Title: Soil microbial CNP and respiration responses to organic matter and nutrient additions: Evidence from a tropical soil incubation

Abstract

Soil nutrient availability has a strong influence on the fate of soil carbon (C) during microbial decomposition, contributing to Earth's C balance. While nutrient availability itself can impact microbial physiology and C partitioning between biomass and respiration during soil organic matter decomposition, the availability of labile C inputs may mediate the response of microorganisms to nutrient additions. As soil organic matter is decomposed, microorganisms retain or release C, nitrogen (N) or phosphorus (P) to maintain a stoichiometric balance. While the concept of a microbial stoichiometric homeostasis has previously been proposed, microbial biomass CNP ratios are not static, and this may have very relevant implications for microbial physiological activities. In this work, we tested the hypothesis that N, P and potassium (K) nutrient additions impact C cycling in a tropical soil due to microbial stoichiometric constraints to growth and respiration, and that the availability of energy-rich labile organic matter in the soil (i.e. leaf litter) mediates the response to nutrient addition. We incubated tropical soil from French Guiana with a ¹³C labeled leaf litter addition and with mineral nutrient additions of +K, +N, +NK, +PK and +NPK for 30 days. We found that litter additions led to a ten-fold increase inmore » microbial respiration and a doubling of microbial biomass C, along with greater microbial N and P content. We found some evidence that P additions increased soil CO₂ fluxes. Additionally, we found microbial biomass CP and NP ratios varied more widely than CN in response to nutrient and organic matter additions, with important implications for the role of microorganisms in C cycling. The addition of litter did not prime soil organic matter decomposition, except in combination with +NK fertilization, indicating possible P-mining of soil organic matter in this P-poor tropical soil. Together, these results point toward an ultimate labile organic substrate limitation of soil microorganisms in this tropical soil, but also indicate a complex interaction between C, N, P and K availability. This draws attention to the difference between microbial C cycling responses to N, P, or K additions in the tropics and explains why coupled C, N and P cycle modeling efforts cannot rely on strict microbial stoichiometric homeostasis as an underlying assumption.« less

Authors:

Soong, Jennifer L. ^[1]; Marañon-Jimenez, Sara ^[2]; Cotrufo, M. Francesca ^[3]; Boeckx, Pascal ^[4]; Bodé, Samuel ^[4]; Guenet, Bertrand ^[5]; Peñuelas, Josep ^[6]; Richter, Andreas ^[7]; Stahl, Clément ^[8]; Verbruggen, Erik ^[9]; Janssens, Ivan A. ^[9]

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+ Show Author Affiliations

1. University of Antwerp, Wilrijk (Belgium); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
2. University of Antwerp, Wilrijk (Belgium); University of Granada (Spain); Global Ecology Unit CREAF-CSIC-UAB, Catalonia (Spain)
3. Colorado State University, Fort Collins, CO (United States)
4. Ghent University, Gent (Belgium)
5. University Paris-Saclay, Gif-sur-Yvette (France)
6. Center for Ecological Research and Forestry Application, Catalonia (Spain); Global Ecology Unit CREAF-CSIC-UAB, Catalonia (Spain)
7. University of Vienna (Austria)
8. University of French Guiana and University of the French West Indies, Kourou (France)
9. University of Antwerp, Wilrijk (Belgium)

Publication Date:

Tue May 15 00:00:00 EDT 2018

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER); European Research Council (ERC)

OSTI Identifier:

1532326

Alternate Identifier(s):

OSTI ID: 1548229

Grant/Contract Number:  

AC02-05CH11231; 610028

Resource Type:

Accepted Manuscript

Journal Name:

Soil Biology and Biochemistry

Additional Journal Information:

Journal Volume: 122; Journal Issue: C; Journal ID: ISSN 0038-0717

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES; 13C; CNP; microbial stoichiometry; priming; soil respiration; tropics