Diurnal temperature variation in surface soils: an underappreciated control on microbial processes.

Area of Science:

• Soil science
• Microbiology
• Biogeochemistry

Background:

• Diurnal temperature changes (DTR) in surface soils are significant globally.
• DTR is often disregarded in studies of microbially-mediated carbon and nitrogen cycling.
• Current understanding of temperature effects on soil processes is incomplete due to ignoring natural temperature cycles.

Purpose of the Study:

• To document the impacts of diurnal temperature changes on microbial respiration and mineralization rates.
• To investigate the effect of large DTR on soil microbial mineralization and redox potentials.
• To highlight the limitations of constant temperature regimes in laboratory soil incubation studies.

Main Methods:

• Review of documented impacts of diurnal temperature changes on microbial respiration rates.
• Observation of surface soils with large DTR affecting microbial mineralization and redox potentials.
• Comparison of in situ soil process rates under DTR with laboratory incubations at constant temperatures.

Main Results:

• Diurnal temperature changes significantly impact microbial respiration and mineralization rates.
• Large DTR (>5°C) affects soil microbial mineralization and redox potentials of biogeochemical reactions.
• Constant temperature incubations may mischaracterize in situ temperature controls, often yielding lower process rates than observed under DTR.

Conclusions:

• Diurnal temperature range (DTR) significantly influences soil microbial processes, leading to higher observed rates than under constant temperatures.
• Genetic mechanisms like circadian clocks or thermophilic activity may explain DTR effects.
• A paradigm shift is needed to incorporate DTR into soil process modeling and laboratory studies for accurate climate change impact assessment.