Koa
Encyclopedia
Acacia koa is a species of flowering
tree
in the pea
family
, Fabaceae
. It is endemic to the Hawaiian Islands
, where it is the second most common tree. The highest populations are on Hawaii
, Maui
and Oahu
. Its name in the Hawaiian language
, koa, also means brave, bold, fearless, or warrior.
Koa is a large tree
, typically attaining a height of 15–25 m (49.2–82 ft) and a spread of 6–12 m (19.7–39.4 ft). In deep volcanic ash
, a koa tree can reach a height of 30 m (98.4 ft), a circumference of 6 m (19.7 ft), and a spread of 38 m (124.7 ft). It is one of the fastest-growing Hawaiian trees, capable of reaching 6–9 m (19.7–29.5 ft) in five years on a good site.
s grow on the koa plant, much like other members of the pea family
. At about 6–9 months of age, however, thick sickle-shaped "leaves" that are not compound begin to grow. These are phyllodes
, blades that develop as an expansion of the leaf petiole
. The vertically flattened orientation of the phyllodes allows sunlight to pass to lower levels of the tree. True leaves are entirely replaced by 7 – long, 0.5 – wide phyllodes on an adult tree.
s of the koa tree are pale-yellow spherical
raceme
s with a diameter of 8–10 mm (0.31496062992126–0.393700787401575 in). Flowering may be seasonal or year round depending on the location.
production occurs when a koa tree is between 5 and 30 years old. The fruit are legumes, also called pods, with a length of 7.5 centimetre and a width of 1.5–2.5 cm (0.590551181102362–0.984251968503937 in). Each pod contains an average of 12 seed
s. The 6 millimetre long, 4–7 mm (0.15748031496063–0.275590551181102 in) wide seeds are flattened ellipsoid
s and range from dark brown to black in color. The pods are mature and ready for propagation after turning from green to brown or black. Seeds are covered with a hard seed coat, and this allows them to remain dormant for up to 25 years. Scarification
is needed before A. koa seeds will germinate
.
of Hawaii
, Molokai
, Maui
, Lānai
, Oahu
, and Kauai
, where it grows at elevations of 100–2300 m (328.1–7,545.9 ft). It requires 850 – of annual rainfall. Acid
ic to neutral soil
s (pH
of 4-7.4) that are either an Inceptisol
derived from volcanic ash
or a well-drained Histosol
are preferred. Its ability to fix nitrogen
allows it to grow in very young volcanic soils. Koa and ōhia lehua (Metrosideros polymorpha
) dominate the canopy
of mixed mesic forests. It is also common in wet forests.
The koa's trunk was used by ancient
Hawaiians
to build waa (dugout
outrigger canoe
s) and papa hee nalu (surfboard
s). Only paipo (bodyboards
), kikoo, and alaia
surfboards were made from koa, however; olo, the longest surfboards, were made from the lighter and more buoyant
wiliwili
(Erythrina sandwicensis). The reddish wood is very similar in strength and weight to that of Black Walnut (Juglans nigra), with a specific gravity of 0.55, and is sought for use in wood carving
and furniture
. Koa is also a tonewood
, often used in the construction of ukulele
s, acoustic guitar
s, and Weissenborn
-style Hawaiian steel guitar
s. B.C. Rich
used koa on some of their electric guitar
s as well, and still uses a koa-veneered
topwood on certain models. Fender made Limited Edition Koa wood models of the Telecaster and the Stratocaster in 2006. Trey Anastasio
, guitarist for the band Phish
, primarily uses a Koa hollowbody Languedoc guitar. Commercial silviculture
of koa is difficult because it takes 20 to 25 years before a tree is of useful size.
of volcanic (non-continental) origin, only Vanuatu
has native Acacia species. A. heterophylla
, from distant Réunion
, is very similar and has been suggested to be the closest relative of koa, but this is far from certain.
A closely related species, koaia or koaie (A. koaia
), is found in dry areas. It is most easily distinguished by having smaller seeds that are arranged end-to-end in the pod, rather than side-by-side. The phyllodes
are also usually straighter, though this character is variable in both species. The wood is denser, harder, and more finely grained
than koa wood. Koaia has been much more heavily impacted by cattle
and is now rare, but can be seen on ranch
land in North Kohala
.
