Fiby urskog soils topography and zonation of a Swedish primitive boreal forest

The majority of northern hemisphere forests have now been heavily influenced by humans, so those such as Fiby urskog (Hytteborn and Packham, 1985; Fig. 2.7) which have been relatively little affected in this way, are especially interesting in showing local natural zonation and variation of forest vegetation. Though the highest parts of the reserve are now 60-65 m above mean sea level, they were exposed to wave action when the land first emerged from the sea, so drift and other sediments were washed down from the present hilly areas. Coarser down-washed sediment is now present amongst the huge granite boulders, while silt and clay occur lower down. Peat formed later. The hill

Boreal Forests First Level Consumers

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Topography Boreal Forest
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Forest dominated by Norway spruce, but with some Scots pine and a few scattered aspen and birch, both silver Betula pendula and downy B. pubescens.

Hallmarkstallskog: granite ridge system dominated by Scots pine but with downy birch and small fragments of mire vegetation also.

Downy birch forest on peat with some alder. Norway spruce is invading while willow species are dominant along the lake margin.

Scots pine dominant on peat.

Minerotrophic mire. Rich fens surround Fibysjon. The small areas in the forest are of poor fen, sometimes with scattered spruce and birch.

gj Scots pine-Labrador tea Ledum palustre bog (ombrotrophic mire).

Figure 2.7 The primitive forest of Fiby urskog, which lies 16 km west of Uppsala, central Sweden, in an area underlain mainly by the Precambrian Baltic Shield of granite and gneissic crystalline rocks. The reserve consists of 65 ha of forest and 13 ha of the lake to the north of it, whose surface is normally some 40 m above mean sea level. T1 is the midpoint of the N-S transect shown in Figs 2.9 and 2.10; 1-5, positions of the forest relev^s described in Fig. 3.3. Sernander's Plot 1 (see Fig. 9.10) was in the southwest of the area dominated by spruce. (Data of Hytteborn and Packham.)

slopes and lower areas are dominated by Norway spruce Picea abies growing on boulder moraine, glacial till and later sedimentary deposits, while Scots pine Pinus sylvestris is the most important tree in the relatively open forest on drier granitic sites of the central area. Shallow soils of low nutrient quality in depressions in the granite have mire vegetation with hare's-tail cottongrass Eriophorum vaginatum, Labrador-tea Ledum palustre, cowberry Vaccinium vitis-idaea and bog moss Sphagnum spp. Outside the depressions, and with the exception of well-worn paths, the granite under the trees is usually covered by a cryptogamic mat of lichens and mosses (see Fig. 2.8). Cryptogams are

Fiby Urskog

Figure 2.8 A young Scots pine established in the cryptogamic mat on Lichen Hill, Fiby urskog. This figure shows part of a 0.25 m2 quadrat dominated by the lichen Cladina arbuscula; other important species were Cladonia uncialis, C. gracilis, C. squamosa, Cladina stellaris and the acrocarpous moss Polytrichum juniperinum. In total ten lichen and two moss species were recorded in this quadrat. (Photograph by John R. Packham.)

Figure 2.8 A young Scots pine established in the cryptogamic mat on Lichen Hill, Fiby urskog. This figure shows part of a 0.25 m2 quadrat dominated by the lichen Cladina arbuscula; other important species were Cladonia uncialis, C. gracilis, C. squamosa, Cladina stellaris and the acrocarpous moss Polytrichum juniperinum. In total ten lichen and two moss species were recorded in this quadrat. (Photograph by John R. Packham.)

plants reproducing by spores rather than seeds; they include the ferns and fern allies. The area of mature forest occupied by broadleaved trees and shrubs is low, though several species are present, including the normally more southern wych elm Ulmus glabra and small-leaved lime Tilia cordata. The uneven size and age structure, rotting logs and standing dead trees are all typical of primeval (= old growth) forest.

The lake to the north of Fiby urskog is humic and dystrophic (very acidic and lacking in important mineral nutrients); it is fringed by wetland vegetation including willows such as the grey Salix cinerea, bay S.pentandra, and creeping S. repens. Plants with the hydrophytic and helophytic life forms described in Section 3.1.1 grow here. At the western margin of the reserve is a small stream with a tract of seral birchwood growing on peat along its eastern edge. This developed after the dam at the southern end of the reserve fell into disrepair in the 1930s, allowing the water level of the stream to fall. Understorey vegetation shows an equally clear zonation around the site. Dwarf shrubs such as heather and bilberry are common in drier areas while mosses (Hylocomium splendens, Plagiothecium curvifolium, Pleurozium schreberi, Ptilium crista-castrensis and various Dicranum species) are prominent in the ground cover of the spruce forest. Wavy hair-grass often has its tillers well scattered in this moss layer but also does well in drier reasonably open areas. There is a good deal of variation on a small-scale creating a mosaic structure (see Section 6.4.3); within the cryptogamic mat adjacent 0.01 m2 quadrats often show appreciable differences.

