Design - Project Planning and Management for Ecological Restoration - page 88

FIGURE 6-5 A,B,C . Three examples of equivalent edge to area designs illustrating the importance of design
to approximate specific habitat requirements of target species.
wildlife species requiring edge for some aspect of their life history. Then again, there are numerous
species that occur in more homogeneous areas and avoid edges. Knowing this habitat requirement
for your target species is especially important when designing your project. If your site is of insuffi-
cient size, you may want to focus on reducing edge because the distances within the various habitats
on your site may be insufficient to have the desired effect on targeted species. Increased abundance
and diversity of wildlife along edges frequently increases biotic interactions, such as predation, brood
parasitism, and competition. Depending on your goals, these outcomes may be acceptable.
Knowing your target species or species guild will assist in the decision-making process of design
(Morrison 2009). In many cases, natural history studies are available that provide sufficient details from
which a design can be formulated. However, this is not always the case, such as for the work the senior
author conducted on the endangered least Bell's vireo in California, for which detailed natural history
studies did not exist. So, in that case, habitat studies were conducted on three rivers that comprised a
little over 10 percent of the known population at that time. These data were synthesized into a design
model that included plant counts, plant heights, and pattern within a quadrant. The results of these
field studies were used successfully to create several projects (figs. 9-3 and 9-5) (Baird and Rieger 1989).
SLOPE ASPECT/ORIENTATION
The duration of direct sun on various slopes contributes to the occurrence of vegetation commu-
nities. Some communities occur consistently or have healthier growth on a specific slope aspect.
Moisture is believed to be the primary factor controlling this distribution. Following the seeding
and planting of containers, we have observed a shifting of vegetation in response to a pattern of
inland sage scrub preferring east- and south-facing slopes and chaparral occurring predominantly
on northern and western slopes.
SOIL AFINITIES
In many cases, a complex of species has adapted to unusual or uncommon soil conditions. Some-
times the distribution of soil may be a few square meters, or other times it may cover hectares. Know-