Implications of Soil Biodiversity for Sustainable Organic Matter Management - Sustainable Management of Soil Organic Matter - page 362

S. O'Flahertyet al. Phenotypic, Functional and Genetic Diversity of Bacterial Communities

5.3

Comparison of Phenotypic,
Functional and Genetic
Diversity of Bacterial
Communities in Soils

S. O'F LAHERTY , S. M C G RATH AND P. H IRSCH

Soil Science Department,IACR-Rothamsted,Harpenden,
Hertfordshire AL5 2JQ, UK.

Introduction

Microorganisms may constitute < 0.5% of the total soil mass, but are
responsible for the majority of nutrient cycling and exert a major influence
on soil fertility (Tate, 1986). Microbial biodiversity has become an
important issue with the realization that changes in microbial communities
within the soil have implications for its overall health. There is concern over
the long-term environmental effects of industrialization and urbanization
during the 19th and 20th centuries, including the possibility of a decline
in the general quality of soils. Soil is not only important as a means of
supporting crop production but is also an essential natural resource, which
should be managed for future generations. Some measure of soil quality is
necessary to determine whether soil is being degraded prior to irreversible
larger scale damage, and biodiversity could be an appropriate indicator.
Some microbial functions are essential for important soil processes, but it
is not clear whether the diversity of metabolic responses, or the genetic
diversity of the population, are the most relevant indicators of soil quality.
In this chapter, methods to study soil microbial populations were
compared using soils amended with either farmyard manure or sewage
sludge over a 30-year period. Because urban sewage sludge contains heavy
metals, the effects of sub-acute levels on soil microorganisms are also
considered. Previous studies have considered losses of microbial functions
resulting from metal contamination in soil with little consideration of the
effects on the biodiversity of the microbial communities (Giller et al .,
1998). The loss of functional and/or genetic diversity in soil could have