Environmental Engineering Reference
In-Depth Information
Finally, according to the degree of availability, and
the choice of restoration method, improvements with
the inclusion of further species, and the reduction of
cultivation varieties or their use through local ecological
types, are possible and desired.
storage of the hay, which often requires the selection
of several mowing dates, sufficient drying is neces-
sary to hinder the attack of mould. The ratio of win-
ning to restoration areas is generally 1 : 1 or 1 : 2.
The hay won in this way, and the seeds it contains,
is to be applied to the restoration area in a uniform
layer to a maximum depth of 2 cm. Over-intensive
application is to be avoided to prevent anaerobic
decomposition processes in the distributed seed.
15.4.3 Plant clippings and nets
Mulch seeding
In the mulch-seeding process, soil and seeds are
covered and protected with various organic materials.
For optimum growth the depth of the layer of mulch
should not be more than 3-4 cm and should be per-
vious to light. The most common mulch materials are
hay and straw. To avoid the inclusion of undesired
seed, in principle only hay of the second or third cut
should be used.
With the simple hay or straw seeding methods,
a 3-4 cm straw or hay cover is applied over the
seeding. The prerequisite for this restoration method
is sites that are protected against the wind and not
too steep. The material expenditure is 300-600 g m −2
in a dry state.
At steep points, especially above the tree line, the
black-green seeding method is suitable. Seeds and
fertilizer are applied into the 3-4 cm straw layer and
an unstable bitumen emulsion sprayed over it (not
to be used in drinking-water-protected areas). Hay is
not as suitable for spraying with bitumen because it
is compressed; due to thinner stalks and better cohe-
sion, hay-cover seeding alone is more stable than straw.
Hay and straw can also acquire sufficient cohesion
through light, organic gluten.
Geological textiles
A number of geological textiles are available com-
mercially. This netting of jute, coconut fibre, synthetic
fibres or wire can be used for all restoration processes
described above. When possible, the use of synthetic
fibres and wire netting as a planting aid in site-specific
restoration should be avoided (galvanized-iron netting
and synthetic netting have lifespans of around 30 years
and are not biologically degraded). Geological textiles
are used predominantly where there is a clear danger
of erosion or extreme site conditions (e.g. on very steep,
ridged banks). They offer the possibility for stronger
surface protection and, according to the materials used,
are more or less stable in the face of natural forces
such as falling rock, snowdrifts and precipitation.
According to the material, site conditions and altitude,
the netting rots within 1- 4 years, leaving no residue.
Hay-flower seeding
Required for this method is the availability of the seed-
rich remains from threshing floors in hay barns,
which above all at high altitudes is still mostly of
sufficient quality. This material should come from
hay that is not older than 1 year or maximally 2 years.
A further prerequisite is that the hay must be cut
sufficiently late, which promotes the forming of
mature seeds in many field grasses and herbs. Sieving
is often recommended to acquire an appropriately high
seed concentration. The hay flowers (0.5 -2.0 kg m −2 )
are sown with their stalks to a maximum depth of
2 cm. An additional layer of mulch is only necessary
when sieved material has been used. To hinder loss
through scattering by the wind, seeding should only
take place on wet soil, or if the hay flowers are watered
after seeding. At high altitudes, seeding weighted
with steel building grids, wire netting or coconut
Hay-mulch seeding
With the availability of appropriate areas, the seeds
can also be won by special mowing in suitable donor
areas. The areas to be mown should generally bear
site-specific vegetation that is appropriate to the aims
of the areas to be restored. Mowing is undertaken at
staggered intervals (with two or three mowing dates)
to include the broadest possible spectrum of species
in a mature state. These mowing dates should be
determined by an expert. The plants to be harvested
should not be in an overly ripe state because a slight
loss of seed can take place. With the intermediate
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