ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

pass with a duckfoot chisel, expressed by the diffusion
constant (k), equals 282 kg/m for up and downslope tillage
and only 139kg/m for contour tillage. Nomograms indicate
that mean denudation rates in almond groves due to tillage
erosion (3 to 5 tillage passes per year) can easily amount to
1.5 - 2.6 mm/year for contour tillage and up to 3.6 - 5.9
mm/year for up- and downslope tillage for a field, 50 m
long and having a slope of 20 0/0. These figures are at least
one order of magnitude larger than reported denudation
rates caused by water erosion in similar environments.
Hence tillage erosion contributes significantly to land degradation.
The downslope soil flux induced by tillage not
only causes considerable denudation on topographic convexities
(hill tops and spurs) and upper field boundaries
but also an important sediment accumulation in topographic
concavities (hollows and valley bottoms) and at
lower field boundaries. Kinetic sieving (i.e. the upward migration
of rock fragments) by the tines of the duckfoot chisel
also concentrates the largest rock fragments in the topsoil
in such a way that a rock fragment mulch develops in
narrow valleys and at the foot of the slopes.
These results clearly indicate that tillage erosion is the
main process responsible for the observed rock fragment
cover pattern in the study area. Since the study area is representative
for many parts of the Mediterranean where almond
groves have expanded since 1970, the results have a
wider application. They show to what extent intensive tillage
of steep slopes has contributed to the increase in soil
degradation, to changes in hillslope morphology (i.e.
strong denudation of convexities, development of lynchets
and rapid infilling of narrow valley bottoms) and to the development
of patterns of leptosols and of rock fragment
cover which control the spatial variability of the hydrological
and water erosion response within such landscapes.
NATALIA PONIATOVSKAIA
L'annalyse geomorphologique de l'aire urbaine de Moscou
Departement de Geographie, Universite d'Etat «M. V. Lomonosov»,
Colline de Lenin, 119899 Moscou, Russie
L' aire urbaine de Moscou, comme toute autre partie de la
surface terrestre, occupe une certaine position geographique,
presente certaines caracteristique du relief et une
somme de processus geomorphologiques. Acause du fort
impact d'un complexe de facteurs techno-genetiques, elle
devient un facteur essentielqui produit un effet apreciable
sur l' atmosphere, hidrosphere, biosphere et lithosphere,
effet qui depasse beaucoup les dimensions de la ville proprement-dite.
En coexistant sous les memes conditions climatique et
structural-tectoniques, les composants naturels et technogeneriques
se developpent en etroit contact, entre eux existant
des interrelations et des interactions varices:
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- des relations naturelles, historiques, genetiques et dynamiques
entre les elements du milieu geologique-geographique;
- echange hydrodynamique entre les elements naturels et
les composants techno-genetiques, qui implique les precipitations,
les eaux de surface et souterrains et les acumulations
liquides. Dans la ville l'echange de l'eau functionne
en meme temps par des voies naturelles (precipitationsdrainage)
et par des instalations hydrotechniques (conduits,
systemes de collection et drainage etc.);
- «engineer» relations, comme l'ecoullement hydrodynamique
dirige par constructions hydrotechniques, et en
plus, des relations entre topographie, hidrosphere, atmosphere
et differentes installations d'ingenierie,
Tous ces relations entre les elements naturels et technogenetiques
du milieu urbain peuvent etre en caractere direct
ou inverse, les objets naturels etant plutot passifs, en
temps que ceux techno-genetiques-plutot actifs.
MARION B. POTSCHIN & HARTMUT LESER
Geomorphological processes and sediments modifying
geoecological conditions in the High Arctic
(N orthwest-Spitsbergen)
Department of Geography, University of Basel,
Spalenring 145, CH-4055 Basel, Switzerland
The investigated (approx.) 5 km 2 drainage basin (compare
figure) was located on the south shore of the Liefdefjorden
at almost 80 0N (13°E) and is partly glacierised (approx,
35 0/0). Because of the influence of the gulfstream, the climate
has to be characterised, despite the high latitude, as
mild.
Field studies were conducted to examine the environmental
factors which influence or control water amount and
soil water chemistry in the high arctic tundra. Specially,
theses studies focussed on variations in solute chemistry
during the high arctic seasons. For this purpose five princi-