Alnus Glutinosa (L.) Gaertn

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<ul><li><p>Alnus Glutinosa (L.) Gaertn.Author(s): D. N. McVeanSource: Journal of Ecology, Vol. 41, No. 2 (Aug., 1953), pp. 447-466Published by: British Ecological SocietyStable URL: .Accessed: 26/10/2013 05:11</p><p>Your use of the JSTOR archive indicates your acceptance of the Terms &amp; Conditions of Use, available at .</p><p> .</p><p>JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact</p><p> .</p><p>British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal ofEcology.</p><p> </p><p>This content downloaded from on Sat, 26 Oct 2013 05:11:05 AMAll use subject to JSTOR Terms and Conditions</p></li><li><p>[ 447 ] </p><p>BIOLOGICAL FLORA OF THE BRITISH ISLES </p><p>L.C. (Ed. 11) No. 1738 ALNUS Mill. </p><p>One British Species. </p><p>Alnus glutinosa (L.) Gaertn. (A. rotundifolia Stokes) </p><p>D. N. MCVEAN </p><p>Botany School, University of Cambridge* </p><p>A tree of moderate size attaining a height of 60-80 ft. (18-24 m.) in cultivation but natural specimens normally 10-40 ft. (3-12 m.) high. Habit variable from the low multiple- stemmed bush form to tall single-bole trees. </p><p>In favourable situations growth is strongly excurrent, the short main branches departing at an acute angle, which becomes a right angle with age, and forking little except at their peripheral ends. In woodland the stems are tall and thin, bearing a small, sparse crown, but the pioneer form is shorter and stouter with stronger, more irregular, open branching. Bark brown, smooth at first, becoming darker, fissured and rough. </p><p>Young twigs triangular in cross-section, green to reddish brown according to illumina- tion (both colours normally visible on opposite sides of the same shoot); lenticels promi- nent, yellow-brown. Long and short shoots present. Leaf buds dark purple with two stipular scales, stalked. Phyllotaxy normally 2/3. </p><p>Leaves plicate in the bud, glutinous when young, orbicular, usually emarginate, finely or coarsely serrate except at the cuneate base, often obscurely lobed or sinuate, dark green and with tufts of hairs in the angles of the principal veins beneath. Laminae 4.5 x 4-0 cm. to 8-0 x 7-0 cm. with petioles one-quarter to one-half as long and green or dark red. </p><p>Male catkins 2-5 at end of branch, long and drooping, green or purplish; female catkins 2-12 on lateral shoot of the same branch, oval, erect, dark crimson enlarging to 1-0-2-5 cm. in length and becoming green in fruit; scales persistent and blackening after the fall of the nutlets. </p><p>Fruit brown, compressed, one-seeded, with lateral corky outgrowths and two persistent styles. </p><p>British varieties have been named according to leaf and catkin size. Moss (1914) gives macrocarpa Loudon-laminae as long as broad (7-8 cm.) and with coarse serrations; pistillate catkins 3 cm. long at maturity, typica Moss-laminae 5.6 x 4-5 cm., pistillate catkins 1-7-2-0 x 1-0-1-4 cm. 'Not yet known for Wales, Scotland or Ireland', microcarpa Rouy-laminae 4-5 x 3-5-4-0 cm., with fine serrations; pistillate catkins 1-5 x 1-0 cm. 'Common form in hilly and northern localities, West Riding of Yorkshire north to Caithness. Also occurs in England as far south as Somerset and Suffolk.' </p><p>There are numerous horticultural varieties in cultivation in Britain (Loudon, 1875; * Now The Nature Conservancy, Edinburgh. This account was prepared while the author was in receipt of </p><p>research grants from the Carnegie Trust for the Universities of Scotland and from the Nature Conservancy. J. Ecol. 41 29 </p><p>This content downloaded from on Sat, 26 Oct 2013 05:11:05 AMAll use subject to JSTOR Terms and Conditions</p></li><li><p>448 Alnus glutinosa Hemsley, 1877; Elwes &amp; Henry, 1906). In