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

Chapter 5 Succession and Restoration of Drained Fens 97
Figure 5.2 Undrained eutrophic alder carr with Alnus glutinosa and Carex acutiformis
in Schaalsee, southeastern Schleswig-Holstein, Germany.
above the surface (Table 5.3). Alder carrs are subdivided into a unit dominated
by mesotrophic species of the Scheuchzerio-Caricetea (vegetation type
1 A, Fig. 5.1) and a eutrophic unit without these species (vegetation type 1 B;
Fig. 5.2). The C/N-ratio of the peat is higher at sites of the mesotrophic carr
than at those of the eutrophic carr. After deforestation, alder carrs develop to
tall sedge reeds (2 A, B). In most cases, the dominant sedges were present in the
previous woody stages. Higher groundwater tables and longer flooding periods
occur at sites of tall sedge reeds compared with sites of alder carrs, indicating
the higher transpiration rate of the alders compared with the sedges. Moderate
drainage and long-term mowing or grazing resulted in the development of small
sedge reeds (3). A high C/N-ratio of the peat of these sites indicates low nitrogen
availability. Standing crop and the LAI of small sedge reeds are much lower
than the respective values for tall sedge reeds (Table 5.3). Increased drainage
transforms small sedge reeds into mesotrophic wet meadows (4 A), whereas
eutrophic wet meadows (4 B) develop after drainage, mowing, and fertilization.
A different trajectory for small sedge reeds to wet pastures (5) results from increased
drainage, higher fertilization, and grazing with high stock densities (2–3
cattle per ha). The main differences between wet meadows and wet pastures
are that the groundwater tables are lower but the flooding duration is higher
in wet pastures. The latter results from high compaction of the 0–20 cm peat
horizon (bulk density 0.7 g cm −3 , Table 5.3). This compaction causes stagnant
water after heavy rainfall (Schrautzer et al. 1996). Secondary succession from
small sedge reeds via wet meadows to wet pastures resulted in an increase of
standing crop and LAI of the vegetation (Table 5.3).
5.2.3.2 Abandonment Seres
The four progressive successional stages shown in Fig. 5.1 following abandonment
are for seral types 3 (small sedge reed), labeled Sere A, 4A (mesotrophic