367 
relatively large blowouts in the 
central and northern part of the 
area. In 1958 still large areas were 
covered with moss/- herb/grass vege 
tations, but blowouts were fixed in 
the mean time. At one of the old 
meadows pine forest was planted, in 
1958 the trees were still small so 
vegetation structure was interpreted 
as open low shrub. Between 1958 and 
1968 there is a considerable 
increase of open low shrub vegeta 
tion. This is the result of the 
sudden decrease of the intensity of 
rabbit-grazing as a outcome of the 
myxomatosis outburst in 1954. This 
probably has favoured the growth of 
woody species In 1979 and 1985, it 
is evident that diversity in vegeta 
tion structure increased.Taller 
and/or more dense shrub vegetation 
and small deciduous woodlots develo 
ped. The landscape has more and more 
been stabilized . The landscape 
succession in the past 50 years is 
represented in the transitions of 
the different structure types (fig. 
6). In 1938 and 1958 about 50 per 
cent of the coverage was open moss 
and grass vegetation. In 1968 the 
considerable increase of open low 
shrub. This succession continued , 
more and more dense and high shrub 
and woodlots arose. Only 0.42 % of 
the surface is covered by blowouts. 
The described developments took 
place not only in this area but also 
in other parts of the Dutch calca 
reous dunes (Van Dorp et. al.,1985). 
5 DISCUSSION 
The use of aerial photographs 
obviously can increase the knowledge 
of developments in a dune landscape. 
Repeated vegetation mapping using 
air photographs are a clear help in 
monitoring vegetation dynamics. The 
perspectives of this method are 
increasing because of the growing 
interest of nature conservation and 
nature managment in the Dutch dune 
area. 
In this study only a small part of 
the dune landscape was examined. The 
conclusions only hold true for this 
special location. Older dunes and 
dune slacks show a different succes 
sion with different vegetation types 
(Van Dorp et. al., 1985). It would 
be interesting to develop a predic 
tion method by extrapolation of 
trends for each individual vegeta 
tion structure. 
fig. 5 Interpretation maps 1938. 1958, 
1968 ,1979 and 1985.