where a semi-arid Mediterranean climate prevails. In addition to the drought imposed by the climate, these soils exert high osmotic pressure, and the high salt concentration creates toxic conditions.Plants have adapted to these extreme environments through various strategies: succulence, selective ion absorption by roots, active salt excretion through leaf glands… One could say that these plants are capable of extracting water from saline soils via reverse osmosis. Although these habitats are low in productivity due to environmental stress, and appear modest because of the absence of large plants, they are of great evolutionary and ecological value and are currently protected under European and regional directives.

Managing these recreated habitats in the botanical garden requires careful and continuous attention, given the high degree of adaptive specialization of their plants. Soil salinity is monitored and adjusted periodically, with different schedules depending on the habitat: in the margins of the saline lagoon, soil conditioning occurs twice a year; in the surrounding esparto grasslands, every two years; and in the rest of the azonal collections, every five to eight years. The result is a zonation of ecosystems that, while not particularly showy, possess remarkable ecological uniqueness and value.

9. Saline Pond

This is the lowest zone of the azonal ecosystems, where water accumulates with dissolved salts, often seasonally. Along its margins grow halophytic plants, which thrive in saline soils, such as Typha domingensis, Limonium carpetanicum, Schoenus nigricans, Scirpus maritimus, Juncus maritimus, Juncus subulatus, Frankenia thymifolia, and Sonchus crassifolius. These plants are able to inhabit seasonally wet soils with high salt concentrations, having adapted to these challenging conditions over thousands of years of evolution.

10. Ocaña Albardine Grassland

To recreate this habitat, dominated by albardine (Lygeum spartum) and protected under European directives, its natural tendency to occupy low-lying areas was taken into account, usually alongside gypsum steppes and salt flats, whose evaporites are carried by rainfall. Lygeum spartum is a perennial, rhizomatous grass native to nutrient-poor, saline, or gypsum-rich soils, widespread throughout the Mediterranean. Its scientific name reflects the traditional uses of its fibers—braiding, rope-making, and basketry—since Lygeum derives from the Latin lygos, meaning “to bind or tie,” and spartum refers to its similarity to another plant in the same family, esparto or “atocha” (Stipa tenacissima). Locally, it is also known as false esparto, female esparto, or ‘atochín’.

Alongside esparto grass, there are some shrubby and herbaceous halophytes, such as Bassia prostrata or Senecio auricula, an Iberian–North African endemic that grows in sub-saline and gypsum steppes accompanying esparto. In Castilla-La Mancha, it has been recorded in Ciudad Real, Toledo, and Albacete. Several species of Limonium (sea lavenders), including L. cossonianum and L. thiniense, are also included.

11. Halonitrophilous Shrubland

Halonitrophilous shrublands develop in areas with high soil salinity and additional nitrogen input, typically from areas frequented by animals. Plants growing in these habitats, unique to the western Mediterranean, have steppe-like habits and thrive in disturbed, dry soils found in hollows, slopes, and depressions, where saline and nitrogen-rich materials accumulate. These conditions expose the plants to a double osmotic challenge, making them exceptional.

Most species in halonitrophilous shrublands are members of the Amaranthaceae family, such as Atriplex halimus (saltbush), Salsola vermiculata (barilla or sisallo), and Bassia prostrata (red sisallo). Accompanying them are species like white wormwood (Artemisia herba-alba).

12. Ocaña Gypsum Steppe

At the highest point of the azonal habitats, opposite the saline lagoon, a gypsum steppe has been recreated, with specialist shrubs adapted to gypsum outcrops. These communities include strict gypsophytes (exclusive to gypsum substrates) such as Gypsophila struthium, G. bermejoi, Lepidium subulatum, red sisallo (Bassia prostrata), Brassica repanda subsp. gypsicola, and facultative species able to live on other soils, such as esparto (Stipa tenacissima) or Matthiola fruticulosa. As gypsum deposits disappear due to terrain elevation, generalist Mediterranean calcicole species like rosemary (Rosmarinus officinalis), Spanish sage (Salvia lavandulifolia), and Cistaceae (Helianthemum hirtum, Cistus albidus, C. clusii) colonize the area.

This is the habitat of the critically endangered Vella pseudocytisus subsp. pseudocytisus (pítano), a shrubby crucifer endemic to central Spain, with a recovery plan in Castilla-La Mancha. It inhabits gypsum steppes around the middle stretch of the Tajo River, in northern Toledo (Ocaña, Ontígola, Villarrubia de Santiago) and southern Madrid (Aranjuez). This strict gypsophyte survives in extremely dry conditions due to low rainfall and the strong osmotic potential of gypsum soils. Threats include urban expansion, ploughing, and reforestation in its habitat.