Browsing by Subject "turvemaa"

Peatlands are a significant carbon and nitrogen reservoirs, making them potential sources of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions. Variations in water table level change the oxygen content of peat, affecting the oxidation-reduction or redox state of the peat, which is known to influence the biochemical processes and thus greenhouse gas (GHG) emissions. The aim of this study was to assess the effect of controlled anoxic redox conditions and inorganic electron acceptors (TEAs) on redox potential (Eh), and N2O, CH4, and CO2 emissions. In this study during an anaerobic incubation experiment, the rates of formation of these GHGs and Eh values as a function of time were measured from drained (D) and undrained (UD) peat of three nutrient levels: mesotrophic (ME), oligotrophic (OL), and ombrotrophic (OM). Redox conditions were controlled to three levels by nitrate (NO3-), ferric iron (Fe3+), and sulphate (SO42-). In addition, measurements were performed on untreated (Ctrl) peat. The peat was in an anoxic state throughout the incubation (Eh < 300 mV) and the values were in the order of TEA reduction, even though they were mainly in the iron and manganese reduction zones, probably due to the naturally high iron content of the peat. As expected, N2O formation was highest in flasks with added NO3-, and N2O formation was weak and ceased without addition. CH4 formation was reduced in flasks with added NO3- or SO42-, and SO42- addition also inhibited CO2 formation on which NO3- addition had no effect. In contrast, the addition of Fe3+ increased both CO2 and CH4 formation compared to Ctrl treatment, and it is possible that methanogens were involved in the reduction of Fe3+. In Ctrl flask, the redox state did not decrease to the lowest level compared to the other treatments as expected, but the Ctrl treated UD ME peat had the highest CH4 formation at the end of incubation. For all treatments, GHG emissions were higher from nutrient-rich peat in the descending order ME > OL > OM. In general, UD peat also had higher gas formation than D peat. All GHGs were formed the most while Eh values were around 0 mV and the value was especially high for CH4 formation, probably due to the linkage between methanogens and iron. The poor ability of the Pt electrode to detect NO3- or oxygen was the most likely reason for the variable and low Eh values of the flasks with NO3- addition. For the same reason, oxygen leakage of the anaerobic chamber was most likely responsible for the varying Eh values measured from Ctrl treated OM peat. This study suggests that Eh measurement is a useful predictor of the redox state and reactions, but it must be considered together with other measurements and analyses such as microbial analysis, nutrient analysis, and GHG measurements to predict redox processes and GHG emissions in anaerobic peatland. In particular, the role of iron on CH4 emissions requires further research.

