Effects of herbivore exclosures on variation in quality and quantity of plants among management and habitat types in a semiarid savanna

  • KR Mbatha
  • D Ward

Abstract

The effects of grazing on plant biomass, plant quality, species evenness, species diversity and species composition were determined among management types (communal, commercial and game) and among habitat types (open savanna, rocky and pan) in a semiarid savanna in South Africa. Over three growing seasons we compared fenced and unfenced plots among all management and habitat types. Fenced plots had greater mean plant height as well as higher crude protein (CP) and phosphorus (P) yields (= concentration x biomass). The only significant difference in species composition between fenced and unfenced plots was observed in the pan habitat type during the third growing season. Negative effects of grazing were more pronounced in the commercially managed area than under other management types, although the higher abundance of poisonous plants under communal management is of considerable concern. The open savanna habitat had the highest plant biomass and lowest CP and P levels, while the reverse was true for the pan habitat type. Most parameters assessed showed significant effects between fenced and unfenced plots towards the end of the study only because species composition in fenced plots was altered by competition between species  normally suppressed by grazing.

Keywords: grazing, herbivory, plant biomass, plant quality, rangeland management

African Journal of Range & Forage Science 2010, 27(1): 1–9

Author Biographies

KR Mbatha
Department of Conservation Ecology, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa; current address: National Zoological Gardens of South Africa, PO Box 754, Pretoria 0001, South Africa
D Ward
School of Biological and Conservation Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, South Africa
Section
Articles

Journal Identifiers


eISSN: 1727-9380
print ISSN: 1022-0119