Geoscience Reference
In-Depth Information
Table 12.2
(
Continued
)
Vegetation
Trees
Shrubs
Grasses
Lower order plant life
(e.g. algae, fungi,
lichens)
Longevity (e.g.
perennial grasses
versus ephemeral
forbs)
Above-ground
characteristics (e.g.
plant density and/or
distribution)
Above-ground
stucture (e.g. height,
width and flexibility
in channel flows)
Root characteristics
(e.g. density and/or
distribution)
Vegetation health
Nature of litter layer
Vegetative factors influence:
Rates and volumes of
hillslope runoff
Rates, volumes and calibre
of hillslope sediment
supply
Channel boundary
(especially bank) strength
Channel flow hydraulics
and sediment transport rates
Australian drylands: typically
well-developed riparian
vegetation assemblages,
including long-lived, deep
rooted trees and various
shrubs and grasses, many of
which establish on lower
channel banks or on
channel beds. Large
vegetative contribution to
channel boundary strength
and flow resistance
Peruvian/Chilean Atacama
desert (coastal setting):
large areas virtually devoid
of vegetation cover but,
where present, vegetation
consists mainly of patchy
dwarf shrubs and some
lower order fog-dependent
plants. Limited vegetative
contribution to channel
boundary strength and flow
resistance
Table 12.3
Generalised characteristics of Mediterranean, southern African and Australian dryland fluvial environments. While
considerable fluvial diversity can be found within each of the three regions (see text for details), these generalisations serve to
highlight some of the main contrasts.
Mediterranean region
Southern Africa
Australia
Subhumid to hyper-arid climates:
Subhumid to hyper-arid climates
Subhumid to arid climates
Dominance of small, steep catchments
Dominance of moderate-size,
moderate-gradient catchments
Dominance of large, low-gradient
catchments
Mainly endogenous rivers, but some
exogenous rivers
Exogenous and endogenous rivers
Mainly partly exogenous and endogenous
rivers
Ongoing tectonism in many areas, albeit
to varying degrees
Limited large-scale tectonism during the
Quaternary
Limited large-scale tectonism during the
Cenozoic
Variable geological structures and
lithologies
Variable geological structures and
lithologies
Variable geological structures and
lithologies
Cenozoic palaeoclimatic changes with
sea-level changes also impacting on
lower reaches of rivers with a coastal
outlet
Cenozoic palaeoclimatic changes but
with limited influence of sea-level
changes on most dryland rivers
Cenozoic palaeoclimatic changes but
with most dryland rivers isolated from
Quaternary sea-level changes
Variable development of native riparian
vegetation communities, many
invasive species
Variable development of native riparian
vegetation communities, many
invasive species
Very well-developed native riparian
vegetation communities, some invasive
species
Long history (1000s of years) of
significant human impacts
Recent history (last 100-150 years) of
significant human impacts
Recent (last 100-150 years) or negligible
history of significant human impacts
