Artikkelit jotka sisältää sanan 'ordination'
Raakahumuksen ja kasvillisuuden yhteisvaihtelu Pohjois-Hämeen vanhoilla ojitusalueilla.
English title: Covariation between raw humus layer and vegetation on peatlands drained for forestry in western Finland.
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The occurrence of raw humus layer and its relationship to the structure of the vegetation and the environmental variables were studied on 501 sample plots located systematically in drained peatland forests. The drainage had been done in the 1930s – 60s. The correlation between the amount of raw humus and the two-dimensional GNMDS (global nonmetric multidimensional scaling) ordination space was 0.57. The thickness of the raw humus layer increased in the direction of the drainage succession gradient. The correlations between the thickness of the raw humus and the measured environmental variables were weak. The strongest correlation was with the stand volume (0.31) and the drainage age (0.21). Weakness of these correlations was most probably due to the regressive succession on many plots. On average, the raw humus layer was thickest , 6.5 cm, in Vaccinium vitis-idaea transformed type I (developed from genuine forested mires) and 5.4 cm in type II (developed from treeless or composite types). In Vaccinium myrtillus types the corresponding mean thickness was 5.2 cm (I) and 3.2 cm (II) and in dwarf-shrub types 3.3 cm (I) and 4.6 cm (II). The secondary succession is slower and the amount of the needle litter (of Pinus sylvestris) smaller in the dwarf-shrub type than in the V. vitis-idaea type. In the V. myrtillus type the origin of the litter is more dominated by deciduous trees, the decomposition faster and the coverage of Pleurozium schreberi clearly smaller than in the nutrient-poorer types. P. schreberi tolerates the litterfall well and together with especially conifer litter, and maybe with slow decaying fine roots, too, it forms a loose raw humus layer on old drained peatlands. Being a poor germination bed, the raw humus makes successful stand regeneration difficult.
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Saarinen,
The Finnish Forest Research Institute, Parkano Research Station, Kaironiementie 54, FIN-39700 Parkano, Finland
Sähköposti:
ei.tietoa@nn.oo
- Hotanen, Sähköposti: ei.tietoa@nn.oo
Kasvillisuuden sukkessio ja monimuotoisuus Teuravuoman koeojitusalueella Pohjois-Suomessa.
English title: Vegetation succession and diversity on Teuravuoma experimental drainage area in northern Finland.
Avainsanat:
fen;
aapa mire;
compositional gradients;
FUPGMA classification;
GNMDS ordination;
peatland vegetation
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This case study deals with the effects of forest drainage on six mire site types represented by 33 permanent sample plots within a Finnish aapa mire complex located in north boreal vegetation zone. We analysed the main compositional gradients, the abundances of plant species and the diversity of vegetation. The vegetation descriptions were made about at the time of drainage in 1933 and after that in 1943, 1950 and 1994. The forest drainage emphasized the importance of spruce mire and hummock-level bog influences (mire margin and mire expanse effects respectively) in controlling the structure of plant communities. The change of plant community was greatest on fertile mire site types, also spruce mire influence promoted the secondary succession. As expected, the shallow-rooted and/or demanding flark-level vascular plants and (eutrophic) fen mosses had not been able to adapt to the ground water level drawdown. At first, after drainage, species number, Shannon's H' and Simpson's D increased: many mire species of hummock and intermediate level microsites had increased while also pioneer and forest species had colonized the plots. By 1994, however, as the mire species were decreasing these measures had turned to decline except on the (most) infertile site types. Pielou's J' and the evenness based on D reacted vaguely, decreasing a little, though, from 1933 to 1994. Thus, in such cases the dominance in the vegetation had increased. The beta-diversity describing here the differences between plant communities (or site types) decreased along with the hydrological conditions becoming more uniform after drainage.
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Hotanen,
The Finnish Forest Research Institute, Joensuu Research Station, P.O.Box 68, FIN-80101 Joensuu, Finland
Sähköposti:
ei.tietoa@nn.oo
- Nousiainen, Sähköposti: ei.tietoa@nn.oo
- Paalamo, Sähköposti: ei.tietoa@nn.oo
Eteläsuomalaisten metsaojitettujen turvemaiden kasvillisuuden numeerinen ryhmittely.
English title: Post-drainage development of vegetation in southern Finnish peatlands studied by numerical analysis.
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The vegetation data from virgin and corresponding drained mire site types collected by Juhani Sarasto in the 1950's were reanalyzed using DCA and TWINSPAN. The main gradient in the material was a complex gradient called the mire margin-mire expanse -effect. During secondary succession, after forest drainage, the variation of mire site types diminished as the importance of hydrology decreased. The difference between the vegetation of treeless plus composite and forested mire site types could still be detected after the site types had reached the drained peatland forest type phase in their post-drainage succession.
Keywords: Classification, ordination, succession
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Hotanen,
The Finnish Forest Research Institute, Joensuu Research Station, P.O. Box 68, SF-80101 Joensuu, Finland
Sähköposti:
ei.tietoa@nn.oo
- Vasander, Sähköposti: ei.tietoa@nn.oo
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