Environmental Engineering Reference
In-Depth Information
Extreme high water
Average high water
CLAY
Average summer water
SAND
Low water
PEBBLES
annual
weeds
flood
plain
grass-
land
reed
bed
Salix
shrubs
Salix
woodland
Alnus
woodland
Ulmus-Quercus
woodland
deciduous
forest
WATER
FLOODPLAIN
WITHOUT TREES
FLOODPLAIN
WITH WOODLAND
OUTSIDE
FLOODPLAIN
Fig. 3.7
Vegetation zonation along rivers in relation to flooding frequency (after Ellenberg 1986). Reproduced by
permission of Verlag Eugen Ulmer.
central town
free company
forestry
crop rotation agriculture
arable fields
three-phased agriculture
low-intensity cattle breeding
250 km
Fig. 3.8
Land use patterns around a town
according to the schema of the German
agricultural economist Von Thünen (1826,
cited in Bieleman 1992). The zonation in
this model is mainly caused by the factor
transport costs
. Reproduced by permission
of the publisher.
Small town
with own region
River
2001, de Meester
et al.
2002) showed that sites with
very similar abiotic conditions could differ consider-
ably in species composition. These results fit very well
with the inhibition model of Connell and Slatyer
(1977), which states that in the case of organisms with
low colonization rates such as plants or low-mobility
insects chance alone would lead to different species
assemblages in otherwise similar sites during the first
phases of the colonization processes. Indeed, existing
theories on invasibility (Elton 1958) state that the resist-
ance of a given area to species enrichment increases
with the number of species already present and this
implies that the first stages can have a significant
impact on the final community composition. How-
ever, this theory is also criticized (e.g. Levine &
D'Antonio 1999).
