Browsing by Subject "biomassatuotos"

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  • Kuuluvainen, Timo (Suomen metsätieteellinen seura, 1989)
  • Pulkkinen, Pertti (Suomen metsätieteellinen seura, 1991)
  • Sormunen, Janne (Helsingin yliopisto, 2014)
    Boreal peatlands are diverse ecosystems and globally significant carbon sinks. Changes in environmental conditions might alter their vegetation and the amount of carbon fixation. The amount and composition of peatland vegetation is determined by air and peat temperature and hydrology. The air temperature is expected to rise on average by 1,2 – 4,8 °C, increasing the amount of droughts and lowering the water table level of fens by 8 – 14 cm. Fens may be especially vulnerable to changes in environmental conditions because they receive most of their nutrient input through groundwater flow and run-off. The aim of the research was to study the effect of warming and drying on the leaf area, phenology, leaf biomass production and composition of the plant community. The study site was an oligo-mesotrophic fen situated in central Finland. Vegetation was monitored throughout the growing season. The site was divided into a ditched area where the water table was lowered on average by 8 cm and to a pristine area where the water table remained at its natural state. Vegetation monitoring plots were warmed with plastic open top chambers. The walls were tilted inward in order to trap solar radiation inside the chamber, warming the air temperature on average by 2,3 °C. The results indicated that climate warming will affect the vegetation mostly through water level drawdown. Water table drawdown had no effect on the leaf biomass production of the whole plant community but it changed its composition. The amount of sedges remained unchanged and they continued to be the dominant plant group. Lowering of the water table increased the amount of evergeen shrubs and promoted the emergence of decidious shrubs. The amount of herbs dropped significantly because they require a more moist environment. Warming had no effect on leaf biomass production or species composition but it increased the development rate of leaf area until peak leaf area was reached. Water level drawdown on the other hand slowed down the development rate of leaf area. Together warming and water table drawdown increased the length of the growing season of sedges and the whole community. The ecosystem seems to adapt to changing environmental conditions through changes in the plant community composition, leaving the amount of leaf biomass production and carbon fixation unchanged despite the changes. The decrease of the more nutrient dependent species and the increase of species accustomed to more nutrient poor habitats might imply the beginning of gradual ombrotrophication of fens as the climate changes.