Britain the species is certainly variable in habit and in leaf and catkin size, and the variation appears to be continuous. Leaf and catkin measurements of eighteen populations (twenty of each from five or ten trees per </p><p>12 10 8 6 4 2 0 2 4 / E 1T~~~~~~~ - h l l30 20 10 0 10 20 30'40 </p><p>English Miles o0 A0 60 0 20 40 60 80 100 . . I I I I I Kilometres eich 30 56 </p><p>0 25 50 75 100 150 "A </p><p>52 _ 58 </p><p>10 8 6Longitude West 4 of Greenwich 2 OLongitudeEast 2 of Greenwich </p><p>Fig. 1. Alnus glutinosa (L.) Gaertn., vice-comital distribution in the British Isles and (inset) limits of distribution as a native species in Europe. </p><p>population) suggest that both leaf and catkin size diminish fairly regularly from south to north and from east to west, the northern and western populations being perhaps less variable (Fig. 2). </p><p>..... .......... .: </p><p>.... 86LongiWofO Lon .E.oflO G ree nwich 30 </p><p>56g. 1. Ainu8 glutinosa (L.) Gaertn.; viee-eomital distribution in the British Isles and (inset) limits of distribuion..s native secies i E urope. </p><p>population) suggest that both leaf and eatkin size diminish fairly regularly from sou.h..o north and from east o west, e northern nd western populat:ions.......... ..... ...... v ar?:?iable (F:.?.ig::::: ... )....... ....... ......... ..j:jjjj::i:::,l:5 f~~::f~;::::::::~~6~~;.... ............ .. 54 ~ ii~iiiii jji~'~ii~:~ ~ ~~ti~ ....... ...... ...... .......:::::: ............... .......:c;::::~: ~5~.??:??%:?::??:??:::?.::.: ? ;i:1::............?s~~:?:~ ,6 :::::::1:.:.:.:.?~.:.:.:.:............. ............. .......~7:i::::::::j :~i:::::;::: :::?-???:?::.;:: ?/.. ??:?::............ .......:~ ~I. ~j?.ijjjjj:r.:-?:::::jjj ;;i::j:?:?:?:?:::r;~~~~:?:?::::::: ??~~~~:~~~ti~:~i~ ~ ~l~iiij~~iii.... ....... ~~ ~~?1~~~~~::j::jjjjjjjj::?~~~~~~~~~~~~la:~~~:`j:............ !:::?:?:?:?:?:?.i?:?~~?~~?:?:?:?~C??:.:?r :::::::::?~::j:i~::::::........ ....... ~:?:?:?:?:::j::~::::::::::~%:::::::?~:?; I::::::::::::i:~::::::::5 4 </p><p>i~:-i~fj~j~.j::::::........ .....:: .......... ...... . .....j::~:i~ ~ 521~i~ ~:? ... ....... . ......... ..... .?: ~~:?:?~~?~i?;?:?:?;?;?C4::?:?:?::~~~~~~1~:5 52 :l:l?:~~'TT :::2~~~~;-~~~i;:?.~~~~??:"?:-~~~~~?;j:: ?~~~~?:i </p><p>j........... </p><p>variable (Fig. 2). </p><p>This content downloaded from on Sat, 26 Oct 2013 05:11:05 AMAll use subject to JSTOR Terms and Conditions</p></li><li><p>D. N. MCVEAN 449 A native species of stream and lake sides and on many flush soils and soils of impeded </p><p>drainage throughout the British Isles. I. Geographical and altitudinal distribution. Occurs in all the vice-counties of the </p><p>British Isles, but only as a planted tree in Shetland. Noted as' not common' in Cambridge- shire and parts of Oxfordshire but abundant elsewhere, its frequency increasing towards the high-rainfall areas of the north and west (Fig. 1). From sea-level to 400 ft. (122 m.) in Arran, 1600 ft. (488 m.) in the Cairngorms (Schlich, 1925), 950 ft. (289 m.) in the north of England (Alt. range Br. P1.), 1200 ft. (366 m.) in West Inverness and Sutherland. </p><p>150 </p><p>E </p><p>100 </p><p>S 52 53 54 55 56 57 58 59 N. Lat. </p><p>Fig. 2. Variation of catkin length with latitude in the British Isles, the standard deviation of the population means being represented by the length of the vertical lines. (Similar figures have been prepared for variation with longitude, and for leaf size variations.) </p><p>Extends through most of Europe except the Arctic, the Mediterranean region (including Sardinia), and the Russian steppes. Also in Asia Minor and North Persia south to 37? 