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

126 Karel Prach et al.
steepness of slopes can be reduced, and the drainage regime altered to achieve
the required moisture conditions. When large-scale earth-moving machinery
is used to change site/soil conditions, it can damage the substrate through
compaction, especially if the soil is wet. Where this occurs, additional treatments
such as surface ripping or drainage may be needed (Montalvo et al.
2002).
Chemical manipulations may also need to be done, especially where there is
a deficiency or toxicity of chemical elements in the soil-forming material. In
many mine wastes, for example, there is almost no organic matter, a very low
nutrient supply, and, depending on parent material, a soil pH between 2 and 12.
Fertilizers will often need to be added if the soil material is very deficient in
major plant nutrients (Bradshaw 1983, Marrs and Bradshaw 1993). Sometimes,
adding soil-forming materials such as green wastes, industrial wastes (e.g.,
paper pulp wastes), or sewage sludge can improve site conditions (Greipsson
2002).
The aim of physical and chemical manipulations is to produce a site that
is well contoured into the local landscape and with appropriate drainage or
irrigation for the target ecosystem to establish, and where the soil is suitable to
allow the required species to establish and grow well.
6.3.3 Biological Manipulation
Adding seeds of the target species to the system is the most common biological
manipulation, although it is possible to use other propagules or transplants
from donor communities (Hodder and Bullock 1997, Antonsen and Olsson
2005). Once introduced, steps must be taken to ensure their establishment and
persistence.
Where seeds are added, they can be treated using germination-promoting
agents to ensure a rapid germination. At the same time it is often sensible
to add microorganisms such as the appropriate mycorrhizas and Rhizobium
bacteria if leguminous plants are to be included in the seed mix (Greipsson
2002; see Chapter 3).
One major issue is the provenance of seeds and of plant material derived
vegetatively. Over the last 20 years, there has been a large increase in the commercial
availability of seeds of seminatural biotopes from native sources, and
in some places seeds of species can be obtained from very localized sources
(e.g., http://www.floralocale.org). On the other hand, most commercial mixtures
or transplants do not respect regionality (McKay et al. 2005). In general,
when selecting material for sowing or transplanting, we advise that whenever
possible, seeds and other propagules should be used from local sources. When
transplanted material is to be used, material of a single clone should be avoided,
in order to maximize genetic diversity. High genetic diversity may reduce the
risk of extinction under fluctuating environments and allow a species to occupy
more microhabitats.
In some situations, succession is circumvented by importing an ecosystem
from elsewhere, either completely in blocks (transplants) or in part. The most
usual case is to import topsoil from elsewhere; where this is done, nutrients,
seed banks, and soil microflora can be imported in one operation, which then
includes both the physicochemical and biological manipulation (Vécrin and
Muller 2003).