Design - Project Planning and Management for Ecological Restoration - page 90

In many instances, we are involved in
project sites that do not afford us the luxu-
ry of using these models entirely; however,
they have some relevance even on the small
scale that is typical for restoration projects
(Morrison 2009).

Species Quantities

The number of individuals planted or seeds
sown per area is influenced by the factors
mentioned earlier: evaluation criteria, time
to meet goals and objectives, and stake-
holder expectations. In addition to these
criteria are the specific site stressors: Is the
site subject to extremes of temperature or
rainfall? Does the potential exist for signif-
icant numbers of exotic species to invade
the site? Does the budget provide for only
a minimum of maintenance? Other factors
that may also impact your project are the
potential for vandalism, the unavailability of
species due to rarity or uniqueness, a natu-
rally high mortality of plants selected, and a
poor seed crop the previous year.
Typical reasons for planting or sowing at
higher rates are to prevent or retard the es-
tablishment of exotic species by creating a
denser plant cover earlier; the site may be
subjected to various herbivores, from insects
to deer; maintenance is not likely to occur
on a regular basis; and the site has a known
pattern of experiencing extremes in one or
more natural processes.
The four graphs (figs. 6-7, 6-8, 6-9, and
6-10) illustrate the relationship between
planting density and some of the most fre-
quent factors involved in restoration proj-
ects. However, these graphs represent only
one factor in an idealized situation. In re-
ality, you will be required to address several

FIGURE 6-7. (Top) Site plant cover can be attained
sooner with high planting density; however, for
some species, higher density (i.e., overcrowding)
will negatively affect plant growth and stature.

FIGURE 6-8. (Bottom) Higher planting density
and the occurrence of competition with exotics.
Higher-density planting is a high competition level
for space and light, which frequently will control
densities of exotics.