25'. In Sierra Morena in Spain south to 38?. Also West Siberia and North Africa (Tansley, Br. Isl., Hegi, Fl. 3, 95). Distribution classified as 'Boreomeridional Sub-montane Oceanic' by Meusel (1943). From sea-level in the Baltic and Mediterranean regions to 289 m. in Norway, 760 m. in Bavaria, 1300 m. in the Tyrol and in Greece, 1800 m. in the Oberengadin and the Caucasus (Hegi, Fl. 3, Rikli, 1943-8). </p><p>Especially abundant as pure alderwood or carr in the Norfolk Broads, and as mixed alder-birch and alder-ash wood in the region of the Great Glen of Scotland. Also in Pennine and Welsh oakwoods, Donegal woodland, Caithness birchwoods, etc. (Tansley Br. Isl.). </p><p>29.2 </p><p>This content downloaded from on Sat, 26 Oct 2013 05:11:05 AMAll use subject to JSTOR Terms and Conditions</p></li><li><p>450 Alnus glutinosa II. (a) Climatic and topographic limitations. Boundary of its Eurasian distribution </p><p>shows close correspondence with the 20 in. (51 cm.) isohyet in south and east. There is little correlation with isotherms or seasonal rainfall. The factors limiting the northward distribution are not clear, nor are the stages of the life cycle at which the limitations operate. In Scandinavia it appears to be limited by the duration of low winter temperature, since it does not extend to those regions having a minimum of 6 months of mean daily temperature of 0? C. or less. At its most northerly station at the head of the Gulf of Bothnia the height of the tree is 12 m. and it bears viable fruit there (Kujala, 1924). </p><p>Groszman &amp; Melzer (1933) give data on climates endured by the species in Eastern Europe. </p><p>Often described as a warmth-demanding species, but this can only be relative to the birches and A. incana. Soil moisture would seem to exercise more control over local and regional distribution than atmospheric humidity. </p><p>In west Britain and Ireland resistant to wind exposure and possibly to a moderate amount of salt spray since it is planted in coastal wind-breaks. </p><p>Not topographically limited to stream sides and low lying, badly drained areas provided rainfall is high. </p><p>Gives straight-boled trees only in moderate shelter, but exposed crowns, though gnarled, are not usually wind cut. Wind-cut forms and die-back of branches have been seen in the hills and at the coast of North Wales and in the Isle of Skye. </p><p>Many alderwoods in the Scottish Highlands are found on south- and west-facing slopes while north-facing slopes carry only stream-side trees. </p><p>Very sensitive to shading, the seedling less so but still requiring a higher light intensity than those of larger-seeded trees, so that internal regeneration of the woodland is prac- tically unknown. </p><p>(b) Substratum. Largely indifferent to the parent material of its soils. Sendtner reports that in Bavaria A. glutinosa and A. incana occur by stream margins, the former in siliceous areas, the latter in calcareous regions, but that, where A. incana is absent, A. glutinosa is 'certainly not a calcifuge' (Lebensg. 1). Alder is absent from the calcareous drifts of Caithness, its place by stream-sides being taken by Corylus avellana. It does occur on the siliceous drifts (Crampton, 1911). </p><p>Trees and saplings may exhibit chlorosis on calcareous soils, e.g. on the chalky boulder clay of East Anglia. </p><p>Restricted to the unstable soils of stream and lake margins, recent alluvia, flush soils and those of impeded drainage or seasonally wet on hill slopes and to hydromorphic meadow soils on the flat. Occurs on deep fen peat or the acid peats of, for example, Molinia-Myrica bog, but not on blanket or raised bog. Profiles are generally those of hydromorphic meadow soils and gleys with or without peat layer. Water-table may be at, or close to, the surface at all seasons, and regeneration then tends to be abundant but the trees are shrubby and badly grown. Water-table often sinks well