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Species
Alnus glutinosa (L.) Gaertn.
IUCN
NCBI
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European alder grows well on acid soils, and its growth is reduced under the alkaline or near-neutral conditions that are desirable for many other species.
The author is Assistant Director, Northeastern Forest Experiment Station, Radnor, PA.
During their first growing season in most types of soils alder seedlings form root nodules that are the site of nitrogen fixation. Seedlings already nodulated grow satisfactorily when outplanted on sites with pH as low as 3.3; plants not already nodulated usually die under these very acid conditions (27,77). Nodules develop satisfactorily at pH as low as 4.2 (8), but seedlings were stunted and had poor root systems and chlorotic leaves when grown in clay soil with pH between 8.0 and 8.5 (63). Optimum soil pH for nodulation appears to be between 5.5 and 7.0 (35). Spoil-bank plantations in Ohio and Kentucky verify the minimum pH for satisfactory European alder growth as about 3.4 (30,55). On very acid (pH 2.9) coal spoils in Indiana, alder survival, growth, and root nodule weight were all increased by liming sufficient to raise pH to at least 6.1 (eventually declining to 4.8) (41). In a greenhouse experiment using acidic Pennsylvania mine spoil, alders did not respond to lime amendments until phosphorus was also added (89).
Both nodulated and nonnodulated alders require molybdenum for nitrogen metabolism (6,42); adequate amounts of Mo are present in most soils, although it may not be available on strongly acid sites. On sites with poor internal drainage, European alder can tolerate iron concentrations normally toxic to many plants (44). On tidal flats adjacent to the English Channel, the chlorine concentration of the soil solution in the root zone of mature alders occasionally rises to 5 percent of that of sea water immediately following equinoctial high tides (78).
European alder is responsive to differences in soil moisture (5,40), and growth often is notably better on lower slopes than on upper slopes. Alder utilizes intermittently moist sites very well (56). It is "a species of stream and lake sides and ... soils of impeded drainage throughout the British Isles," although not topographically limited to such sites if rainfall is high (60). Even though alder tolerates heavy soils better than most trees, reduced soil oxygen (especially below 5 percent) inhibits root nodulation and the growth of nodulated plants (57).
In a species with such a broad natural range, altitudinal distribution is bound to be related to latitude. European alder is found at sea level at the northern limits of its range, up to 300 in (985 ft) in Norway, 600 in (1,970 ft) in the Harz Mountains of Saxony, 850 in (2,790 ft) in the Bavarian Mountains, 1300 in (4,270 ft) in the Tyrol and in Greece, and 1800 in (5,900 ft) in the Caucasus (60,88). The most common soils on which it grows in North America occur in the orders Histosols, Inceptisols, and Entisols.
Alnus glutinosa, the common alder, black alder, European alder or just alder, is a species of tree in the family Betulaceae, native to most of Europe, southwest Asia and northern Africa. It thrives in wet locations where its association with the bacterium Frankia alni enables it to grow in poor quality soils. It is a medium size, short-lived tree growing to a height of up to 30 metres (100 ft). It has short-stalked rounded leaves and separate male and female flower in the form of catkins. The small, rounded fruits are cone-like and the seeds are dispersed by wind and water.
The common alder provides food and shelter to wildlife, with a number of insects, lichens and fungi being completely dependent on the tree. It is a pioneer species, colonising vacant land and forming mixed forests as other trees appear in its wake. Eventually common alder dies out of woodlands because the seedlings need more light than is available on the forest floor. Its more usual habitat is forest edges, swamps and riverside corridors. The timber has been used in underwater foundations and for manufacture into paper and fibreboard, for smoking foods, for joinery, turnery and carving. Products of the tree have been used in ethnobotany, providing folk remedies for various ailments, and research has shown that extracts of the seeds are active against pathogenic bacteria.
