Do freeze‐thaw events enhance C and N losses from soils of different ecosystems? A review

Summary

This review synthesises literature on how freeze–thaw cycles affect soil organic matter turnover and C and N losses from soils in arable and natural vegetation systems. The authors conclude that whilst freeze–thaw events can increase gaseous (N₂O) and solute (nitrate) fluxes, the pool of C and N susceptible to such cycles is limited, and at annual timescales freeze–thaw cycles may have little effect or even reduce overall soil C losses. Greatest N₂O emissions (≈2 kg N₂O–N ha⁻¹) and nitrate losses (≈13 kg N ha⁻¹) were typically associated with exceptional frost years, particularly in alpine, arctic, and forest soils.

Regional applicability

This review's findings are particularly relevant to United Kingdom upland and northern regions where winter soil frost and repeated freeze–thaw cycles occur. The emphasis on arable versus natural vegetation responses is applicable to UK farming systems, though most pronounced effects were observed in colder climatic zones (alpine, arctic); transferability to milder UK lowlands requires caution, as UK freeze–thaw intensity and frequency differ markedly from the colder ecosystems emphasised in the review.

Key measures

Carbon dioxide (CO₂) emissions, nitrous oxide (N₂O) emissions (cumulative, in kg N₂O–N ha⁻¹), nitrate losses (kg N ha⁻¹), soil frost temperature (°C), microbial biomass changes, solute and gaseous flux rates

Outcomes reported

The review synthesised evidence on whether freeze–thaw events enhance carbon and nitrogen losses from soils, examining mechanisms, temperature thresholds, and differences between arable and natural vegetation soils. Key findings addressed gaseous and solute fluxes of C and N following freeze–thaw cycles at annual timescales.

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