Included here are the pampas and campos regions of South America comprising the central parts of Argentina, all of Uraguay and the southern extremities of Brazil.

The largely natural vegetation of the south Pampas coastal dunes in the southern Buenos Aires Province of Argentina show a clear zonation pattern comprising three major vegetation types: 1. Upper beach, active frontal dunes and active inner dunes, 2. fixed/semi-fixed dunes and 3. dune slacks. The dunes support a number of threatened species such as Adesmia filipes and Neosparton ephedroides and several endemic taxa.

Upper Beach, Active Frontal Dunes and Active Inner Dunes

Here sand movement and salt spray are major environmental factors which only a few species can tolerate and vegetation cover is typically below 40%. The dominant species is Panicum urvilleanum together with Calycera crassifolia and the local endemic Senecio bergii (Asteraceae).  However, the vegetation could be resolved into two sub-associations. The most diverse of these was jointly dominated by Panicum urvilleanum and Calycera crassifolia and mostly found in the upper beach and active dunes. Other characteristic species include Hyalis argentea var. latisquama, Senecio bergii and Sporobolus rigens, but nearer the sea the salt-tolerant species Spartina ciliata and Sporobolus rigens become more prolific, while the dune-builder Panicum urvilleanum mainly dominates the active frontal dunes. A less species rich association is located exclusively in the active inner dunes where vegetation cover is less than 5%. Here the main species are the pampas grass Cortaderia selloana together with the native shrub Hyalis argentea var. latisquama and the Argentinian endemic Neosparton ephedroides (Verbenaceae).

Fixed and Semi-Fixed Dunes

Here the vegetation is much more stable helped by a network of root systems and by the fact that vegetation cover is up to 97%.  The dominant species are Poa lanuginosa and the subshrub Hyalis argentea var. latisquama, while other common species are Glycyrrhiza astragalina and Oenothera mollissima. In species-rich stands woody taxa such as Achyrocline satureioides, Discaria americana, Senecio subulatus var. erecta, Schinus johnstonii and the local endemic Baccharis divaricata (Asteraceae) are frequent together with Aristida spegazzinii, Hydrocotyle bonariensis and the introduced Aira caryophyllea. Other less species-rich stands included Poa lanuginosa, Cortaderia selloana together with Adesmia filipes and the endemic Senecio bergii. Scattered throughout are species such as Margyricarpus pinnatus and the introduced Senecio madagascariensis.

Dune Slacks

Much of the vegetation here is complex and may also be associated with fixed or semi-fixed dunes. The species rich stands are dominated by Hydrocotyle bonariensis together with a variety of grass, rush and sedge species such as Carex vixdentata, Eleocharis macrostachya, Imperata brasiliensis, Juncus acutus, Juncus scirpoides, Juncus tenuis var. dichotomus and Schoenoplectus americanus.  Species poor stands are mainly composed of Cortaderia selloana and Tessaria absinthioides, while some stands are almost exclusively dominated by Typha.   Other dunes slack species include Achyrocline satureioides, Agalinis genistifolia, Ambrosia tenuifolia, Solidago chilensis and the introduced Meliotus indicus.

References

Monserrate, A. L., Celsi, C. E. & Fontana, S. L. 2012. Coastal dunes vegetation of the Southern Pampas (Buenos Aires, Argentina) and Its Value for Concervation. Journal of Coastal Research, 28: 23-35.