fulltext - DiVA

56HUGO SJORS·the growth of deciduous trees and shrubs), and thefew existing pines and multistemmed spruces lookas poor and non-reproductive as before. See furtherSELANDER (1914), RoMELL (1915, 1921), Du RIETZ(1925d, 1948 b, 1950d) and ALMQUIST (1929, withmap p. 500).CoNIFEROUS FOREST.-As stated above, the coniferousforests nearly always prevail in this region.Spruce covers a larger area than pine, but mixedstands are also common. The pine (Pinus silvestris)is supreme on rocky ground, on the marginal partsof acid mires and on most gravelly or sandy sediments.It also regenerates well on clear-cut areas,where seed-trees can be left (this is not practicalwith spruce), and grows faster than the spruceduring the first twenty years or so. At a later stage,spruce may take the lead, and in certain areasspruce may even regenerate between the stems of apine forest. On all nutrient-rich soils, and even onmesic soils of modest nutritional status, spruce ispreferred as it is in these sites the more productivespecies, which after having reached an age of abouttwenty to thirty years, starts to grow faster thanother trees on these soils.It is to be regretted that very few studies havebeen made on the sociology of coniferous forests insouthern Sweden. This trivial vegetation withineasy reach does evidently not attract analyticalinterest very much, possibly because some of itstypes are easy to observe and therefore are alreadysuperficially known without close study. However,there are some studies from Uppland {ALMQUIST1929, v. KRUSENSTJERNA 1945). Mainly developmentalstudies from the old, now fairly natural(but hardly strictly primeval) "Fiby urskog" to .the NW of Uppsala were published by SERNANDER(1936).Among the principal communities (on the associationlevel, but often with a complex sub-structure)a few may be mentioned. The sociologicaldesignations are tentative only.Pineto - Rhacomitrietum lanuginosi or pinewoodon acid rock is a complex type of vegetation, for itincludes several successional stages growing on therock surfaces and leading to ·humus-inhabitingRhacomitrium lanuginosum cushions usually colo-.Acta Phytogeog1·. Suec. 50nized by Cladonia rangiferina, silvatica (sens. lat.),alpestris or uncialis in their middle. The final stageof a continuous Cladonia mat is usually not reached,because on exposed sites the cushions becomedetached and blow away, so the succession has tobegin anew on bare rock. Mats of the same Cladoniasand a sparse field layer of Calluna vulgaris, Arctostaphylosuva-ursi, etc., grow on shallow mineralsoil, and on moist deep, almost peaty soil in fissures,spec!es of mesic woodland and even bog speciesoccur (e.g. Ledum palustre, Vaccinium uliginosum,. Sphagnum nemoreum and parvifolium). The pines .are typically low and stunted and grow extremelyslowly on account of inadequate soil volume forrooting and periodical water deficiency. This typeof vegetation is very common in the eastern partsthat have such an abundance of clean-washed rock.See also v. KRUSENSTJERNA's and SKYE's papers.Floristically very similar but growing on gravellyor sandy soil is the lichen-pine forest (Pineto ­Cladinetum), which is quite widespread in theinterior. It lacks the epilithic component, however,and only in extreme cases is the lichen mat developedwithout a field layer. The forest stand growsslowly but attains medium height. It consistsusually almost exclusively of pine, and regeneratesfreely after clear-felling.Pineto -Vaccinietum vitis-idaeae or whortleberrypineforest has a bottom layer with alternatinglichens and bryophytes (mainly Pleurozium Schreberiand Dicranum rugosum =undulatum), andthe field layer is often well developed. This isusually a productive kind of forest. It merges intoricher types with, e.g., Pteridium aquilinum orCalamagrostis arundinacea, species that are bestdeveloped after cutting or thinning and in areasearlier used as pastures.Piceeto - Vaccinietum myrtilli or bilberry-spruceforest is the prevailing kind of forest on mesic soilwith a typical mor humus layer. Although not sopredominant as in the north, it is very widespreadin the Boreo-nemoral zone, too. The forest standis either formed by spruce exclusively or has pine,birch, oak or other trees mixed in. The undervegetationis usually dominated by Vacciniummyrtillus with constant presence and occasionaleo-dominance of V. vitis-idaea or Deschampsia