. Many wet forest areas, where the largest koa grow, have been logged out, and it now comes largely from dead or dying trees or farms on private lands. Although formerly used for outrigger canoe
s, there are few koa remaining which are both large and straight enough to do so today. In areas where cattle
are present, koa regeneration is almost completely suppressed. However, if the cattle are removed, koa are among the few native Hawaiian plants able to germinate
in grassland, and can be instrumental in restoring native forest
. It is often possible to begin reforestation
in a pasture
by disk harrowing
the soil, as this scarifies
seeds in the soil and encourages large numbers of koa to germinate. Experiments at the Hakalau Forest National Wildlife Refuge
have shown that ōhia lehua (Metrosideros polymorpha
) survives best in pasture when planted under koa. This is because koa trees reduce radiative cooling
, preventing frost
damage to ōhia lehua seedlings.
plant for the caterpillar
s of the Green Hawaiian Blue (Udara
blackburni), which eat the flowers and fruits. Adults drink nectar from the flowers. Koa sap
is eaten by the adult Kamehameha Butterfly (Vanessa tameamea).
Flowering plant
The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...
tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
in the pea
Pea
A pea is most commonly the small spherical seed or the seed-pod of the pod fruit Pisum sativum. Each pod contains several peas. Peapods are botanically a fruit, since they contain seeds developed from the ovary of a flower. However, peas are considered to be a vegetable in cooking...
family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
, Fabaceae
Fabaceae
The Fabaceae or Leguminosae, commonly known as the legume, pea, or bean family, is a large and economically important family of flowering plants. The group is the third largest land plant family, behind only the Orchidaceae and Asteraceae, with 730 genera and over 19,400 species...
. It is endemic to the Hawaiian Islands
Hawaiian Islands
The Hawaiian Islands are an archipelago of eight major islands, several atolls, numerous smaller islets, and undersea seamounts in the North Pacific Ocean, extending some 1,500 miles from the island of Hawaii in the south to northernmost Kure Atoll...
, where it is the second most common tree. The highest populations are on Hawaii
Hawaii (island)
The Island of Hawaii, also called the Big Island or Hawaii Island , is a volcanic island in the North Pacific Ocean...
, Maui
Maui
The island of Maui is the second-largest of the Hawaiian Islands at and is the 17th largest island in the United States. Maui is part of the state of Hawaii and is the largest of Maui County's four islands, bigger than Lānai, Kahoolawe, and Molokai. In 2010, Maui had a population of 144,444,...
and Oahu
Oahu
Oahu or Oahu , known as "The Gathering Place", is the third largest of the Hawaiian Islands and most populous of the islands in the U.S. state of Hawaii. The state capital Honolulu is located on the southeast coast...
. Its name in the Hawaiian language
Hawaiian language
The Hawaiian language is a Polynesian language that takes its name from Hawaii, the largest island in the tropical North Pacific archipelago where it developed. Hawaiian, along with English, is an official language of the state of Hawaii...
, koa, also means brave, bold, fearless, or warrior.
Description
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
, typically attaining a height of 15–25 m (49.2–82 ft) and a spread of 6–12 m (19.7–39.4 ft). In deep volcanic ash
Volcanic ash
Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...
, a koa tree can reach a height of 30 m (98.4 ft), a circumference of 6 m (19.7 ft), and a spread of 38 m (124.7 ft). It is one of the fastest-growing Hawaiian trees, capable of reaching 6–9 m (19.7–29.5 ft) in five years on a good site.
Leaves
Initially, bipinnately compound leaves with 12–24 pairs of leafletLeaflet
A leaflet in botany is a part of a compound leaf. A leaflet may resemble an entire leaf, but it is not borne on a stem as a leaf is, but rather on a vein of the whole leaf. Compound leaves are common in many plant families...
s grow on the koa plant, much like other members of the pea family
Fabaceae
The Fabaceae or Leguminosae, commonly known as the legume, pea, or bean family, is a large and economically important family of flowering plants. The group is the third largest land plant family, behind only the Orchidaceae and Asteraceae, with 730 genera and over 19,400 species...
