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Subtropical humid forest |
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Subtropical very humid forest |
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Subtropical pluvial forest |
The most important agricultural regions of the country are found in this life zone.
In the North, the Subtropical humid forest is found in the valleys of those rivers flowing into the Atlantic Ocean; these areas go from sea level to 500 m of altitude, in the northern foothills of the Cordillera Septentrional. It goes along the southern foothills of the range, covering most of the Eastern Cibao Valley and the valleys in the low portion of Yuna river watershed. In the Samaná peninsula, it is found from sea level till 400 m. In the Northwest, if is found south of Dajabón, in the valleys of the Yaque del Norte river's tributaries, from 400 m to 800 m of altitude.
In the West, it is found in the valleys of the left bank tributaries of the Artibonito river and in the southern foothills of the Cordillera Central and the northern ones of Sierra de Neyba.
In the Southwest, this life zone is found in the southern foothills of Sierra de Neyba, at altitudes from 400 m to 800 m. In the foothills of Sierra de Bahoruco, it is restricted to narrow strips between the Subtropical very humid forest and the Subtropical dry forest or to its transitional zone to humid forest; altitudes go from sea level (Barahona) to 700 m.
In the southern foothills of Cordillera Central, it is found in the valleys of the tributaries of the Yaque del Sur river and those of the rivers Ocoa, Nizao and Haina.
In the Southeast region, it is found in almost all the Coastal Caribbean Plain, between San Cristóbal, the southern foothills of the Cordillera Oriental and San Rafael del Yuma. It is found also in parts of narrow valleys found in the northern and eastern foothills of the Cordillera Oriental.
The ecological conditions in this life zone result from a complex climatic system under the main influence of the subtropical anticyclones and the direction of the trade winds which prevail most of the year. The continental anticyclone has variable and temporal effects but the oceanic anticyclone has permanent effects.
The raining season is from April to December, with different intensities related the orographic location. In general, rainfalls begin after disappearing the influence of the continental anticyclone, determining so an atmospheric instability over the island. By the other hand, since April the eastern trade winds get loaded with humidity; those winds, when they pass over the island, determine both convective and orographic rainfalls.
Those places located in the western half portion have a rainfall pattern that diminishes from 1,500 mm to 1,000 mm as mean annual average but those located in the eastern half show an increase in the mean annual average from 1,500 mm to 2,000 mm.
Temperature in this life zone is variable, depending on location. In those open places close to the coast, the mean annual biotemperature is 23 ° - 24 °C but in higher places o in those next to the mountain ranges the mean annual biotemperature is 21 ° or less.
Potential evapotranspiration could be estimated to be, on average, 20% lesser than the mean total annual rainfall. In this life zone, a fourth of the rain water is not evapotranspirated and is lost by running off, above all in those months with the higher rainfalls.
The original natural vegetation of this formation was composed by forests which very few remain because most of them has been cut to be used in agriculture. Only secondary stands remain around the field crops or along riverbanks.
Hispaniolan royal palm |
The main indicative species, useful to recognize this life zone, are roble (Catalpa longissima), mainly in well drained lands, and caoba (Swietenia mahagoni), a characteristic species of this life zone. In calcareous soils, the Hispaniolan royal palm ("palma real") (Roystonea hispaniolana) is commonly found.
The small secondary stands are composed by Juan Primero (Simaruba glauca), anón de majagua (Lonchocarpus pentaphyllus) and jagua (Genipa americana); the species more commonly found in the Caribbean Coastal Plain and the foothills of Cordillera Septentrional are guaraguao or grigrí (Bucida buceras), yaya (Oxandra lanceolata) and amacey (Tetragastris balsamifera). It is possible to find some isolated trees of fustete (Chlorophora tinctoria), common in Luperón, Imbert and Villa Isabel; campeche (Haematoxylon campechianum), found in Puerto Plata and surrounding Santiago; lirio (Hippeastrum puniceum), common in the calcareous soils of San Pedro de Macorís; caracolí (Pithecellobium glaucum), found in Enriquillo, Barahona and Azua; guácima (Guazuma ulmifolia) and palo de leche (Rauwolfia nitida), common in the Caribbean Coastal Plain and in the Barahona peninsula; penda (Citharexylum fruticosum) and córbano (Pithecellobium berterianum), common in places of San José de las Matas, Santiago, La Romana and Barahona.
The vegetation of savannas or shallow soils is characterized by the presence of the shrubs peralejo (Curatella americana), hojancha (Coccoloba pubescens), memiso (Trema micrantha) and roble (Tabebuia spp.). Cajuil (Anacardium occidentale) is found in very marginal places with rainfalls close to those in the Subtropical dry forest.
The vegetation of swamps and mangroves is formed mainly by drago (Pterocarpus officinalis), higo (Ficus spp.), mangle colorado (Rhizophora mangle), mangle prieto (Conocarpus erecta), mangle (Avicennia nitida) and mangle blanco (Laguncularia racemosa).
