Environmental Engineering Reference
In-Depth Information
Krautzer & Hacker 2006); similar approaches are now
being tested in the French Pyrenees (Malaval 2006)
and in Iceland (Aradottir & Johannsson 2006 ).
One common obstacle to widespread acceptance of
relatively high-priced, propagated seed material is
related to lack of transparency with respect of the area
of origin of the material used. To be able to give con-
sumers confi dence regarding seed material offered for
sale, several countries are working on the implementa-
tion of certifi cation procedures for the producers. In
this way, the origin or provenance of seed, as well its
purity and viability are guaranteed to meet predeter-
mined standards.
Another possibility is the use of shoots or rosettes
from mechanically separated turf segments that are
randomly distributed onto the restoration site. At sites
accessible to vehicles, distribution can be performed
mechanically. In this way, larger areas can be restored
than by using the labour-intensive transplanting of
turf segments. However, the resulting vegetation cover
is usually sparser and as a result, the risk of erosion
will be higher. In the eastern Alps, a new approach was
developed with the production of ready-made sward
(sod rolls) that is well known in conventional horticul-
ture. Site - specifi c plant species based sod rolls are cul-
tivated for about 12 months, which ensures satisfactory
plant development (Gottschlich 2008). According to
needs and restoration aims, various plant species mixes
can be produced on demand. Sod rolls are then har-
vested and transported to the restoration site. The sod
roll method has the advantage of providing a complete
topsoil vegetation cover. However, this method is costly
and, as a result, mostly used for
interventions
in
small areas and in extremely diffi cult locations. Turf
segments, sod clippings, grass swards and seeds are of
course all living materials, and careful handling and
expert attention are therefore indispensable.
In practice, a combination of two or more of the
above-listed methods is often used, for example the turf
transfer method with application of seeds (Wittmann
& Rücker 1995). Here, vegetation swards (or sod rolls)
are initially arranged in a scattered pattern, for example
like a chess board. Subsequently, site-specifi c seeds are
sown into the intervening areas (Figure 15.5). Germi-
nating seeds reduce erosion between vegetation swards,
while sward-based plants are allowed to invade inter-
mediate areas. In this way, plant species not available
as seeds are able to establish. Combining erosion
control mats and seeding is a commonly used method
for restoring steep slopes (>30%) where there is a high
risk of erosion. The use of combined methods also
serves to reduce negative impacts on donor sites and to
promote the rapid establishment of a diverse vegeta-
tion cover.
Site - s pecifi c p lant m aterial
As for seed collection, site-specifi c species with gener-
ally high vegetative reproduction potential should be
used (Grabherr & Hohengartner 1989). Selected plant
material can be cultivated in pots until they have a
well-developed rootstock and are then planted into res-
toration sites. The potted plants can either be grown
from vegetatively reproduced mother plants or locally
harvested vegetative or seed material. Given an appro-
priate selection of species, this method can give excel-
lent results, even at sites with extremely harsh climatic
conditions.
The 'turf transfer method' transfers partial soil-
plant segments from donor to restoration sites. Depend-
ing on whether turfs are obtained manually or
mechanically, unit size usually varies between 0.15 to
0.50 m
2
. To avoid drying, stifl ing and rotting, turfs
should not be stored in pits or stacked on pallets in
layers more than 100 cm wide and 60 cm high. Moreo-
ver, storage period should not exceed a maximum of
2-3 weeks in summer. Wherever possible, the trans-
planting of turfs should take place as early as possible
at the beginning of the vegetation period or after the
start of the autumn vegetation pause, thus just after
the melting of snow or directly before the onset of
winter. Vegetation turf segments are especially suitable
for the rapid site-specifi c restoration of disturbed sites.
Accessible soil vegetation segments are removed before
disturbance, stored and returned to the site after level-
ling. On steep slopes it is recommended to stabilize
grass turfs with, for example, wooden stakes or nails.
With proper planning, grass turfs from building and
construction sites can be directly transferred to resto-
ration sites without intermediate storage (Krautzer
et al
. 2006 ).
15.4.3. Improving site conditions
with mulch
Depending on prevailing environmental conditions,
the successful re-establishment of plants in disturbed
sites is commonly supplemented by a combination of
seeding and microclimate improving measures. Such