. At about 6–9 months of age, however, thick sickle-shaped "leaves" that are not compound begin to grow. These are phyllodes
Petiole (botany)
In botany, the petiole is the stalk attaching the leaf blade to the stem. The petiole usually has the same internal structure as the stem. Outgrowths appearing on each side of the petiole are called stipules. Leaves lacking a petiole are called sessile, or clasping when they partly surround the...
, blades that develop as an expansion of the leaf petiole
Petiole (botany)
In botany, the petiole is the stalk attaching the leaf blade to the stem. The petiole usually has the same internal structure as the stem. Outgrowths appearing on each side of the petiole are called stipules. Leaves lacking a petiole are called sessile, or clasping when they partly surround the...
. The vertically flattened orientation of the phyllodes allows sunlight to pass to lower levels of the tree. True leaves are entirely replaced by 7 – long, 0.5 – wide phyllodes on an adult tree.
Flowers
FlowerFlower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
s of the koa tree are pale-yellow spherical
Sphere
A sphere is a perfectly round geometrical object in three-dimensional space, such as the shape of a round ball. Like a circle in two dimensions, a perfect sphere is completely symmetrical around its center, with all points on the surface lying the same distance r from the center point...
raceme
Raceme
A raceme is a type of inflorescence that is unbranched and indeterminate and bears pedicellate flowers — flowers having short floral stalks called pedicels — along the axis. In botany, axis means a shoot, in this case one bearing the flowers. In a raceme, the oldest flowers are borne...
s with a diameter of 8–10 mm (0.31496062992126–0.393700787401575 in). Flowering may be seasonal or year round depending on the location.
Fruit
FruitFruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
production occurs when a koa tree is between 5 and 30 years old. The fruit are legumes, also called pods, with a length of 7.5 centimetre and a width of 1.5–2.5 cm (0.590551181102362–0.984251968503937 in). Each pod contains an average of 12 seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
s. The 6 millimetre long, 4–7 mm (0.15748031496063–0.275590551181102 in) wide seeds are flattened ellipsoid
Ellipse
In geometry, an ellipse is a plane curve that results from the intersection of a cone by a plane in a way that produces a closed curve. Circles are special cases of ellipses, obtained when the cutting plane is orthogonal to the cone's axis...
s and range from dark brown to black in color. The pods are mature and ready for propagation after turning from green to brown or black. Seeds are covered with a hard seed coat, and this allows them to remain dormant for up to 25 years. Scarification
Scarification (botany)
Scarification in botany involves cutting the seed coat using abrasion, thermal stress, or chemicals to encourage germination.-In botany:Scarification is a natural process important for germination of many species' seeds. This process involves the breaching of the natural seed coating by mechanical,...
is needed before A. koa seeds will germinate
Germination
Germination is the process in which a plant or fungus emerges from a seed or spore, respectively, and begins growth. The most common example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm. However the growth of a sporeling from a spore, for example the...
.
Habitat
Koa is endemic to the islandsHawaiian Islands
The Hawaiian Islands are an archipelago of eight major islands, several atolls, numerous smaller islets, and undersea seamounts in the North Pacific Ocean, extending some 1,500 miles from the island of Hawaii in the south to northernmost Kure Atoll...
of Hawaii
Hawaii (island)
The Island of Hawaii, also called the Big Island or Hawaii Island , is a volcanic island in the North Pacific Ocean...
, Molokai
Molokai
Molokai or Molokai is an island in the Hawaiian archipelago. It is 38 by 10 miles in size with a land area of , making it the fifth largest of the main Hawaiian Islands and the 27th largest island in the United States. It lies east of Oahu across the 25-mile wide Kaiwi Channel and north of...
, Maui
Maui
The island of Maui is the second-largest of the Hawaiian Islands at and is the 17th largest island in the United States. Maui is part of the state of Hawaii and is the largest of Maui County's four islands, bigger than Lānai, Kahoolawe, and Molokai. In 2010, Maui had a population of 144,444,...
