94 
There are 4 main ecological regions: 
1. the Low Karst in the west shows a widespread 
natural afforestation of abandoned farmland, 
2. the Nanos and Javorniki mountains in the SE-NW 
direction are heavily forested, 
3. the continental part in the northeast features 
fragmented forest cover and 2 large marshy 
depressions, 
4. the tip of the Vipava valley in the northwest and the 
Brkini hills in the south represent an intensively 
cultivated sub-mediterranean landscape. 
THE DATA 
The continuous process of widespread natural 
afforestation renders the drawing of a clear line between 
forest and non-forest impossible. There are several 
transitional vegetation successions from managed 
farmland to full-grown forest, but not all of them can be 
identified from Landsat TM and GIS data, nor are they all 
interesting for most users. It was decided to distinguish 
the following 4 land cover classes in the final map: 
1. Non-forest, 
2. Abandoned pasture, 
3. Shrub, 
4. Forest. 
Because of the heterogeneity of the non-forested areas 
and in order to reduce the within-class variability in the 
satellite image, the "Non-forest" class was additionally 
partitioned into the "Unvegetated", "Water", "Marsh" and 
"Farmland" subclasses (see also Table 1). In the 
intermediate stages of our study we thus considered 7 
classes (termed CLC_G classes). Only the final result of 
classification was reclassified back into the 4 main 
classes. 
Table 1: Aggregation of the original CLC classes (EC 1993) into the more general CLC_G classes of the reference data 
set 
Attribute / GIS layer 
Content 
CLC_G 
The generalized CLC classes for training (see Table 1) 
UNSUPERVISED_RESULT 
Result of the unsupervised classification 
FOREST81 
Presence / absence of forest in 1981 (SMAS 1995b) 
DEM 
Digital elevation model, 100 m resolution (SMAS 1995a), interpolated to 25 m 
resolution 
SLOPE 
Slope in degrees, derived from DEM 
LAPLACE 
Surface roughness, derived by the Laplace filter from DEM 
INSOLATION 
Yearly global insolation in MJ/rn^ (Gabrovec 1996) 
POP_DENSITY 
Population density at a geographical subregion level (Perko et al. 1998) 
POP_AGE_INDEX 
Ratio of population aged under 20 to aged over 60 (adapted from Perko et al. 1998) 
PROX_SET_HW 
Proximity to the nearest settlement or highway in meters, based on a digized maps of 
settlements (SMAS 1995b); the highway was digitized on-screen from the Landsat TM 
image 
PROX_WATER 
Proximity to the nearest stream or lake, based on a digitized hydrology map (SMAS 
1995b) 
PROX_LAKE 
Proximity to the nearest lake, based on a digitized hydrology map (SMAS 1995b) 
TM2 
Ortorectified, topographicaly normalized image channels of Landsat TM, acquired July 
26, 1995 (EC 1997, NLR 1997). TM1 was not used because of a considerable 
stripping. 
TM3 
TM4 
TM5 
TM7 
NDVI 
NDVI = (TM4 - TM4) / (TM4 + TM4); Normalized difference vegetation index was 
computed from the Landsat TM image channels prior to topographic normalization. 
Table 2: Attributes of each pixel