Environmental Engineering Reference
In-Depth Information
Figure 15.5
The schematic depiction of the principle of the seed-sod combination process: through the grid-like vegetation
parts covered - and despite relatively short distribution distances of alpine vegetation - the entire area can be colonized. (From
Wittmann and R ü cker 2006 .)
measures generally consist of applying a thin layer
of organic material to improve soil surface microcli-
matic conditions. This practice, known as
mulching
, is
common in gardening in hot, dry areas. It is highly
suitable in Arctic-alpine environments where an
organic-based soil surface protector can be applied to
improve and accelerate restoration results. Mulching
reduces erosion, helps retain moisture, and provides
nutrients and organic matter that contribute to soil
development as it decays. This in turn promotes seed
germination and enhanced plant growth. The most
commonly used mulch materials in Arctic-alpine res-
toration projects are hay and straw or fresh-cut plant
clippings (e.g. Claridge & Mirza 1981). To avoid the
spreading of non - site - specifi c seeds from mulch, only
hay or clippings from the second or third cut should
be used. If an appropriate donor site is available,
hay-mulch material containing mature seeds can also
be useful.
For optimum seed germination and plant develop-
ment, the applied mulch layer should not be so thick
that it blocks the penetration of sunlight. Experience
shows that approximately 300-500 g of dry material
per square metre is a good average to aim for. Due to
thinner stalks and fi rmer structure, hay-mulch gener-
ally yields a more stable cover than straw-mulch. The
mulch seeding method is generally used on relatively
wind protected, gently sloping sites. At steeper loca-
tions (slopes > 15 - 20 ° ), the well - known
black - green
seeding method
can be applied. Here the mulch layer is
stabilized by a bitumen emulsion sprayed on top. The
bitumen normally decomposes within a few months.
However, this technique is in most countries not
allowed to be used in watersheds providing drinking
water; there, light, organic gluten can be used as a
substitute for bitumen ( Ö AG 2000 ).
The addition of foreign soil organic substrates (e.g.
peat moss from nearby wetlands) can also improve
plant establishment (Rausch & Kershaw 2007).
However, one should ensure that physical and che-
mical properties of the supplemented organic matter,
for example the pH (Deshaies
et al
. 2009 ), are com-
plementary to the physiological requirements of the
plants used.
15.4.4
Long-term restoration efforts
A certain degree of aftercare is usually required to
insure the long-term success of restoration program-
