Soil microbial activity and community composition: Impact of changes in matric and osmotic potential

Chowdhury, Nasrin, Marschner, Petra and Burns, Richard G. (2011) Soil microbial activity and community composition: Impact of changes in matric and osmotic potential. Soil Biology and Biochemistry, 43 6: 1229-1236. doi:10.1016/j.soilbio.2011.02.012

Author Chowdhury, Nasrin
Marschner, Petra
Burns, Richard G.
Title Soil microbial activity and community composition: Impact of changes in matric and osmotic potential
Journal name Soil Biology and Biochemistry   Check publisher's open access policy
ISSN 0038-0717
Publication date 2011-01-01
Year available 2011
Sub-type Article (original research)
DOI 10.1016/j.soilbio.2011.02.012
Open Access Status Not yet assessed
Volume 43
Issue 6
Start page 1229
End page 1236
Total pages 8
Place of publication Kidlington, Oxford, United Kingdom
Publisher Pergamon
Language eng
Subject 1111 Nutrition and Dietetics
2404 Microbiology
Abstract As saline soils dry, the salt in the remaining solution phase is concentrated and the microbes are subjected to both water and osmotic stress. However, little is known about the interactive effect of matric potential (MP) and osmotic potential (OP) on microbial activity and community structure. We conducted an experiment in which two non-saline soils, a sand and a sandy loam, were pre-incubated at optimal water content (for microbial activity) but different osmotic potentials achieved by adding NaCl. The EC of the saturated paste (ECe) ranged between 1.6 and 11.6 dS m -1 in the sand and between 0.6 and 17.7 dS m -1 in the sandy loam. After the 14-day pre-incubation, the soils were dried to different water contents: 25-35 g kg -1 in the sand and 95-200 g kg -1 in the sandy loam. Water potential (WP, the sum of osmotic + matric potential) ranged from -0.7 to -6.8 MPa in the sand and from -0.1 to -4.4 MPa in the sandy loam. After addition of ground pea straw to increase the concentration of readily available substrate, respiration was measured over 14 days and microbial community composition was assessed by phospholipid fatty acid analysis (PLFA) at the end of the experiment. In both soils, cumulative respiration at a given soil water content (WC) decreased with decreasing osmotic potential, but the effect of decreasing water content differed between the two soils. In the sand, cumulative respiration at the two lowest water contents (WC25 and WC28) was always significantly lower than that at the highest water content (WC35). In the sandy loam, cumulative respiration was significantly lower at the lowest water content (WC95) compared to the highest water content (WC200) only in treatments with added salt. The reduction of cumulative respiration at a given WP was similar in the two soils with a 50% reduction compared to the control (optimal water content, no salt added) at WP -3 MPa. In the sand at WP <-2 MPa, the reduction in fungal fatty acids was greater than that of bacterial fatty acids whereas in the sandy loam, the response of bacteria and fungi to decreasing WP was similar. In both soils, microbial biomass decreased by 35-50% as WP decreased to about -2 MPa but then remained stable with further decreases of WP. Microbial community composition changed with WP in both soils. Our results suggest that there are two strategies by which microbes respond to water potential. A decrease in WP up to -2 MPa kills a proportion of the microbial community, but the remaining microbes adapt and maintain their activity per unit biomass. At lower WP however, the adaptation mechanisms are not sufficient and although the microbes survive, their activity per unit biomass is reduced.
Keyword Bacteria
Soil water content
Water potential
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Agriculture and Food Sciences
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Citation counts: TR Web of Science Citation Count  Cited 52 times in Thomson Reuters Web of Science Article | Citations
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