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badlands of North Dakota). The results of Cerda and
Garcıa-Fayos (1997) suggest that slope-related differ-
ences may relate more to different erosional behaviour,
rather than differences in runoff production. Regues,
Guardia and Gallart (2000) demonstrate an opposite
asymmetry related to aspect, where the north-facing
slopes in Pyrenean badlands have lower vegetation cover
and higher erosion rates as a result of frost action in
the winter. Once significant erosion episodes have taken
place, the seedbank will be severely depleted or ab-
sent (Guardia and Recatala, 1992; Garcıa-Fayos, Garcıa-
Ventoso and Cerda, 2000; Guardia, Gallart and Ninot,
2000), so the ability of plants to disperse seeds over long
distances was identified by Bochet, Garcıa-Fayos and
Poesen (2009) as a primary trait of colonising species.
They also suggested that plants producing seeds with
mucilaginous coatings that are able to bind to biologi-
cal crusts also have a significant advantage in the col-
onization process. Some grass species in the Mediter-
ranean seem to have adapted specially to colonising in
these types of condition (Danin, 2004; Guardia, Ravent os
and Caswell, 2000). Garcıa-Fayos, Garcıa-Ventoso and
Cerda (2000) noted that the extreme badland environ-
ment - even in relatively temperate conditions in the Pyre-
nean foothills - leads to high rates of seedling mortality
even once germination takes place. Pintado et al . (2005)
point to higher lichen covers on north-facing slopes in
the Tabernas badlands in southern Spain. This difference
may be an important differential stabilisation mechanism
here (e.g. Alexander et al . 1994). Once colonisation takes
place and runoff and erosion are reduced, plants that repro-
duce vegetatively may take over (Bochet, Garcıa-Fayos
and Poesen, 2009), although Guerrero-Campo, Palacio
and Montserrat-Martı (2008) also found that plants with
vegetative reproduction were best able to sustain them-
selves on actively eroding slopes.
As well as vegetation, Torri, Calzolari and Rodolfi
(2000) identified lithology, structure and bedrock, climate
and human activities as significant controls on badland
formation and behaviour. Lithological controls may relate
to regional variation - not least the localization of uncon-
solidated bedrocks - as well as to smaller-scale variability.
Cerda (2002) notes that badlands near Alacant in Spain
may be forming as a result of diapiric behaviour of the
clays in the bedrock, leading to incision of the main river
channel and thus gullying and badland development. Salt
diapirs near to the terres noires badlands studied by Wain-
wright (1996a) in southern France (Figure 10.5) may have
a similar effect. At Cerda's study site, the behaviour of sur-
faces varies spatially as a function of whether marl, clay
or sandy bedrocks are at the surface. The former two sur-
faces undergo shrink-swell changes as a result of wetting
and drying cycles, producing heavily cracked conditions,
especially in the dry summer months (Figure 10.6). As a
result, ponding and runoff occur more rapidly, and runoff
coefficients are higher in autumn, when the surfaces are
less cracked. The marls produced most runoff, followed
by the sands, due to the presence of a surface crust (see the
Figure 10.5 Localized badlands near to Propiac, Drome, France, showing a small runoff event in 1993 with well-developed rill
flows (Wainwright, 1996b). Note the control of lithology - the alluvial deposits in the foreground are used for vine cultivation but
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