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Contrasting Soil pH Effects on Fungal and Bacterial Growth Suggest Functional Redundancy in Carbon Mineralization

Author:
  • Johannes Rousk
  • Philip C. Brookes
  • Erland Bååth
Publishing year: 2009
Language: English
Pages: 1589-1596
Publication/Series: Applied and Environmental Microbiology
Volume: 75
Issue: 6
Document type: Journal article
Publisher: American Society for Microbiology

Abstract english

The influence of pH on the relative importance of the two principal decomposer groups in soil, fungi and bacteria, was investigated along a continuous soil pH gradient at Hoosfield acid strip at Rothamsted Research in the United Kingdom. This experimental location provides a uniform pH gradient, ranging from pH 8.3 to 4.0, within 180 m in a silty loam soil on which barley has been continuously grown for more than 100 years. We estimated the importance of fungi and bacteria directly by measuring acetate incorporation into ergosterol to measure fungal growth and leucine and thymidine incorporation to measure bacterial growth. The growth-based measurements revealed a fivefold decrease in bacterial growth and a fivefold increase in fungal growth with lower pH. This resulted in an approximately 30-fold increase in fungal importance, as indicated by the fungal growth/bacterial growth ratio, from pH 8.3 to pH 4.5. In contrast, corresponding effects on biomass markers for fungi (ergosterol and phospholipid fatty acid [PLFA] 18:2 omega 6,9) and bacteria (bacterial PLFAs) showed only a two- to three-fold difference in fungal importance in the same pH interval. The shift in fungal and bacterial importance along the pH gradient decreased the total carbon mineralization, measured as basal respiration, by only about one-third, possibly suggesting functional redundancy. Below pH 4.5 there was universal inhibition of all microbial variables, probably derived from increased inhibitory effects due to release of free aluminum or decreasing plant productivity. To investigate decomposer group importance, growth measurements provided significantly increased sensitivity compared with biomass-based measurements.

Keywords

  • Biological Sciences

Other

Published
  • Microbial carbon-use efficiency
  • Carbon drivers and microbial agents of soil respiration
  • Effect of environmental factors on fungal and bacterial growth in soil
  • Interaction between fungi and bacteria in soil
  • Microbial Ecology
  • ISSN: 0099-2240
Erland Bååth
E-mail: erland [dot] baath [at] biol [dot] lu [dot] se

Professor emeritus

MEMEG

+46 46 222 42 64

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