Contents
Description[edit]
Alnus glutinosa is a tree that thrives in moist soils, and grows under favourable circumstances to a height of 20 to 30 metres (66 to 98 ft) and exceptionally up to 37 metres (121 ft).[4] Young trees have an upright habit of growth with a main axial stem but older trees develop an arched crown with crooked branches. The base of the trunk produces adventitious roots which grow down to the soil and may appear to be propping the trunk up. The bark of young trees is smooth, glossy and greenish-brown while in older trees it is dark grey and fissured. The branches are smooth and somewhat sticky, being scattered with resinous warts. The buds are purplish-brown and have short stalks. Both male and female catkins form in the autumn and remain dormant during the winter.[5]
The leaves of the common alder are short-stalked, rounded, up to 10 cm (4 in) long with a slightly wedge-shaped base and a wavy, serrated margin. They have a glossy dark green upper surface and paler green underside with rusty-brown hairs in the angles of the veins. As with some other trees growing near water, the common alder keeps its leaves longer than do trees in drier situations, and the leaves remain green late into the autumn. As the Latin name glutinosa implies, the buds and young leaves are sticky with a resinous gum.[5][6][7]
The species is monoecious and the flowers are wind-pollinated; the slender cylindrical male catkins are pendulous, reddish in colour and 5 to 10 cm (2 to 4 in) long; the female flowers are upright, broad and green, with short stalks. During the autumn they become dark brown to black in colour, hard, somewhat woody, and superficially similar to small conifer cones. They last through the winter and the small winged seeds are mostly scattered the following spring. The seeds are flattened reddish-brown nuts edged with webbing filled with pockets of air. This enables them to float for about a month which allows the seed to disperse widely.[5][6][7]
Unlike some other species of tree, common alders do not produce shade leaves. The respiration rate of shaded foliage is the same as well-lit leaves but the rate of assimilation is lower. This means that as a tree in woodland grows taller, the lower branches die and soon decay, leaving a small crown and unbranched trunk.[8]
Taxonomy[edit]
Alnus glutinosa was first described by Carl Linnaeus in 1753, as one of two varieties of alder (the other being A. incana), which he regarded as a single species Betula alnus.[9] In 1785, Jean-Baptiste Lamarck treated it as a full species under the name Betula glutinosa.[10] Its present scientific name is due to Joseph Gaertner, who in 1791 accepted the separation of alders from birches, and transferred the species to Alnus.[2] The epithet glutinosa means "sticky", referring particularly to the young shoots.[11]
Within the genus Alnus, the common alder is placed in subgenus Alnus as part of a closely related group of species including the grey alder, Alnus incana,[12] with which it hybridizes to form the hybrid A. × hybrida.[13]
Distribution and habitat[edit]
The common alder is native to almost the whole of continental Europe (except for both the extreme north and south) as well as the United Kingdom and Ireland. In Asia its range includes Turkey, Iran and Kazakhstan, and in Africa it is found in Tunisia, Algeria and Morocco. It is naturalised in the Azores.[14] It has been introduced, either by accident or by intent, to Canada, the United States, Chile, South Africa, Australia and New Zealand. Its natural habitat is in moist ground near rivers, ponds and lakes but it can also grow in drier locations and sometimes occurs in mixed woodland and on forest edges. It tolerates a range of soil types and grows best at a pH of between 5.5 and 7.2. Because of its association with the nitrogen-fixing bacterium Frankia alni, it can grow in nutrient-poor soils where few other trees thrive.[15]
Ecological relationships[edit]
The common alder is most noted for its symbiotic relationship with the bacterium Frankia alni, which forms nodules on the tree's roots. This nitrogen-fixing bacterium absorbs nitrogen from the air and fixes it in a form available to the tree. In return, the bacterium receives carbon products produced by the tree through photosynthesis. This relationship, which improves the fertility of the soil, has established the common alder as an important pioneer species in ecological succession.[16]
