Artikkelit jotka sisältää sanan 'secondary succession'
Fosforin ainekierto rämemännikön puustossa ja pintakasvillisuudessa ojituksen jälkeen.
English title: Post-drainage dynamics of P uptake by trees and ground vegetation in Scots pine dominated peatlands.
Avainsanat:
mire;
secondary succession;
ecosystem functioning;
drainage for forestry;
nutrient cycling;
nutrient upatake;
Pinus sylvstris
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We investigated long-term dynamics of phosphorus (P) in ground vegetation, tree stand biomass and litterf all in two undrained and four drained oligotrophic pine fens in southern Finland. The study sites, which encompassed observation periods up to six decades after drainage, were chosen to form a chronosequcncc of sites initially similar floristically, showing different stages of the forest succession induced by drainage. The pattern of P allocation to above- and below-ground plant biomass followed the changes in growth form dominance from mosses, graminoids and shrubs to trees. Overall, net vascular plant uptake of P increased after drainage and remained on a higher level compared to that in the pristine fen. The amount of P in the drained ecosystem seems to remain high enough to support the uptake and continuing forest succession.
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Laiho,
Peatland Ecology Group, Department of Forest Ecology, University of Helsinki, P.O. Box 27, FI-00014 Helsinki University, Finland
Sähköposti:
ei.tietoa@nn.oo
- Penttilä, Sähköposti: ei.tietoa@nn.oo
- Vasander, Sähköposti: ei.tietoa@nn.oo
- Laine, Sähköposti: ei.tietoa@nn.oo
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
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