ABSTRACT
Grasslands are complex ecosystems comprising numerous biotic and abiotic components. The biotic components are the herbaceous grass and forb plants, soil organisms and grazing graminivores which have biological and physiological requirements. The abiotic components include radiant energy from sunlight; the essential major elements of carbon, hydrogen, nitrogen and oxygen, and the minor essential elements of macro-and microminerals required by living organisms. The major elements and some of the minor elements have biogeochemical cycles which transform the elements between organic and inorganic forms. Grassland ecosystems are therefore functioning units of co-acting biotic organisms interacting with the abiotic components and environmental factors (Manske 2014c). Grass plants, soil microorganisms and large graminivores have developed complex symbiotic relationships. The grazing graminivores depend on grass plants for nutritious forage; grass plants in turn depend on rhizosphere organisms for the mineralisation of essential elements (primarily nitrogen) from the soil organic matter; rhizosphere organisms depend on grass plants for energy in the form of the short carbon chains released by grass plants into the rhizosphere following partial defoliation by grazing graminivores. The management of grassland ecosystems must therefore meet the biological and physiological requirements
of the plants, soil organisms and graminivores; stimulate internal plant mechanisms; and enhance the rhizosphere organism biomass and the ecosystem biogeochemical processes that cycle essential elements (Manske 2014c).