The natural regeneration of native species is easy because of the soil humidity. Species in this life zone have a moderate growth.
From a climatic viewpoint, these lands are the most appropriate for the development of agriculture due to the optimal combination of temperature and rain. In these places are located the populated centers with the higher demographic density. Most of inhabitants are dedicated to agriculture and cattle raising. Because of those favorable climatic conditions, the rural populations here are in better economic conditions that in any other life zone.
The regions with this life zone are found mainly in the foothills of the Septentrional, Central and Oriental mountain range. Many of the humid forest cultivated fields extend into this zone what makes sometimes very difficult to establish the limit between these two formations. Normally this life zone limits with both bh-S and bmh-MB life zones.
In the northern region it is found mainly in the hilly lands of the Cordillera Septentrional. In the Northeast, it occupies the Promotorio de Cabrera, getting to sea level. In Samaná Peninsula, it is found from 200 m to the highest elevations found in that peninsula.
In the East, this formation occupies the higher places of Sierra de Yamasá and Cordillera Oriental. In the eastern end of Cordillera Oriental, it extends over slightly hilly lands and to sea level.
In the southern and eastern Cordillera Central, it is found in the tributaries of the rivers Yuna, Nizao, Haina and Ozama. In the northern and western parts, it is found in the tributaries of the rivers Yaque del Norte, Dajabón and Artibonito.
The climatic conditions corresponding to this life zone are variable because the influences of the anticyclones and the trade winds that pass over the country. Rainfall is similar to those of the Subtropical humid forest, except that the orographic rains are more intense. These rains, because they last longer, have influence on the flora composition and in the physiognomy of the vegetation. Rainfalls in this life zone range, on average, from 2,200 mm to 4,400 mm.
Temperature varies in relation to the localization. Those areas close to the coast has an annual mean biotemperature of 24 °C. However, those areas that are in the foothills of the mountain rages have mean biotemperatures as low as 18 °C.
The potential evapotranspiration could be estimated to be, on average, 60% lower than the mean total average annual rainfalls. In this life zone, 3/5 of the rain waters are lost by running off, arising rivers with water the whole year.
In this life zone, most of the lands are in the mountains. Altitude ranges from sea level to 850 m.
The main species that help to identify this life zone are guaraguao (Buchenavia capitata), mainly in the Septentrional and Oriental mountain ranges; and, in a general way, sablito (Didymopanax morototoni), peralejo o madroño (Byrsonima spicata) and aguacatillo (Alchornea latifolia).
The natural vegetation in this life zone is formed mainly by the following species: membrillo or almendrito (Prunus myrtifolia), in the forests of Los Haitises and of the northern foothills of Cordillera Central; mara or baría (Calophyllum brasiliense), cocuyo (Hirtella triandra) and cabirma (Guarea guidonia), in those forested areas close to Jarabacoa, around the Isabel de Torres mountain, Samaná peninsula and the foothills of Cordillera Oriental; palo de yagua (Casearia arborea), found in areas close to Barahona and Nagua; algarrobo (Hymenea courbaril), found in the proximity of Bonao, La Vega and Miches; balatá (Manilkara domingensis), common in the areas of the Samaná peninsula and in the foothills of the Septentrional and Oriental mountain ranges; and the palm manacla (Prestoea montana), that occurs in forests with a specific soil. Another common species is pino (Pinus occidentalis), mostly in lateritic soils.
The climatic conditions in this life zone are favorable to an easy natural regeneration and the fast growing of the plants.
In general terms, only very fertile alluvial soils could be used for intensive agriculture, and it would be profitable only with very remunerative crops. Those lands with shallow soils and slight slopes are appropriate for perennial crops such as cacao, rubber, some subtropical fruits and, in lesser proportion, coffee.
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The location of this zone is related to the physiographic position within the bmh-S. The largest area is found between the sources of Masipedro and Jima rivers, in the Casabito mountain. Other small areas are found in the Oriental and Septentrional mountain ranges.
The surplus of rainfall in this area is due, without any doubts, to orographic rains. Potential evapotranspiration could be estimated, on average, to be 75% lesser than the annual mean rainfall. In this life zone, 3/4 or more of the rain waters are lost through running off, and so the rivers have water along the whole year
This are mountainous areas and their altitudes range from 400 m to 850 m.
The natural vegetation is composed by trees, markedly covered with parasitic and epiphytic plants. Among the main indicative species are the tree fern (Cyathea spp.) and lirio (Linociera spp.).
In this life zone, the native species grow faster than those of the bmh-S and their natural regeneration is abundant.
From the forestry and agriculture viewpoint, this lands of the Subtropical pluvial forest are worthless due to the excessive humidity. This lands will have to remain with their natural cover as a means to control the running off and soil erosion.
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