Included here are coastal zones around the Caribbean Sea.

Yucatan Peninsula Coastal Dunes

The Yucatan Peninsula dunes can be broadly divided into beach, embryo dunes, foredunes, wet and humid slacks, humid sheltered dunes and dry dunes, but there are no blowouts. They tend to be sheltered apart from a few hurracanes and their coarse sand prevents much mobility. Overall they support about 31 dune community types. In terms of their physiognomy and floristics they are similar to the dunes of the Caribbean islands.  

Beach (Pioneer Zone)
Salt spray and wind are the main factors here but there is little sand movement and the vegetation tends to be monospecific. Typical species include Cakile edentula and Cakile lanceolata and Suaeda linearis. 

Embryo Dunes
The main species here include Canavalia rosea, Euphorbia buxifolia, Ipomoea pes-caprae, Sesuvium portulacastrum and Sporobolus virginicus. All are classed as nitrophiles able to tolerate the high nutrient enrichment resulting from stranded material and sea spray.

Foredunes
Most of the foredune vegetation here consists of woody species standing up to 4 m high in places. They are all tolerant of salt spray and sand deposition and characteristically have succulent leaves.  Depending on location the dominant species may include Croton punctatus, Euphorbia buxifolia, Scaevola plumieri, Suriana maritima or Tournefortia gnaphalodes.

Humid and Wet Slacks
These are not typical slacks but more accurately described as flat humid plains flooded during summer. They also receive more salt spray than typical slacks and most species are salt tolerant. In fact, the herbaceous flora has much in common with the saltmarshes of North America. Typical species include Ambrosia hispida, Conocarpus erectus, Eleocharis geniculata, Flaveria linearis, Gossypium hirsutum, Hymenocallis americana, Hymenocallis caribaea, Iresina stricta, Lippia nodiflora, Lycium carolinianum, Maytenus phylantoides, Melanthera nivea, Opuntia stricta, Scaevola plumieri, Sesuvium portulacastrum, Suaeda linearis, Suriana maritima and Waltheria indica.  

Fixed Dunes
In humid areas thickets up to 4 m tall develop with a well developed vertical structure. These typically have three layers comprising small trees and palms, shrubs and an inconspicuous herb layer. All have some tolerance to saline conditions. Depending on location the dominant species may include the shrubs Chrysobalanus icaco or Ernodea littoralis, the small tree Coccoloba uvifera or the palms Pseudophoenix sargentii or Thrinax radiata. The endemic Coccothrinax readii and poisonous Metopium brownei is often found in association with Thrinax radiata.

In dry areas thickets dominated by succulent spiny species develop with few palm but herbs are more abundant. Depending on location the characteristic species may include the shrubs Bravaisia tubiflora, Brumelia retusa, Caesalpinia vesicaria or Pithecellobium keyense or the small tree Cordia sebestena.

In open dry areas on ridges which are independent of ground water levels the characteristic species are either Agave angustifolia or endemic shrub Enriquebeltrania crenatifolia (Rhamnaceae). However the former may be derived from planted populations since it was previously cultivated for ‘sisal’ leaf export. Frequent associates in the stands of Enriquebeltrania crenatifolia include the herb Justicia carthaginensis and the succulent, thorny shrubs such as Acanthocereus pentagonus, while Cyrtopodium punctatum and Schomburkia tibiscinis are common field layer orchids.

References

Moreno-Casasola, P & Espejel, I. 1981. Classification and ordination of coastal sand dunes vegetation along the Gulf and Caribbean Sea of Mexico. Vegetatio, 66, 147-182.