species is supposed to be due to the reduced influence of the sea upon an increasing
proportion of the dune area, caused by the seaward development of new foredunes.
A large proportion (54 %) of the species recorded in 2002 specializes in seed
dispersal by wind. This indicates that the dune system after 24 years was still at an
early stage of succession (Fenner 1985; Prach and Pysek 1999). However, for
many species it is not possible to demonstrate evident morphological specialization for long-distance dispersal. Andersen (1993) points to humans as important
dispersal agents for such species. This could well be the case in the seaside park,
considering the strong recreational pressure in the area (Nielsen 1990; Andersen
1995). Many species with no special spreading device can, however, be dispersed
by wind because of the small diaspore size (\2 mm; Andersen 1993). Thus, F.
rubra, which dominated the later stages of succession in the dune, has small and
light diaspores (Grime et al. 1988), which could easily have been blown into the
dunes from the sown grassland just landward to the initial, man-made dune by the
frequent westerly winds.
4.4.3 Species and Life Form Dynamics
The increase in species richness of the dune system from 1979 to 2002 implied
a change in the proportion of the plant life forms in a spatial–temporal pattern
also observed during primary succession in other beach and dune systems, e.g.,
Hundt (1985).
In the original, man-made dune, the A. arenaria that had been planted declined
because of a decreasing supply of fresh, wind-borne sand (van der Putten 1989;
van der Putten and Peters 1995; De Rooij-van der Goes 1995; van der Stoel et al.
2002), while F. rubra as well as inland annuals increased. A. arenaria expanded
seaward, however, into the area of mobile sand and was the primary colonizer
initiating and forming new foredunes on the beach.
In the new dunes, beach annuals, e.g., Cakile maritima and Salsola kali, which
are typically limited to open, salty and unstable beach sand (Davy and Figueroa
1993; Packham and Willis 1997), were present during the first years of dune
development, when the plant cover was sparse and the substrate was fresh marine
sand. During the following years the beach annuals were replaced in the sequence
‘‘dune 2’’ ? ‘‘dune 3’’ ? ‘‘dune 4’’ by the dune-forming rhizome geophytes
A. arenaria, A. x baltica, L. arenarius, Elytrigia junceiforme, which are tolerant to
or even favored by deposition of fresh sand (Ranwell 1972; Packham and Willis
1997). During the last years of the study period hemicryptophytes, especially
F. rubra, began to play a role in the sequence ‘‘dune 2’’ ? ‘‘dune 3.’’
Besides the plant groups mentioned, some additional plant groups colonized the
dunes during the latter part of the study period: root geophytes, e.g., Chamaenerion angustifolium; hemicryptophytic dicots, e.g., Erigeron acre, Fabaceae, e.g.,
L. japonicus, Anthyllis vulneraria, Trifolium arvense; shrubs, e.g., Rosa rugosa,
Hippophaë rhamnoides.
4 Natural Plant Diversity Development on a Man-Made Dune System
61
proportion of the dune area, caused by the seaward development of new foredunes.
A large proportion (54 %) of the species recorded in 2002 specializes in seed
dispersal by wind. This indicates that the dune system after 24 years was still at an
early stage of succession (Fenner 1985; Prach and Pysek 1999). However, for
many species it is not possible to demonstrate evident morphological specialization for long-distance dispersal. Andersen (1993) points to humans as important
dispersal agents for such species. This could well be the case in the seaside park,
considering the strong recreational pressure in the area (Nielsen 1990; Andersen
1995). Many species with no special spreading device can, however, be dispersed
by wind because of the small diaspore size (\2 mm; Andersen 1993). Thus, F.
rubra, which dominated the later stages of succession in the dune, has small and
light diaspores (Grime et al. 1988), which could easily have been blown into the
dunes from the sown grassland just landward to the initial, man-made dune by the
frequent westerly winds.
4.4.3 Species and Life Form Dynamics
The increase in species richness of the dune system from 1979 to 2002 implied
a change in the proportion of the plant life forms in a spatial–temporal pattern
also observed during primary succession in other beach and dune systems, e.g.,
Hundt (1985).
In the original, man-made dune, the A. arenaria that had been planted declined
because of a decreasing supply of fresh, wind-borne sand (van der Putten 1989;
van der Putten and Peters 1995; De Rooij-van der Goes 1995; van der Stoel et al.
2002), while F. rubra as well as inland annuals increased. A. arenaria expanded
seaward, however, into the area of mobile sand and was the primary colonizer
initiating and forming new foredunes on the beach.
In the new dunes, beach annuals, e.g., Cakile maritima and Salsola kali, which
are typically limited to open, salty and unstable beach sand (Davy and Figueroa
1993; Packham and Willis 1997), were present during the first years of dune
development, when the plant cover was sparse and the substrate was fresh marine
sand. During the following years the beach annuals were replaced in the sequence
‘‘dune 2’’ ? ‘‘dune 3’’ ? ‘‘dune 4’’ by the dune-forming rhizome geophytes
A. arenaria, A. x baltica, L. arenarius, Elytrigia junceiforme, which are tolerant to
or even favored by deposition of fresh sand (Ranwell 1972; Packham and Willis
1997). During the last years of the study period hemicryptophytes, especially
F. rubra, began to play a role in the sequence ‘‘dune 2’’ ? ‘‘dune 3.’’
Besides the plant groups mentioned, some additional plant groups colonized the
dunes during the latter part of the study period: root geophytes, e.g., Chamaenerion angustifolium; hemicryptophytic dicots, e.g., Erigeron acre, Fabaceae, e.g.,
L. japonicus, Anthyllis vulneraria, Trifolium arvense; shrubs, e.g., Rosa rugosa,
Hippophaë rhamnoides.
4 Natural Plant Diversity Development on a Man-Made Dune System
61