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

Chapter 5 Succession and Restoration of Drained Fens 95
successional stages was obtained from a data set of about 3100 releves from fen
sites in Schleswig-Holstein (northernmost federal state of Germany). The data
of Schrautzer and Jensen (2006) were used to develop a relationship between
light availability (PAR), standing crop, and the number of small-growing species
(mean height ≤30 cm) for different successional stages at the fen sites. PAR
(photosynthetically active radiation) was expressed as relative irradiance (RI),
which characterizes the light intensity within the stand relative to that existing
above the canopy.
The relationships between the mass of seeds planted at litter depths of 3 and
8 cm and the establishment of wet grassland species originate from Jensen
and Gutekunst (2003). These authors investigated 30 species from fen sites belonging
to Scheuchzerio-Caricetea, Molinietalia, and Arrhenatheretalia (mesic
grassland) plant communities.
In ecosystems where plant species composition changes during degradation,
knowledge about the longevity of seed in soils is of particular importance to
assess their biotic development potentials after the introduction of management
measures. To determine seed longevity of fen species we used an indirect
classification scheme developed by Thompson et al. (1997) based on extensive
seed bank data from northern Germany and other European studies and our
own data from seed burial in glasshouse experiments. The analysis integrates
data of a seed bank database and additional results of seed bank investigations
in Germany. The classification rules of Thompson et al. (1997) are based on
(a) presence or absence in current vegetation and seed bank, (b) depth distribution
of seeds in the soil, and (c) the period since the last record of a
species in the current vegetation. The “Longevity-Index (LI)” of the species
was calculated using the method of Bekker et al. (1998a). Longevity-Index is
defined as the ratio of the number of short-term, persistent seed bank records
(seeds viable for 1–4 years) and long-term persistent records (seeds viable
for >4 years) to the sum of transient (seeds viable for