Restoration of dry grasslands and heathlands - Restoration Ecology - page 102

dominant grasses spread again rapidly after burning,
this practice is no longer applied. The afore-mentioned
sod-cutting and grazing practices are nowadays
widely adopted. Fire is adopted as a management prac-
tice in North American tallgrass prairie (Knapp et al .
1998)

stripping is effective in reducing the nutrients avail-
able, and it accelerates the succession of reversion
(Mitchell et al . 1998). P. aquilinum encroachment can
be reduced in terms of removal of fronds to allow
persistence of other vegetation by both cutting and
herbicide application. The success after some years of
Pteridium control treatments depends on the rhizome
reserves. In this respect cutting seemed to be more
successful than herbicide application (Pakeman et al .
2002). However, cutting will favour grass species
over ericaceous species, and so is not appropriate where
the intention is to restore a C. vulgaris community.
Herbicide application in combination with grazing
revealed different results depending on the stocking
density of sheep. At low stocking rate and sufficient
shelter to prevent rapid Pteridium litter loss, Calluna
could become established. At high stocking rate and
minimal shelter, the vegetation became dominated by
Rumex acetosella (Pakeman et al . 2000). Addition of
a source of Calluna propagules is necessary. Experi-
ments with cutting and herbicide application lasting
18 years demonstrated that after an initial increase of
Calluna a transition took place towards a typical Breck
grass heath. This was probably caused by increased
atmospheric nitrogen deposition and extreme weather
conditions, factors beyond the reach of managers
(Marrs & Le Duc 2000).
R. ponticum is being controlled by cutting down
bushes, and burning and excavating the stumps.
When herbicide use is allowed, cut stumps are treated
with amcide or glyphosphate. Re-invading seedlings
can be removed by hand. Cleared areas do not
possess a persistent seed bank of Rhododendron ,
since the viability of seeds lasts only 7 months. The
control is extremely labour-intensive and hence
expensive (Gritten 1995).
The encroachment of J. communis at the alvar of
Öland, Sweden, is nowadays counteracted by cutting
of the scrub and subsequent re-introduction of live-
stock grazing in the framework of subsidies to
farmers. The subsidies are provided by the European
Union in the LIFE programme (Rosén & Bakker
2005). Dunes in the Netherlands get overgrown by
Hippophaë rhamnoides and Salix repens . In order to
re-establish the communities of pioneer habitats, the
shrubs are cut and the remaining vegetation is re-
moved by shovels to give the wind free access (van Til
& van Mourik 2001).

8.5 Removal of late-successional
invasive species

Local biodiversity can be reduced when a single plant
species becomes dominant, and monopolizes resources
such as light and nutrients. The invasive species can
be an alien introduced from another continent, but
it can also be a locally existing species taking over
in the process of succession after a change in land
use such as abandonment. Remarkably, a strong
separation seems to exist in the literature on invasive
species and succession. The examples given below
include both. Irrespective of the threats for biodivers-
ity, successional invasive species may replace native
species and take over their functional role. In that case
we may have to 'live with exotics' (D'Antonio &
Meyerson 2002). The removal of invasive species may
change ecosystems completely. Ideally, there should
be (i) pre-eradication assessment, to tailor removal and
to avoid unwanted ecological effects, and (ii) post-
removal assessment of eradication effects, on both the
target organism and the invaded ecosystem (Zavaleta
et al . 2001).
A variety of techniques can be adopted to remove
invasive alien species from reserves or restoration sites.
These most commonly include hand removal, mech-
anical removal, herbicides, fire or some combination
of the above. In the USA system-wide management
plans called for more than 535 species to be managed
between 1996 and 2000 at a cost of over $80 million,
but less than 10% of this money was made available
(D'Antonio & Meyerson 2002).

8.5.1 Reducing single species' dominance

First we deal with examples concerning the dominance
of a single species. Many lowland heaths in the UK
have been invaded by Betula spp., Pinus sylvestris , P.
aquilinum and the alien species R. ponticum . Litter