The common alder is susceptible to Phytophthora alni, a recently evolved species of oomycete plant pathogen probably of hybrid origin. This is the causal agent of phytophthora disease of alder which is causing extensive mortality of the trees in some parts of Europe.[17] The symptoms of this infection include the death of roots and of patches of bark, dark spots near the base of the trunk, yellowing of leaves and in subsequent years, the death of branches and sometimes the whole tree.[15]Taphrina alni is a fungal plant pathogen that causes alder tongue gall, a chemically induced distortion of female catkins. The gall develops on the maturing fruits and produces spores which are carried by the wind to other trees. This gall is believed to be harmless to the tree.[18] Another, also harmless, gall is caused by a midge, Eriophyes inangulis, which sucks sap from the leaves forming pustules.[19]
The common alder is important to wildlife all year round and the seeds are a useful winter food for birds. Deer, sheep, hares and rabbits feed on the tree and it provides shelter for livestock in winter.[15] It shades the water of rivers and streams, moderating the water temperature, and this benefits fish which also find safety among its exposed roots in times of flood. The common alder is the foodplant of the larvae of a number of different butterflies and moths[20] and is associated with over 140 species of plant-eating insect.[19] The tree is also a host to a variety of mosses and lichens which particularly flourish in the humid moist environment of streamside trees. Some common lichens found growing on the trunk and branches include tree lungwort (Lobaria pulmonaria), Menneguzzia terebrata and Stenocybe pullatula, the last of which is restricted to alders.[19] Some 47 species of mycorrhizal fungi have been found growing in symbiosis with the common alder, both partners benefiting from an exchange of nutrients. As well as several species of Naucoria, these symbionts include Russula alnetorum, the milkcaps Lactarius obscuratus and Lactarius cyathula, and the alder roll-rim Paxillus filamentosus, all of which grow nowhere else except in association with alders. In spring, the catkin cup Ciboria amentacea grows on fallen alder catkins.[19]
As an introduced species, the common alder can affect the ecology of its new locality. It is a fast-growing tree and can quickly form dense woods where little light reaches the ground, and this may inhibit the growth of native plants. The presence of the nitrogen-fixing bacteria and the annual accumulation of leaf litter from the trees also alters the nutrient status of the soil. It also increases the availability of phosphorus in the ground, and the tree's dense network of roots can cause increased sedimentation in pools and waterways. It spreads easily by wind-borne seed, may be dispersed to a certain extent by birds and the woody fruits can float away from the parent tree. When the tree is felled, regrowth occurs from the stump, and logs and fallen branches can take root.[15]A. glutinosa is classed as an environmental weed in New Zealand.[21]
Cultivation and uses[edit]
The common alder is used as a pioneer species and to stabilise river banks, to assist in flood control, to purify water in waterlogged soils and to moderate the temperature and nutrient status of water bodies. It can be grown by itself or in mixed species plantations, and the nitrogen-rich leaves falling to the ground enrich the soil and increase the production of such trees as walnut, Douglas fir and poplar on poor quality soils. Although the tree can live for up to 160 years, it is best felled for timber at 60 to 70 years before heart rot sets in.[8]
On marshy ground it is important as coppice-wood, being cut near the base to encourage the production of straight poles. It is capable of enduring clipping as well as marine climatic conditions and may be cultivated as a fast-growing windbreak. In woodland, the seedlings cannot tolerate dense shade and as the forest matures, the alder trees in it die out.[22] The species is cultivated as a specimen tree in parks and gardens, and the cultivar 'Imperialis' has gained the Royal Horticultural Society's Award of Garden Merit.[23]
Timber[edit]
