View/Open - ResearchSpace - University of KwaZulu-Natal

underlying mechanisms is needed, before the strengths and weaknesses of each
approach can be assessed (Hirsch et al., 2010).
This chapter examines the nature and significance of biodiversity as well as current
information on the influence of land use and soil management practices on soil
microbial diversity. Some of the more important approaches for analyzing soil
microbial diversity, including their advantages and shortcomings, are also reviewed.
Emphasis is placed on the molecular and metabolic fingerprinting methods that are
applied later in this study.
2.2 THE NATURE AND SIGNIFICANCE OF BIODIVERSITY
2.2.1 Numbers and interrelationships
Soil harbours high biodiversity with fertile surface soils typically containing several
billion prokaryotes (bacteria and archaea) per gram of soil and often an equivalent
fungal biomass (Tiedje et al., 2001). Representatives of all groups of microorganisms,
algae and almost all animal phyla are present in the soil biota and include macrofauna,
mesofauna, microfauna and microflora (Pankhurst, 1997; Nannipieri et al., 2003).
Estimates of the number of species in some of the groups are (Pankhurst, 1997):
• bacteria: 30 000;
• fungi: 1 500 000;
• algae: 60 000;
• nematodes: 500 000; and
• earthworms: 3 000.
Other invertebrates commonly found in soil in large numbers include ants, termites,
collembola and mites (Pankhurst, 1997; Benckiser and Schnell, 2007). The size of
individual organisms in the soil varies greatly, ranging from the smallest bacterium
with a diameter of < 1 µm and a mass of 10 -12 g, to the largest earthworm with a
length of > 1 m, a diameter of > 20 mm and a mass of > 500 g. In fertile soils,
organism biomass may exceed 20 t ha -1 (Pankhurst, 1997).
6