River Ecology and Restoration - River Dynamics and Integrated River Management - page 703

Large-scale restoration work sometimes includes panting of understory species, particularly if they are
required to meet specific objectives such as providing essential components of endangered species
habitat. However, it is often difficult to establish understory species, which typically are not tolerant to full
sun, if the restoration area is open. Where understory species are unlikely to establish themselves for
many years, they can be introduced in adjacent forested sites, or planted after the initial tree growth to
create appropriate understory conditions. Understory species seeds are commonly broadcast by hydroseeding,
requiring a special tank truck with a pump and nozzle for spraying the mixture of seeds, fertilizer, binder,
and water (Fig. 10.58). A wider range of seed species can be planted more effectively with a seed drill
towed behind a tractor (Haferkamp et al., 1985). Where access is limited, hand planting or aerial
spreading of seeds might be feasible.
Fig. 10.58 Hydroseeding of a streambank for restoration of understory riparian vegetation. Special tank trucks
carrying seed, water, and fertilizer are used in the revegetation efforts (after FISRWG, 1997)
In the past, stream corridor planting programs often included nonnative species selected for their rapid
growth rates, soil binding characteristics, ability to produce abundant fruits for wildlife, or other perceived
advantages over native species. These actions sometimes have unintended consequences and often prove
to be extremely detrimental (Olson and Knopf, 1986). As a result, many local agencies discourage or
prohibit planting of nonnative species within wetlands or prohibit planting streamside buffers. It may be
feasible in some cases to focus restoration actions on encouraging the success of local seed-fall to ensure
that locally adapted populations of vegetation are maintained on the site (Friedman et al., 1995).
Nest structures —Loss of riparian or terrestrial habitat in stream corridors has resulted in the decline
of many species of birds and mammals that use associated trees and tree cavities for nesting or roosting.
The most important limiting factor for cavity-nesting birds is usually the availability of nesting substrate
(von Haartman, 1957), generally in the form of snags or dead limbs in live trees (Sedgwick and Knopf,
1986). Snags for nest structures can be created using explosives, girdling, or topping of trees. Artificial
nest structures can compensate for a lack of natural sites in otherwise suitable habitat since many species
of birds will readily use nest boxes or other artificial structures. For example, along the Mississippi River
in Illinois and Wisconsin, U.S., where nest trees have become scarce, artificial nest structures have been
erected and constructed for double-crested cormorants using utility poles (Yoakum et al., 1980). In many
cases, increases in breeding bird density have resulted from providing such structures (Strange et al.,
1971; Brush, 1983). Artificial nest structures can also improve nestling survival (Cowan, 1959).
Nest structures must be properly designed and placed, meeting the biological needs of the target
species (FISRWG, 1997). They should also be durable, predator-proof, and economical to build. Design
specifications for nest boxes include hole diameter and shape, internal box volume, distance from the