The wood is soft, white when first cut, turning to pale red; the knots are attractively mottled. The timber is not used where strength is required in the construction industry, but is used for paper-making, the manufacture of fibreboard and the production of energy.[8] Under water the wood is very durable and is used for deep foundations of buildings. The piles beneath the Rialto in Venice, and the foundations of several medieval cathedrals are made of alder. The Roman architect Vitruvius mentioned that the timber was used in the construction of the causeways across the Ravenna marshes.[24] The wood is used in joinery, both as solid timber and as veneer, where its grain and colour are appreciated, and it takes dye well. As the wood is soft, flexible and somewhat light, it can be easily worked as well as split. It is valued in turnery and carving, in making furniture, window frames, clogs, toys, blocks, pencils and bowls.[5]
Tanning and dyeing[edit]
The bark of the common alder has long been used in tanning and dyeing. The bark and twigs contain 16 to 20% tannic acid but their usefulness in tanning is limited by the strong accompanying colour they produce.[25] Depending on the mordant and the methods used, various shades of brown, fawn, and yellowish-orange hues can be imparted to wool, cotton and silk. Alder bark can also used with iron sulphate to create a black dye which can substitute for the use of sumach or galls.[26] The Laplanders are said to chew the bark and use their saliva to dye leather. The shoots of the common alder produce a yellowish or cinnamon-coloured dye if cut early in the year. Other parts of the tree are also used in dyeing; the catkins can yield a green colour and the fresh-cut wood a pinkish-fawn colour.[25]
Other uses[edit]
It is also the traditional wood that is burnt to produce smoked fish and other smoked foods, though in some areas other woods are now more often used. It supplies high quality charcoal.[5]
The leaves of this tree are sticky and if they are spread on the floor of a room, their adhesive surface is said to trap fleas.[25]
Chemical constituents of Alnus glutinosa include hirsutanonol, oregonin, genkwanin,[27]rhododendrin {3-(4-hydroxyphenyl)-l-methylpropyl-β-D-glucopyranoside} and glutinic acid (2,3-pentadienedioic acid).[28]
Health[edit]
Pollen from the common alder, along with that from birch and hazel, is one of the main sources of tree pollen allergy. As the pollen is often present in the atmosphere at the same time as that of birch, hazel, hornbeam and oak, and they have similar physicochemical properties, it is difficult to separate out their individual effects. In central Europe, these tree pollens are the second most common cause of allergic conditions after grass pollen.[29]
The bark of common alder has traditionally been used as an astringent, a cathartic, a hemostatic, a febrifuge, a tonic and an alterative (a substance able to restore normal health). A decoction of the bark has been used to treat swelling, inflammation and rheumatism, as an emetic, and to treat pharyngitis and sore throat.[28] Ground up bark has been used as an ingredient in toothpaste, and the inner bark can be boiled in vinegar to provide a skin wash for treating dermatitis, lice and scabies. The leaves have been used to reduce breast discomfort in nursing mothers and folk remedies advocate the use of the leaves against various forms of cancer.[22] Alpine farmers are said to use the leaves to alleviate rheumatism by placing a heated bag full of leaves on the affected areas. Alder leaves are consumed by cows, sheep, goats and horses though pigs refuse to eat them. According to some people, consumption of alder leaves causes blackening of the tongue and is harmful to horses.[25]
In a research study, extracts from the seeds of the common alder have been found to be active against all the eight pathogenic bacteria against which they were tested, which included Escherichia coli and methicillin-resistant Staphylococcus aureus. The only extract to have significant antioxidant activity was that extracted in methanol. All extracts were of low toxicity to brine shrimps. These results suggest that the seeds could be further investigated for use in the development of possible anti-MRSA drugs.[30]
Details of Alder structure and galls[edit]
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Alder Tongue Gall fungus, Taphrina alni
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Black alder in Ås, Norway
References[edit]
- ^ Participants of the FFI/IUCN SSC Central Asian regional tree Red Listing workshop, Bishkek, Kyrgyzstan (11–13 July 2006) (2007). "Alnus glutinosa". IUCN Red List of Threatened Species. Version 2014.2. International Union for Conservation of Nature. Retrieved 8 October 2014.
- ^ a b "Alnus glutinosa". The International Plant Names Index. Retrieved 2014-08-31.
- ^ "Alnus glutinosa". World Checklist of Selected Plant Families. Royal Botanic Gardens, Kew. Retrieved 2014-08-31.
- ^ "Spitzenbäume". Land Brandenburg. Retrieved 2009-01-19.
