U.S. Virgin Islands Dry Forest | |
---|---|
Ecology | |
Realm | Neotropic |
Geography | |
Country | United States |
Territory | U.S. Virgin Islands |
The U.S. Virgin Islands dry forest is a sub-tropical dry forest [1] spanning the United States Virgin Islands with varying degrees of coverage on each island. A dry forest is a habitat type defined by the World Wide Fund for Nature as being a predominantly deciduous forest located in a climate that is warm year-round, and may receive several hundred centimeters of rain per year, they have long dry seasons which last several months. Dry forests can receive 850-1100mm of precipitation per year. [2] In the case of the U.S. Virgin islands forest high quantities of sea salt from the ocean decreases the growth height of the trees, aiding in the creation of two canopy layers that are commonly found at an elevation below 300 meters. [3] Additionally the unique wind pattern that the islands create may have added to this effect.
Within the three islands that make up the United States Virgin Islands, St. John has maintained a higher percentage of dry forest cover competing with St. Thomas at 43.1%; St. Croix has limited dry forest cover (9.22%). [3] St. John and St. Thomas topography has significant steep hills and slopes compared to St. Croix. St. John is the most protected of the three islands, and as such it has the largest extensive tropical dry forests in the U.S. Virgin Islands. The island contains 650 native plants, 5,000 or more terrestrial insects, over 180 species of birds, of which 90% are native, and six native mammal bat species. One of the most common trees in the “native dry forest garden” is the amarat. They are acacias, (casha bush) but do not have thorns likes most other varieties. [4]
The Virgin Islands Dry Forest are divided into four zones, Semi-evergreen, Semi-deciduous, Drought-deciduous, and Gallery semi-deciduous forest. Precisely 70-75% of Semi-evergreen forest consists of transitional characteristics of moist and dry forest. [3] These characteristics consist of trees that maintain an evergreen pigmentation annually. Semi-evergreen forest usually grows in area that has the most moisture in the dry forest. This tends to be the edge of the dry forest at altitudes of 984 feet and decreasing. [3] Semi-evergreen forest can be found on the steep slopes of St. John at Maho Bay, Crown Mountain St. John and Mount Eagle St. Croix. Common plants found in Semi-evergreen forest are Epiphytic plants, commonly referred as air-plants. These air-plants are often sited midcenter of the forest in Estate Grove on St. Croix.
Semi-deciduous forest consist of 25% of evergreen trees and 75% of trees that tend to abandon their leaves, during cooler months. [3] Semi-Deciduous forest relatively covers majority of land on all three islands. This is zone usually forms on Northern hill regions of each island. Semi-Deciduous forest can easily be found mid-island and Estate Northside on St. Croix. However, this location is limited to St. Croix, this division of forest can also be found Southern Magens Bay, Leinster Bay St. John and Southern Spray Bay on Water Island. [3] Researchers speculate Semi-deciduous forest were not as dry as it seems, it is possible a community of plants that thrived in moist soil were present more than a decade before observations were recorded. The morphology of trees are quite distinct. In addition, this forest is separated in subdivisions classified as upper layer and bottom layer. The upper layer consists of small trees ranging from 8–11 meters and large trees 15–20 meters high. [3] Bottom region is filled with a variety of saplings that grows from the leaf undercover. A few plants commonly found in this area are tan-tan (Leucaena leucocephala) and guinea grass (Megathyrsus maximus).
Drought deciduous forest and Gallery semi-deciduous forest has high quantities of deciduous trees (75%) unlike semi-evergreen forest and semi-deciduous forest. [3] However, the distinct difference between Drought-deciduous and Gallery semi-deciduous forest is where they develop. Drought-deciduous tends to form on slopes, although, Gallery semi-deciduous forest grow in guts that lacks moisture. Gallery semi-deciduous forest are only found in guts in St. John, St. Thomas and St. Croix. The forest is found in upper land area in St. John, Peterborg hillside in St. Thomas and Mahogany Gut/ Caledonia in St. Croix. This forest is quite too semi-deciduous forest, however, in comparison to trees of the same species grow taller in Gallery semi-deciduous forest vs. semi-deciduous forest due to the saturation of moisture from the rain in the guts.
Drought Deciduous forest are not as popular as semi-evergreen and semi-deciduous. Less than 1% of this forest inhabits St. Croix and Water Island, however, St. John has the greatest abundance located in eastern hillside regions. [3] In addition, St. Thomas also occupies Drought Deciduous forest in Peterborg.
