Browsing by Subject "hiilivarastot"

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  • Pienimäki, Arttu (Helsingfors universitet, 2014)
    The most extensive dry forest and woodland formation in sub-Saharan Africa, including Mozambique, is formed by miombo woodlands. Because of their wide distribution, the miombo woodlands carry significance in global carbon cycle. Previous studies have indicated that while the miombo aboveground carbon stocks appear modest in comparison with tropical rainforests, they have a potential to retain high stocks of soil organic carbon. The miombo landscape is nowadays characterized by widespread deforestation and forest degradation, with woodlands being replaced by anthropogenic land uses such as small-scale agriculture and charcoal harvesting. A new land use type spreading in northern Mozambique is formed by industrial forest plantations. The emerging plantations further change the landscape in transition, allegedly affecting the carbon stocks in the process as well. The purpose of this study was to quantify carbon stocks on locally relevant land use classes in Niassa province, northern Mozambique, and evaluate the change of carbon stocks caused by forest plantations. Six major land use classes were identified: dense miombo, open miombo, other woody vegetation, fallow land, eucalypt plantations and pine plantations. A sample plot grid was laid on chosen areas representing each of the classes. Vegetation aboveground carbon stocks (trees, shrubs and herbaceous vegetation) were recorded in the inventory and topsoil (30 cm) was sampled for soil organic carbon content, to be determined in laboratory. Vegetation belowground carbon stocks were calculated based on existing root to shoot ratios. Since plantations were generally juvenile on the study area, their average yield during rotation period was estimated based on growth models to provide comparable results. Forest plantations were found to have carbon stocks of the same order of magnitude as the two miombo land use classes. Open and dense miombo carried mean vegetation aboveground carbon stocks of 27.47 ± 5.77 and 37.65 ± 7.20 Mg ha-1 respectively, and mean total carbon stocks of 67.81 ± 17.09 and 86.81 ± 18.91 Mg ha-1 respectively, which was consistent with pre-existing results. Pine plantations placed in between with a partially modelled total aboveground mean carbon stock of 34.59 Mg ha-1, whereas the corresponding figure for eucalypt plantations was 21.04 Mg ha-1. Dense miombo had the highest mean total carbon stock of all the land use classes, and fallow land the smallest with 42.59 Mg ha-1. Soil organic carbon did not demonstrate statistically significant differences between any of the land use classes. The result was unexpected, and may be explained either by (i) limited time frame since the land use conversions or (ii) soil mineralogical properties buffering carbon stock changes.
  • Siintola, Asko (Helsingfors universitet, 2012)
    Climate change has been found to be one of the most serious challenges humankind has to face in the future. The link between climate change and forests is based on trees’ ability to use carbon dioxide as a raw material for growth. The growing stock sequesters carbon dioxide from the air to itself and ultimately as the forest is harvested the carbon stored is released and it moves from carbon pool of forests to another carbon pool. As the concept of emissions’ trading is applied to the investigation, a price for sequestered and released carbon can be determined. With the market price for carbon dioxide known, a net present value for the revenues and costs during the forest’s rotation period can be calculated. Using wood for different purposes, however, can result in various climatic benefits. These climatic benefits are described in this study by carbon displacement factors which can be used in determining how much the costs of releasing carbon from forests can be deducted. This study investigates the significance of forest management in a stand level from the climate change mitigation point of view in three Norway spruce (Picea abies, L.) and three Scots pine (Pinus Sylvestris, L.) stands as the previous carbon accounting aspects are taken into consideration. Stand Management Assistant (SMA) software is used in the optimization and simulation calculations. The SMA software is used for calculating the carbon accounting net present values and average carbon storages during the rotation periods of the stands included in the study with different intensities of bioenergy biomass harvesting. This way the level of biomass harvesting for bioenergy that returns with the highest net present value for carbon accounting and/or the highest average carbon storage can be calculated. The calculations are made with two interest rates, two carbon dioxide prices and with climatic benefits from bioenergy or with climatic benefits from bioenergy and forest products included. According to the results it can be stated that the intensification of forest biomass recovery for bioenergy production does not always result in the optimal climate change mitigation. The use of Norway spruce is considered of being the most potential forest-based bioenergy source in Finland. As the climatic benefits from bioenergy use were only taken into consideration, the intensification of recovery of Norway spruce biomass for bioenergy seemed to be most profitable. If, however, the climatic benefits from forest products are included in the investigation as well, the bioenergy use of Norway spruce is no longer optimal for the climate change mitigation. The climatic benefits from Norway spruce material use exceed the benefits from bioenergy use. This means that biomass recovery for bioenergy production does not necessarily result in optimal climate change mitigation.