below the surface during summer months and tree growth is then better. Seedlings will only establish on a soil surface that comes within the capillary'fringe of the water-table so that the surface layers remain continuously moist for 20-30 days in the period April-June. In regions of high summer rainfall the water-table does not dominate the situation in the same way. </p><p>Worms and usual soil fauna absent from the wetter soils. Soils oxidizing and with </p><p>This content downloaded from on Sat, 26 Oct 2013 05:11:05 AMAll use subject to JSTOR Terms and Conditions</p></li><li><p>D. N. MCVEAN 451 </p><p>nitrate in summer, tending to be reducing in winter and without nitrate; pH&gt; 38 (Pearsall, 1938). Godwin &amp; Turner (1933) record soil surface pH of 4-6-7-0 over the range of alder growth in the succession at Calthorpe Broad. </p><p>Table 1 presents results of the analysis of some alderwood soils. </p><p>Table 1. Soil analysis (a) Conway Valley, North Wales. Data kindly supplied by R. E. Hughes; analysis by H. Hagger. </p><p>Ca (p.p.m.) mg P205/100g. K (p.p.m.) (1) Seasonally wet gley 2312-5 3-3 485-0 (2) Equably moist site 1250-0 0-2 85-0 (3) Permanently wet gley 1012-5 0-6 20-0 (4) Seasonally wet gley </p><p>0-6 in. (0-15 cm.) 1087-5 2-2 150-0 6-12 in. (15-30 cm.) 1037-5 2-1 50-0 12-15 in. (30-37-5 cm.) 662-5 2-0 25-0 C horizon 850-0 1-9 25-0 </p><p>(b) Scottish sites: (i) open wood on slopes of Meall a' Bhata, Sutherland (a free-draining brown earth with seasonally wet gley in places); (ii) dense wood on alluvial fans, Glen Nevis, Inverness-shire. (Free drainage); (iii) as (ii); (iv) alder scrub on Molinia-Myrica bog, Glen Nevis. (Permanently wet peat.) All samples composite to a depth of 9 in. (17-5 cm.). Analysis by D. Thomson. </p><p>Mechanical analysis (%) </p><p>Loss on Coarse Fine pH Ex. CaO (%) ignition (%) sand sand Silt Clay </p><p>(1) 5-13 0-0360 24-64 31-52 26-96 6-79 6-09 (2) 5-14 0-0184 6-26 (3) 6-66 0-0140 9-50 (4) 5-12 0-1282 45-67 - </p><p>Table 2. Soil tests at Chippenham Fen Tests </p><p>Diphenylamine Sapling Misra-Comber Sulphide sulphate </p><p>1 Surface 0/0 0/0 0/0 30 cm. 1/4 2/4 1/4 </p><p>2 Surface 0/0 0/0 0/0 30 cm. 0/4 0/4 0/4 </p><p>3 Surface 0/0 0/0 0/0 30 cm. 0/4 0/4 0/4 </p><p>Table 2 gives the results of some soil tests carried out at Chippenham Fen, Norfolk, in the neighbourhood of the saplings described in VI(a). The tests are as described by Pearsall &amp; Mortimer (1939), and results show that the saplings were rooted in a reducing substratum though nutritional rootlets were confined to the oxidizing surface layers. </p><p>III. Communities. Occurs with oak, ash, birch and willow, particularly the last three, forming ash-alder wood on low-lying ground of high soil fertility and moisture, alder- willow thickets in areas liable to seasonal flooding, and alder-birch wood on higher-lying less fertile, generally acid soils in the north and west of Britain (Anderson, 1950). Pure stands are of common occurrence, but are not as extensive in Britain as, for example, in north-west Germany. </p><p>The status of the alder in Quercetum is still uncertain. Tansley (Br. Isl., p. 325) states that alder occurs scattered throughout the Welsh oakwoods. In closed oakwood, alder societies in the damper places, with scattered trees by stream-sides only, is more typical. </p><p>This content downloaded from on Sat, 26 Oct 2013 05:11:05 AMAll use subject to JSTOR Terms and Conditions</p></li><li><p>452 Alnus glutinosa The species of eleven representative British alder communities are listed in Table 3. First-year seedlings and 2- to 3-year-old plants of up to 5 cm. in height are frequent in </p><p>some woods but complete internal regeneration is seldom seen. Regeneration tends to be peripheral, or...</p></li></ul>