Environmental Engineering Reference
In-Depth Information
region. Further, species proposed for reintroduction
must be shown not to have a long-term persistent
seed bank or adaptations for long-distance dispersal
(>100 m) such that they could re-establish at the
site spontaneously. When a species for a certain region
matches the aforementioned criteria, reintroduction
can be considered. Nowadays, information on the
crucial life history traits can be derived from large data-
bases (Kleyer
et al
. 2008). However, there is always the
caveat that the target site should have the right abiotic
conditions. Additionally, as a result of global climate
change, what was present in the past at a site may have
little relevance to what occurs there in future, come
what may!
In an overview of species introduction projects in
grasslands in central and north-western Europe, Kiehl
et al
. (2010) discuss the effects of various techniques.
They deal with seeding of site-specifi c seed mixtures,
transfer of fresh seed-containing hay, vacuum harvest-
ing of seeds and transfer of turves or seed-containing
soil. In fact, seed limitation can be overcome success-
fully by most of the aforementioned measures for
species introduction. Old fi eld sites with bare soil result-
ing from tilling or topsoil removal, or both, or aban-
doned soils, for example in mined areas, have proven
most successful for seeding experiments, whereas
species-poor grassland without soil disturbance and
older arable fi elds with dense weed stands were less
successful (Kiehl
et al
. 2010 ).
micals toxic to native species that cannot be detoxi-
fi ed by local soil communities. For the future, research
programmes are needed to unravel interactions
between native and invasive plant species, and their
interactions with native and invasive animal species
and with soil communities. Otherwise, measures for
counteractions against dominant invasive species
remain trial and error.
14.5.4
Confl icting targets
Dry grasslands, dune grasslands and heathlands with
most or at least part of the characteristic species still
present and connected to similar areas can be managed
by the continuation or reinstatement of practices
inherent to the former low-intensity farming systems,
such as mowing, sod cutting, grazing and burning.
However, it is possible that more detailed knowledge of
former agricultural practices should be known for suc-
cessful restoration. In Europe, this implies continua-
tion of the still-existing low-intensity farming system
in countries such as Greece, Spain, Portugal, parts of
France and the United Kingdom (Bignal & McCracken
1996) or eastern European countries (Veen
et al
.
2009). Here, characteristic grasslands and heathlands
still exist outside nature reserves, and are exploited by
farmers. In order to maintain these systems, farmers
can be compensated fi nancially for the continuation
of their current practices, and intensifi cation can be
avoided. Here, agri-environment schemes can be
extremely successful. In other European countries and
regions with intensive agriculture, dry grasslands,
dune grasslands and heathlands with nature conser-
vation interest are often protected inside set-asides or
nature reserves. Here the administration and per-
sonnel in charge of restoration and management
have more or less to take over the former farming prac-
tices or provide some proxy to replace them. Agri-
environment schemes outside nature reserves perform
poorly (Kleijn & Sutherland 2003).
Sites targeted for restoration and conservation man-
agement should be monitored before and during the
establishment of target species of plants, invertebrates
- such as butterfl ies, grasshoppers and carabid beetles
- and vertebrates, including those present in adjacent
reference sites. This will help elucidate background
and on-site rates of dispersal and re-establishment of
different groups of organisms and suitability of target
sites. Many species of invertebrates, birds, mammals
14.5.3
Invasive species
It is likely that some plant species from southern Europe
will spread into north-western Europe as a result of
global and continental
climate change
. Some of
these new species may become
invasive
and outcom-
pete the currently, and historically,
native species
. In
order to understand the mechanisms playing a role in
this process, knowledge must fi rst be gained on the
interaction of the exotic invasive plant species and the
soil communities with which they interact. Inderjit
and van der Putten (2010) suggest three kinds of inter-
action. First, plant-soil feedback interactions may be
neutral to positive, whereas native species suffer from
negative feedback effects. Second, exotic species can
manipulate local soil communities by enhancing path-
ogen levels or disrupting communities of root sym-
bionts, while suffering less from this than native
species. Third, exotic species may produce alleloche-
