Environmental Engineering Reference
In-Depth Information
hindered by fencing on steep and footfall-sensitive
areas, in favour of mowing.
When cover is less than 50% in the year following
restoration, further necessary measures are to be
taken, such as reseeding or replanting with a site-
specific seed mixture (30 -50 kg ha
−1
) or plant mater-
ial. When necessary, appropriate improvement work
must be undertaken in small areas.
mined by the restoration aims in terms of vegetation
type. The species-specific annual condition of the
plants is to be taken into account when defining the
degree of cover. Nursery vegetation and alien vege-
tation should not be a part of the required degree of
cover. Divergent degrees of cover or states of decrease,
above all in the restoration of difficult sites, are to be
agreed upon and taken into account during evaluation.
The sown or planted vegetation in high locations
must have survived two rest periods and two frost
phases before evaluation can be conclusive. In
special cases (e.g. re-introduction projects) individual
evaluation criteria are necessary.
15.5 Concluding remarks
A state of acceptance is normally not given before the
site being restored shows signs of development that
ensures the achievement of the restoration aims or is
appropriate to the same. Confirmation of the work
carried out and the achievement of an acceptable state
of development is in certain cases to be executed
through proper and successful care until completion.
Therefore, an exact evaluation of success and failures
is an important foundation.
15.5.2 Failures
Restoration can easily fail in extreme locations or at
extreme altitudes. The most common causes for such
a lack of success are listed below.
False restoration methods
15.5.1 Evaluation of success
The more extreme the conditions, the more specific
must be the planning of the restoration or rehabilita-
tion measures. The securing of valuable pieces of
vegetation, the gathering, restoration, intermediate
storing and expert reapplication of the topsoil, the sub-
sequent prevention against erosion, the use of special
restoration methods and the choice of donor areas for
the combined seed/sward technique or for hay-mulch
seeding, require planning by appropriately experienced
experts. Successful high-location restoration at over
2000 m has always been planned and maintained by
trained experts.
Evaluation of the success of restoration requires
special criteria in high-altitude sites. The primary aim
of every restoration is sufficient protection against
erosion following restoration until the vegetation
has developed to be able to fulfil the task adequately.
This immediate protection against erosion is enabled
by the use of recommended application techniques
with the covering of the topsoil. As an essential limit
for sufficient erosion protection created by the devel-
oping vegetation, ground cover of 70 - 80% is con-
sidered appropriate by experts (Stocking & Elwell
1976, Mosimann 1984). With a site-specific choice of
species, the vegetation can be considered stable from
this point in time. Restoration created by seeding should
form vegetation that is as uniform as possible, which
when left uncut, unless otherwise agreed, must show
at least 70% of the projected ground cover. In justified
cases, a divergent ground cover can be agreed upon.
Vegetation-free areas of over 20
False seed
A common mistake, even in less than extreme con-
ditions, is the choice of unsuitable seed. Not only the
use of lowland seed in the subalpine and alpine
zones, but also the lack of attention given to decisive
criteria, such as the degree of acidity of the soil, or
the availability of nutrition, are causes for insufficient
restoration success. Also valid here is the maxim that
the more extreme the conditions, the more necessary
is the use of trained experts.
20 cm
2
are not
permitted in cases where potted plants are used. Up
to 60% of the projected cover should be comprised of
the species specified in the seed mixture, or as deter-
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