, Lānai
Lanai
Lānai or Lanai is the sixth-largest of the Hawaiian Islands. It is also known as the Pineapple Island because of its past as an island-wide pineapple plantation. The only town is Lānai City, a small settlement....
, Oahu
Oahu
Oahu or Oahu , known as "The Gathering Place", is the third largest of the Hawaiian Islands and most populous of the islands in the U.S. state of Hawaii. The state capital Honolulu is located on the southeast coast...
, and Kauai
Kauai
Kauai or Kauai, known as Tauai in the ancient Kaua'i dialect, is geologically the oldest of the main Hawaiian Islands. With an area of , it is the fourth largest of the main islands in the Hawaiian archipelago, and the 21st largest island in the United States. Known also as the "Garden Isle",...
, where it grows at elevations of 100–2300 m (328.1–7,545.9 ft). It requires 850 – of annual rainfall. Acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
ic to neutral soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
s (pH
Soil pH
The soil pH is a measure of the acidity or basicity in soils. pH is defined as the negative logarithm of the activity of hydrogen ions in solution. It ranges from 0 to 14, with 7 being neutral. A pH below 7 is acidic and above 7 is basic. Soil pH is considered a master variable in soils as it...
of 4-7.4) that are either an Inceptisol
Inceptisols
Inceptisols are a soil order in USDA soil taxonomy. They form quickly through alteration of parent material. They are older than entisols. They have no accumulation of clays, Iron, Aluminum or organic matter. They have an Ochric or Umbric horizon and a cambic subsurface horizon....
derived from volcanic ash
Volcanic ash
Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...
or a well-drained Histosol
Histosol
In both the FAO soil classification and the USA soil taxonomy, a histosol is a soil consisting primarily of organic materials. They are defined as having or more of organic soil material in the upper . Organic soil material has an organic carbon content of 12 to 18 percent, or more, depending on...
are preferred. Its ability to fix nitrogen
Nitrogen fixation
Nitrogen fixation is the natural process, either biological or abiotic, by which nitrogen in the atmosphere is converted into ammonia . This process is essential for life because fixed nitrogen is required to biosynthesize the basic building blocks of life, e.g., nucleotides for DNA and RNA and...
allows it to grow in very young volcanic soils. Koa and ōhia lehua (Metrosideros polymorpha
Metrosideros polymorpha
The ōhia lehua is a species of flowering evergreen tree in the myrtle family, Myrtaceae, that is endemic to the six largest islands of Hawaii. It is a highly variable tree, being tall in favorable situations, and much smaller when growing in boggy soils or on basalt...
) dominate the canopy
Canopy (forest)
In biology, the canopy is the aboveground portion of a plant community or crop, formed by plant crowns.For forests, canopy also refers to the upper layer or habitat zone, formed by mature tree crowns and including other biological organisms .Sometimes the term canopy is used to refer to the extent...
of mixed mesic forests. It is also common in wet forests.
Uses
Ancient Hawaii
Ancient Hawaii refers to the period of Hawaiian human history preceding the unification of the Kingdom of Hawaii by Kamehameha the Great in 1810. After being first settled by Polynesian long-distance navigators sometime between AD 300–800, a unique culture developed. Diversified agroforestry and...
Hawaiians
Native Hawaiians
Native Hawaiians refers to the indigenous Polynesian people of the Hawaiian Islands or their descendants. Native Hawaiians trace their ancestry back to the original Polynesian settlers of Hawaii.According to the U.S...
to build waa (dugout
Dugout (boat)
A dugout or dugout canoe is a boat made from a hollowed tree trunk. Other names for this type of boat are logboat and monoxylon. Monoxylon is Greek -- mono- + ξύλον xylon -- and is mostly used in classic Greek texts. In Germany they are called einbaum )...
outrigger canoe
Outrigger canoe
The outrigger canoe is a type of canoe featuring one or more lateral support floats known as outriggers, which are fastened to one or both sides of the main hull...
s) and papa hee nalu (surfboard
Surfboard
A surfboard is an elongated platform used in the sport of surfing. Surfboards are relatively light, but are strong enough to support an individual standing on them while riding a breaking wave...
s). Only paipo (bodyboards
Bodyboarding
Bodyboarding is a surface water sport . The average board consists of a small, rectangular piece of hydrodynamic foam, sometimes containing a ridged spine called a 'stringer'...
