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

many cases unassisted succession can produce late-successional stages in a
reasonable time. For example, in various human-made sites in central Europe,
such stages develop quite spontaneously after 20–30 years since abandonment,
which is an acceptable time for restoration purposes (Prach and Pyˇsek 2001).
On the other hand, restoration as a reverse process from the late-successional
communities toward younger ones may also be considered, thus going against
the natural direction and rate of succession.
6.2.2.2 Role of Timing
The impact of timing of manipulation depends to a large extent on the treatment
being used and the system being manipulated. For example, when managing
succession to establish/maintain moorlands with a dominant Calluna
vulgaris, a burning/cutting frequency of 6–14 years would be appropriate
(Gimingham 1992), but for a species-rich grassland flora annual mowing is
needed (WallisDeVries et al. 1998). In a 10-year experiment to control a latesuccessional
species, Pteridium aquilinum, in a heathland, herbicide treatment
applied in the first 2 years gave a rapid reduction in P. aquilinum, but the reduction
in plant density was temporary. Annual cutting treatments were needed to
maintain the heathland (Tong et al., 2006).
Manipulation applied at different times of the growing season may have very
different and often opposing effects. For example, dominant grasses can be
maintained by cutting late in the season, when reserves have been translocated
to underground organs, or suppressed if the cutting is applied early in the
season (Klimeˇs and Klimeˇsová 2002). Similarly, spring grazing of calcareous
grassland in England led to a higher species diversity and vegetation containing
more target species than autumn grazing (Gibson et al. 1987). Eradication
of invasive species is usually effective only if conducted at an appropriate
phenological phase, usually at the time of their intensive growth and, of course,
before the invasive species set seed (Pyˇsek et al. 1995).
Seeding of target species must be carried out in an appropriate “colonization
window,” the duration of which depends on the species and sere (Johnstone
1986). It is logical within a restoration scheme to use these colonization windows
to maximum benefit. The opportunity for intervention appears to occur
at the point when dominant species or life forms change due to spontaneous
processes (Prach 2003). These colonization windows can be influenced dramatically
by extreme weather events (Marrs and Le Duc 2000, Bartha et al.
2003).
In some restoration projects it is reasonable to distinguish between short-term
and long-term restoration goals, but these may conflict. For example, planting
alien ground-cover species to minimize short-term erosion slowed down longterm
restoration of target vegetation in coal mine sites (Ninot et al. 2001, Holl
2002).
6.2.3 Position of a Restored Site on Environmental Gradients
The effort to find environmental variables best correlated with successional
pattern is as old as studies on succession. However, it is difficult to find clear
and generally valid correlations, despite the commonly accepted role of climate
(Morecroft et al. 2004), site moisture, and nutrients (Tilman 1988). Soil pH is
often a useful predictor of vegetation succession in terms of species composition
(Christensen and Peet 1984), and it was the only soil characteristic significantly
Chapter 6 Manipulation of Succession 123