Inter‐related floristic changes associated with different long‐term grazing treatments in Sourish Mixed Bushveld¹

Based on part of an M.Sc. Agric. thesis at the University of Pretoria

Abstract

Eight camps, grazed annually during different seasons by steers, were surveyed. Herbaceous species were grouped into Decreaser and Increaser categories according to their reaction to grazing. The Increaser IIa (light overgrazing) and IIb (moderate overgrazing) herbaceous species were the most abundant and were significantly negatively correlated. Woody plants and aloes (Aloe transvaalensis) were positively correlated (P≤0.01) with Increaser IIb herbaceous species. The latter were negatively correlated (P≤0.01) with grass production. The production of Panicum maximum was negatively correlated (P≤0.01) with tree canopy cover, owing to its intolerance to severe grazing which contributed to an increased canopy cover. While representing the same amount of animal unit grazing days ha⁻¹ (stocking density × period of occupation during growing season), a relatively high stocking density and occupation for part of the growing season had a less severe long‐term effect on the floristic composition than a relatively low stocking density and occupation for the whole growing season.

Agt kampe, jaarliks bewei deur osse gedurende verskillende seisoene, is ondersoek. Na aanleiding van hul reaksie op beweiding is grasspesies en kruide in Afnemer‐ en Toenemergroepe ingedeel. Die Toenemer IIa (ligte oorbeweiding) en Toenemer IIb (matige oorbeweiding) kruidagtige spesies was die talrykste en was betekenisvol negatief gekorreleer. Houtagtige plante en aalwyne (Aloe transvaalensis) was positief gekorreleer (P≤0.01) met Toenemer IIb kruidagtige spesies. Laasgenoemde was negatief gekorreleer (P≤0.01) met grasproduksie. Die produksie van Panicum maximum was negatief gekorreleer (P≤0.01) met persentasie boom kroonbedekking, hoofsaaklik as gevolg van sy swak toleran‐sie vir strawwe beweiding wat tot ‘n verhoogde kroonbedekking bygedra het. Terwyl dit ‘n gelyke aantal vee‐eenheid weidae ha⁻¹ (veedigtheid × besettingsperiode gedurende die groeiseisoen) verteenwoordig, het ‘n relatiewe hoë veedigtheid en besetting vir ‘n gedeelte van die groeiseisoen ‘n minder nadelige langtermyn effek op floristiese same‐stelling gehad as ‘n relatiewe lae veedigtheid en besetting vir die voile groeiseisoen.

Additional index words:

• Grass production
• grazing gradient
• Increasers
• species composition
• tree density

Notes

Based on part of an M.Sc. Agric. thesis at the University of Pretoria