Specific antibiotics and nematode trophic groups agree in assessing fungal:bacterial activity in agricultural soil

doi:10.1016/j.soilbio.2012.05.018

Soil Biology and Biochemistry

Volume 55, December 2012, Pages 17-19

https://doi.org/10.1016/j.soilbio.2012.05.018 Get rights and content

Abstract

There are no methods at hand with a long and proven record for assessing the relative contribution of fungi and bacteria to decomposer activity in soil. Whereas a multitude of methods to determine fungal and bacterial biomass are available, activity assays traditionally relied on the substrate-induced respiration (SIR) inhibition approach. Here we compare fungal contribution to the microbial active biomass assessed by the SIR inhibition method with the contribution of fungal-feeding nematodes to the microbial-feeding nematode community. Four cultivation systems on the same soil that differ in carbon inputs with a factor two ranked exactly the same with the two methods. A conventionally farmed rotation with low organic input had the lowest fungal fraction, while three organically farmed soils ranked higher.

Highlights

► Two methods: antibiotic inhibition and nematode trophic groups were employed. ► The methods agree in assessing ratio of fungal activity to bacterial activity in soil. ► Fungal fraction of decomposer activity higher in organic than conventional farming.

References (10)

H. Ferris et al.
A framework for soil food web diagnostics: extension of the nematode faunal analysis concept
Applied Soil Ecology
(2001)
W.M. Williamson et al.
Changes in soil microbial and nematode communities during ecosystem decline across a long-term chronosequence
Soil Biology and Biochemistry
(2005)
J. Zhao et al.
Effects of vegetation removal on soil properties and decomposer organisms
Soil Biology and Biochemistry
(2011)
J.P. Anderson et al.
Quantification of bacterial and fungal contributions to soil respiration
Archiv Für Mikrobiologie
(1973)
V.L. Bailey et al.
Novel antibiotics as inhibitors for the selective respiratory inhibition method of measuring fungal: bacterial ratios in soil
Biology and Fertility of Soils
(2003)

There are more references available in the full text version of this article.

Cited by (6)

Natural <sup>13</sup>C abundance reveals age of dietary carbon sources in nematode trophic groups
2019, Soil Biology and Biochemistry
Citation Excerpt :
Nematodes are prey to microarthropods (Heidemann et al., 2014) and perhaps also contribute to the diet of earthworms (Curry and Schmidt, 2007). Except for phytophagous nematodes, the abundance of individual nematode trophic groups often mirror growth responses of their respective food sources (Ferris, 2010; Christensen et al., 2012). Together with protozoa, microbivorous nematodes are the main grazers of microorganisms and regulate the size, composition and activity of microbial communities as well as rates of C and nitrogen turnover (Rønn et al., 2012).
We determined the ¹³C/¹²C ratio (expressed as δ¹³C ‰) of microbial biomass and nematode trophic groups in a small-plot field experiment with soil converted from C3- to C4-crop (silage maize) 20 years ago. During this period, the plots were subjected to three different organic input treatments: 1) maize stubbles and roots left after harvest (MS), 2) MS plus annual addition of aboveground maize biomass (MS + B), and 3) MS plus annual addition of faeces from sheep fed exclusively with maize (MS + F). The different δ¹³C value of C3- and C4-crops allowed us to distinguish between old (>20 years old) C3-derived C and recent (<20 years old) C4-derived C incorporated into microbial biomass and nematodes.
The δ¹³C value of phytophagous nematodes closely matched that of the maize. Bacterivorous nematodes had higher δ¹³C values than fungivorous nematodes and microbial biomass indicating that the C sources of bacterivorous nematodes are more recent than those of fungivorous nematodes and microbial biomass. At low abundance of fungivorous nematodes (MS and MS + F), the microbial biomass had higher δ¹³C values than the fungivorous nematodes, whereas their δ¹³C values were comparable at higher densities of fungivorous nematodes (MS + B). The higher C4-derived input in MS + F and MS + B treatments increased the δ¹³C values of bacterivorous nematodes and microbial biomass.
In MS and MS + B treatments, recent C4-derived C accounted for 50 and 70% of microbial biomass-C, respectively. Corresponding values for fungivorous and bacterivorous nematodes were 30 and 75%, and 65 and 85%, respectively.
We conclude that fungal-based decomposition pathways contribute more to the turnover of old soil C than bacterial-based decomposition. A substantial fraction of the microbial biomass and fungivorous nematode C in the MS treatment (50 and 70%, respectively) was C deposited in the soil more than 20 years ago, confirming that decade-old SOC remains biologically active.
The relative importance of the bacterial pathway and soil inorganic nitrogen increase across an extreme wood-ash application gradient
2018, GCB Bioenergy
Elevated CO<inf>2</inf> increases fungal-based micro-foodwebs in soils of contrasting plant species
2017, Plant and Soil
Effects of optimized fertilization on nematode community in greenhouse soils
2017, Chinese Journal of Applied Ecology
Sources of nitrogen for winter wheat in organic cropping systems
2013, Soil Science Society of America Journal
SSU Ribosomal DNA-Based Monitoring of Nematode Assemblages Reveals Distinct Seasonal Fluctuations within Evolutionary Heterogeneous Feeding Guilds
2012, PLoS ONE

View full text

Short communicationSpecific antibiotics and nematode trophic groups agree in assessing fungal:bacterial activity in agricultural soil

Abstract

Highlights

Applied Soil Ecology

Soil Biology and Biochemistry

Soil Biology and Biochemistry

Quantification of bacterial and fungal contributions to soil respiration

Archiv Für Mikrobiologie

Novel antibiotics as inhibitors for the selective respiratory inhibition method of measuring fungal: bacterial ratios in soil

Biology and Fertility of Soils

Short communication
Specific antibiotics and nematode trophic groups agree in assessing fungal:bacterial activity in agricultural soil