Design - Project Planning and Management for Ecological Restoration - page 89

ing if you are in a location with unusual soil
and species associations adapted to those soils
will be critical in the planning of where and
how to obtain specimens. Serpentine plant
community is found primarily on serpentine
soils, and several species in this community
are considered rare because they occur only
on these soils. In situations such as this, it is
important to determine the subspecies or vari-
ants; it is not uncommon for species to have
locally adapted forms. This is very important
to project success because available inventory
may not grow adequately on your site.

MOISTURE REQUIREMENTS OR TOLERANCE
Moisture level strongly influences the sorting
of species in the vegetation. As previously dis-
cussed in zonation, this moisture level is more
general and manifests itself as isolates or col-
onies within a larger, contrasting vegetation
community. Seeps, or perched water tables,
often contribute to this situation. Areas with
several soil types with varying abilities in water
retention will also permit some species to per-
sist in an otherwise unsuitable location. Small
pockets of soil can create significant changes
in the vegetation. In some cases, plantings
will not survive, because the extremes of the
moisture exceed the tolerance of the plant.
Given all of these factors, you still have
several decisions that must be made to com-
plete the design of a project. Studies on
islands have demonstrated a relationship
between larger size islands, in either land
mass or vegetation area, and an increase in
species diversity. Using the findings of these studies and his personal observations in New Guinea,
Jared Diamond (1975) developed a hypothetical configuration graphic that illustrates immigration
potential (fig. 6-6). The preferred geometric design typically has more area to edge, less distance,
or a connection by corridor. When working on large tracts of land, it may help to approach your
restoration projects with these models in mind. The size of these islands also factors into the ex-
pected species supported (Howell, Harrington, and Glass 2012).

FIGURE 6-6. The ease and frequency of
wildlife movement from one island to the next
is determined by distance and size of the island.
Occupation of an island is also influenced by the
configuration. (Adapted from Diamond 1975 and
used with permission by Elsevier Science.)