It is important to bear in mind that this zonation is not static. Long-term weathering and soil development, together with climate change (natural or otherwise), will lead to changes. In the shorter-term, successional changes are also important: the mature spruce forest is prone to tree-loss by storms, creating gaps which are recolonized (described in Section 9.3), and spruce is becoming increasingly important in the streamside birchwood.

The above description may tend to imply that forest types are uniform with sharp boundaries. In practice even a particular community such as spruce forest is far from uniform across its area; all the plants within it are responding individually to their immediate environments. This is illustrated by the transect in Fig. 2.9, a 1-m wide strip, recorded on a slope in the spruce forest; see also Fig. 2.10 which shows the main features of the canopy, positions of tree trunks and fallen logs. It can be seen that topography and soil conditions strongly influence distribution patterns of herbs and dwarf shrubs along the transect. Thirty-one species were recorded along the transect (only some of which are shown in the figure) with species density being highest near the bottom of the slope. Some species (such as wood horsetail) are very restricted

Soil Sweden Maps

Figure 2.9 Transect 1 at Fiby urskog along a sloping area of old-growth spruce forest. The diagram shows: (1) abundance values (using the Domin scale) for the major field layer species: wood horsetail Equisetum sylvaticum, wood anemone Anemone nemorosa, wavy hair grass Deschampsia flexuosa, twinflower Linnaea borealis, May lily Maianthemum bifolium, small cow-wheat Melampyrum sylvaticum, raspberry Rubus idaeus, bilberry Vaccinium myrtillus and cowberry V. vitis-idaea; (2) the percentage of ground covered by bryophytes within each m2 quadrat; (3) the difference between the soil pH at 0-3 and 10 cm depth (the dot for each quadrat is placed at the value for the surface soil so it is easy to see which of the two values for a particular quadrat was the greater); (4) species density per m2; (5) topographic profile; (6) the indicator species groups to which the stands belong (see text). (Data of Packham, Hytteborn and Moberg. From Packham et al., 1992. Functional Ecology of Woodlands and Forests. Chapman and Hall, Fig. 4.10. With kind permission of Springer Science and Business Media.)

Boreal Forest Hill
Figure 2.10 Fallen trunks, tree and shrub canopy in the forest area surrounding Transect 1, Fiby urskog. Paired marks at the top and bottom of the map show

in their distribution, while others such as bilberry and May lily are less exacting in their requirements and consequently more widespread along the slope. Variation in the distributions of the 31 species present has been used to divide the quadrats observed in the field layer vegetation into successively smaller groups using the statistical technique of indicator species analysis (Hill et al, 1975). This creates 'polythetic' groups, so called because all the species data available are taken into account.

The six major polythetic groups identified along the transect in Fig. 2.9 run smoothly from the bottom of the hill in a sequence given the numbers 010,011, 001, 000, to 11 and 10 towards the top. This is a hierarchical grouping: the first digit shows that the first four groups (Group 0) are quite different from the last two (Group 1). Within Group 0, the second digit shows that the first two groups (010 and 011) are different from the second two (001 and 000), and each of these groups is finally subdivided by the last digit. Indicator species for Group 0 are wood anemone, oak fern Gymnocarpium dryopteris, twinflower, hairy wood-rush Luzulapilosa, chickweed-wintergreen Trientalis europaea and bilberry. Wood anemone is found only in Group 0, and is therefore an excellent indicator. Though not such a good indicator, bilberry is considerably more likely to be found in Group 0 than Group 1. Common cow-wheat Melampyrum pratense, small cow-wheat and raspberry are indicators for Group 1, which dominates the upper southern portion of the transect where the field and bryophyte layers are rather open. Soil conditions vary considerably here; the lowest quadrats (1-9 m) have a shallow peat layer resting on clay with the clay continuing until 14 m. The lower slopes are the most moist and this favours higher species density, though this is reduced by the very marked shade exerted by small spruces at the bottom of the hill. Low boulders are prominent from 24-59 m.

A number of species grow in very distinct habitats, for example downy willow Salix lapponum is found on a quaking mire, while the liverwort Ptilidium

Caption for Figure 2.10 (cont.)

the position of the metre-wide strip recorded for herbs and dwarf shrubs. The star marks the mature spruce (no. 7), released by the great storm of 1795, whose increment diagram is shown in Fig. 9.11. Numbers 1-8 refer to spruce whose diameters at 1.3 m (= breast height) in cm, heights (m), and estimated age in years are as follows 1: 4.6, 6, 37; 2: 8,12,110; 3: 50,30,132+; 4:42.6,28, 167; 5, 46.6, 30, 181; 6, 35.5, 28, 170+; 7: 35, 26, 166+; 8: 35, 30, 144+; 9: 64, 30, 160 (aspen). (Data of Packham, Hytteborn, Claessen and Leemans. From Packham et al., 1992. Functional Ecology of Woodlands and Forests. Chapman and Hall, Fig. 4.11. With kind permission of Springer Science and Business Media.)

pulcherrimum occasionally occurs on rock and is frequent on fallen trunks and wood. The larger P. ciliare is fairly common in the bryophyte mat.

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