Tsuga mertensiana
Mountain hemlock ( Tsuga mertensiana )
The mountain hemlock ( Tsuga mertensiana ) is a coniferous tree from the species of hemlock. It differs in several characteristics from other types of hemlock and is a separate subgenus assigned. So the needles are dense and radially on the branches, the pins are much larger, and the pollen have two air bags. Its distribution area stretches along the southern coast of Alaska and the west coast of Canada and the United States over a length of 4000 kilometers. It grows in the snowiest areas of North America and comes with extremely short growing seasons from. Economically it was of only minor importance and is rarely used as ornamental tree.
Description
The mountain hemlock is a slow- growing evergreen tree, the growth heights of 10 to 30, rarely up to 46 meters reached. The maximum diameter at breast height is 150 centimeters. The crown is narrow and conical, the branches are thin and overhanging. In Alaska and in the Sierra Nevada remains small near the tree line and also accepts shrubby forms. Very old isolated trees have irregular, grobastige and often crooked crowns. The 2.5 to 3.8 centimeters thick bark of older trees is dark gray-brown, deeply furrowed and hard. Young trees have a light gray to gray, smooth bark. The wood is densely fibred and has a nearly white sapwood and a red to light brown core. The root system is shallow and far-reaching.
The young branches have a reddish-brown and hairy in the first two to three years cortex. Winter buds grow to a length of up to 5 millimeters. They are pointed- ovate and have reddish- brown, subulate pointed bud scales. Here, flower buds and leaf buds are different. The female flower buds of a branch are about 3 millimeters longer than the leaf buds; both of which are covered by 25 bud scales. The outer scales are bright and hairy, the inner glossy dark brown. The male flower buds are about 2 millimeters long and have ten bud scales, the outer and the inner thin and white are light brown and slightly thickened.
The needles are tight and unlike other hemlock radially arranged on the branches, where they stand a little closer to the top. They are 0.5 to 2.5 inches long and 1 to 1.2 millimeters wide. The needles are linear, obtuse and entire, and from blue -green to silver-white color. They run at the base of a slender stalk. The top surface is curved and the front part is provided on both sides with the gap opening strips. The needles of the mountain hemlock remain about three to four years on the tree.
The mountain hemlock hemlock, like all monoecious getrenntgeschlechtig ( monoecious ) and with about 20 years of marriageable age. The female cones are in the upper third, the males in the lower part of the crown. The female cones stand upright at the ends of young branches and have shiny purple, rarely, yellow and green seeds shed. The bracts are not visible. The male cones are on the side of the branches in the axils of last year's needles and have a violet to purple color. The pollen have two air bags, which distinguishes them from the pollen of other Tsuga species. After dusting the empty male cones remain on the tree for several months. The flowering period begins in June, in northern locations until July. Pollination takes place about the beginning of August. The trees bloom once a year. Bloom every two to eight years and they bear fruit particularly strong (mast years), on wet surfaces also rare.
The adolescent cones are reddish to purple and stain brown when ripe in mid-September. You then have a length of 3 to 8 centimeters, are oblong - cylindrical and tapered at both ends. They consist of 80 to 100 fan- shaped scales, each with two ovules. The edge of the shed is thin, irregularly dentate or slightly frayed. The outermost shed at the pin nose and the pin base usually do not form seeds. Usually, about 70 seeds per pin are formed, of which about 30 whole grains. They are released from mid-October from the pin by bending back the shed far, which will fill again with moisture then. Empty cones may remain on the tree another year. The seeds are 3 mm long, light brown and have a about 8 millimeters long, rectangular wings. They are spread by the wind and germinate epigeal.
The chromosome number is as with all hemlock.
