Environmental Engineering Reference
In-Depth Information
quality (Chapin & Chapin 1980). An additional benefi t
to preserving all available topsoil is its possible content
of propagules and vital roots fractions. Even after a
partial mixing of the topsoil with mineral layers, which
are devoid of a
seed bank
, seed densities can be con-
siderable (Diemer & Prock 1993; Peratoner 2003).
Whenever possible, topsoil should therefore be stored
and returned in association with the removed vegeta-
tion type. Where site-specifi c topsoil from the site to be
restored or from an appropriate donor site is not avail-
able, an organic slow-release fertilizer, such as well-
rotted farmyard manure or certifi ed biological compost,
should be used. Inorganic mineral fertilizers with slow
but long-term release of nutrients can also be used. A
single, moderate dose of fertilizer is generally suffi cient
to achieve plant establishment (Krautzer
et al
. 2006 ).
Fertilization with nitrogen and phosphorous will
generally promote plant growth; however, for many
Arctic plants the specifi c amounts required are not
known. Deshaies
et al
. (2009) invested the effects of
fertilization on the performance of three indigenous
plant species from subarctic Québec. They found that
mineral fertilizer in principal could promote cover of
Lathyrus japonicas
and
Trisetum spicatum
under fi eld
conditions. However, under greenhouse conditions
effects of mineral fertilizer were negative on both
species, particularly at elevated levels. Results sug-
gested that either species performs better when grown
in nutritionally poor substrate, at least under control-
led conditions (Deshaies
et al
. 2009 ). Furthermore,
several studies show that fertilizer cannot promote
growth of plants that are not adapted to cold soil
(McCown 1973). Fertilization can in fact favour growth
of introduced, nitrophilous species, at the expense of
site - specifi c species that were targeting at the outset.
Over-fertilization and fertilization in the wrong season
often increase plant susceptibility to pathogens such as
fungi (Johnson & van Cleve 1976; McKendrick &
Mitchell 1978) and retard winter hardening. Over-
fertilization may also cause changes in vegetation com-
position to the advantage of 'weedy' species or cause
an increase in moss cover (Klokk & Rønning 1987).
However, phosphorus fertilizer promotes fl owering and
consequently seed development. It is important to
achieve a balanced nutritional relationship (Heer &
K ö rner 2002 ). Insuffi cient vegetation cover in the
second year of revegetation may demand further ferti-
lization measures (Holaus & Partl 1996 ). Supplemen-
tary fertilizer applications can effectively be combined
with over - seeding of a site - specifi c seed mixture.
15.4.2 Exploitation of site-specifi c
plant material
Ecological restoration
requires much more than
revegetation. It implies the recognition of a site-specifi c
reference system
. In general, site-specifi c vegetation
is mainly composed of site-specifi c species and does not
require any management measures, with the excep-
tion of different grassland communities that depend on
extensive management measures such as mowing,
haymaking or grazing. The advantage of using site-
specifi c species is that they are adapted to the site-
specifi c ecological conditions and thus can grow and
reproduce without further support. It is important to
notice again that even if a species is site-specifi c, in the
broad sense that it grows naturally in the geographical
region, it might still not be adapted to the specifi c con-
ditions of the restoration site itself (e.g. different alti-
tude and pH).
Seeds
Seeding is in general the most commonly used restora-
tion method in Arctic-alpine environments. Conven-
tional, commercially available seed mixtures mainly
comprise fast-growing species originally bred for grass-
lands used for livestock grazing, ornamental purposes,
or sport fi elds. Plant species within such mixtures are
commonly adapted to warmer locations with a pro-
longed growing season and are thus generally not
suitable for restoration of ecosystems in Arctic-alpine
environments (Urbanska 1986). Introduced plant
species from more temperate regions are not adapted
to Arctic light conditions and thus will not develop
suffi cient winter hardiness (e.g. Klebesadel
et al
. 1964 ).
Florineth (1992) indicates that, with the exception of
Festuca rubra
, the common commercially bred grass-
land species are not persistent under alpine climatic
and soil conditions. Light climate, a combination of
day length and light quality, is of vital importance for
winter acclimatization of Arctic plants.
Introduced species that are bred to maximize biomass
production, run counter to restoration goals in Arctic-
alpine environments. Such ' commercial ' seed mixtures
are for example often used in
revegetation
of ski slopes.
Beside the necessity for regular cutting, grazing or
removal of accumulating biomass, the high nutritional
needs of these species can require long-term, costly
fertilization measures. Without such supporting meas-
ures, these species may not survive when introduced
