Applied Soil Ecology 16 2001 131–139
Predation on fungal and bacterial biomass in a soddy-podzolic soil amended with starch, wheat straw and alfalfa meal
Anvar Sh. Mamilov
a
, Boris A. Byzov
b
, Dmitri G. Zvyagintsev
b
, Oliver M. Dilly
a,∗
a
Ökologie-Zentrum, Universität Kiel, Schauenburgerstraße 112, 24118 Kiel, Germany
b
Department of Soil Biology, Faculty of Soil Science, Moscow State University, 119899 Moscow, Russia Received 6 December 1999; received in revised form 13 July 2000; accepted 13 July 2000
Abstract
The variation in bacterial, fungal and total microbial biomass and activity was studied together with the abundance of soil nematodes and microarthropods after the addition of substrates differing in nitrogen availability to a soddy-podzolic soil. The
experiments were carried out in microcosms with native and defaunated soil to evaluate stimulatory and suppressive effects of the microfauna on soil micro-organisms. Predation by microfauna nematodes and mesofauna microarthropods reduced
the microbial biomass and microbial respiration by approximately 25 after addition of nitrogen rich alfalfa meal. When starch and wheat straw were supplied, the microbial biomass and activity were stimulated by up to 30 by grazing. Thus, the
effect of predation on the microbiota depended on the composition of the available substrates and available nitrogen seems to be an important factor controlling stimulation or suppression of soil micro-organisms by the soil fauna when fresh organic
compounds are accessible. The presence of soil fauna stimulated bacteria and, thus, reduced the fungalbacterial ratio during the course of decomposition. In contrast, the fungalbacterial ratio declined due to decreasing fungal biomass in defaunated
soil. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Fauna; Litter decomposition; Micro-organisms; Nitrogen; Stimulation; Suppression
1. Introduction
The interaction between fauna and micro-organisms in soil is of great importance for the decomposition of
natural substrates and, thus, for the biogeochemistry of ecosystems Brussaard, 1998. The mineralisation
of organic substances in soil is mainly performed by micro-organisms, but soil fauna have a modulating and
stimulatory impact Anderson et al., 1983. The rate of nitrogen and phosphorus liberation in soil is affected
by the presence of soil animals Ingham et al., 1985.
∗
Corresponding author. Tel.: +49-431-880-4085; fax: +49-431-880-4083.
E-mail address: oliverecology.uni-kiel.de O.M. Dilly.
However, these processes are regulated by the commu- nity structure and the complex nutritional interactions
within the soil biota Huhta and Setälä, 1990; Ingham et al., 1985; Setälä et al., 1990.
Several studies showed that the presence of soil animals increased the content of available nutrients,
decomposition rate of organic substances, microbial growth and respiration rate Ineson et al., 1982;
Clarholm, 1985; McGonigle, 1995; Alphei et al., 1996. However, some investigations indicate that soil
fauna may also suppress microbiological components and microbial growth Larsen and Jakobsen, 1996;
Groffmann, 1999. The interaction between fauna and micro-organisms seems to depend on the nutritional
conditions that vary between different soil horizons
0929-139301 – see front matter © 2001 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 9 - 1 3 9 3 0 0 0 0 1 0 9 - 8
132 A.Sh. Mamilov et al. Applied Soil Ecology 16 2001 131–139
Dilly and Munch, 1998; e.g. Kandeler et al. 1999 showed that microarthropods did not significantly af-
fect substrate-induced respiration or microbial C, N and P content in the LF layer containing fresh organic
substances but promoted microbial biomass, protease activity and phosphate content in the deeper H layer.
Hence, it is still unclear how microbial growth and predation interact under various environmental con-
ditions.
Therefore, we studied the effect of natural sub- strates with different quality on the outcome of faunal–
microbial interaction, namely microbial suppression and stimulation. The dynamics of bacterial, fungal and
total microbial biomass and respiration rates in the presence of available litter components were deter-
mined with regard to the abundance of the micro- and meso-fauna. Substrates having high nitrogen content
were compared to those containing low or no nitrogen reserves.
2. Materials and methods