), kikoo, and alaia
Alaia
An Alaia is a thin, round-nosed, square-tailed surfboard ridden in pre-20th century Hawaii. The boards were between long, weighed up to , and were generally made from the wood of Acacia koa...
surfboards were made from koa, however; olo, the longest surfboards, were made from the lighter and more buoyant
Buoyancy
In physics, buoyancy is a force exerted by a fluid that opposes an object's weight. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the...
wiliwili
Wiliwili
Wiliwili is a species of flowering tree in the pea family, Fabaceae that is endemic to the Hawaiian Islands. It is the only species of Erythrina that naturally occurs there. It is typically found in dry forests on leeward island slopes up to an elevation of .Wiliwili is occasionally seen in...
(Erythrina sandwicensis). The reddish wood is very similar in strength and weight to that of Black Walnut (Juglans nigra), with a specific gravity of 0.55, and is sought for use in wood carving
Wood carving
Wood carving is a form of working wood by means of a cutting tool in one hand or a chisel by two hands or with one hand on a chisel and one hand on a mallet, resulting in a wooden figure or figurine, or in the sculptural ornamentation of a wooden object...
and furniture
Furniture
Furniture is the mass noun for the movable objects intended to support various human activities such as seating and sleeping in beds, to hold objects at a convenient height for work using horizontal surfaces above the ground, or to store things...
. Koa is also a tonewood
Tonewood
Tonewood generally refers to any wood which may be used in the construction of a musical instrument. Many acoustic properties are often assigned to specific wood species; however the description of these properties is itself a large subject and beyond the scope of this article...
, often used in the construction of ukulele
Ukulele
The ukulele, ; from ; it is a subset of the guitar family of instruments, generally with four nylon or gut strings or four courses of strings....
s, acoustic guitar
Acoustic guitar
An acoustic guitar is a guitar that uses only an acoustic sound board. The air in this cavity resonates with the vibrational modes of the string and at low frequencies, which depend on the size of the box, the chamber acts like a Helmholtz resonator, increasing or decreasing the volume of the sound...
s, and Weissenborn
Weissenborn
Weissenborn or H. Weissenborn is a brand of lap slide guitar manufactured by Hermann Weissenborn in Los Angeles in the 1920s and 1930s....
-style Hawaiian steel guitar
Steel guitar
Steel guitar is a type of guitar or the method of playing the instrument. Developed in Hawaii in the late 19th and early 20th centuries, a steel guitar is usually positioned horizontally; strings are plucked with one hand, while the other hand changes the pitch of one or more strings with the use...
s. B.C. Rich
B.C. Rich
B.C. Rich is a manufacturer of guitars and bass guitars founded by the late Bernardo Chavez Rico in 1969. Currently, most B.C. Rich guitars are manufactured in Asia, but luthiers of the company's custom shop continue to hand-make instruments. The Hanser Music Group, based in Kentucky, operates B.C....
used koa on some of their electric guitar
Electric guitar
An electric guitar is a guitar that uses the principle of direct electromagnetic induction to convert vibrations of its metal strings into electric audio signals. The signal generated by an electric guitar is too weak to drive a loudspeaker, so it is amplified before sending it to a loudspeaker...
s as well, and still uses a koa-veneered
Wood veneer
In woodworking, veneer refers to thin slices of wood, usually thinner than 3 mm , that are typically glued onto core panels to produce flat panels such as doors, tops and panels for cabinets, parquet floors and parts of furniture. They are also used in marquetry...
topwood on certain models. Fender made Limited Edition Koa wood models of the Telecaster and the Stratocaster in 2006. Trey Anastasio
Trey Anastasio
Trey Anastasio is an American guitarist, composer, and vocalist most noted for his work with the rock band Phish...
