Refinement for a model describing forage production, animal production and profitability as a function of bush density in the false thornveld of the Eastern Cape

An existing model describing the influence of Acacia karoo density on forage production, animal production and profitablility is reviewed and amended to introduce recent research results.The refined model predicts that maximum forage production can be attained at 1 220 tree equivalents (TE) per ha, maximum livemass production at 1320 TE per ha and maximum gross margin at 1 000 TE per ha. This compares with 850, 2600 and 1 620 TE per ha, respectively, in the original model. The original model over-estimated the potential for livestock production by approximately 51% and generally presented an over-optimistic view of the potential of bush utilisation. Its direct application could help in overstocking by as much as 67%.An algorithm is developed as a field guide for determining optimal long-term stocking rates of grazers and browsers.'n Bestaande model, wat die invloed van Acacia karoo digtheid op voerproduksie, veeproduksie en winsgewendheid beskryf, is nagegaan en verbeter om nuwe navorsing resultate in te sluit. Die verfynde model voorspel dat maksimum voerproduksie by 1 220 boomekwivalente (BE) per ha, maksimum lewende massa produksie by 1 320 BE per ha en maksimumum brutomarge by 1 000 BE per ha bereik kan word. In vergelyking hiermee het die onverfynde model ondeskeidelik 847, 2 600 en 1 620 BE per ha vir die voorgenoemde parameters voorspel. Gevolglik het die tradisionele model die potensiaal vir veeproduksie met ongeveer 51% oorskat en oor die algemeen 'n ooroptimistiese beeld van bosbenutting gestel. Die direkte toepassing daarvan kan 'n oorbelading met soveel as 67% tot gevolg h&#234.'n Algoritme is ontwikkel om, op 'n toegepaste manier, die langtermyn veelading vir gras- en struikvreters te bereken.Keywords browsers, grazers, savanna, stocking rateJournal of the Grassland Society of Southern Africa 1987, 4(1): 18–24