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

Chapter 5 Succession and Restoration of Drained Fens 93
of the energy, water, and matter budgets become more complex, the significance
of storage grows, and consequently the residence times of inputs
increase. Due to the high degree of mutual adaptation, the efficiencies of single
transfer reactions rise, cycling is optimized, and thus losses of matter are
reduced. The correlated ecosystem functions are usually investigated within
three classes of processes:
–Ecosystem energy balance: Exergy capture (uptake of usable energy) and
exergy storage (biomass, organic matter, and information) regularly increase
during succession (Schneider and Kay 1994, Joergensen 2001). The
total system throughput increases (Odum et al. 2000) and the energy demand
for maintenance and respiration also increases (Svirezhev and Steinborn
2001).
–Ecosystem water balance: As terrestrial ecosystems and landscapes develop
without disturbance, more and more structural elements have to be
supplied with water. Thus, water flows through vegetation compartments
show a typical orientor behavior (optimization of biotic water flows, see
Kutsch et al. 1998 and 2001). These fluxes are prerequisites for all cycling
activities in terrestrial ecosystems. In this study, the hydrological features
have been related to ecosystem productivity, hence representing a waterbased
efficiency measure.
–Ecosystem matter balance: During undisturbed ecosystem succession, imported
nutrients are transferred throughout the biotic community with increased
partitioning into more structures. Therefore, the biological nutrient
fractions increase as well as the abiotic carbon and nutrient storages; the
cycling rate also increases and efficiencies improve.
5.2.2 Data Sets
5.2.2.1 Successional Models
To describe retrogressive successional changes during land-use intensification
we use a model based on results of repeated vegetation mappings in fen areas
of northern Germany (Schrautzer 1988). Secondary succession after abandonment
of fens uses the sequence described in the model of Jensen and Schrautzer
(1999) that uses structural characteristics of the vegetation to define developmental
stages. Most of the developmental stages have been studied on permanent
plots or by repeated vegetation mapping. To assess the effect of rewetting
on structure and processes of degenerated fens, we construct a successional
sere that starts with intensively used wet pastures (Lolio-Potentillion), proceeds
in time to eutrophic communities dominated by tall sedges and reeds
(henceforth “tall sedge reeds,” Caricion elatae), and ends in the long run with
eutrophic wet alder carrs (Alnion glutinosae). The retrogressive succession from
wet alder carrs to wet pastures due to land-use intensification, and the succession
from wet meadows to dry alder carrs following abandonment are shown
in Fig. 5.1.
5.2.2.2 Site Factors and Vegetation Parameters
To characterize the site factors and productivities of the successional stages we
used data from Schrautzer (2004), Schrautzer and Jensen (2006), and unpublished
data. LAI (leaf area index) data were obtained from Schieferstein (1997),
Trepel (2000), and Kutsch et al. (2000). Species richness (vascular plants) of