Skogsbränslets elementära sammansättning med tanke på förbränningsprocessen och för näringsämnesförluster i ekosystemet

There are several reasons for increasing the usage of forest biomass for energy in Finland. Apart from the fact that forest biomass is a CO2 -neutral energy source, it is also a domestic resource distributed throughout the country. Usage of forest biomass in the form of logging residues decreases Finland’s dependence of energy import and increases both incomes and employment. Wood chips are mainly made from logging residues, which constitute 64 % of the raw material. A large-scale use of forest biomass requires heed also to the potential negative aspects. Forest bioenergy is used extensively, but its impacts on the forests soil nutrition and carbon balance has not been studied much. Nor have there been many studies on the heavy metal or chlorine content of logging residues. The goal of this study was to examine the content of carbon, macronutrients, heavy metals and other for the combustion harmful substances in Scots pine and Norway spruce wood chips, and to estimate the effect of harvesting of logging residues on the forests carbon and nutrient balance. Another goal was to examine the energy content of the clear cut remains. The Wood chips for this study were gathered from pine and spruce dominated clear cut sites in southern Finland, in the costal forests between Hankoo and Siuntio. The number of sample locations were 29, and the average area was 3,15 ha and the average timber volume 212,6 m3 ha -1. The average logged timber volume was for Scots pine timber 70 m3 ha -1 and for Norway spruce timber 124 m3 ha -1 and for deciduous timber (birch and alder) 18,5 m3 ha -1. The proportion of spruce in the logging residues and the stand-volume were relevant for how much nutrients were taken from the forest ecosystem when harvesting logging residues. In this study it was noted that the nutrient content of the logging residues clearly increased when the percentage of spruce in the timber volume increased. The S, K, Na and Cl -contents in the logging residues in this study increased with an increasing percentage of spruce, which is probably due to the fact that the spruce is an effective collector of atmospheric dry-deposition. The amounts of nutrients that were lost when harvesting logging residues were less than those referred to in the literature. Within a circulation period (100 years), the forest soil gets substantially more nutrients from atmospheric deposition, litter fall and weathering than is lost through harvesting of logging residues after a clear cut. Harvesting of the logging residues makes for a relatively modest increase of the quantity of carbon that is removed from the forest compared to traditional forestry. Due to the fact that the clear cut remains in my study showed a high content of chlorine, there is a risk of corrosion in connection to the incineration of the logging residues in power plants especially at coastal areas/forests. The risk of sulphur -related corrosion is probably rather small, because S concentrations are relatively low in woodchips. The clear cut remains showed rather high heavy metal contents. If the heavy metal contents in this study are representative for the clear cut remains in the coastal forests generally, there might be reason to exert some caution when using the ash for forest fertilizing purposes.

Management of semi-natural grasslands for butterfly and moth communities

This work focuses on the factors affecting species richness, abundance and species composition of butterflies and moths in Finnish semi-natural grasslands, with a special interest in the effects of grazing management. In addition, an aim was set at evaluating the effectiveness of the support for livestock grazing in semi-natural grasslands, which is included in the Finnish agri-environment scheme. In the first field study, butterfly and moth communities in resumed semi-natural pastures were com-pared to old, annually grazed and abandoned previous pastures. Butterfly and moth species compo-sition in restored pastures resembled the compositions observed in old pastures after circa five years of resumed cattle grazing, but diversity of butterflies and moths in resumed pastures remained at a lower level compared with old pastures. None of the butterfly and moth species typical of old pas-tures had become more abundant in restored pastures compared with abandoned pastures. There-fore, it appears that restoration of butterfly and moth communities inhabiting semi-natural grass-lands requires a longer time that was available for monitoring in this study. In the second study, it was shown that local habitat quality has the largest impact on the occurrence and abundance of butterflies and moths compared to the effects of grassland patch area and connec-tivity of the regional grassland network. This emphasizes the importance of current and historical management of semi-natural grasslands on butterfly and moth communities. A positive effect of habitat connectivity was observed on total abundance of the declining butterflies and moths, sug-gesting that these species have strongest populations in well-connected habitat networks. Highest species richness and peak abundance of most individual species of butterflies and moths were generally observed in taller grassland vegetation compared with vascular plants, suggesting a preference towards less intensive management in insects. These differences between plants and their insect herbivores may be understood in the light of both (1) the higher structural diversity of tall vegetation and (2) weaker tolerance of disturbances by herbivorous insects due to their higher trophic level compared to plants. The ecological requirements of all species and species groups inhabiting semi-natural grasslands are probably never met at single restricted sites. Therefore, regional implementation of management to create differently managed areas is imperative for the conservation of different species and species groups dependent on semi-natural grasslands. With limited resources it might be reasonable to focus much of the management efforts in the densest networks of suitable habitat to minimise the risk of extinction of the declining species.