Seed cones
Ripe cones
Distribution, habitat requirements and risk
The natural range of mountain hemlock extends from southern Alaska through British Columbia ( Canada) and the Pacific Northwest to California, Idaho and Montana over a length of about 4000 kilometers. The southern border of their range is in the Sequoia National Park in southern California's Sierra Nevada. It often grows in subalpine elevations of the Coast Mountains, the Cascade Range and the Siskiyou Mountains. Particularly rich in closed forests is also in Crater Lake National Park. Their habitat ranges from the coast of Alaska to altitudes of 3000 meters in the Sierra Nevada. In Canada they are found at altitudes 750-1800 m.
The mountain hemlock thrives in cool - to - cold maritime climate, with mild to cool winters and warm to cool summers. It settles the snowiest areas in North America, often forms the timberline and comes with very short growing seasons from. So is the frost- free period in the Sierra Nevada only about 50 to 60 days. The air temperature in the distribution area varies throughout the year 3-4 ° C, the average temperature in January is between -7 ° C and -3 ° C in Alaska, British Columbia. The mean July temperature is between 11 and 13 ° C. The rainfall spread more and are between about 1000 and 3000 mm per year. The snowpack may remain lying to August and can reach a height of 7.5 meters. Most of the snow in the area of distribution is heavy and wet and young trees can press for months to the ground without causing failures.
The mountain hemlock grows on soils of volcanic and glacial origin, on metamorphic rocks and sandstone. Calcareous soils are avoided. Optimally, loose, coarse-grained, well-drained, fresh soils. The pH of the soil ranges from 3.4 to 6.2. In Alaska and British Columbia they are also found on the edge of bogs, but where it remains dwarfed and crooked. In the coastal mountains and the Sierra Nevada it often grows on bare rock.
They are usually found in mixed stands, pure stands are available in Alaska and in the Cascade Range. In deeper areas they are found together with the Western White Pine (Pinus monticola ) and the superb fir ( Abies magnifica), at higher altitudes with the lodgepole pine (Pinus contorta ) and the White -Russians Pine ( Pinus albicaulis ) in Canada well with the Engelmann spruce (Picea engelmannii ), the Subalpine larch ( Larix lyallii ), the Subalpine Fir (Abies lasiocarpa ) and purples - fir ( Abies amabilis ).
In the IUCN Red List, the mountain hemlock will be listed as endangered ( " Lower Risk / least concern "). It is noted, however, that a re-evaluation of risks is required.
Pathology
The mountain hemlock is rarely attacked by pests, damaged, root and Stammfäuleerreger. Among them, the pore sponge Phellinidium weirii leads to major outages, with huge stretches of forest are affected. In the cascade chain that led to the death of trees on areas of up to 40 acres. However, the renewable young trees remain largely unaffected. Damage caused schweinitzii by the root fungus ( Heterobasidion annosum ), the Fichtenporling ( Fomitopsis pinicola ), Phellinus pinII and Phaeolus. More rarely it is attacked by Echinodontium tinctorium.
The dwarf mistletoe Arceuthobium tsugense var mertensiana leads to the formation of witches' broom bushy adhesions in the tree crown. One can find this variety as a parasite on the purple - fir ( Abies amabilis ), the Subalpine Fir (Abies lasiocarpa ) and the noble fir ( Abies procera ), but it is missing on the west American hemlock ( Tsuga heterophylla ).
Storms cause because of the shallow root system and fire because the low-hanging branches damage. After fires newly grown stocks but usually achieve very high stem density 10000-25000 stems per hectare.
System
The mountain hemlock ( Tsuga mertensiana ) is a species from the genus of hemlock ( Tsuga ). There she is the only species of the subgenus Hesperopeuce. It differs by several features of the other species of hemlock:
- It forms both on top as well as bottom of the needles stomata, similar to the firs (Abies ), cedar (Cedrus ), Keteleeria and Nothotsuga longibracteata. In other hemlock they are only on the bottom.
- The seed cones are upright as the firs (Abies ), cedar (Cedrus ), Keteleeria and the Gold Larch ( Pseudolarix ) during pollination. In other hemlock seed cones hanging.
- The pollen two air bags as the most representative of the (Pinaceae ), the other only a hemlock as only larches ( Larix) and Nothotsuga longibracteata.
