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Functions
& Conditions -
Evaluating the Biological Features
Vegetation
plays a critical part in the health of a riparian area. It is also
important for management because plant communities often provide
the first indicators of changes to the system. Important factors
to consider when looking at riparian vegetation include: (1) the
types and amounts of plants present; (2) how well they are fulfilling
riparian functions; (3) the amount of foraging and browsing pressure
being exerted on certain plants; and (4) the mix of age classes
of woody species if present.
Streambank
protection provided by a deep, binding root mass
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Figure
2-18
The root systems of sedges and rhizomatous grasses provide
effective streambank protection along low gradient,
narrow channels such as this one. |
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Vegetation is
important in slowing flow velocity, stabilizing streambanks, and
reducing erosion. Different types and species of plants provide
differing amounts of protection. The best soil stabilizers and streambank
holders are woody species (trees and shrubs). The extensive root
systems of woody species are especially effective in the development
of overhanging banks, which provide habitat for fish and other aquatic
organisms. On some streams--for example, low gradient, sinuous types--the
proper herbaceous (non-woody) species can provide the necessary
protection (Figure 2-18).
Annual herbaceous
species (such as cheatgrass) generally lack sufficiently dense,
deep root systems to provide much protection. Perennial herbaceous
species vary greatly in their soil-binding capabilities. Many species
with rhizomatous root systems (such as sedges and prairie cordgrass)
are very effective at holding streambanks together. Bunchgrasses
often provide only limited protection. Regardless of the species,
the more vigorous the plants and the denser they are, the better
protection they can provide.
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