- ^ a b c d e Vedel, Helge; Lange, Johan (1960). Trees and Bushes. Methuen. pp. 143–145. ISBN 978-0-416-61780-1.
- ^ a b Trees for Life Species Profile: Alnus glutinosa
- ^ a b Flora of NW Europe: Alnus glutinosa
- ^ a b c Claessens, Hugues; Oosterbaan, Anne; Savill, Peter; Rondeux, Jacques (2010). "A review of the characteristics of black alder (Alnus glutinosa (L.) Gaertn.) and their implications for silvicultural practices". Forestry 83 (2): 163–175. doi:10.1093/forestry/cpp038.
- ^ "Betula alnus var. glutinosa". The International Plant Names Index. Retrieved 2014-08-31.
- ^ "Betula glutinosa". The International Plant Names Index. Retrieved 2014-08-31.
- ^ Coombes, Allen J. (1994). Dictionary of Plant Names. London: Hamlyn Books. p. 8. ISBN 978-0-600-58187-1.
- ^ Chen, Zhiduan & Li, Jianhua (2004). "Phylogenetics and Biogeography of Alnus (Betulaceae) Inferred from Sequences of Nuclear Ribosomal DNA ITS Region". International Journal of Plant Sciences 165: 325–335. doi:10.1086/382795.
- ^ Stace, Clive (2010). New Flora of the British Isles (3rd ed.). Cambridge, UK: Cambridge University Press. p. 296. ISBN 978-0-521-70772-5.
- ^ "Alnus glutinosa". Flora Europaea. Royal Botanic Garden Edinburgh. Retrieved 2014-08-09.
- ^ a b c d "Alnus glutinosa (tree)". Global Invasive Species Database. IUCN SSC Invasive Species Specialist Group. 2010-08-27. Retrieved 2014-08-04.
- ^ Schwencke, J.; Caru, M. (2001). "Advances in actinorhizal symbiosis: Host plant-Frankia interactions, biology, and application in arid land reclamation: A review". Arid Land Research and Management 15 (4): 285–327. doi:10.1080/153249801753127615.
- ^ Phytophthora Disease of Alder
- ^ Ellis, Hewett A. (2001). Cecidology. Vol.16, No.1. p. 24.
- ^ a b c d Featherstone, Alan Watson (2012-11-26). "Common or black alder". Trees for life. Retrieved 2014-08-07.
- ^ Carter, David James; Hargreaves, Brian (1986). A field guide to caterpillars of butterflies and moths in Britain and Europe. Collins. ISBN 978-0-00-219080-0.
- ^ Clayson, Howell (May 2008). Consolidated list of environmental weeds in New Zealand. Wellington: Department of Conservation. ISBN 978-0-478-14412-3.
- ^ a b "Alnus glutinosa - (L.)Gaertn.". Plants For A Future. 2012. Retrieved 2014-08-05.
- ^ "Alnus glutinosa Imperialis". Royal Horticultural Society. Retrieved 2014-08-06.
- ^ Paterson, J. M. "The Alder Tree". A Tree in Your Pocket. Retrieved 2014-08-03.
- ^ a b c d Grieve, M. "Alder, Common". Botanical.com: A Modern Herbal. Retrieved 2014-08-05.
- ^ Adrosko, Rita J. (2012). Natural Dyes and Home Dyeing. Courier Dover Publications. pp. 41–42. ISBN 978-0-486-15609-5.
- ^ O'Rourke, Ciara; Sarker, Satyajit D.; Stewart, Fiona; Byres, Maureen; Delazar, Abbas; Kumarasamy, Yashodharan; Nahar, Lutfun. "Hirsutanonol, oregonin and genkwanin from the seeds of Alnus glutinosa (Betulaceae)". Biochemical Systematics and Ecology 33 (7): 749–752. doi:10.1016/j.bse.2004.10.005. ISSN 0305-1978.
- ^ a b Sati, Sushil Chandra; Sati, Nitin; Sati, O. P. (2011). "Bioactive constituents and medicinal importance of genus Alnus". Pharmacognosy Review 5 (10): 174–183. doi:10.4103/0973-7847.91115. PMC 3263052. PMID 22279375.