Researchers typically identify Drought Deciduous forest near low elevations ranging lower than 250 meters usually, yet not limited to southern arid slopes. In addition, this zone also consisted of upper and lower layers; upper layers consist of the canopy ranging from 7–10 meters, with a minimum of tall trees up to 15 meters tall. Lower layers consist of shrub species that dries out rapidly compared to tall tree species. [3] Trees commonly found in this forest is turpentine (Syncarpia glomulifera).
The Solanum conocarpum also to referred as the Marron bacora is considered a rare plant that was discovered in the evergreen forest in St. John. Dispersal biology and organisms that consume the plant are uncertain (Gibney and Ray). In the late 1990s, five individuals were sighted and recorded in the mid-elevation forests of St. John. Subsequently, in February 2003, over 150 additional individuals were found by David Hamada on the island of St. John. As part of its conservation effort, the plant has since been planted at various other locations, including St. George's Village Botanical Gardens on St. Croix, the University of the Virgin Islands' St. Thomas campus and Fairchild Botanical Gardens in Miami. Researchers have established the lack of seedlings is correlated to the lack of saplings. The seeds derived from a fruit that has fragile seed coating. With the lack of individuals in the wild, cross fertilization is challenging. Therefore, achieving reproduction in the wild is primarily unsuccessful.
The most common disturbances of Semi-evergreen disturbances are development of roads caused by human invasion. Creating new roads dirt and paved roads cause soil erosion that leads to depleted soil nutrients. The development of roads, buildings and rock crushing companies significantly decrease plant diversity and animal diversity. A dramatic example is the development of roads on Crown Mountain St. Thomas. [3] This leads to extinction of plants, fungi and animals diversity. The lack of tree cover leads to an increase of arid regions.
Semi-Deciduous forest also has challenging issues of disturbances. Disturbance effects are mainly caused by human interference. The land is manipulated for agriculture use frequently.
Due to the unique diversity of the forests and animal species, the Virgin Islands dry forests need to be protected. In 2004, 315 terrestrial species in the Virgin Islands were on the International Union for Conservation of Nature Red List (IUCN Red List) of Threatened Species. The islands serve as a wintering ground for birds such as the Cape May Warbler (Dendroica tigrine), Black-throated Blue Warbler (D. caerulescens), and Prairie Warbler (D. discolor). The intact forests are then necessary for the perpetuation of these Warbler species . [4]
St. Croix Anole lizards tend to prey on ants significantly. [2]
In botany, an evergreen is a plant which has foliage that remains green and functional through more than one growing season. This contrasts with deciduous plants, which completely lose their foliage during the winter or dry season.
In the fields of horticulture and botany, the term deciduous means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, after flowering; and to the shedding of ripe fruit. The antonym of deciduous in the botanical sense is evergreen.
Sclerophyll is a type of vegetation that is adapted to long periods of dryness and heat. The plants feature hard leaves, short internodes and leaf orientation which is parallel or oblique to direct sunlight. The word comes from the Greek sklēros (hard) and phyllon (leaf). The term was coined by A.F.W. Schimper in 1898, originally as a synonym of xeromorph, but the two words were later differentiated.
Groundcover or ground cover is any plant that grows over an area of ground. Groundcover provides protection of the topsoil from erosion and drought.
The tropical and subtropical dry broadleaf forest is a habitat type defined by the World Wide Fund for Nature and is located at tropical and subtropical latitudes. Though these forests occur in climates that are warm year-round, and may receive several hundred centimeters of rain per year, they have long dry seasons that last several months and vary with geographic location. These seasonal droughts have great impact on all living things in the forest.
Tropical and subtropical moist broadleaf forests (TSMF), also known as tropical moist forest, is a subtropical and tropical forest habitat type defined by the World Wide Fund for Nature.
Delonix regia is a species of flowering plant in the bean family Fabaceae, subfamily Caesalpinioideae native to Madagascar. It is noted for its fern-like leaves and flamboyant display of orange-red flowers over summer. In many tropical parts of the world it is grown as an ornamental tree and in English it is given the name royal poinciana, flamboyant, phoenix flower, flame of the forest, or flame tree.
The Puerto Rican dry forests are a tropical dry forest ecoregion located in southwestern and eastern Puerto Rico and on the offshore islands. They cover an area of 1,300 km2 (500 sq mi). These forests grow in areas receiving less than 1,000 mm (39 in) of rain annually. Many of the trees are deciduous, losing their leaves during the dry season which normally lasts from December to April.
