Linking Restoration and Ecological Succession (Springer ... - Inecol

Chapter 5 Succession and Restoration of Drained Fens 103
that characterize tall sedge reeds and dominate in stages II and III of the successional
seres, are larger.
Seeds collected from species of all successional stages were buried in 3 cm
and 8 cm of litter in a greenhouse to test establishment characteristics. The
results show positive relationships between seed mass and establishment; the
greatest establishment was in 3 cm of litter (Fig. 5.7A and Fig. 5.7B). Seed
weights of target species from the sociological groups characterizing small
sedge reeds and wet meadows (Scheuchzerio-Caricetea, Molinietalia) varied
over a wide range (Fig. 5.7C).
The longevity indices of Thompson et al. (1997) for seeds of these target
species as well as species that are less specific to fen sites were between 0.3 and
0.5 (Fig. 5.7D). Although seeds from species of the Molinietalia had the lowest
mean LI, the differences were not great and all species fell into the category
“transient seed banks.” Taking the results of the burial experiment into account,
mean longevity indices of the same species groups were much higher. There
were no significant differences between the groups (Fig. 5.7D).
5.3.5 Change of Species Richness by Mowing and Grazing
Results of field experiments in the wet meadow sites (4A and 4B) (Table 5.6)
showed that after a period greater than 5 years species richness was increased
by mowing once in summer and by mowing two times a year. Autumn mowing
showed a smaller increase in species numbers, and mowing three to four times
in summer showed a small decrease (Table 5.6). In the wet pastures (5), mowing
in autumn and summer (one or two cuts) increased species numbers by a
small amount. Species increases were relatively small and variation between
plots was high, nevertheless the overall results show that mowing once in summer
or mowing twice increased species numbers in the meadow and pasture
plots (Fig. 5.8). In contrast, abandonment of meadows or pastures resulted in a
significant decrease in species number.
To evaluate the success of management measures aimed at the increase of biodiversity,
it is important to consider the dynamics of the target species (Fig. 5.9).
Mesotropic and eutrophic wet meadows (4A and 4B) had increased cover of target
species with mowing two times per year. The increases in cover values were
evident after about 10 years. Numbers of target species remained relatively constant
in the wet meadows during the investigation period. Reestablishment of
mowing in late successional stages of eutrophic wet meadows and wet pastures
Table 5.6 Mean change of species number of wet meadows and wet pastures
after establishment of different mowing regimes. In brackets: number of field
experiments; x = not investigated. Ecosystems types are from Fig. 5.1.
Duration of experiment:
< 5 years 6–10 years
Ecosystem type 4B 5 4A 4B 5
Abandonment −2 (7) −2 (7) −5 (9) −6 (8) −2 (5)
Mowing (autumn, 1 cut) x 0 (7) −1(13) x 3 (5)
Mowing (summer, 1 cut) 5 (11) 2 (9) 2 (13) 5 (11) 4 (7)
Mowing (2 cuts) 4 (7) 1 (15) 3 (13) x 3 (7)
Mowing (3–4 cuts) 2 (7) x -2 (13) x x