Skip to main content
ARS Home » Research » Publications at this Location » Publication #314096
Title: Soil respiration is not limited by reductions in microbial biomass during long-term soil incubations

Author
item BIRGE, HANNAH - Colorado State University
item CONANT, RICHARD - Colorado State University
item FOLLETT, RONALD - Retired ARS Employee
item HADDIX, MICHELLE - Colorado State University
item MORRIS, SHERRI - Bradley University
item SNAPP, SIEGLINDE - Michigan State University
item WALLENSTEIN, MATTHEW - Colorado State University
item PAUL, ELDOR - Colorado State University

Submitted to: Journal of Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2014
Publication Date: 12/15/2014
Citation: Birge, H., Conant, R., Follett, R., Haddix, M., Morris, S., Snapp, S., Wallenstein, M., Paul, E. 2014. Soil respiration is not limited by reductions in microbial biomass during long-term soil incubations. Journal of Soil Biology and Biochemistry. 18:304-310.

Interpretive Summary: Declining rates of soil respiration are reliably observed during long-term laboratory incubations, but the cause is uncertain. To test the ability of long-term carbon- and microbial biomass-depleted soils to respire labile organic matter, we exposed soils to a second, 42 day incubation (30 C) with and without an addition of plant residues. Extra-cellular enzyme pools in the incubation-depleted soils were sometimes slightly reduced and did not respond to addition of labile substrate and did not limit soil respiration. Our results support the idea that available soil organic matter, rather than a lack microbial biomass and extracellular enzymes, limits soil respiration over the course of long-term incubations. The decomposition of both wheat and corn straw residues did not change after major changes in the soil biomass during extended incubation supports, thus supporting the omission of biomass values from biogeochemical models.

Technical Abstract: Declining rates of soil respiration are reliably observed during long-term laboratory incubations, but the cause is uncertain. We explored different controls on soil respiration during long-term soil incubations. Following a 707 day incubation (30 C) of soils from cultivated and forested plots at Kellogg Biological Station in MI, USA, the soils were significantly depleted of both soil carbon and microbial biomass. To test the ability of these carbon- and biomass-depleted soils to respire labile organic matter, we exposed soils to a second, 42 day incubation (30 C) with and without an addition of plant residues. We controlled for soil carbon and microbial biomass depletion by incubating field fresh (“fresh”) soils with and without an amendment of wheat or corn residues. Respiration was consistently higher in the fresh versus incubation-depleted soil (2 and 1.2 times higher in the fresh cultivated and fresh forested soil, respectively), the ability to respire substrate did not differ between the fresh and incubation-depleted soils. Further, at the completion of the 42 day incubation, levels of microbial biomass in the incubation-depleted soils remained unchanged, while levels of microbial biomass in the field-fresh soil declined to levels similar to that of the incubation-depleted soils. Our results indicate that available soil organic matter, rather than a lack microbial biomass and extracellular enzymes, limits soil respiration in these long-term incubations. Decomposition of wheat and corn residues did not change following depletion of the microbial biomass thus supporting the omission of biomass values from biogeochemical models.