Fjölrit RALA - 05.12.1999, Blaðsíða 96

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Rangeland degradation in Northern China
more rapid for lightly or moderately grazed range than for heavily grazed range. One
of the main conclusions from the analysis is that, in general, we have a very non-linear
system. The responses of rangeland to these disturbances, nature-induced or human-
induced, are very non-linear and somewhat shown as cumulative environmental
change. Linear projections can not be made unless for some special controlled com-
ponents.
In the study area, yearly mean overgrazing rate is lower than 20%, even negative in
some cases, but when rainfall becomes less than average, the stocking rates are far be-
yond the carrying capacity and the vegetation is badly overgrazed. Many perennials
are destroyed and progressively replaced by unpalatable species. It is suggested that
constant stocking rate, accompanied by fluctuations in carrying capacity of the land
may be the main reason for regional rangeland degradation. The decreasing of stock
diversity is another reason (Bell 1971, Jia 1996).
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