Coupled carbon and nitrogen losses in response to seven years of chronic warming in subarctic soils. (July 2019)

• Record Type: Journal Article
• Authors: Marañón-Jiménez, S.; Peñuelas, J.; Richter, A.; Sigurdsson, B.D.; Fuchslueger, L.; Leblans, N.I.W.; Janssens, I.A.
• Is Part Of: Soil biology and biochemistry. Volume 134(2019)
• Page Start: 152
• Page End: 161
• Publication Date: 2019-07
• Subjects: Substrate induced respiration -- Microbial biomass -- Temperature increase -- Nitrogen immobilization -- Microbial carbon and nutrients limitation -- Nitrogen loss; Soil biochemistry -- Periodicals; Soil biology -- Periodicals; Sols -- Biochimie -- Périodiques; Sols -- Biologie -- Périodiques; Sols -- Microbiologie -- Périodiques; Bodembiologie; Biochemie; 631.46
• DOI: 10.1016/j.soilbio.2019.03.028
• Languages: English
• ISSNs: 0038-0717

Abstract

Abstract: Increasing temperatures may alter the stoichiometric demands of soil microbes and impair their capacity to stabilize carbon (C) and retain nitrogen (N), with critical consequences for the soil C and N storage at high latitude soils. Geothermally active areas in Iceland provided wide, continuous and stable gradients of soil temperatures to test this hypothesis. In order to characterize the stoichiometric demands of microbes from these subarctic soils, we incubated soils from ambient temperatures after the factorial addition of C, N and P substrates separately and in combination. In a second experiment, soils that had been exposed to different in situ warming intensities (+0, +0.5, +1.8, +3.4, +8.7, +15.9 °C above ambient) for seven years were incubated after the combined addition of C, N and P to evaluate the capacity of soil microbes to store and immobilize C and N at the different warming scenarios. The seven years of chronic soil warming triggered large and proportional soil C and N losses (4.1 ± 0.5% °C −1 of the stocks in unwarmed soils) from the upper 10 cm of soil, with a predominant depletion of the physically accessible organic substrates that were weakly sorbed in soil minerals up to 8.7 °C warming. Soil microbes met the increasing respiratory demands under conditions of low C accessibility at the expenses of a reduction of the standing biomass in warmer soils. This together with the strict microbial C:N stoichiometric demands also constrained their capacity of N retention, and increased the vulnerability of soil to N losses. Our findings suggest a strong control of microbial physiology and C:N stoichiometric needs on the retention of soil N and on the resilience of soil C stocks from high-latitudes to warming, particularly during periods of vegetation dormancy and low C inputs. Highlights: Warming triggered large and proportional C and N losses from these subarctic soils. Weakly sorbed organic substrates in soil minerals were depleted predominantly. Warmed soils were able to sustain a lower microbial biomass. Strict microbial C:N stoichiometric demands also constrained N retention. This impaired soil N storage and increased its vulnerability to C losses.