Design Approach - Project Planning and Management for Ecological Restoration - page 73

tions may no longer exist, but the species or assemblage may have matured to a point where they
can persist. Determining the age of the vegetation or assemblage will enable you to determine the
climatic conditions during the time when the vegetation was established and will permit compar-
ison with the present-day climatic conditions. If current climatic conditions are similar, then es-
tablishing this assemblage may be feasible. Aging the vegetation can be done in a number of ways,
from coring of tree trunks or cutting cross sections of shrubs and analyzing the rings to analyzing
a series of old aerial photographs.
In some cases, the primary issue is the soil surface condition and the possible accumulation of
chemicals and heavy metals. In many arid-land systems of the world, salts accumulate in the up-
per soil layers and prevent the natural reproduction of plants. However, because the more mature
plants have roots several inches to several feet below the surface, they are unaffected by the build-
up at the surface. In these cases, it would not be advisable to plant or sow seed in the currently
unvegetated locations because the conditions of the site have obviously been altered.
Another consideration in using a reference database is the distance the reference data was
collected from the project site. Even though you may be in the same vegetation community and
at similar altitude, the reference database may be considerably different. How far away from your
site can you rely on reference site data? Unfortunately, there is no rule of thumb. We have collect-
ed data for an endangered bird species in southern California scrubland. Only fifty miles farther
north along the coast, the vegetation, composition, and structure of southern California scrubland
differs markedly in species composition and cover characteristics. It is always advisable to conduct
some initial data collection and compare it with your intended database before committing too
many resources to the project. This simple preliminary step can eliminate lost time and resources.
As with almost anything involving sampling, it is best to have a number of locations so that
these differences can be merged and variation ranges can be determined and incorporated in the
planning and design. A significant project in Scotland has, for the past fourteen years, been restor-
ing an entire watershed using data collected from the adjacent extant stands of native vegetation as
well as using library resources to compile their reference model (box 4-2). Figure 5-3 shows Carri-
fran Valley at the beginning of the planting operations in its first year. After twelve years, essentially
all of the areas designated for forest restoration have been completed, with the focus on monitoring
and adding the more rare species from the area. In this example, the predominant approach is a
reference model; however, they have used historical reconstruction and remnant approaches to
further enhance their model and increase the diversity of species reintroduced onto the site.
Historical Reconstruction
The historical reconstruction approach refers to the past condition, frequently targeting a time of
some significance to the region or community of the project. Although aspects of this approach
include preservation techniques, this approach relies on restoring landscapes that for whatever
reason were removed from the site.
Historical parks, monuments, and sites of cultural significance have their models based on the
historic, and sometimes the archeological, record from the region (Egan and Howell 2001). Re-