Slovakia is acountry with limited natural resources, therefore its essential task is to search for new renewable sources of energy to reduce its dependence on imported fossil fuels. The results of research confirmed that the Common Reed (Phragmites australis(Cav.) Trin.) has considerable potential of phytomass production and energy storage (calorific value reached 17,448 J g−1d.w.). Biomass production of Common Reed under natural conditions of the lower Liptov region reached 12.702 tons of a dry mater per hectare with the calculated energy storage of 221.622 GJ ha−1. The average biogas production was 351.31 l kg−1of a dry matter of which the methane (CH4) content represents 185.21 l kg−1(52.72%). With regards to the values of combustion heat, a calorific value and the production of methane it can also be noted that in case of Common Reed it is more profitable to focus on direct combustion of biomass than the production of biogas and methane.

Tree resin is a macroergic component that has not yet been used for energy purposes. The main goal of this work is to determine the energy content of the resin of spruce, pine, and larch and of wood components—pulp and turpentine. The combustion heat of resin from each timber was determined calorimetrically. Approximately 1.0 g of liquid samples was applied in an adiabatic calorimeter. The energy values of the tree resin (>38.0 MJ·kg−1) were 2.2 and 2.4 times higher than that of bleached and unbleached cellulose, and the highest value was recorded for turpentine (>39.0 MJ·kg−1). Due to the high heating values of the resin, it is necessary to develop approaches to the technological processing of the resin for energy use. The best method of resin tapping is the American method, providing 5 kg of resin ha−1 yr−1. The tapped resin quantity can be raised by least 3 times by applying a stimulant. Its production cost compared to other feedstocks was the lowest. Tree resin can be applied as a means of mitigating global warming and consequently dampening climate change by reducing the CO2 content in the atmosphere. One tonne of tree resin burned instead of coal spares the atmosphere 5.0 Mt CO2.

A shelterwood system is widely used in forest management practice. Favourable ecological conditions for the growth of desired natural seedlings are provided by a successive canopy reduction. The impact of these changed conditions is reflected to the greatest extent in the morphology and structure of beech leaves. Differences in the leaf structure can mainly be seen between sunlit and shaded leaves and are themselves manifested in changes of element contents in leaves according to the respective conditions. The relationships between analysed variables were studied during research (1996)(1997) in stands of different initial stand density (0.3, 0.5, 0.7 and 0.9), resulting from the shelterwood cut of different intensity (1989). The second criterion was the social status of a tree in stands (dominant, codominant and subdominant) and the third one was the position of leaves in the tree crown (upper, middle and lower part of crown). In the framework of this research the concentrations of Mn and Fe including other macronutrients in beech leaves were evaluated. This paper deals only with manganese and iron due to a limited range of pages. The concentrations of Mn a Fe were studied in beech leaves collected from upper, middle and lower parts of beeches with a different social status. In some cases, statistically significant influences of shelterwood cutting intensity on the analysed variables (metal concentration, dry weight, etc.) were proved at a significance level α = 0.05. It applies to manganese quantity accumulated in leaves of dominant, codominant, and subdominant trees, unit trees, Mn concentration in assimilatory organs, dry mass, iron concentration, etc.

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The effect of maturation pretreatment on development and growth of Abies numidica De Lann. somatic embryos was studied. The most beneficial was pre-culturing on Schenk and Hildebrandt medium without growth regulator for 2 weeks. Dry mass accumulation of emblings was lower than that of seedlings after 50 d of culturing. Contents of microelements in seedlings were higher than in emblings, but macroelements contents were higher in emblings. Contents of chlorophyll a and chlorophyll b in cotyledons were higher in seedlings than in emblings while no qualitative differences were detected between the protein profiles of seedlings and emblings.