Many of the drained peatland forests in Finland have already reached or soon reaching the regeneration stage and large proportion of the trees growing there are suitable for timber production. New investments of the forest industry have created a pressure to harvest timber also in peatlands. Usually drained peatlands are regenerated by clearcutting and site preparation. Since the amendments to the Forest Act in 2014, uneven-aged management such as canopy gap cuttings has been allowed. The intent of uneven-aged forestry in peatlands is to prevent or reduce the negative environment impacts e.g. greenhouse gas emission and water runoffs or water quality. However, the lack of experience and scientific knowledge are preventing the large-scale use of alternative cutting methods on drained peatlands. The aim of this thesis was to study the usability of forest canopy gap cut method and examine the quality of spruce seedlings and the condition for further development of spruce mire stands in northern Finland. Two field experiments were established in winter 2004-2005. 18 canopy gaps of 15, 20 and 25 m in diameter were cut in Asmonkorpi and 24 canopy gaps of 10, 15 and 20 m in diameter in Lintupirtti. Circular sample plots were created within the gaps and in the surrounding residual stands and the samples were collected in the summer 2018. The one-way analysis of variance (ANOVA) was used to test the significance of gap size and the location of seedlings within the gap on the height and the annual height growth of the seedlings and the number of vigorous and healthy seedlings. Logistic regression was used to evaluate the factors affecting the quality of seedlings. In addition, the linear mixed model was used to simulate the number of seedlings in residual stands. The average number of seedlings within the gaps was 2800 ha-1 in Asmonkorpi and 2400 ha -1 in Lintupirtti and the average height was 116 cm and 102 cm, respectively. The average number of seedlings in residual stands was 2600 ha-1 in Asmonkorpi and 900 ha-1 in Lintupirtti and the average height was 107 cm and 130 cm, respectively. The results showed that the annual height growth of seedlings was higher within the gaps and especially in the larger gaps. The annual height growth of seedlings in the residual stands was approximately better on those closer (5 m from the edge) to the gap edge than on the ones further away (15 m from the edge) in 25 m gaps of Asmonkorpi. The position within the gap was significant only with the number of seedlings in Asmonkorpi 25 m gaps where the number of seedlings was highest in the northern part of the gaps. The number of seedlings within the gaps increased with the rising gap size in both field experiments. Decreasing basal area or increasing distance from the nearest old spruce or gap size 25 m affected the increasing number of seedlings in the residual stands. Approximately 70 % of the seedlings have external defectiveness in both field experiments. Bends and curves in the stems were more commonly detected inside the gaps than in the residual stands. The probability of leader shoot change and decay was lower in the seedlings which were emerged after harvesting. The increasing stem base diameter of seedling, the number of changed leader shoot and the diameter of the nearest old spruce all increased the probability of decay in the seedlings. Based on this research the canopy gap cut method seems to be useful forest regeneration method in spruce mire stands in northern Finland. In addition to the existing undergrowth in residual forest, new seedlings have emerged since the clear cut. The quality of seedlings varied but mainly they had a potential to grow into a size of dominant tree. A surprisingly large proportion of seedlings were affected by decay. Based on the biggest annual height growth and the number of the seedlings, light conditions and root conditions in within the gaps were most favourable in the gaps of 20 m and 25 m.

The main problems with cultivated peat soil are its weak carrying capacity, high greenhouse gas emissions, coldness, and acidity. There is very little research on using industrial by-products as soil amendments in peat soil. The aim of this thesis was to study the effects of industrial by-products paper mill sludge and gypsum on the sustainability of soil structure, greenhouse gas (CO2 and N2O) emissions and soils heat and gas dynamics in peat soil. The study was performed in the laboratory on samples taken from a field test. The tested treatments were unfertilized, control, gypsum 3 kg m-2, paper mill sludge 3 kg m-2, paper mill sludge 15 kg m-2 and paper mill sludge 15 kg m-2 + gypsum 3 kg m-2. The water-stable aggregates were determined by wet sieving with 0.25 mm mesh and 2 mm mesh at three different moisture contents. The greenhouse gas emissions of the soil were determined by gas chromatography at field capacity. The thermal properties of the soil were determined by measuring the thermal conductivity and diffusivity of the soil at field capacity and at saturation. In addition, soil pH, hydraulic conductivity of saturated soil, and water-holding capacity at matrix potentials pF 0; 0.4; 1; 2 and 4.2 were measured. Soil amendments had no effect on the water-stable aggregates in field moisture. The soils CO2 emissions increased with paper mill sludge treatments and decreased with gypsum treatment. Individual soil amendments had no effect on the N2O emissions of the soil, but the combined effect of paper mill sludge and gypsum increased the N2O emissions. The soils CH4 consumption decreased with gypsum treatment. Soil amendment treatments had no effect on soil thermal conductivity or thermal diffusivity at field capacity. However, in water-saturated samples the thermal conductivity and heat diffusivity of the soil was increased by the combined effect of paper mill sludge and gypsum. Unlike gypsum, paper mill sludge was found to have a clear liming effect. Soil amendments had no effect on the hydraulic water conductivity or water-holding capacity of saturated soil at any matrix potential. Based on the results, the soil amendments used did not have a major impact on the cultivation problems in peat soil, but further research on their use as soil amendments is needed.