Metrosideros umbellata
South Island Ironwood ( Metrosideros umbellata )
The South Island Ironwood ( Metrosideros umbellata ) on Māori " Rata ", English "southern rata ," German occasionally "Southern Rata ", in addition to originating from the same genus North Island ironwood and Pohutukawa is one of the most well-known tree species in New Zealand. It is particularly conspicuous by occurring in December and January, bright red flowers. The home especially on the South Island of New Zealand populations are threatened by browsing by the harmful Australian brushtail possum.
Description
Habit
The evergreen South Island ironwood trees are 15 meters and higher, and can thereby achieve trunk diameter of more than one meter, together with the down -growing aerial roots but this can be exceeded significantly. The tribes have a 2 to 3 mm thick bark, the outer layers decreases in paper-like pieces. The habit can vary greatly depending on the location of this appearance but also. While largely free standing trees take a round tree shape, form especially trees in densely populated habitats from an umbrella- shaped crown. An overgrown banks South Island ironwood trees often grow with a nearly horizontal strain to grow out under the crowns of other trees. Partial plants are formed on extremely rocky ground only shrubby and already in size from 15 to 25 cm flowering size. Occasionally, epiphytic living specimens in the crowns of Libocedrus bidwillii and rare of Podocarpus or Dacrydium hallii cupressinum be found. These trees are highly branched above the original essay point; the growing down roots envelop the host increasingly, partially so far that he dies.
Vegetative growth
The first velvety, later smooth, leathery leaves have a size of (25 ) -30-50 - (60 ) mm × (10 ) -15-20 mm are opposite, nebenblattlos and sit at about 5 mm long petioles. The leaf shape varies from medium to narrow - oval or elliptical.
Mature plants terminate a vegetative growth spurt with the formation of vegetative buds couple trained for the last pair of leaves sits against constantly between this. They consist of five to six pairs of modified, scale-like leaves, of which the second pair completely encloses the bud. These buds are during winter 1.5 mm long and gummy. In the spring, the resin dissolves the outer two pairs of scales are discarded, and the remaining three to four pairs enlarge initially to protect the developing leaves until they too are dropped.
Younger plants form at the end of the growth period of no vegetative buds, although even here the growth ends with the formation of a pair of leaves. However, this is often not completely formed and dies during the winter.
Vegetative growth is mostly limited to the already formed in the vegetative buds leaves, so that each growth period only two to four pairs of leaves are formed with the corresponding node. The branching of the shoots is usually dichotomous. The division of the shoot of young seedlings usually begins after the fourth growing season.
The annual rings in the trunk appear at least in young plants in annual intervals, the lighter, former wood alternating with the darker wood of the late growth phase. After about 50 to 100 annual rings, the growth is irregular, in some rings is a regular growth can be seen, while in others the growth is almost set and the transitions are difficult to detect.
The growing roots in the soil are very thin, branched often only 0.2 mm thick and strong. Since most shoot tips of the roots are very short-lived, they are replaced with new roots growing from the center of the plant to the outside. Are root hairs present, they are verbündelt only sporadically or close and are 0.5 mm long.
Grows the South Island ironwood in moist areas, ie mainly in the valleys below the Franz Josef and Fox Glacier with a stem thickness of at least 23 to 30 cm, are formed in plants from aerial roots. This is the size the plants are already about 100 years old. These aerial roots hanging freely at first or grow down the trunk. When they reach the ground, they thicken to stilt roots, and often grow together with other air or stilt roots or the trunk.
Although plants have usually trained aerial root systems in lowland areas, the plants die off in almost all cases when they fall over, while often grow at higher altitudes from the trunks of new trees, so that they form a dense tangle of fallen and wedged trunks.
Propagation
The heyday of the South Island ironwood can themselves vary greatly within a habitat. During the main flowering period in December and January, flowering trees are partially visible until about March also.
The flowers appear singly or in groups of two to three in the axils of the inner one to three (usually two) bud scales, individual flowers is matched by a leaf, flower groups whorl of four to six leaves. The vegetative shoot bud is usually before the opening of the flower, growth, and since the pedicels usually longer than the internodes, it seems, as the flowers would occur in groups of up to nine flowers.
The flowers consist of five about 3 mm long, oblong, triangular to ovate sepals and five about 5 mm long, almost round red petals. The numerous red stamens are also about 2 cm long. Chance of plants also come with orange front to yellow flowers. The base of the style is slightly above the placenta.
The rich nectar flowers are visited and fertilized mainly by the Tui ( Prosthemadera novaeseelandiae ) and the Korimako ( Anthornis melanura ), and honey bees.
The fertilized flowers develop large seed capsules to 0.75 to 1 cm. Thus, they are larger than those of related species, such as North Island ironwood or Pohutukawa. During the growth of the capsules increases the tissue between stylus and placenta, so that they are far apart in completely trained capsules. Reif approximately 250 to 300 seeds are containing, first green capsules in following the summer bloom, as with most Myrtengewächsen contain only a few of the seed embryo and are capable of germination. During the winter the seedpods burst open, so that the following November the seed capsules are nearly empty. The only 2.0 × 0.4 mm and less than 0.1 mg of heavy seeds are dispersed by the wind. Empty capsules remain still for a few months on the plant before they fall off.