- ^ "Erle: Schwarzerle, Alnus glutinosa". Alles zur Allergologie (in German). Retrieved 2014-08-05.
- ^ Middleton, P.; Stewart, F.; Al-Qahtani, S.; Egan, P.; O'Rourke, C.; Abdulrahman, A.; Byres, M.; Middleton, M.; Kumarasamy, Y.; Shoeb, M.; Nahar, L.; Delazar, A.; Sarker, S. D. (2005). "Antioxidant, Antibacterial Activities and General Toxicity of Alnus glutinosa, Fraxinus excelsior and Papaver rhoeas". Iranian Journal of Pharmaceutical Research 4 (2): 101–103.
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This tree is typically 40-70' tall. It has a single or 2-3 trunks and a variably shaped crown. Trunk bark of mature trees is grey or brownish grey, dividing into flattened plates that are separated by broad shallow furrows. The bark of young trees is light gray to greenish gray and more smooth with transverse white lenticels. Alternate leaves up to 5" long and 3½" across occur along the smaller branches and twigs; they are obovate or orbicular-obovate in shape, while their margins are crenate-dentate and slightly undulate. The leaf tips are rounded or slightly indented, while their bases are wedge-shaped (cuneate) to rounded. The upper leaf surface is dark green and glabrous (or nearly so), while the lower surface is more pale and either glabrous or slightly hairy along the undersides of the veins. Young leaves and shoots are often sticky from a resin. The slender petioles are light green, glabrous, and up to 1" long. Black Alder is monoecious, producing separate male (staminate) and female (pistillate) florets on the same tree. The male florets are produced in clusters of 2-5 catkins. Mature male catkins are 2-3" long, reddish yellow, narrowly cylindrical, and drooping. Within each of these catkins, there are tiny clusters of 3-6 florets that are partially hidden by individual bractlets. Each male floret consists of a 4-lobed calyx and 4 stamens, while each bractlet is oval in shape. The female florets are produced in branching clusters of 2-5 cone-like catkins (less often, occurring as a single catkin). These catkins are initially about ¼" long, but they later become ¾-1" long and ½" across. Within each of these catkins, there are tiny clusters of 2-3 female florets that are partially hidden by individual bractlets. Each female floret consists of a naked ovary with a pair of tiny styles at its apex. The blooming period occurs during the spring before the leaves develop; the florets are cross-pollinated by wind. After the blooming period, the male catkins wither away, while the female catkins persist through the summer, releasing their seeds during the fall. At this time, the bractlets of the cone-like female catkins have become brown and woody; individual bractlets are narrowly oblanceolate with 4-5 short stubby lobes. Individual seeds are obovoid and flattened; their margins are not significantly winged. The female catkins usually persist on the tree through the winter. The root system is woody and branching. Cultivation
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The alder is primarily a pioneer and opportunist species, and is capable of direct colonization of even the rawest of soil material.... The species acts as a pioneer on hydroseres, being capable of colonizing at very early stages in the primary succession if good seed is available. Alder carr (deciduous woodland or scrub on a permanently wet, organic soil) does not succeed an earlier Salix and Rharnnus carr, though these species may colonize simultaneously, and pure alder carr eventually results from the greater vigour and longevity of the alders" (65).
In central Switzerland, alder is considered to be more shade tolerant than willow (Salix spp.), larch (Larix spp.), poplar (Populus spp.), birch (Betula spp.), or Scotch pine (Pinus syluestris); equal in tolerance to ash Traxinus spp.); apd less tolerant than eastern white pine (Pinus strobus) or Douglasfir (Pseudotsuga menziesii) (50). Overall, it is classed as intolerant of shade (18).
In Yugoslavia and Germany, European alder is grown on 40- to 80-year rotations, depending on intensity of thinning and products desired. The stand is clearcut at the end of the rotation and replanted with 1-year seedlings or 1-1 transplants.
