368 
Table 2 Photo-units and dominating plant species 
PHOTO-UNIT 
DOMINATING SPECIES 
1 SAND 
none 
2 OPEN VEGETATION 
Calamagrostis epigejos 
Carex arenaria 
Agrostis sps. 
Moss & Lichens 
3 OPEN LOW SHRUB 
Mixture of 2 & 5 
4 OPEN TALL SHRUB 
Mixture of 2 & 6 
5 DENSE LOW SHRUB 
Hippophae rhamnoides 
Ligustrum vulgare 
Salix xepens 
6 DENSE TALL SHRUB 
Crataegus monogyna 
Sambucus nigra 
7 DECIDUOUS WOODLANDS 
Betula pendula 
Crataegus monogyna 
8 MIXED FOREST 
Pinus nigra var. nigra 
Acer pseudoplatanus 
9 PINE FOREST 
Pinus nigra var.nigra 
HAASVELDERDUINEN 
too 
Q) 
<0 90 
a) 
> 80 
O 
Ü 
oV» 7 ^' 
60H 
50 
40 
30- 
20- 
10 
0 J 
M 
Msiêfc 
ôïïrVi;' 
'I 
ü 
HH pineforest 
mm deciduous mixed woods 
dense high shrub 
open high shrub 
1 "—J dense low shrub 
open low shrub 
I 1 grass/moss vegetation 
1 1 sand 
1938 
1958 1968 1979 
1985 
fig. 6 Cover percentages of the main vegetation structures.