We'd like to understand how you use our websites in order to improve them. Register your interest. Mangrove forests along the Pacific Coast of Central America cover around 4, km 2. Rainfall and runoff alter structure and floristic composition from site to site. Reproductive phenology and mortality appear to be related to soil water availability. Avicennia bicolor forests reach a density of 4, plants that are taller than 0.
|Published (Last):||15 February 2014|
|PDF File Size:||7.55 Mb|
|ePub File Size:||7.88 Mb|
|Price:||Free* [*Free Regsitration Required]|
Classification of the American humid tropics Classification of the Central Selva within the American humid tropics Protection of major ecosystems in the humid tropics Conflicts between protected areas and other types of natural resource use Bibliography. Classification of the American humid tropics The green mantle which covers the majority of the American humid tropics hides an impressive diversity of habitats.
This variety is, in large part, the result of mountainous topography. Because tropical humid conditions exist from sea level to 3, meters or more, this diversity is also found in Bolivia, Ecuador, Colombia, Venezuela, Panama, and Central America. Relatively minor mountain ranges and flooding in low lying areas also contribute to the mix. Annual precipitation is greater than mm, with no more than two dry months, and no frosts occur NRC, The Holdridge method of classifying natural life zones provides useful information for regional development planning.
Table illustrates how the Holdridge system corresponds with the Brack system regarding the Peruvian Central Selva. The latter system corresponds closely with the biogeographical classification of Udvardy as well as that of Cabrera and Willink Table Provinces lying within the American humid tropics contain some million hectares, of which the most important are the Amazonian These five provinces contain more than 84 percent of the American humid tropics. The Peruvian Central Selva lies chiefly within the Yungas province, and to a lesser degree, in the Amazonian.
Yungas Province In the Peruvian Central Selva the Yungas Province lies between 3, and 3, meters above sea level, where annual rainfall averages 2,, mm but varies from a minimum of to a maximum of approximately mm. Elfin Forest District Monte Chico The Elfin Forest district is found between 3,, meters and 2,, meters above sea level. This district corresponds to the Tropical Montane Wet Forest and the Tropical Montane Rain Forest of Holdridge Table , Annual mean precipitation varies between and 1, mm in the wet forest and between 2,, mm in the rain forest.
This district is characterized by irregular relief, with slopes of over 60 percent in its higher regions adjacent to the Puna Province, with steep hillsides of more than 75 percent at lower elevations. Soils are relatively deep at the highest altitudes and very thin in the Tropical Montane Rain Forest life zone.
Higher soils are slightly acid, of medium and heavy texture, and are classified as phaeozems or luvisols. Dystric and eutric cambisols also exist. At lower altitudes, lithosols predominate, but transitional forms approaching cambisols also occur. At the highest altitudes, the vegetation is mostly scrub, with isolated trees that scarcely reach 3 to 5 meters in height.
These genera increase in proportion, density, and development in the lower sections of the district, where they can grow to 15 meters in height. Grass species that occur at the higher altitudes completely disappear at lower altitudes, where forest openings are invaded by the bamboo Chusquea.
Many Melastomaceae also occur, the trees usually appear covered with epiphytes, and tree ferns of the genera Cyathea, Alsophila, and Dicksonia are common Tosi, Faunal species from both the Puna and the Yungas occur together here, but many species from other districts in the Yungas which are common in the Amazonian province are not present in the Monte Chico Elfin Forest.
It lies between 2,, meters and 1,, meters above sea level and has an annual mean precipitation from to 1, mm in the Tropical Lower Montane Moist Forest and reaches almost 4, mm in the Tropical Lower Montane Rain Forest. Topography here is predominantly sloping, with few flat areas.
Soils are generally moderately acid to slightly basic and of moderate depth, have medium or fine texture, and high cation exchange capacity. They can include kastanozems and, to a lesser degree, lithosols and redzinas on the steepest sites. Other life zones in this district are characterized by considerable relief, with 70 percent or steeper slopes, and shallow soils, primarily lithosols. The vegetation, like the fauna, is characteristic of the Yungas province and is very rich in endemic forms.
