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

158 Richard J. Hobbs, Anke Jentsch, and Vicky M. Temperton
the continuing dynamics that control the community assembly—establishment
and turnover—of individuals and the successional dynamics of communities.
For instance, disturbances act directly as filters on plant traits (Keddy 1992,
Díaz et al. 1999, White and Jentsch 2004), e.g., on survival, reproduction, colonization,
or dispersal traits. In addition, disturbances are dynamic mechanisms
that modify the process of community assembly through time, e.g., by modifying
competitive interactions, successional pathways, and trajectories (Noble
and Slatyer 1978 and 1980). Disturbances also modify the process of invasion
by alien species (see Chapters 3 and 6), which may lead to sudden changes
in successional pathways. For example, introduced grasses in western North
America (Billings 1990) and invasive exotic trees in the Florida Everglades
have substantially modified the fire regime in that they increased fire frequency
and intensity (Bodle et al. 1994), thereby modifying the limiting disturbance
filter for community assembly. Disturbance-mediated invasion calls for flexible
management strategies (Huston 2004).
In summary, to help inform restoration projects, we need to learn more about
the impacts of different kinds of disturbance as a tool in restoration: which disturbance
and how much of it produces desired effects (such as native species establishment)
and which disturbance tends to favor the invasion of alien species.
Much of this information will, of course, depend on the surrounding species
pool at local and regional levels, but inevitably also on the disturbance regime
of the site.
7.7 Applying Assembly, Succession, and Disturbance Concepts to
Restoration
In order to be applicable to restoration, theoretical considerations need to reach
a certain degree of internal consistency, generality, and proven applicability
in particular systems. There are a variety of ways in which the relationship
between assembly, succession, and disturbance concepts and the practice of
restoration can be depicted (Fig. 7.2). At worst, each area can be visualized as
being developed and pursued in complete isolation from the others (Fig. 7.2a).
Alternatively, we would argue that the concepts are increasingly being linked
in meaningful ways. One interpretation of this is that succession and ecosystem
assembly are nonoverlapping sets of ideas, but that the processes encompassed
by each are mediated by disturbance and in this way feed into restoration
practice (Fig. 7.2b). Another viewpoint is that succession and assembly share
some concepts and ideas in common (Fig. 7.2c), while a more extreme view
might be that assembly is simply a current “bandwagon” that merely restates
some of the concepts originally developed in a successional context (Fig. 7.2d).
We do not offer a definitive statement on which of these viewpoints is correct,
because this partially depends on the experience and training of the observer.
What we do suggest, however, is that such discussions actually have little
relevance to the practice of restoration. The practitioner really will not care
too much about the finer arguments distinguishing between succession and
assembly, and will instead want to know what the theoretical discussions mean
for what actually has to be done in real-world applications. Therefore, we need
to get our scientific house in order and clarify where concepts and theories can
provide useful input to these applications. In this chapter, we have attempted