, guitarist for the band Phish
Phish
Phish is an American rock band noted for its musical improvisation, extended jams, and exploration of music across genres. Formed at the University of Vermont in 1983 , the band's four members – Trey Anastasio , Mike Gordon , Jon Fishman , and Page McConnell Phish is an American rock band...
, primarily uses a Koa hollowbody Languedoc guitar. Commercial silviculture
Silviculture
Silviculture is the practice of controlling the establishment, growth, composition, health, and quality of forests to meet diverse needs and values. The name comes from the Latin silvi- + culture...
of koa is difficult because it takes 20 to 25 years before a tree is of useful size.
Relation to other species
The relationships of koa are not clear. Among other Pacific IslandsPacific Islands
The Pacific Islands comprise 20,000 to 30,000 islands in the Pacific Ocean. The islands are also sometimes collectively called Oceania, although Oceania is sometimes defined as also including Australasia and the Malay Archipelago....
of volcanic (non-continental) origin, only Vanuatu
Vanuatu
Vanuatu , officially the Republic of Vanuatu , is an island nation located in the South Pacific Ocean. The archipelago, which is of volcanic origin, is some east of northern Australia, northeast of New Caledonia, west of Fiji, and southeast of the Solomon Islands, near New Guinea.Vanuatu was...
has native Acacia species. A. heterophylla
Acacia heterophylla
Acacia heterophylla, the Highland tamarin, is a tree endemic to Réunion island where it is commonly named Tamarin des Hauts...
, from distant Réunion
Réunion
Réunion is a French island with a population of about 800,000 located in the Indian Ocean, east of Madagascar, about south west of Mauritius, the nearest island.Administratively, Réunion is one of the overseas departments of France...
, is very similar and has been suggested to be the closest relative of koa, but this is far from certain.
Acacia koaia
Acacia koaia, known as koaia or koaie in Hawaiian, is a tree in the pea family, Fabaceae, that is endemic to Hawaii. It is closely related to koa , and is sometimes considered to be the same species...
), is found in dry areas. It is most easily distinguished by having smaller seeds that are arranged end-to-end in the pod, rather than side-by-side. The phyllodes
Petiole (botany)
In botany, the petiole is the stalk attaching the leaf blade to the stem. The petiole usually has the same internal structure as the stem. Outgrowths appearing on each side of the petiole are called stipules. Leaves lacking a petiole are called sessile, or clasping when they partly surround the...
are also usually straighter, though this character is variable in both species. The wood is denser, harder, and more finely grained
Wood grain
In speaking of wood the term grain refers to the alternating regions of relatively darker and lighter wood resulting from the differing growth parameters occurring in different seasons . The term is used in several ways. Perhaps most important is that in woodworking techniques...
than koa wood. Koaia has been much more heavily impacted by cattle
Cattle
Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
and is now rare, but can be seen on ranch
Ranch
A ranch is an area of landscape, including various structures, given primarily to the practice of ranching, the practice of raising grazing livestock such as cattle or sheep for meat or wool. The word most often applies to livestock-raising operations in the western United States and Canada, though...
land in North Kohala
Kohala, Hawaii
thumb|right|300px|The districts of the [[Hawaii |Big Island]]. From Northernmost, clockwise; Kohala , [[Hamakua|Hāmākua]], [[Hilo, Hawaii|Hilo]], [[Puna, Hawaii|Puna]], [[Kau, Hawaii|Kaū]], [[Kona District, Hawaii|Kona]]...
.
Conservation
The koa population has suffered from grazing and loggingLogging
Logging is the cutting, skidding, on-site processing, and loading of trees or logs onto trucks.In forestry, the term logging is sometimes used in a narrow sense concerning the logistics of moving wood from the stump to somewhere outside the forest, usually a sawmill or a lumber yard...
