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Simulated pattern formation around artificial waterholes in the semi‐arid Kalahari
Author(s) -
Jeltsch Florian,
Milton Suzanne J.,
Dean W. Richard J.,
Rooyen Noel
Publication year - 1997
Publication title -
journal of vegetation science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 115
eISSN - 1654-1103
pISSN - 1100-9233
DOI - 10.2307/3237346
Subject(s) - shrub , arid , trampling , vegetation (pathology) , environmental science , grazing pressure , grazing , stocking , hydrology (agriculture) , ecology , rangeland , agroforestry , geology , geography , forestry , biology , medicine , geotechnical engineering , pathology
. Sinking boreholes to tap groundwater supplies facilitated expansion of all‐year round livestock production into the semi‐arid Kalahari. Increased grazing and trampling pressure around the boreholes often caused vegetation changes and range degradation. The long‐term influences of cattle grazing on vegetation pattern around watering points in the southern part of the semi‐arid Kalahari are investigated using a grid‐based simulation model. Shrub‐grass dynamics are modelled for two regimes with high and low rainfall and under various stocking rates. Results indicate the formation of distinct vegetation zones (‘piosphere’ zones) at the high rainfall site. Under all tested stocking rates distinct zones of bare soil, woody shrubs and a mixed grass‐shrub savanna develop. The piosphere zones expand outwards at a rate correlated with the grazing pressure. At the lower‐rainfall site zone development is limited and influenced by rainfall. Under abnormally high stocking rates an increase in shrub cover occurs within 50 yr under the low rainfall regime, leading to less distinct zones than under the high rainfall scenario. Modelling results suggest that the recovery potential of shrub‐encroached piosphere zones after withdrawal of cattle is negligible in a time span of 100 yr.