- The pollination mechanism is similar to the firs (Abies ) and cedar (Cedrus ) and differs from that of the other hemlock.
It is therefore classified as a separate subgenus Hesperopeuce, the other hemlock Tsuga the subgenus. Some authors assign them as Hesperopeuce mertensiana ( Bong. ) Rydb. the monotypic genus Hesperopeuce to, it is therefore not counted among the hemlocks. Due to the different characteristics was also considered that it is in the mountain hemlock a hybrid between American Western Hemlock ( Tsuga heterophylla ) and Sitka spruce (Picea sitchensis) is that jeffreyi (Henry) Henry was described as Tsuga ×. For talked apparent intermediate forms between Tsuga heterophylla and Tsuga mertensiana that were found in the overlapping area of the two species. More detailed studies have shown, however, that it, in such forms usually these representatives of Tsuga heterophylla, which have adapted to extreme snow layers. A hybrid status can not be deduced from the investigations. Also, attempts to cross the two species artificially unsuccessful.
Phylogenetic analyzes of the nucleic acids of the cell nucleus and the chloroplasts show, however, that the mountain hemlock, a sister species of West American hemlock ( Tsuga heterophylla ), and these two form a sister group to the other hemlock. From the classification in its own subgenus, one would expect that the mountain hemlock is a sister species to all other hemlock.
We distinguish the following subspecies and varieties:
- Tsuga mertensiana subsp. mertensiana var mertensiana: The seed cones have a length of 3 to 5.5 centimeters, rarely only 2 or up to 6 centimeters. Are formed 50-72 dark brown seed scales that are 10 to 13 millimeters long and 7-10 mm wide.
- Tsuga mertensiana subsp. mertensiana var jeffreyi (A. Henry) C.K. Cutting. The needles are arranged more or less in a comb shape, and the short impulses can not be distinguished from the cross- drives. The seed cones are similar to those of the variety mertensiana. The variety was described by finds from Vancouver Iceland, however, could be found either on the island or on the nearby mainland in 2005.
- Tsuga mertensiana subsp. grandicona Farjon: The seeds are larger than the pins mertensiana subspecies having a length from 3.5 to 8.1 centimeters in diameter and 1.9 to 3.3 centimeters. There shall be 40 to 52 light brown seed scales that are 12 to 18, a maximum of 20 millimeters long and 10 to 15 millimeters wide. The distribution area is located in California in the Siskiyou Mountains and the Sierra Nevada, and possibly also in southern Oregon.
History of Research
The mountain hemlock was designed by German biologist Karl Heinrich Mertens (1796-1830) at Sitka in Alaska found. The collection of Mertens was evaluated by the German botanist August Gustav Heinrich von Bongard in St. Petersburg, which has the type first described in 1832 as Pinus mertensiana ( basionym ) in the journal Mémoires de l' Academie Imperiale des Sciences de St. - Petersbourg. The French Gardener and botanist Élie -Abel Carrière she put 1867 in the second edition of his work Traite General of Coniferes as Tsuga mertensiana in the genre of hemlock ( Tsuga ). Another synonym for Tsuga mertensiana ( Bong. ) Carriere is Tsuga pattoniana ( A.Murray ) Engelm.
The selected Carrière scientific genus name Tsuga is Japanese and it describes the Südjapanische Hemlock ( Tsuga sieboldii ). The specific epithet honors the mertensiana Finder Karl Heinrich Mertens.
Use
The mountain hemlock has little economic significance, which can also be attributed to the normally inaccessible locations. The wood is usually together with the wood of the American West Hemlock ( Tsuga heterophylla ) and plywood, used construction wood for the interior and for the production of pulp and paper. It is rarely used as an ornamental plant, it is found in Europe, mostly in collections. More often, the cultivar ' Glauca ' is used as an ornamental plant, which differs from the wild type by a slower growth and the blue- green and blue frosted white needles. Variety Trials in Central Europe, however failed. She has hardly any meaning for the erosion protection.