Attributing the surface temperature difference between a northern boreal mire and forest to the differences in their surface biophysical properties

Restoration of drained peatlands aims to recover the natural carbon sink and storage functions of a mire but also leads to changes in the ecosystems’ biophysical surface properties and, consequently, to their local climate. Impacts of land cover changes on local temperatures are governed by both radiative and non-radiative processes, i.e. changes in albedo and energy partitioning, respectively, with the latter typically as the dominant factor.

There is evidence that the land surface temperature (LST) in degraded peatlands will tend to become similar to that in nearby intact ecosystems¹. Therefore, quantifying how the differences in the surface properties between pristine mires and forests contribute to the differences in their LST is relevant to understanding the biophysical effects of peatland restoration. However, data on LST changes following a forest to mire transition are scarce.

We attribute the difference in LST between a boreal mire and forest to the differences in their biophysical surface properties: albedo, energy storage, aerodynamic resistance and bulk surface resistance to evapotranspiration. We use eddy covariance measurements of sensible and latent heat fluxes as well as supporting meteorology. The attribution methodology is the two-resistance mechanism², but compared to previous studies we also include auto- and cross correlations between the attributed variables using second-order Taylor series expansion³. The attribution is compared between seasons based on vegetation phenology and between weather events based on climatic indicators of warm, cool, wet or dry days.

We hypothesized that contributions to LST difference from the differences in surface resistance would be important because of the very different hydrology and vegetation in the compared ecosystems. However, our results show that the importance of surface resistance was minor compared to aerodynamic resistance which is the dominant factor during spring, summer and autumn. The lower surface roughness of the open mire leads to higher aerodynamic resistance, which has been identified as a strong warming factor also in previous literature comparing forests and open ecosystem such as croplands (e.g. ref.⁴). During late winter with a continuous snow cover still on the mire, the higher albedo values in the mire explain most of the lower LST there. The interdependencies between the attributed variables emerge as important factors, especially when comparing between different weather conditions.

 

References

1. Burdun, I. et al. Satellite data archives reveal positive effects of peatland restoration: albedo and temperature begin to resemble those of intact peatlands. Environ. Res. Lett. 20, 084037 (2025).

2. Rigden, A. J. & Li, D. Attribution of surface temperature anomalies induced by land use and land cover changes. Geophys. Res. Lett. 44, 6814–6822 (2017).

3. Chen, C., Wang, L., Myneni, R. B. & Li, D. Attribution of Land-Use/Land-Cover Change Induced Surface Temperature Anomaly: How Accurate Is the First-Order Taylor Series Expansion? J. Geophys. Res. Biogeosciences 125, e2020JG005787 (2020).

4. Chen, C. et al. Biophysical effects of croplands on land surface temperature. Nat. Commun. 15, 10901 (2024).