A sand forest is a type of rare subtropical forest region, distinctive due to its unique combination of plant (often rare plant) and animal species, and their restriction to ancient coastal dunes. Sand forests are found in Maputaland in South Africa, as well as parts of the Amazon basin in Brazil, Peru, and Colombia, along with Malaysia and Indonesia in Asia. [1]
They are typically composed of clay soils and nutrient poor white sands. These forests are commonly referred to as "sand forests" in the South African regions. However, in Mozambique, they are known as the "Lucauati forests". In the Amazon, they are colloquially known as campinaranas and campinas , whereas in Asia they are referred to as kerangas . [2] Few studies have been carried out on the sand forests. Those studies that have been conducted, the majority of the research has been on the plant diversity within these forests.
There have been no comprehensive studies undertaken in the white sand forests. A full understanding of the process in which they have emerged is lacking. However, it is thought that the sand forests are the fragments of coastal dunes which were separated from the ocean over millions of years as the shoreline and water level slowly shifted. Researchers have speculated that these forest systems have been related to the Late Pleistocene and Holocene dry periods.
Podsolization is a process in which the upper layer of soil becomes acidic due to the leaching of nutrients. This process combined with the lack of nutrients in the upper horizon results in only white sand being left behind. [3] Because sandy soils can result from a number of different processes (nutrient leaching, tectonic activity, river dynamics, etc.), the sand forests are unique and, oftentimes, different from sand forests found elsewhere. [3]
Sand forests are well known for their unique biodiversity and high levels of endemism. [4] To date there have been more than 2,500 species of vascular plants and of those, 230 species are endemic within the Maputaland region. Distinct sclerophylly, or vegetation with thickened, hardened foliage that slows moisture loss, is a characteristic of a vast number of the plants found in this region. [4] Due to nutrient and water restrictions, the vegetation that grows in the sand forests is very specialized. Many of the trees and shrubs have evolved anti-herbivorous defenses. [4] Herbivores seemed to favor vegetation of plants in clay soils over the white sandy soils. In no presence of herbivores however, the clay soil vegetation survived just as well as white sand specialists, but grew much taller and produced more leaf area. [4]
Sand forests have a thick humus layer due to the extremely low decomposition rates. [5] Some sandy forests have even been recorded to have more than a meter of leaf litter on top of the white sand. Multiple reasons exist as to why there is such a large accumulation of organic matter including high acidity of the soil, high content of toxic compounds in the litter, and low nutrient quality of the litter. [6] [7]
It is very common to find epiphytes, such as the wiry orchid ( Microcoelia exilis), and other lichens growing on the trees. They derive their moisture and nutrients from the air, rain, and debris that has accumulated over time. [8]
In contrast to tropical rainforests, campinas are "reduced in biomass and have relatively high light penetration." [9] Due to nutrient deficiencies in campina soils, "shrubs and small trees typically have a dwarfed and rachitic aspect with reduced quantities of foliage" with many of the species being perennials and evergreens [9]
Sand forests have vegetation gradients that closely coincide with saturation gradients. [10] These saturation gradients are affected by rainfall and topography and, therefore, the vegetation is also affected by these same factors. [10] Vegetation lower to the ground tends to congregate in areas that have been saturated for the longest period of time. [10]
Blackwater rivers (e.g. the Rio Negro) commonly begin in these sand forests due to their accumulation of humic matter that is easily washed downstream, particularly after heavy rainfall. [10]
The majority of bird species found in sand forests is known to prefer sand forest habitat and are found rarely, if at all, in other types of habitats. [11] There have been no studies, however, evaluating the habitat specialization of sand forest birds to determine whether these habitats have unique bird fauna.
The majority of these birds are small ground dwellers. They often forage in the underbrush to find food because of the thick organic layers found in the sand forests. [12] Their sharp beaks allow them to break through the thick coating of fruits and obtain the seeds inside. [13] [14]
The exact role of fires in sand forests is not known and most studies disagree on the matter. [10] However, evidence has shown that fires can help increase species diversity, particularly those that are specialized for such areas. [10] For example, fire tolerant species may be more likely to colonize here.
Historically speaking, some sand forests may have been the result of anthropogenic burning done by indigenous people. [10] They would burn swaths of sand forest to obtain better hunting and farming grounds. [10]
Fires of any kind can have both positive and negative effects on the ecosystem. In some instances, a fire can cause one or just a few species to predominate when the forest begins to regenerate. [10] However, fire can also promote more diversity within the regenerated forest. [10]
Because sand forests are isolated in small patches, they have been mostly protected from the destruction of the Amazon rainforest. However, they are still at risk of disturbance. Sand forests are extremely sensitive to destruction due to the harsh growth and survival conditions. [10] Since the conditions are so tough to thrive in once an ecosystem declines, it may take hundreds of years for it to develop again.
Some sand forests overlap with protected areas and indigenous lands, but most do not. Although they are not immediately threatened, sand forests are still in danger from ever-increasing deforestation, hydroelectric projects, and mineral extractions. [10]
Peru has actively incorporated sand forests in three protected areas. Authors who have done research in campinas have also made recommendations for conservation in their work. [10]
Rainforests are forests characterized by a closed and continuous tree canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforests can be generally classified as tropical rainforests or temperate rainforests, but other types have been described.
The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about 7,000,000 km2 (2,700,000 sq mi), or about 35.5 percent of the South American continent. It is located in the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, Suriname, and Venezuela, as well as the territory of French Guiana.
Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as lowland equatorial evergreen rainforest. True rainforests are typically found between 10 degrees north and south of the equator ; they are a sub-set of the tropical forest biome that occurs roughly within the 28-degree latitudes. Within the World Wildlife Fund's biome classification, tropical rainforests are a type of tropical moist broadleaf forest that also includes the more extensive seasonal tropical forests.