Trees can reach 40 meters in height, although they average meters. The bamboo Chusquea, the tree ferns Cyathea, and one nonaerial Carludovica, as well as numerous shrubs, vines, epiphytes, ferns, mosses, and lichens also abound Tosi, On the whole, this district is very rich in fauna, especially birds, bats, and batrachians among the vertebrates, and a great variety of insects. Characteristic fauna are the cock-of-the-rock Rupicola , the torrent duck Merganetta , toucans Aularohrynchus, Pteroglossus , the pudu Pudu mephistopheles , the false paca Dinomys branickii and the spectacled bear Tremarctos ornatus also found in the elfin forest.
The High Forest District The High Forest district is located between meters and 1,, meters above sea level, and is a transition zone separating the Amazonian and Yungas provinces. Mean annual rainfall of this district varies between and 1, mm, with the least amount of rainfall occurring in the Tropical Premontane Moist Forest. In the Tropical Premontane Rain Forest portion of the district, the topography varies between rolling and moderately steep.
The soils are comparatively deep, relatively acid, and of medium to heavy texture. Among the edaphic groups, the ortic acrisols, urvisols and the eutric and dystric cambisols predominate. Gleysols and fluvisols, which are the most fertile soils of the region, are also present. In the other two zones in the district, the topography is steep, with slopes of 70 percent or more. Palms belonging to the genera Euterpe, Bactris, Wettinia, and Geonoma are abundant.
In abandoned clearings one finds communities of Cecropia, Psidium, Visma, and Melastomaceae, as well as the bamboos Chusquea and Guadua and in less developed soils, the fern Pteridium Tosi, Much of the district's fauna is also found in the Amazonian province, such as the mammals Tayassu, Tapirus, Felis, Panthera. Lutra, Mazama, Hydrochoerus, Myrmecophaga, and Priodontes, as well as a large number of birds, reptiles, and batrachians.
The diversity of fishes is greater than in the districts mentioned above, but is still low compared with the Amazonian province. It extends from meters in altitude to near sea level, although in the Central Selva its lowest altitude is approximately meters.
Climatically, an enormous difference exists between the Tropical Dry Forest, which receives an average , mm of annual rainfall, and the Tropical Wet Forest which, while usually boasting an average mean precipitation greater than 4, mm, sometimes experiences almost double that amount.
In contrast, the average annual rainfall of the Tropical Moist Forest ranges from 1, to 3, mm. The topography of this province is predominately rolling or hilly although in the Tropical Wet Forest Zone it is occasionally steep. The soils are usually deep, fine-textured, and either acid or, in the dry areas, neutral. Acrisols predominate in the humid and very humid life zones. Vertisols and cambisols predominate in the dry life zone.
In the humid life zones, vegetation is typically lush high forest, rich in bromeliads, orchids, vines, and reeds. Tree trunks are usually covered by epiphytes and vines, including Araceae, ferns, lichens, and mosses.
The highest trees rise more than 50 meters. Four plant strata can be distinguished although five may occur in the very humid zone.
Stands of Mauritia, Euterpe and Jessenia occur in hydromorphic areas and in poorly-drained sites. Secondary growth is usually dominated by Cecropia, which sometimes forms pure stands. In the Tropical Dry Forest the vegetation is shorter and forms three forest strata; scattered trees reach 30 meters in height. In this forest are seen various cacti, conspicuous arboreal plants belonging to the genera Cedrela, Amburana, Hymenaea, Manilkara, Tabebuia, and Schinopsis, and palms of the genera Scheelea, Phytelephas, and Astrocarym.
The fauna is typical of the Amazonian plain and includes a great diversity of primates Ateles, Alouatta, Cebus, Saimiri, Lagothrix, Saquinus , bats, and rodents. Conspicuous mammals include peccary, tapir, capybara, deer, jaguar, ocelot, puma, otter, and nutria.
