Silviya Wolkerstorfer^1,2*, Sabine Rosner², and Peter Hietz²

¹Forest Research Institute - BAS, St. Kliment Ochridski 132, 1756 Sofia, Bulgaria.
²Institute of Botany, University of Natural Resources and Life Sciences, 1180 Vienna, Austria. ^*E-mail: svelichkova.fri@gmail.com; sabine.rosner@boku.ac.at; peter.hietz@boku.ac.at

The hydraulic effectiveness of the xylem affects tree growth and the ability to survive drought conditions. Under drought stress the water transport system can fail. Trees differ in their capacity to maintain a functional xylem at low water potential, which is described by xylem vulnerability. In this study we present a method for measuring xylem vulnerability curves in small samples. Using tangential sections of Norway spruce (Picea abies (L.) Karst.) wood, we quantify the loss in hydraulic conductivity by measuring the number of ultrasound acoustic emissions, which result when water-containing tracheids cavitate. At the same time the water potential of the sample was measured with a thermocouple psychrometer. To test the method we measured vulnerability to cavitation in samples of different wood types. The comparison between juvenile wood and mature earlywood spruce samples indicates that juvenile wood is more resistant to cavitation than mature wood. The anatomy of studied wood samples was also analyzed and was related to xylem functionality.
Key words: hydraulic diameter, juvenile wood, mature wood, Picea abies, tracheid thickness to span ratio, xylem vulnerability.

Youlin Tepeliev and Radka Koleva^*

Universityof Forestry, Faculty of Foretry, Department of Forest Management. 10 Kliment Ohridski Blvd., 1756 Sofia, Bulgaria. ^*E-mail: rad_koleva@abv.bg

The main aims of the Pan-European project CORINE Land Cover (38 countries participating, including Bulgaria) are to identify and map the changes in land cover/land use for the period 2000-2006 using multispectral satellite imagery and producing a 1:100 000 digital map of Europe for the year 2006 (creating a geospatial database). The change detection is a process of a comparison and analysis of vector and raster data from the two time horizons. The adopted unified nomenclature for the 44 interpreted and mapped land cover classes includes 6 classes directly and closely connected with the thematic mapping of timber productive areas of the forest fund. Three of the most frequent changes in the Bulgarian forests are analysed by means of the CORINE Land Cover database - clear cuts, burnt areas and spots of sport and leisure facilities construction. A large scaled research has been also carried out for assessing the locations, the areas of the Mountain pine (Pinus mugo Turra) associations in Bulgaria and their long period changes.
Key words: satellite images, computer assisted image interpretation, land cover classes, clear cuts, burnt areas, Mountain pine (Pinus mugo Turra) associations.

Jan-Erik Nylund¹ and Juan Gowda²

¹Department of Forest Products, SLU Swedish University of Agricultural Sciences, PO Box 7008, 75007 Uppsala, Sweden. E-mail: jan-erik.nylund@sprod.slu.se
²Laboratorio ecotono CRUB, Universidad Nacional de Comahue, 8400 Bariloche, Argentina. E-mail: juan.gowda@gmail.com

All legislation implies compromises between conflicting interests. In forestry, the stakeholder groups can be defined as forest owners, timber users, general public and ideological interests groups such as conservationists. Furthermore, a single actor may have ties to more than one group. Forestry legislation in its narrow sense usually has the owners as their primary target group, by issuing prohibitions, restrictions and mandatory actions, as well as in some cases incentives such as subsidy and advisory services. In many countries, forest owners are poorly organized, or there may be a strong polarity between the interests of family, corporate and public owners. Legislators tend to take law compliance for granted, but the process of making laws and regulations operative involves many steps, including communicative and value-based process. These aspects are frequently dealt with in forest policy research. Yet, forest owners can also be seen as economically rational actors. Much well intended legislation may never be effective, as the cost of law compliance is high to the owners. We examine three cases: Sweden in the 17^th century, and in the first half of the 20^th century, and Argentina today, and discuss the current situation in (mainly) Europe, where broadened societal targets such as sustainability and multifunctionality have to match the interests of family foresters.
Key words: goal conflicts, law compliance, rational choice.

Panagiotis P. Koulelis¹ and Panagiotis Lefakis²

¹Technical Institution of Kavala, Department of Forestry and Natural Environment, Drama A. Papandreou 14 Asvestohori Thessaloniki 57010 Greece. E-mail: pkuleli@ath.forthnet.gr
²Aristotle University of Thessaloniki, Schoolof Forestry and Natural Environment.

Main objective of this research is the study of the wood market and the wood products for the four Mediterranean member states of the European Union (Greece, Italy, France and Spain) and how the multiple regression could estimate the relationship between production, imports, exports and consumption for each wood product for every country, with explanatory demographical and economical variables and the time periods. The econometric research became using linear regression. The use of these simple models could be a useful tool in the hands of policy makers to take critical decisions about the future of the Mediterranean European timber market and how this market could strengthen the domestic economies generally.
Key words: wood products, European Mediterranean wood market, forest sector, timber production, forecasts.

Georgi Vukov

Faculty of Forest Industry, University of Forestry, 10 Kliment Ohridski Bulv., 1756 Sofia, Bulgaria. E-mail: georgiv@abv.bg

This paper investigates some possibilities for suitable modeling of variable external loads in a regime of exploitation of a kind of wind turbines. On the base of the developed original model of wind turbines it is possible to study dynamical processes in different specific work regimes of this kind of wind turbines. This model allows to examine the behavior of the system in extraordinary situations and different work regimes and to define some recommendations for more effective work of that kind of wind turbines.
Key words: effectiveness, multibody dynamics, wind turbines.