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

Chapter 8 Integrating Restoration and Succession 175
include multiple growth forms and functional groups to promote spatial mosaics
of community types and use local mature vegetation as a guide but not as
an exact model for restoration (see Chapter 2). Involvement of soil biologists
in restoration planning can address impacts of aboveground manipulations on
belowground processes (see Chapter 3). There is also a need to recognize the
age of landscapes when stabilizing agricultural systems (see Chapter 4) and
realize that disturbance intensity strongly impacts recovery pathways and often
leads to multiple restoration scenarios, especially in cultural landscapes such
as in Europe (see Chapter 5). Further, one must always determine the minimal
restoration effort needed to achieve desirable results, even if that means doing
nothing at all (other than removing the source of disturbance or degradation)
(see Chapter 6). Many other topics in the preceding chapters address additional
issues involved in restoration planning (e.g., how to incorporate or exclude
invasive species, thicket-forming competitors, appropriate fertilization levels,
strategic grazing or exclusion of grazers, rewetting wetlands, defining achievable
end-points, or gaps in knowledge). These various perspectives suggest the
value of considering all applicable inputs from successional knowledge before
beginning any restoration activities.
8.7.2 Species Trajectories
Once restoration is underway (Fig. 8.1, R2), there is ample opportunity for
inputs from succession to modify trajectories and plant community composition
and to verify if ecosystem development is conforming to expectations. Much
work in succession has focused on the dynamics of species replacements and
resulting community properties such as assembly, composition, and structure.
Understanding succession can clarify the most likely impacts of nurse plants for
facilitation or species combinations where competition will impede restoration.
For example, shrubs in the succulent karoo habitat of South Africa were more
likely to inhibit seedlings under dry, nutrient-rich conditions than under either
wet or dry, nutrient-poor conditions (Riginos et al. 2005). In many restoration
sites, excessive fertilization leads to plant monocultures and reduction in species
diversity (see Chapters 2 and 6).
An understanding of succession can aid restoration actions by defining a
framework of possible trajectories within which restoration can occur (Fig. 8.2;
see Chapter 6). If restoration exceeds those boundaries, it will likely fail (unless
other endpoints are deemed acceptable). Returning to the most direct path to the
target will reduce time and costs. Knowledge about succession is also useful
in selecting vulnerable points in the developmental sequence when strategic
restorative manipulations can be most efficient and effective. These vulnerable
points are often when there is a shift in dominant species or life forms
(see Chapter 7) and the community is most susceptible. Alternatively, successional
insights may help the practitioner of restoration overcome bottlenecks
by identifying their causes (e.g., impermeable hardpan and water logging) and
suggesting solutions (e.g., by modifying the water cycle to harvest surplus water
and improve the organic content of surface soil; see Chapters 4 and 5). In
addition, information about successional changes can suggest how to increase
the rate of change, e.g., by adding critical soil nutrients or appropriate mycorrhizae
(see Chapter 3) or how to enlarge the final target (Walker and del Moral
2003; see Chapter 6).