Artikkelit jotka sisältää sanan 'nutrient status'

Phosphorus and potassium deficiencies are common in Scots pine stands growing on drained peatlands. In this study, the foliar nutrient concentrations and stand growth were monitored after the application of phosphorus and potassium fertilisers of different solubility in four experiments on thick-peated drained peatlands in northern central Finland. The studied stands involved three fertilisation treatments: (i) unfertilised control, (ii) rock phosphate and potassium chloride, and (iii) apatite and biotite. The growth of stands was monitored 20–25 years after the fertilisation. Needles were sampled four times: 4–9, 11–14, 16–19 and 21–24 years after the fertilisation. According to foliar analyses, the trees on the control plots suffered from severe phosphorus and potassium deficiencies. Rock phosphate and apatite fertilisation increased the foliar phosphorus concentrations above the deficiency limit, and the effect was still noticeable 21–24 years after the application. Both potassium sources, that is, the slowly soluble biotite and the water-soluble potassium chloride increased the foliar potassium concentration to an adequate level. Potassium chloride increased the concentrations faster and stronger than biotite during the first years (4–9) after the applications. The situation was reversed when 11–14 years or more had passed from the fertilisation: the biotite fertilised stands had higher potassium concentrations. The fertilisation treatments decreased the foliar nitrogen, zinc, manganese, copper and boron concentrations. The fertiliser applications increased the stand volume growth considerably. Raw phosphate and potassium chloride increased the volume growth significantly already during the first five-year period. The effect of the apatite and biotite treatment was weaker during the first 10 years, but became stronger with time. During the period 19–24 years after the fertilisation, the stand growth on the biotite plots was equal to that of the plots fertilised with potassium chloride. However, during the whole study period the differences between the treatments remained insignificant. The results showed that slowly soluble apatite and biotite are suitable sources of phosphorus and potassium for pines on drained peatlands. However, to avoid boron deficiency, also boron should be added simultaneously.

• Moilanen, Finnish Forest Research Institute, Muhos Research Station, Kirkkosaarentie 7, FIN-91500 Muhos, Finland Sähköposti: ei.tietoa@nn.oo
• Pietiläinen, Sähköposti: ei.tietoa@nn.oo
• Issakainen, Sähköposti: ei.tietoa@nn.oo

Methane fluxes were measured using a static chamber technique on a minerotrophic fen and an ombrotrophic peat bog site located on the Lak-kasuo mire complex in central Finland. Both sites consisted of a virgin area and an area drained in 1961 by ditching. The measurements in 1991 were made biweekly from spring thaw to winter freezing. During this period, the mean CH4 emission from the virgin minerotrophic site and virgin ombrotrophic site was 98 mg m-2 d-1 and 40 mg m-2 d-1 , respectively. The mean emission of CH4 from the drained ombrotrophic site was 18 mg m-2 d-1. The drained minerotrophic site consumed methane during most of the measuring period, the average uptake was 0.13 mg m-2 d-1. Draining had lowered the average water table by 4 cm at the ombrotrophic site and by 20 cm at minerotrophic site. The possible reasons for the different development of the water table and methane fluxes at ombrotrophic and minerotrophic sites after draining are discussed. Keywords: Drainage, methane flux, methane oxidation, nutrient status, peat soil

• Martikainen, Department of Environmental Microbiology, National Public Health Institute, P.O. Box 95, FIN-70701 Kuopio, Finland Sähköposti: ei.tietoa@nn.oo
• Nykänen, Sähköposti: ei.tietoa@nn.oo
• Crill, Sähköposti: ei.tietoa@nn.oo
• Silvola, Sähköposti: ei.tietoa@nn.oo

Former and present peatland forestry studies by the Department of Forest Soils of the Swedish University of Agricultural Sciences (Umeå) are presented, based on a tour to field experiments in north, mid and south Sweden. Up to the 1970s, major interest was paid to the nutrition of drained, originally treeless or sparsely treed fens and bogs. Several fertilization experiments since the first wood ash trials in Norra Hällmyren have indicated the necessity of P and K application to ensure afforestation and satisfactory growth of Scots pine on such sites. Silvicultural problems on drained peatlands, such as regeneration on highly productive peatlands, planting techniques, commercial thinnings, as well as gas exchange in peat and the distribution of nutrients in a peatland forest ecosystem are the focus of a large-scale project started in 1985. The preliminary results of the regeneration experiments, i.e. the effectiviness of spruce shelter wood (140-200 trees per ha) against frost damage during the growing season, are discussed. A brief description of the present classification and post-drainage site index system for peatlands is also given. Keywords: Classification, drainage, nutrient status, regeneration

• Hökkä, Finnish Forest Research Institute, Rovaniemi Research Station, P.O. Box 16, SF-96301 Rovaniemi, Finland Sähköposti: ei.tietoa@nn.oo
• Penttilä, Sähköposti: ei.tietoa@nn.oo