Canadian Forest Service Publications

Temperature sensitivity of biomass‐specific microbial exo‐enzyme activities and CO2 efflux is resistant to change across short‐and long‐term timescales. Min, K., Buckeridge, K., Ziegler, S. E., Edwards, K., Bagchi, S., & Billings, S. A. (2019). Global change biology, 25(5), 1793-1807.

Year: 2019

Issued by: Atlantic Forestry Centre

Catalog ID: 40406

Language: English

Availability: PDF (request by e-mail)

Available from the Journal's Web site.
DOI: 10.1111/gcb.14605

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Accurate representation of temperature sensitivity (Q10) of soil microbial activity across time is critical for projecting soil CO2 efflux. As microorganisms mediate soil carbon (C) loss via exo‐enzyme activity and respiration, we explore temperature sensitivities of microbial exo‐enzyme activity and respiratory CO2 loss across time and assess mechanisms associated with these potential changes in microbial temperature responses. We collected soils along a latitudinal boreal forest transect with different temperature regimes (long‐term timescale) and exposed these soils to laboratory temperature manipulations at 5, 15, and 25°C for 84 days (short‐term timescale). We quantified temperature sensitivity of microbial activity per g soil and per g microbial biomass at days 9, 34, 55, and 84, and determined bacterial and fungal community structure before the incubation and at days 9 and 84. All biomass‐specific rates exhibited temperature sensitivities resistant to change across short‐ and long‐term timescales (mean Q10 = 2.77 ± 0.25, 2.63 ± 0.26, 1.78 ± 0.26, 2.27 ± 0.25, 3.28 ± 0.44, 2.89 ± 0.55 for β‐glucosidase, N‐acetyl‐β‐d‐glucosaminidase, leucine amino peptidase, acid phosphatase, cellobiohydrolase, and CO2 efflux, respectively). In contrast, temperature sensitivity of soil mass‐specific rates exhibited either resilience (the Q10 value changed and returned to the original value over time) or resistance to change. Regardless of the microbial flux responses, bacterial and fungal community structure was susceptible to change with temperature, significantly differing with short‐ and long‐term exposure to different temperature regimes. Our results highlight that temperature responses of microbial resource allocation to exo‐enzyme production and associated respiratory CO2 loss per unit biomass can remain invariant across time, and thus, that vulnerability of soil organic C stocks to rising temperatures may persist in the long term. Furthermore, resistant temperature sensitivities of biomass‐specific rates in spite of different community structures imply decoupling of community constituents and the temperature responses of soil microbial activities.

Plain Language Summary

To project the efflux (loss to the atmosphere) of carbon dioxide from soil, it is critical to gather an accurate representation of the temperature sensitivity of soil microbial activity in response to short and long-term temperature changes. Various factors can lead to potential changes in microbial temperature responses. We collected soils from boreal forest sites of the Newfoundland and Labrador Boreal Ecosystem Latitudinal Transect (NL-BELT) experiencing different climate conditions and exposed the soils to various laboratory temperature manipulations for 84 days. We assessed temperature sensitivity of microbial activity (respiration and enzyme activity), and determined bacterial and fungal community structure. Our results suggest that although community structure may change with temperature, carbon loss through respiration and other important microbial processes can remain constant over time, meaning that the loss of soil organic carbon stocks to the atmosphere due to rising temperatures will continue in the long term. These results can help to inform modeling and to reduce uncertainty in projections related to climate change.