Artikkelit jotka sisältää sanan 'temperature'

Wood production capacity on drained peatlands depends on the site type and temperature sum. Site type is closely related to the peat total nitrogen concentration. This study aims at clarifying the effect of peat nitrogen, fertilization and refertilization on the foliar nitrogen concentration of Scots pine in different temperature sum conditions (850, 950 and 1080 d.d.) on peatland sites with a wide peat nitrogen gradient (0.79- 2.80% in the 0-10 cm layer). In the coldest region, regardless of the peat total nitrogen concentrations in the 0-10 cm surface peat layer and PK- fertilization or PK-refertilization (37 and 26 years earlier respectively), the needle nitrogen concentrations were mostly below the severe deficiency limit (N = 1.2%) and also the arginine concentrations revealed a nitrogen shortage (<0.5 mg g-1). In the middle region the mean nitrogen concentrations in the needles were clearly higher and in the PK- fertilization and PK-refertilizations (32 and 22 years earlier respectively) surpassed the slight nitrogen deficiency limit (N = 1.3%). Also the arginine concentrations surpassed the deficiency limit (0.5 mg g-1 ) in both fertilization treatments although the mean arginine concentrations were near or under the deficiency limit. In the warmest region 25-26 years after the spot fertilization the mean nitrogen concentration was 1.84% and the arginine concentration was 3.04 mg g-1 revealing a surplus of nitrogen caused by phosphorus and potassium deficiencies. The PK-fertilization given 10 years later decreased the nitrogen concentration to 1.56% and the arginine concentration to 0.58 mg g-1. In the more favourable conditions the nitrogen and arginine in the needles increased when the nitrogen in the peat increased. In conclusion, tree growth in the middle and the warmest temperature sum region would respond to PK-refertilisation above a certain total peat nitrogen level but in the coldest temperature sum region tree growth would not respond to PK-refertilization in any of the studied peat total nitrogen conditions because of nitrogen deficiency.

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

Methane production and consumption in drained minerotrophic and ombrotrophic peat was investigated using a combination of field measurement and laboratory incubations. In the field, methane fluxes were measured at intervals over a seven (minerotrophic) and ten (ombrotrophic) month period together with measurements of methane concentrations and temperature at various depths. In the laboratory, aerobic incubations of drained peat samples from various depths were conducted over a range of temperatures to determine rates of potential methane oxidation. The maximum potential methane oxidation rate occurred at a depth close to that of the water table. The oxidation rate was much higher in the ombrotrophic peat than in the minerotrophic peat. However, field measured methane fluxes were lower in the minerotrophic peat. This is attributed to a relatively low water table. Methane oxidation increased over the temperature range 2 to 30°C and decreased at temperatures >34°C. Methane production in the aerobic incubation experiment was measured by inhibition of methane oxidation with dimethyl ether. Production rates were only 1-7% of net oxidation rates. Thus, the measured net rates of methane absorption in aerobic incubations largely reflect gross oxidation rates. Keywords: Bog, fen, temperature, water level

• Lien, Department of Biotechnological Sciences, Agricultural University of Norway, P.O. Box 5040, N-I432 Aas, Norway Sähköposti: ei.tietoa@nn.oo
• Martikainen, Sähköposti: ei.tietoa@nn.oo
• Nykänen, Sähköposti: ei.tietoa@nn.oo
• Bakken, Sähköposti: ei.tietoa@nn.oo

Perhaps the most important function of the fine root system of forest trees is in the uptake of water and mineral nutrients. To perform this function adequately, the root system must be extensive and active enough to meet the needs of the canopy. Literature indicates that fine root production is substantial and that the seasonal pattern of fine root production is different from that of foliage production. Carbon incorporation into the soil in the form of dead roots is an important pathway in the total carbon flow through forest ecosystems. Root growth is sensitive to various climatic factors which are often imposed or strengthened by human activities. Factors that lead to growth suspension may or may not be the same as those that result in root shedding or senescence. The use of minirhizo-trons to study fine root dynamics means that ecologists are no longer justified in claiming that below-ground production is impossible to quantify in forest ecosystems. Keywords: Carbon budget, fine root production, liming, fertilization, minirhizotron, mycorrhiza, root tip, soil temperature, soil water

• Persson, Department of Ecology and Environmental Research, Swedish University of Agricultural Sciences, Box 7072, S-750 07 Uppsala, Sweden Sähköposti: ei.tietoa@nn.oo