期刊
APPLIED VEGETATION SCIENCE
卷 3, 期 2, 页码 261-268出版社
WILEY-BLACKWELL
DOI: 10.2307/1479005
关键词
Equilibrium; Herbivory; Kalahari; Land degradation; Large herbivore; Non-equilibrium; Overgrazing; Merxmilller (1966) for plant species
资金
- Animal Production Research Unit at Botswana Ministry of Agriculture
- Swedish International Development Authority (SIDA)
- EU [INCO-DC ERBIC18CT970162]
. It is remarkable that after many thousands of years of pastoralism in arid and semi-arid savannas, there is still no clear answer to the basic question: Does livestock grazing have more than a marginal effect on the dynamics of arid and semi-arid land vegetation? A small study of semi-arid savanna vegetation along a spatial gradient in grazing pressure, repeated three times over 19 years is used as a basis for discussing the behaviour of dry land vegetation under heavy grazing. Three basic theories are compared: (1) the theory that heavy grazing causes desertification; (2) the theory that heavy grazing causes no directed change in the vegetation of arid and semi-arid rangelands; and (3) the theory that heavy grazing leads to a switch between alternative states of vegetation. On the basis of the current data the first two theories are rejected, but the conclusion is that there is much evidence for a more complex behaviour of dry rangelands under grazing than what is accommodated in any of the three theories. Probably, site-specific properties including interactive and indirect effects of herbivory in the system are important for vegetation development under grazing in arid and semi-arid rangelands.
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