The Sundaland heath forests, also known as Kerangas forest, is a type of tropical moist forest found on the island of Borneo, which is divided between Brunei, Indonesia, and Malaysia, as well as on the Indonesian islands of Belitung and Bangka, which lie to the west of Borneo.
The Cerrado is a vast ecoregion of tropical savanna in eastern Brazil, being present in the states of Goiás, Mato Grosso do Sul, Mato Grosso, Tocantins, Maranhão, Piauí, Bahia, Minas Gerais, São Paulo, Paraná and the Federal District. The core areas of the Cerrado biome are the Brazilian highlands – the Planalto. The main habitat types of the Cerrado consist of forest savanna, wooded savanna, park savanna and gramineous-woody savanna. The Cerrado also includes savanna wetlands and gallery forests.
The Peruvian spider monkey, also known as the black-faced black spider monkey, is a species of spider monkey that lives in Peru, as well as in Brazil and in Bolivia. At 60 centimetres long, they are relatively large among species of monkey, and their strong, prehensile tails can be up to 1 m (3 ft) long. Unlike many species of monkey, they have only a vestigial thumb, an adaptation which enables them to travel using brachiation. Peruvian spider monkeys live in groups of 20–30 individuals, but these groups are rarely all together simultaneously. The size and dynamics of the resulting subgroups vary with food availability and sociobehavioral activity. They prefer to eat fleshy fruit, but will change their diet in response to scarcity of ripe fruit. Individuals of this species also eat small animals, insects and leaves based on availability. Females separate from the band to give birth, typically in the fall. These females inhabit a group of core areas where resources are abundant in certain seasons. Typically, males exhibit ranging over longer distances than females, with movement of individuals enhancing the fluidity of subgroup size. Peruvian spider monkey are independent at about 10 months, with a lifespan of about 20 years.
The grey-legged tinamou, alternatively, the gray-legged tinamou, is a small ground-dwelling bird endemic to the neotropics. It is a rarely seen bird due to its small size and discreet appearance.
The azure-naped jay is a species of bird in the family Corvidae. It is found in Brazil, Colombia, and Venezuela.
The white-plumed antbird is a small species of insectivorous bird found in the understories of rainforests. It is smaller than most species of its family (Thamnophilidae), weighing 26 grams on average. The family Thamnophilidae is known commonly as the antbirds, as they use the presence of ants to locate food. This species is largely solitary except during the breeding season, and different individuals will follow individual ant swarms.
The Mishana tyrannulet is a species of bird in the family Tyrannidae. It is endemic to two geographically separated regions in northeastern Peru. It is speculated that the two populations might represent separate species entirely.
Plant litter is dead plant material that have fallen to the ground. This detritus or dead organic material and its constituent nutrients are added to the top layer of soil, commonly known as the litter layer or O horizon. Litter is an important factor in ecosystem dynamics, as it is indicative of ecological productivity and may be useful in predicting regional nutrient cycling and soil fertility.
Igapó is a word used in Brazil for blackwater-flooded forests in the Amazon biome. These forests and similar swamp forests are seasonally inundated with freshwater. They typically occur along the lower reaches of rivers and around freshwater lakes. Freshwater swamp forests are found in a range of climate zones, from boreal through temperate and subtropical to tropical. In the Amazon Basin of Brazil, a seasonally whitewater-flooded forest is known as a várzea, which is similar to igapó in many regards; the key difference between the two habitats is in the type of water that floods the forest.
Southern African Sand Forest is a sand forest, or a subtropical forest plant community of the tropical and subtropical dry broadleaf forests biome. It grows on ancient sand dunes in northern KwaZulu-Natal and southern Mozambique. In South Africa these forests are known simply as Sand Forest, while in Mozambique they are known as Licuati Forest. The Southern African sand forest is part of the Maputaland coastal forest mosaic ecoregion.
The Southwest Amazon moist forests (NT0166) is an ecoregion located in the Upper Amazon basin.
A várzea forest is a seasonal floodplain forest inundated by whitewater rivers that occurs in the Amazon biome. Until the late 1970s, the definition was less clear and várzea was often used for all periodically flooded Amazonian forests.
Heliconius hermathena, the Hermathena longwing, is a species of butterfly of the family Nymphalidae. It is endemic to white sand areas of the Amazon basin. Heliconius hermathena is a sand forest nymphalid butterfly and they are typically lowland tropical forest organisms although a handful subspecies can be found in southeastern Brazil and part of the dry forests of Peru.
The Amazon biome contains the Amazon rainforest, an area of tropical rainforest, and other ecoregions that cover most of the Amazon basin and some adjacent areas to the north and east. The biome contains blackwater and whitewater flooded forest, lowland and montane terra firma forest, bamboo and palm forest, savanna, sandy heath and alpine tundra. Some areas of the biome are threatened by deforestation for timber and to make way for pasture or soybean plantations.
Campinarana, also called Rio Negro Campinarana, is a neotropical ecoregion in the Amazon biome of the north west of Brazil and the east of Colombia that contains vegetation adapted to extremely poor soil. It includes savanna, scrub and forest, and contains many endemic species of fauna and flora.
Campina is a Neotropical ecoregion found in the Amazon biome. It refers to vegetation that grows on infertile sandy soil with poor drainage. The term may be used to include open forest, shrubland and meadow, or may be restricted to treeless meadows.
Annona hypoglauca, also known as Wild Cherimoya, occurs along Amazon floodplains between Columbia and Bolivia. A. hypoglauca is a member of the Annonaceae family along with other fruiting plants like pawpaws, soursops, and cherimoyas. A. hypoglauca is currently cultivated scarcely outside of its native range and is classified as rare.