The Sundaland heath forest, also known as ''Kerangas''

forest A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...

, is a type of tropical moist forest found on the island of

Borneo Borneo (; id, Kalimantan) is the third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java, west of Sulawesi, and ea ...

, which is divided between

Brunei Brunei ( , ), formally Brunei Darussalam ( ms, Negara Brunei Darussalam, Jawi: , ), is a country located on the north coast of the island of Borneo in Southeast Asia. Apart from its South China Sea coast, it is completely surrounded by t ...

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

, and

Malaysia Malaysia ( ; ) is a country in Southeast Asia. The federation, federal constitutional monarchy consists of States and federal territories of Malaysia, thirteen states and three federal territories, separated by the South China Sea into two r ...

, as well as on the Indonesian islands of

Belitung Belitung ( Belitung Malay: ''Belitong'', formerly Billiton) is an island on the east coast of Sumatra, Indonesia in the Java Sea. It covers , and had a population of 309,097 at the 2020 Census. Administratively, it forms two regencies ( Beli ...

and Bangka, which lie to the west of Borneo.

Setting

The word ''Kerangas'', which means "land which cannot grow rice", comes from the

Iban language The Iban language () is spoken by the Iban, a branch of the Dayak ethnic group, who live in Brunei, the Indonesian province of West Kalimantan and in the Malaysian state of Sarawak. It belongs to the Malayic languages, a Malayo-Polynesian branc ...

. Heath forests occur on acidic sandy soils that are the result of the area's siliceous parent rocks. Permanently waterlogged heath forests are known as ''kerapah'' forests. The sandy soil of the heath forest are often lacking in nutrients; it is generally considered that

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

is the nutrient which is most lacking for plant growth in these forests. This is in contrast to many other lowland rain forests where

phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...

is considered to be lacking. A more recent hypothesis, proposed by Proctor (1999), is that these forests are growing on soils which are highly acidic, such that hydrogen ion toxicity prevents the growth of non-adapted species. Moreover, heath forests' low soil pH hampers organic matter decomposition thus further slowing nutrient cycling.

Flora

The Sundaland heath forests are distinct from the surrounding

Borneo lowland rain forests The Borneo lowland rain forests is an ecoregion, within the tropical and subtropical moist broadleaf forests biome, of the large island of Borneo in Southeast Asia. It supports approximately 15,000 plant species, 380 bird species and several m ...

in species composition, structure, texture, and color. The heath forests have a low, uniform canopy, with thick underbrush and rich growth of moss and epiphytes. Many tree and plant species in the nutrient-deprived heath forests have developed unconventional ways to get their nutrients. Some tree species (''

Gymnostoma ''Gymnostoma'' is a genus of about eighteen species of trees and shrubs, constituting one of the four genera of the plant family Casuarinaceae. The species grow naturally in the tropics, including at high altitudes having temperate climates, in ...

nobile'', for example) utilise rhizobia (

nitrogen fixing Nitrogen fixation is a chemical process by which molecular nitrogen (), with a strong triple covalent bond, in the air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. Atmo ...

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...

) in their root nodules.

Myrmecophyte Myrmecophytes (; literally "ant-plant") are plants that live in a mutualistic association with a colony of ants. There are over 100 different genera of myrmecophytes. These plants possess structural adaptations that provide ants with food and ...

s, including ''

Myrmecodia ''Myrmecodia'' is a genus of epiphytic myrmecophytes (mər′mek•ə‚fīt; literally "ant-plant"), native to Southeast Asia, but also present in Indochina, Malaysia, the Southwest Pacific, the Philippines, Fiji, and extending south to Queens ...

'' spp. and ''

Hydnophytum ''Hydnophytum'' is a genus of epiphytic myrmecophytes (ant plants) native to Southeast Asia, the Pacific region and also extending into Queensland in northern Australia. The name is derived from the Ancient Greek ''hydnon'' "tuber", and ''phyton ...

'' spp., are tree species that develop symbiotic associations with ants to get their nutrients. Other plants, including

pitcher plant Pitcher plants are several different carnivorous plants which have modified leaves known as pitfall traps—a prey-trapping mechanism featuring a deep cavity filled with digestive liquid. The traps of what are considered to be "true" pitcher p ...

s ''( Nepenthes'' spp.),

sundew ''Drosera'', which is commonly known as the sundews, is one of the largest genera of carnivorous plants, with at least 194 species. 2 volumes. These members of the family Droseraceae lure, capture, and digest insects using stalked mucilaginou ...

s ''(

Drosera ''Drosera'', which is commonly known as the sundews, is one of the largest genera of carnivorous plants, with at least 194 species. 2 volumes. These members of the family Droseraceae lure, capture, and digest insects using stalked mucilaginou ...

'' ssp.), and

bladderwort ''Utricularia'', commonly and collectively called the bladderworts, is a genus of carnivorous plants consisting of approximately 233 species (precise counts differ based on classification opinions; a 2001 publication lists 215 species).Salmon, Br ...

''(Utricularia'' ssp.), are carnivorous, trapping and digesting insects. The heath forests are characterized by many plants of Australasian origin, including trees of families Myrtaceae and

Casuarinaceae The Casuarinaceae are a family of dicotyledonous flowering plants placed in the order Fagales, consisting of four genera and 91 species of trees and shrubs native to eastern Africa, Australia, Southeast Asia, Malesia, Papuasia, and the Pacifi ...

and the southern hemisphere conifers '' Agathis'', ''

Podocarpus ''Podocarpus'' () is a genus of conifers, the most numerous and widely distributed of the podocarp family, the Podocarpaceae. The name comes from Greek πούς (poús, “foot”) + καρπός (karpós, “fruit”). ''Podocarpus'' species ...

'', and ''

Dacrydium ''Dacrydium'' is a genus of conifers belonging to the podocarp family Podocarpaceae. Sixteen species of evergreen dioecious trees and shrubs are presently recognized. The genus was first described by Solander in 1786, and formerly included many m ...

''.

References

*Proctor, J. (1999) "Heath forests and acid soils". ''Botanical Journal of Scotland'' 51, 1-14. *Wikramanayake, Eric; Eric Dinerstein; Colby J. Loucks; et al. (2002). ''Terrestrial Ecoregions of the Indo-Pacific: a Conservation Assessment.'' Island Press;

Washington, DC ) , image_skyline = , image_caption = Clockwise from top left: the Washington Monument and Lincoln Memorial on the National Mall, United States Capitol, Logan Circle, Jefferson Memorial, White House, Adams Morgan ...

External links

* {{Borneo Borneo Ecoregions of Asia Ecoregions of Indonesia Ecoregions of Malaysia Ecoregions of Malesia * * Indomalayan ecoregions Tropical and subtropical moist broadleaf forests