Semi-deciduous or semi-evergreen is a botanical term which refers to plants that lose their foliage for a very short period, when old leaves fall off and new foliage growth is starting. This phenomenon occurs in tropical and sub-tropical woody species, for example in Dipteryx odorata. Semi-deciduous or semi-evergreen may also describe some trees, bushes or plants that normally only lose part of their foliage in autumn/winter or during the dry season, but might lose all their leaves in a manner similar to deciduous trees in an especially cold autumn/winter or severe dry season (drought).
The Guánica State Forest, popularly known as the Guánica Dry Forest is a subtropical dry forest located in southwest Puerto Rico. The area was designated as a forest reserve in 1919 and a United Nations Biosphere Reserve in 1981. It is considered the best preserved subtropical dry forest and the best example of dry forest in the Caribbean.
The Coastal forests of eastern Africa, also known as the East African Coastal Forests or Zanzibar–Inhambane forests, is a tropical moist forest region along the east coast of Africa. The region was designated a biodiversity hotspot by Conservation International.
Myrcia neothomasiana, commonly known as Thomas' lidflower, is a rare species of plant in the family Myrtaceae. It is found on three Caribbean islands. There are fewer than 250 individuals total divided amongst the islands of Vieques in Puerto Rico, St. John in the United States Virgin Islands, and Virgin Gorda in the British Virgin Islands. It has been extirpated from the wild on Saint Thomas, U.S. Virgin Islands, where it was first described in 1855, and now only grows there in cultivation.
The Cuban dry forests are a tropical dry forest ecoregion that occupies 65,800 km2 (25,400 sq mi) on Cuba and Isla de la Juventud. The ecoregion receives 1,000–2,000 mm (39–79 in) of rainfall annually. Cuban dry forests can be differentiated into evergreen forests, semi-deciduous forests, mogotes, and sclerophyllous low forests.
A plant community is a collection or association of plant species within a designated geographical unit, which forms a relatively uniform patch, distinguishable from neighboring patches of different vegetation types. The components of each plant community are influenced by soil type, topography, climate and human disturbance. In many cases there are several soil types present within a given plant community. This is because the soil type within an area is influenced by two factors, the rate at which water infiltrates or exits the soil, as well as the rate at which organic matter enters or decays from the soil. Plant communities are studied substantially by ecologists, due to providing information on the effects of dispersal, tolerance to environmental conditions, and response to disturbance of a variety of plant species, information valuable to the comprehension of various plant community dynamics.
Ecotourism in the United States is commonly practiced in protected areas such as national parks and nature reserves. The principles and behaviors of ecotourism are slowly becoming more widespread in the United States; for example, hotels in some regions strive to be more sustainable.
The Banda Sea Islands moist deciduous forests is a tropical moist forest ecoregion in Indonesia. The ecoregion includes several island groups in the southwestern Banda Sea, including the Tanimbar Islands, Kai Islands, and the Barat Daya Islands except for Wetar.
The Timor and Wetar deciduous forests is a tropical dry forest ecoregion in Indonesia and East Timor. The ecoregion includes the islands of Timor, Wetar, Rote, Savu, and adjacent smaller islands.
Drought deciduous, or drought semi-deciduous plants refers to plants that shed their leaves during periods of drought or in the dry season. This phenomenon is a natural process of plants and is caused due to the limitation of water around the environment where the plant is situated. In the spectrum of botany, deciduous is defined as a certain plant species that carry out abscission, the shedding of leaves of a plant or tree either due to age or other factors that causes the plant to regard these leaves as useless or not worth keeping over the course of a year. Deciduous plants can also be categorised differently than their adaptation to drought or dry seasons, which can be temperate deciduous during cold seasons, and in contrast to evergreen plants which do not shed leaves annually, possessing green leaves throughout the year.
Seasonal tropical forest, also known as moist deciduous, semi-evergreen seasonal, tropical mixed or monsoon forest, typically contains a range of tree species: only some of which drop some or all of their leaves during the dry season. This tropical forest is classified under the Walter system as (i) tropical climate with high overall rainfall and (ii) having a very distinct wet season with dry season. These forests represent a range of habitats influenced by monsoon (Am) or tropical wet savannah (Aw) climates. Drier forests in the Aw climate zone are typically deciduous and placed in the Tropical dry forest biome: with further transitional zones (ecotones) of savannah woodland then tropical and subtropical grasslands, savannas, and shrublands.
The Southwestern Arabian foothills savanna, also known as the Southwestern Arabian Escarpment shrublands and woodlands, is a desert and xeric shrubland ecoregion of the southern Arabian Peninsula, covering portions of Saudi Arabia, Yemen, and Oman.
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(help)Tropical and subtropical dry broadleaf forests Tropical and subtropical dry broadleaf forests St. George Village Botanical Garden