Age
Evidence gathered correlations with glacial data of the adjacent glacier from the valleys of the Fox River and Rivers Waiho that the South Island ironwood trees have a life span of 400 to 500 years.
Distribution and habitat
The South Island - iron wood is the most common in New Zealand members of the genus Metrosideros. It usually takes him at altitudes 0-760 meters above sea level, on northbound cliffs some stocks are also known at altitudes above 1100 meters. At best it grows in cooler regions with a high average rainfall, so it is mainly found on the West Coast of the South Island of New Zealand. However, there are also on the entire North Island some habitats, for example, on the Coromandel Peninsula and the northern highlands, the southernmost occurrences are found on the sub-Antarctic Aucklandinseln, thus forming the southernmost forests of New Zealand.
Typically, the South Island ironwood is associated with other trees such as the " kamahi " ( Weinmannia racemosa ), the Podocarpus Podocarpus type hallii or the " mountain Neinei " ( Dracophyllum traversii ) and shrubs such as Coprosma and Pseudopanax different species. In the ferns and herbaceous layer can be found, for example, various ferns of the genus Blechnum, and Gleichenia cunninghamii, the sour grass greenhouse Gahnia procera, the Tagliliengewächs Phormium cookianum, the Madder family Nertera dichondraefolia or Astelia nervosa from the family Asteliaceae.
Since young seedlings of the South Island ironwood can not compete with other plants that can be found South Island ironwood trees often sparsely populated areas with poor soils or otherwise harsh environmental conditions. Through their ability to epiphytic life one finds the plant but also occasionally, but in small amounts, in densely populated habitats. As steinaufsitzende plant specimens can be found on limestone, shale, greywacke, andesite, gneiss, granite and quartzite.
System
The genus Metrosideros is divided into two subgenera, the subgenus Metrosideros with about 26 species and sub- species Mearnsia with about 24 species. Phylogenetic studies have shown that the South Island Ironwood ( Metrosideros umbellata ) is one of the basal body of the subgenus Metrosideros and thus also for basal three independent strains within the subgenus. Four species of the genus are endemic to New Zealand, five in Hawaii and seven in New Caledonia. It is believed that on the basis of M. umbellata initially created the species in New Caledonia, later the other New Zealand species. From New Caledonia from the subgenus widespread in the Western Pacific, which probably recent Hawaiian species have their ancestors probably again in New Zealand. This theory for the dissemination of the subgenus from M. umbellata is supported by the phylogenetic division into three tribes. The wide distribution of the genus across the Pacific from New Zealand is different glacial weather phenomena that are comparable with the current El Niño awarded.
Endangering
Since the 1950s, an increased forest decline is noted within the populations of the South Island ironwood and examined. In some cases more than 30 % of the trees of a population have died. The main cause is the browsing by introduced mammals in New Zealand, called especially the Australian brushtail possum ( Trichosurus vulpecula ). However, larger mammals such as the red deer (Cervus elaphus scoticus ) use the plants for food. The weakened by the grim trees are consequently also more susceptible to wind damage, fungal and insect infestation, and drought. The mortality rate of the ironwood trees is sometimes very different from population to population. On the one hand seem populations where there is a lack of hardwood shrubs in the undergrowth, over bites to be particularly vulnerable by the Fuchskusus, on the other older trees die rather by the grim consequences from than younger specimens. Since the Fuchskusus often visit already weakened trees to feed, often dying individual trees of a population from complete, while others are still completely healthy.
In order to contain the damage caused by the brushtail possum, various programs have been launched to reduce the number of animals. These were used, among other things, by air -dropped or designed by hand, poisoned bait, but also made traps. In addition, fences are erected, but this can be costly and ineffective, especially for larger areas. Isolated trees can be protected by a metal ring around the trunk. From 1951 to 1961, the New Zealand government paid a premium for fishing brushtail possum. Since these were mostly caught in easily accessible areas where endangered plants were barely home, this method had proved to be ineffective and was discontinued.
Almost completely destroyed forest areas that are largely from South Island ironwood and kamahi ( Weinmannia racemosa ) were previously populated, were able to decrease even after the brushtail possum numbers in this area will not regenerate. There, especially those plants settled after the destruction of the originally prevailing plants, which are not eaten by the brushtail possum, such as Quintinia acutifolia.
Origin of the name
The scientific genus name Metrosideros derives from the Greek metra in the meaning of the uterus, Mark, core of plants ( mother metra ) and of sideros (iron ) from which refers to the extremely hard wood. The specific epithet umbellata means " umbels bearing " and refers to the umbrella-shaped arranged flowers that spring from a single peduncle.
Economic Importance
The South Island ironwood trees have little economic significance, but are linked because of their main flowering period in December and characteristic, showy red flowers along with the pohutukawa and the North Island ironwood with Christmas. Although the wood of the South Island - iron wood is very hard and belongs to the class of wood iron wood, the wood is rarely used as wood. The reason for this is mainly the usually very strong ossified form of trees, just enough grown specimens are very rare. The honey obtained from the flowers is offered as " Rata honey ," the timber is partly used as firewood.