It is known that physical geographical processes are not
pictured directly on aerial photos because they are not clear vi-
gible. But there is a close correlation between visible and non-
visible elements of nature. So one can use visible elements as in-
dicators. Topography, vegetation and in some cases soils (if vege-
tation is absent) are the visible elements.
Desert vegetation belongs to one of the important indica-
tors of geographical processes. The possibility of its identifica-
tion depends of the photographic image scale. Oomposition of low
and sparse desert vegetation on morhologic features can be estima-
ted on large scale photos (I:2 O00 - I:5 000), and in some cases -
one extra large scale photos (I:1000). But large scale photography
is very expensive. Taking into account this consideration large
scale photography schould be used selectively in combination with
photography of smaller scale. Uo
The most suitable scales to study geographical processes
are I:IO OOO - I:25 O00. One also can use photographic mosaics and
maps compiled on the base of aerial photos.
Repeated aerial photography is an important tool to: study MM
a desert Landscape as a whole or to study the dynamics of natural [Ath
processes. The comparison of repeated photos allow to study diffe-
rent stages of desert landscapes development. Such photos give the
possibility to study trends in this development.
On the key area in: south-east Karakum we studied the chan-
ges of desert-environment under the human pressure (Karakum canal
construction). Interpretation of aerial photos, field and literatu-
re study gave the information for the estimation of the following
stages of desert landscape development:
I. Natural state of desert enviroment before the Karakum
Canal construction. Sand ridges and depressions (7-I0 m in depth and
30-50 m in width) formed the topography. Plant ässociation Haloxy-
lon persicum + Salsola richteri + Calligonum sp. dominated here.
In some places shifting sands occured on upper parts of ridges. Un-
derground water is deep, depending on topograhy its level changed
from 5-IO m till 20-40 m. The content of salt in the soil was very
low. The human pressure was limited, moderate grazing caused the
formation of desertification spots around the desert wells.
II. The sate of desert environment during the construction
of the Karakum Canal. Along the canal route natural’ desert lands-
cape was changed by numerous machines. At the distance of 500-1 000
m the sand relief was levelled by the soil excavated from the canal
and laterby the pulp.. While the garthwork by the canal construction
a great amount of sand (70 mln. m^) was excavated (O.N. Nurgeldyev,
I969). Vegetation cover was also destroyed on a large area. The const-
ruction of the Canal accellerated the wind erosion on its way and
formation of barkhan dunes, I-2 m in height.
III. The sate of desert environment in IO years period
after the Canal construction. During this period on the construction
sites where the wind erosion process occured new plants species
(sand binders) appeared. But vegetation cover on this stage was com-
paratively sparse; it mainly consisted of Aristida karelini, a pio-
ner plant species, On the areas with strong wind erosion special
fences were established. Behind the strip of barkhan dunes a narrow
Strip of semi-stable dunes appeared. It is a transitional strip bet-
ween semi-stable sand dunes. Density of shrubs is here 50-IOO plants
per I hektar. Near to this area a belt of filtration lakes began.
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