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In-Depth Information
A.Fließbachet al.
'DOC' Long-term Farming Systems Trial
5.2
'DOK' Long-term Farming
Systems Trial: Microbial
Biomass, Activity and Diversity
Affect the Decomposition of
Plant Residues
A. F
LIEßBACH
1
, F. E
YHORN
1
, P. M
ÄDER
1
, D.I. R
ENTSCH
2
AND
R. H
ANY
2
1
Research Institute of Organic Agriculture (FiBL),Ackerstrasse,
CH-5070 Frick; and
2
Swiss Federal Laboratories for Materials
Testing and Research (EMPA),Überlandstrasse, CH-8600
Dübendorf, Switzerland
Introduction
The role of biological diversity in natural or man-made ecosystems is poorly
understood. Current knowledge, based on ecosystem theories, starts from
the idea that ecosystem stability increases with increasing diversity, while
the ratio of community respiration to community growth decreases (Odum,
1969). However, this assumption has rarely been proven experimentally,
especially in below-ground systems (Wardle and Giller, 1996). Soil micro-
organisms are an important factor of soil fertility. They are not only respon-
sible for most nutrient-releasing processes, but their presence also indicates
soil quality with respect to habitat function. From a functional point of
view, biomass and the activity of soil microbiota are important factors of
nutrient and energy flow. The metabolic quotient
q
CO
2
(soil respiration to
soil microbial biomass ratio) often has been applied to address the question
of soil quality for soil microorganisms. On the one hand, it indicates carbon
mineralization, but under steady-state conditions it may also serve as an
indicator of the amount of energy used by the community for maintenance
of biomass (Wardle and Ghani, 1995). When discussing changes in
q
CO
2
,
however, community shifts or changes in the ratio of fungi and bacteria are
often assumed (Anderson and Domsch, 1990) but hardly stated.
Only recently, community structure has been combined with eco-
system data sets to address the question of whether a greater number or
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