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

92 Joachim Schrautzer et al.
basis of theoretical considerations to represent the functionality of landscape
units and elements of environmental thermodynamics (Joergensen 2001). This
selection is achieved by coupling gradient theory (Müller 1998) and orientor
theory (Müller and Fath 1998). The result is a small set of indicators capable of
representing ecosystem states and ecosystem integrity as a whole, i.e., focusing
on the potential to develop self-organized processes (Müller et al. 2006). These
characteristics are represented by orientors, that is, ecosystem variables that
should increase throughout an untreated succession following abandonment
(Müller and Joergensen 2000). Changes in the indicators associated with fen
restoration measures (rewetting, grazing, and mowing without fertilization) or
abandonment are modeled using a data set from our long-term experimental
sites to parameterize the model. The Water and Substance Simulation Model
WASMOD of Reiche (1994) was used for the simulations. Simulation modeling
is used because data concerning the long-term changes in the process drivers
of the water, carbon, and nutrient budgets are scarce. We use our own data to
illustrate the establishment of species on fen sites, and what happens to species
richness on these sites given cattle grazing and mowing. Finally, we include
data concerning the longevity of seeds in the soils to assess the potential for
reintroduction of target species in degraded fens. We conclude with a discussion
of factors limiting the success of these restoration measures and the broader
implications for the restoration of fens elsewhere in the region.
5.2 Methods, Concepts, and Data Sets
5.2.1 The Basic Set of Ecosystem Indicators
The indicators chosen for this study have been compiled to represent ecosystem
states as holistic entities. The variables refer to the following components of
ecosystems (see Table 5.2):
Ecosystem structures: Following the orientor approach for successional phases
in undisturbed ecosystems, it can be hypothesized that the number of species
increases through time, and that abiotic mechanisms become more complex.
These changes are accompanied by increased ecosystem heterogeneity and
complexity.
Ecosystem functions: Ecosystem processes can follow orientor behavior during
succession. Due to increasing numbers of structural elements, the processes
Table 5.2 Indicators selected to represent basic ecosystem components.
Ecosystem component Indicator(S)
Biotic structures Number of plant species
Energy budgets, exergy capture Net primary production (NPP)
Energy budgets, entropy production Microbial soil respiration (MSR)
Energy budgets—metabolic efficiency NPP/soil respiration
Hydrological budgets—biotic water flows NPP/transpiration
Chemical budgets—nutrient loss Net nitrogen mineralization (NNM)
Nitrate leaching
Denitrification
Chemical budgets, storage capacity Nitrogen balance
Carbon balance