River Ecology and Restoration - River Dynamics and Integrated River Management - page 638

Assessing habitat function at small scales can also be viewed in terms of patches and corridors. It is
also at local scales that transitions among the various habitats within the river can become more important.
Two basic types of habitat structure: interior and edge habitat can be found in stream corridors. Connectivity
and width greatly influence the functions of habitats at the corridor scale. A stream corridor provides a
better habitat if it is wide and if it has greater connectivity. Changes in plant and animal communities can
be caused by river valley morphology and environmental gradients, such as gradual changes in soil
wetness, solar radiation, and precipitation. Species usually find ideal habitats in broad, unfractured, and
diverse streams, rather than narrow and homogenous ones.

Fig. 10.12 The Fazi River, an urban stream in Taichong City, provides habitats for benthic invertebrates, fish and birds

Factors such as climate, microclimate, elevation, topography, soils, hydrology, vegetation, and human
uses, cause the habitat conditions within a river to vary. When planning to restore a stream, its width is of
great importance to wildlife. The size and shape of a stream corridor must be sufficiently wide for a
species to populate. This must be considered when trying to maintain a certain wildlife species. If the
corridor is too narrow, from the point of view of the species, it is as if there is a piece of the corridor
missing.
Riparian forests provide diversity not only in their edge and interior habitats but also offer vertical
habitat diversity in their canopy, sub-canopy, shrub, and herb layers. Within the channel itself, riffles,
pools, glides, rapids, and backwaters all provide different habitat conditions in both the water column
and the streambed. These examples, all described in terms of physical structure, yet again show that there
is a strong correlation between structure and habitat function.

10.1.4.2 Conduit Function
To act as a route for the flow of energy, materials, and organisms is known as the conduit function, as
shown in Fig. 10.13. A stream is foremost a conduit that was formed by and for collecting and transporting
water and sediment. As well as water and sediment, aquatic fauna and other materials use the stream
corridor as a conduit. Since there is movement across as well as along the stream and in many other
directions, the corridor can be considered to have lateral and longitudinal conduit functions. If the stream
corridor is covered by a closed canopy, then birds and mammals may cross over the stream through the
vegetation. The food supply for fish and invertebrates may be enriched or increased by the movement of
organic debris and nutrients from higher to lower floodplains.
Corridors can act as pathways and habitats at the same time for migratory or highly mobile wildlife.
The migration of songbirds from their wintering habitat in the neo-tropics to a summer habitat further