. Many wet forest areas, where the largest koa grow, have been logged out, and it now comes largely from dead or dying trees or farms on private lands. Although formerly used for outrigger canoe
Outrigger canoe
The outrigger canoe is a type of canoe featuring one or more lateral support floats known as outriggers, which are fastened to one or both sides of the main hull...
s, there are few koa remaining which are both large and straight enough to do so today. In areas where cattle
Cattle
Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
are present, koa regeneration is almost completely suppressed. However, if the cattle are removed, koa are among the few native Hawaiian plants able to germinate
Germination
Germination is the process in which a plant or fungus emerges from a seed or spore, respectively, and begins growth. The most common example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm. However the growth of a sporeling from a spore, for example the...
in grassland, and can be instrumental in restoring native forest
Forest
A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...
. It is often possible to begin reforestation
Reforestation
Reforestation is the natural or intentional restocking of existing forests and woodlands that have been depleted, usually through deforestation....
in a pasture
Pasture
Pasture is land used for grazing. Pasture lands in the narrow sense are enclosed tracts of farmland, grazed by domesticated livestock, such as horses, cattle, sheep or swine. The vegetation of tended pasture, forage, consists mainly of grasses, with an interspersion of legumes and other forbs...
by disk harrowing
Harrow (tool)
In agriculture, a harrow is an implement for breaking up and smoothing out the surface of the soil. In this way it is distinct in its effect from the plough, which is used for deeper tillage. Harrowing is often carried out on fields to follow the rough finish left by ploughing operations...
the soil, as this scarifies
Scarification (botany)
Scarification in botany involves cutting the seed coat using abrasion, thermal stress, or chemicals to encourage germination.-In botany:Scarification is a natural process important for germination of many species' seeds. This process involves the breaching of the natural seed coating by mechanical,...
seeds in the soil and encourages large numbers of koa to germinate. Experiments at the Hakalau Forest National Wildlife Refuge
Hakalau Forest National Wildlife Refuge
Hakalau Forest National Wildlife Refuge is a protected area on the Big Island of Hawaii. It is one of two units, along with the Kona Forest National Wildlife Refuge that is managed as part of the Big Island National Wildlife Refuge Complex...
have shown that ōhia lehua (Metrosideros polymorpha
Metrosideros polymorpha
The ōhia lehua is a species of flowering evergreen tree in the myrtle family, Myrtaceae, that is endemic to the six largest islands of Hawaii. It is a highly variable tree, being tall in favorable situations, and much smaller when growing in boggy soils or on basalt...
) survives best in pasture when planted under koa. This is because koa trees reduce radiative cooling
Radiative cooling
Radiative cooling is the process by which a body loses heat by thermal radiation.- Earth's energy budget :In the case of the earth-atmosphere system it refers to the process by which long-wave radiation is emitted to balance the absorption of short-wave energy from the sun.The exact process by...
, preventing frost
Frost
Frost is the solid deposition of water vapor from saturated air. It is formed when solid surfaces are cooled to below the dew point of the adjacent air as well as below the freezing point of water. Frost crystals' size differ depending on time and water vapour available. Frost is also usually...
damage to ōhia lehua seedlings.
Ecology
Koa is the preferred hostHost (biology)
In biology, a host is an organism that harbors a parasite, or a mutual or commensal symbiont, typically providing nourishment and shelter. In botany, a host plant is one that supplies food resources and substrate for certain insects or other fauna...
plant for the caterpillar
Caterpillar
Caterpillars are the larval form of members of the order Lepidoptera . They are mostly herbivorous in food habit, although some species are insectivorous. Caterpillars are voracious feeders and many of them are considered to be pests in agriculture...
s of the Green Hawaiian Blue (Udara
Udara
Udara is a genus of butterflies in the family Lycaenidae.-Species:*Subgenus Udara Toxopeus, 1922** Udara akasa - White Hedge Blue ** Udara aristinus ** Udara aristius...
blackburni), which eat the flowers and fruits. Adults drink nectar from the flowers. Koa sap
Plant sap
Sap is a fluid transported in xylem cells or phloem sieve tube elements of a plant. It transports water and nutrients throughout the plant....
is eaten by the adult Kamehameha Butterfly (Vanessa tameamea).
External links
- Photos of Acacia koa at Hawaiian Ecosystems at Risk Project (HEAR)
- UCLA botanical garden and home
- Historic photos and descriptions of Acacia koa