Nursery practice for European alder is fairly routine, and 1-year seedlings are usually large enough for outplanting. Liberal irrigation following sowing is essential for good seed germination.
Alder has generally beneficial effects on associated plants. Part of the nitrogen fixed by alders soon becomes available to other species in mixed stands, especially through mineralization of nitrogen leached from litter. Norway spruce (Picea abies) grown in pots with European alder "obtained nitrogen fixed in the root nodules of alder although leaves falling in autumn were always carefully removed" (98).
In a 3-year-old Wisconsin plantation, hybrid poplars in a plantation spaced at 1.2 by 1.2 in (3.9 by 3.9 ft) grew 21 percent taller in a 1:2 mixture with European alder than when grown without alder (4.9 m versus 4.0 m; 16.0 ft versus 13.1 ft). This growth increase corresponded closely with that achieved through optimal ammonium nitrate fertilizer treatment, which stimulated a 24 percent increase (39). Similar results were obtained in Quebec where mixed plantings of two alders per poplar yielded slightly more total biomass at age 3 than pure alder plantings and 50 percent more than pure hybrid poplar (16).
European alder often is recommended for use in mixed plantings with other species on nitrogen-poor sites. On strip-mined sites in eastern Kentucky, 10 coniferous and broadleaved species were grown in alternate rows with European alder at 2.1 by 2.1 m (6 : 9 by 6.9 ft) spacing; after 10 years, trees grown in mixture with alder were 11 to 84 percent taller and 20 to 200 percent larger in diameter than the same species grown without alder (75).
In northern Bohemia, Populus x berolinensis used for strip-mine reclamation averaged 12.5 m (41 ft) tall at age 14 in pure plantings but grew to 14 m (46 ft) in mixture with Alnus glutinosa; poplars in the mixed planting were also much straighter (24).
In southern Indiana, European alder seedlings were interplanted into a 2-year-old plantation of black walnut (Juglans nigra) on well-drained silt loam soil. Ten years after interplanting, walnuts grown in mixture with alder averaged 5.3 in (17.5 ft) tall against 4.2 in (13.8 ft) in pure stands; alder stimulated an increase in walnut diameter from 5.6 cm (2.2 in) to 6.9 cm (2.7 in) (14). In contrast, at four locations in Illinois and Missouri, alder interplanted with walnut suddenly declined and died after 8-13 years. Allelopathy caused by juglone was the only cause of death that could be substantiated (80).
Please contact your local agricultural extension specialist or county weed specialist to learn what works best in your area and how to use it safely. Always read label and safety instructions for each control method. Trade names and control measures appear in this document only to provide specific information. USDA, NRCS does not guarantee or warranty the products and control methods named, and other products may be equally effective.
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Alder has been characterized as possessing an extensive root system of both surface and deep branches, which enables it to survive on either waterlogged soils or those with a deep water table (60). In Germany, European alder is considered to be the deepest rooting indigenous tree species (86). Alder's deeply penetrating taproots often extend well below normal water table; if the water level falls, these roots are well situated to use deep-lying soil moisture not available to the upper portion of the root system. This may explain alder's outstanding success on spoil banks (37,64).
Generally, there are two kinds of alder root nodules. One is a large, perennial, usually single nodule sometimes 5 cm (2 in) or more in diameter (21) and most often situated near the root crown. These nodules may persist as long as 10 years, with those in the 4- to 5-year age class making up the greatest proportion of the weight of nodules per tree (1). The other type is ephemeral, much smallertypically 1.5 to 3 mm (0.06 to 0.12 in) in diameterand generally distributed throughout the surface root system. Becking found that molybdenum-deficient alder plants formed many small nodules of much reduced total dry weight and exhibited associated nitrogen deficiency. Plants with an adequate molybdenum supply had mainly single large nodules (6).
