Grasslands of the World.pdf - Disasters and Conflicts - UNEP

386
Grasslands of the world
was to be refined and effected for land management and, ultimately, grassland
improvement . Both the objective and framework of the approach were prescribed.
However, more than elsewhere in the world, classification in the country
lost itself in attempts to be all-USSR in compass, ending up with hundreds
of codes and numbers. Colloquial terms could have summed it all up in one
word (e.g. mochazina – non-peaty swamp; liman – flooded steppe in the lower
reaches of rivers). Impeded drainage means swamp in the northern forest country,
but lush pasture in the steppe. Conversely, overgrazing can lead to bareness
to an extent that the vegetation assumes the appearance of a drier climate than
rainfall data suggest. Grasslands – and steppe are no exception – are an integration
of climate, soil, animal and man-made conditions. Vegetation may often
provide a better guide to the agricultural environment than the instruments of
meteorologist or geologist (Whyte, 1974). “What are the main species and what
do they tell us?” is often a most relevant question.
Grasslands are subject to fluctuations in composition, but recurring patterns
are recognized. The major features, physiognomy (the aspect in terms
of height, density and cover) and species, are fairly constant or they oscillate
around a certain equilibrium, both between and within woody and herbaceous
species. Major changes are usually a long-term affair. Only when grassland
is artificially drained permanently of excess water, or altered dramatically by
repeated ploughing and cropping, can changes in the vegetation become irreversible.
As we will see, steppe is relatively quick to restore.
ECOLOGICAL (SITE) POTENTIAL
Much as early classifications were based on botanical composition , awareness
was growing that ecological potential could be related to a recognizable
vegetation group . To many observers, however, current vegetation is a very
poor indicator of ecological potential and possible land use. The problem is then
how to reconcile current vegetation with ecological potential. Classification
means one thing to the specialist in phytogeography, but quite another to the
planner concerned with grassland improvement . Site potential – that is, the
vegetation that ecological factors indicate should dominate – is the guiding
factor. A climax vegetation can be reconstructed based on natural succession
towards an equilibrium with the environment. This process may be interrupted
and vegetation may then be described as, say, a “fire subclimax ” or a “grazing
subclimax”. The concept of climax should relate to site potential as determined
by physical factors of the environment: climate, soil and topography. Tundra,
steppe and semi -desert are then ecoclimatic zones , which can be characterized
further by plant species and associations to delineate recognizable types of
vegetation.
The term grassland or steppe is here used to denote a vegetation that is
dominated by grasses and occasionally herbs, whatever the plant succession.
The grasses used in cultivation today are those found growing in the wild