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A. Poljanec & A. Boncina 2010. Changes in structure and composition of forest stands at regional and national level
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al., 2009). The aim of this study was thus 1) to study spatiotemporal changes in forest structure
and tree species composition in the last four decades at regional and national level and 2) to
determinate impact of different environmental, natural and social factors on changes of forest
structure and species composition.
2. Methodology
2.1 Study area
Slovenia lies in the south-eastern part of Central Europe, between Austria, Italy, Hungary and
Croatia. Due to diverse environmental conditions (the Alps, the Mediterranean, the Dinaric
Mountains, and the Panonian Basin), different forest management practices in the past decades
and centuries and available archival data on forest stand structure and composition, Slovenia is
appropriate study area to study changes in forest stand structure and composition on the
landscape level. Forests cover 11,400 km 2 , which represents 58% of the total land area. The
underlying characteristic of the study area is a considerable variation of relief and climatic
conditions (Poljanec et al., 2010). Zonality of forest vegetation in Slovenia is quite clearly
defined due to distinctive orographic factors, different soil substrata and well-preserved forest
structure. For the purpose of the research, forest vegetation was classified in eight forest types
according to the terminology of the Ministerial Conference on the Protection of Forests in
Europe (MCPFE) (European forest types…, 2006), reflecting distinctive and unique patterns of
human impacts, modification of species composition, latitudinal/altitudinal zonation of
vegetation, climatic and edaphic variability, silvicultural systems applied and forest
management intensity: Alpine coniferous forest (EFC 3; 225 km 2 ), acidophilous oakwood (EFC
4.1; 241 km 2 ), sessile oak–hornbeam forest (EFC 5.2; 577 km 2 ), Central European
submountainous beech forest (EFC 6.4; 1,901 km 2 ), Illyrian submountainous beech forest (EFC
6.6; 1,505 km 2 ), Illyrian mountainous beech forest (EFC 7.4; 2,612 km 2 ), thermophilous
deciduous forests (EFC 8; 77 km 2 ) and floodplain forest (EFC 12; 45 km 2 ).
2.2. Data description and analysis
The study is based on data acquired from the spatial information system Silva-SI (Poljanec,
2008), which covers the entire forest area of Slovenia (N of compartments = 32,597;
11,400 km2). The analysis included 22,220 compartments (7,183 km2) with an average area of
34 ha for which reliable data on forest condition for 1970 and 2008 are available. An attributive
database comprising seven dependent and 20 independent variables describing the site, forest
management and social conditions of the compartments was designed. Among 20 independent
variables, the first 11 describe site conditions (INC - mean incline, INC_SD - standard deviation
of incline, ELV - mean elevation, ELV_SD - standard deviation of elevation, ASP - aspect,
ASP_VAR - variation of aspect, ROC - proportion of area covered with rocks, BEDR - bedrock,
T - mean annual temperature, PRCEP - mean annual precipitation, RK – site productivity), the
next 4 are social variables (OWN - ownership, N_OWN – number of owners in the
compartment, HS - holding size, SUCC - share of abandoned land), 3 variables describing state
of the stands in 1970 (GS1970 - growing stock in 1970, VOL_C - proportion of large-size
diameter trees in growing stock, P_CON - proportion of conifers in growing stock) and the last
2 variables describe the intensity of management (FMR – forest management region, CUT -
annual allowable cut (m3 ha-1) in the period 1970-2008). Data were acquired from various
sources, mostly through forest inventories; this is a combination of a field description of all
stands and of tree measurements (dbh ≥ 10 cm) at permanent 500 m2 sampling plots
(N = 100,178) with a dominant sampling network size of 250 m × 250 m and 250 m × 500 m
(Poljanec et al., 2010).
Forest Landscapes and Global Change-New Frontiers in Management, Conservation and Restoration. Proceedings of the IUFRO Landscape Ecology
Working Group International Conference, September 21-27, 2010, Bragança, Portugal. J.C. Azevedo, M. Feliciano, J. Castro & M.A. Pinto (eds.)
2010, Instituto Politécnico de Bragança, Bragança, Portugal.