The most striking effect of alders on soil is nitrogen enrichment. Not only is alder leaf litter rich in nitrogen (68), but many nitrogenous compounds are heavily concentrated in alder roots and root nodules (99). In European alder seedlings, rate of nitrogen fixation is closely related to nodule fresh
weight and total plant dry weight, suggesting that selection for growth should also achieve gains in nitrogen fixation (4). In Quebec, 3- and 4-year-old alders planted at 33 cin by 33 cm (13 in by 13 in) spacing fixed nitrogen at an annual rate of 53 kg/ha (47 lb/acre) (15).
Fixation of atmospheric nitrogen by alders takes place in root vesicles (67) and nodules (8). In a greenhouse experiment, maximum nitrogen fixation in young European alder plants occurred in late August; throughout the growing season about 90 percent of the nitrogen fixed was steadily transferred from the nodules to the rest of the plant (91). In an alder grove growing on peat in the Netherlands, nitrogen fixation was also found to peak in August (1).
European alder (as well as other Alnus species) differs from most deciduous tree species in retaining much foliar nitrogen in the leaves until they fall (17). In a southern Illinois plantation, nitrogen content of leaves decreased by only one-sixth from midsummer until leaf fall. At the time of the last collection, in mid-November, leaf nitrogen content was about 2.6 percent; thus there was a substantial quantity of nitrogen to be dropped in the leaf litter (21).
In Finland, a 13-year-old European alder plantation and a 55-year-old natural stand were sampled for 4 years. Alder litter averaged 2690 and 3705 kg/ha (2,400 and 3,305 lb/acre) per year (ovendried), respectively, and contributed about 82 percent of the total annual litter production. Total nitrogen content of the leaf litter averaged 77 kg/ha (69 lb/acre) per year, reaching a high of 101 kg/ha (90 lb/acre) in 1 year in the plantation. NH4-nitrogen in the upper 3-cm layer of soil rose from 180 mg/kg (180 p/m) before leaf fall to 270 mg/kg (270 p/m) after leaf fall, indicating that at least part of the nitrogen of alder leaf litter was rapidly mineralized (69).
Prodigious amounts of litter can accumulate under alder stands. For instance, 10 species of pines and deciduous trees were planted on a Kentucky strip mine with and without alternate rows of European alder. After 10 years, 28.7 t/ha (12.8 tons/acre) of litter accumulated in the plantings without alder, while 61.7 t/ha (27.5 tons/acre) built up under the stands with a 50 percent alder component. The relative contribution of alder leaf fall and increased litter production of the other species, stimulated by the alder, could not be determined. In the spring of the 10th growing season, the pH of the spoil beneath the stand containing alder was significantly lower than the plantings without alder. Similarly, the concentration of total soluble salts was consistently higher, both spring and fall, in the stands with alder than in those without (75).
European alder leaf litter readily gives up watersoluble organic substances, losing 12 percent of its dry weight after only 1 day's leaching in cold water. Alder litter was also found to decompose faster than that of beech or oak (70). The C:N ratio of alder foliage suspended in a stream declined rapidly from 19 to about 13 within a month after leaf fall, then more slowly to 11 (near the effective mineralization optimum) after 6 months (13).
Other components of alders also accumulate considerable nitrogen. In a plantation on a good alluvial site in western Kentucky the following nitrogen contents (percent dry weight) were measured at the end of the fourth growing season (adapted from 104):
Even young alders can fix and add significant amounts of nitrogen to soil. A Padus silt loam in Wisconsin averaged 966 mg/kg (966 p/m) of nitrogen in the upper 4 cm (1.5 in) of dry soil before 1-year-old European alder seedlings were planted. After two growing seasons, soil nitrogen (at the same depth) had increased 222 mg/kg (222 p/m) in soil immediately adjacent to the alders and by 158 mg/kg (158 p/m) at a distance of 15 cin (6 in) (39).
None have been released in the US. A few nurseries produce this tree to meet the needs of orchard and mine revegetation interests.
IV, RM, VIII, X
License | http://creativecommons.org/licenses/by-nc-sa/3.0/ |
Rights holder/Author | Pablo Gutierrez, IABIN |
Source | No source database. |