Also occurring are the rare canids Atelocynus and Speothos, the procyonids Nasua and Potos, diverse mustelids, and a large number of edentates. Dolphins live in the rivers but not manatees. Birds are abundant and there are many reptiles and batrachians. The reptiles include Caiman, Crocodylus, Melanosuchus niger, and the turtles Podocnemis unifilis and P.
Classification of the Central Selva within the American humid tropics Now that we have seen something of the diversity of the major ecosystems in the Peruvian Central Selva we must remember that this region comprises scarcely 0.
Numerous mountain ranges, although less significant than the Andes, also contribute to the region's complexity. As the climatic, topographic, geologic, and edaphic characteristics all vary, so also do biota, although they may share similar characteristics.
Many plant genera and species of both flora and fauna may occur throughout the large majority of biogeographic provinces, but a great many are also endemic to each province and occasionally to each life zone.
For example, some conspicuous mammals, like the peccary Tayassu tajacu , the jaguar Panthera onca , the ocelot Felis pardalis , the puma Felis concolor , and the deer Mazama americana have a wide distribution. Others, like Tapirus terrestris, have extensive ranges, but only in certain provinces.
Tapirus bairdi, meanwhile, appears in Central America, while Tapirus pinchaque is only found in certain districts in Peru, Colombia, and Ecuador. Other species are endemic to one or a few Holdridge life zones. For example the yellow-tailed monkey Lagothrix flavicauda is found only in the Atlantic province, and the monkeys of the genera Leontopithecus occur only in the Sierra del Mar province of Brazil.
Soils Only 7 percent of the American humid tropics contain moderately fertile soils. The remainder is covered with soils that are acid and infertile oxisols and ultisols , poorly-drained, sandy and infertile, or shallow. Both are acid and poor in nutrients, although oxisols have good physical properties and are deep and well-drained. The ultisols are similar morphologically since they are also well drained and deep.
However, they exhibit a marked increase in the percentage of clay in their deeper portions and their physical properties are less favorable, since they usually occur on hillsides and are thus susceptible to erosion NRC, , Sanchez and Cochrane, Oxisols and ultisols also contain serious chemical deficiencies: high acidity, toxic levels of aluminum, deficiencies in phosphorus, calcium, magnesium, sulfur, zinc, and other micro-nutrients; low cation exchange capacity, and high phosphorus-fixing capacity.
Some oxisols have low water retention capacity. On the other hand, evidence now indicates that these soils are not as susceptible to laterization as previously believed NRC, The young soils called inceptisols, entisols, gleysols, andosols, cambisols and fluvisols, and regosols and litosols in the Central Selva description may be either fertile or infertile and cover 14 percent of the American humid tropics.
The remaining 4 percent are covered with alfisols luvisols, eutric nitosols, planosols , spodosols podzols and vertisols. Unfortunately, different nomenclature systems have been used in the edaphology of the humid tropics.
Each method has its positive points, but it can become confusing for professionals who are not soil specialists. The U. National Research Council NRC, has provided information Table that can prove useful in correlating different classification systems. Soils Survey Staff Dudal Baldwin et al, Cline et al, Aubert Costa de Lemos Source: NRC, Ecosystems Each biographic province, or district, and each life zone contains a number of units that are sufficiently differentiated, organized, and stable to be considered ecosystems themselves.
Ecologia basada en zonas de vida
Scientific Research An Academic Publisher. Relations were inferred from temperature and rainfall data recorded at weather stations and by sampling the vegetation around these stations. Climate data were used to construct climatograms, calculate forty one variables and detect main latitudinal and longitudinal gradients. In order to identify the best functions able to relate our variables, polynomial and non-polynomial regressions were performed. The k-means algorithm was the clustering method used to validate the variables that could best support our bioclimatic classification.
ecologia basada en zonas de vida
Ecología basada en zonas de vida