Harmonized global datasets of soil carbon and heterotrophic respiration from data-driven estimates, with derived turnover time and Q10

We collected all available global soil carbon (C) and heterotrophic respiration (R_H) maps derived from data-driven estimates, sourcing them from public repositories and supplementary materials of previous studies (Table 1). All spatial datasets were converted to NetCDF format for consistency and ease of use.

Because the maps had varying spatial resolutions (ranging from 0.0083° to 0.5°), we harmonized all datasets to a common resolution of 0.5° (approximately 50 km at the equator). We then merged the processed maps by computing the mean, maximum, and minimum values at each grid cell, resulting in harmonized global maps of soil C (for the top 0–30 cm and 0–100 cm depths) and R_H at 0.5° resolution.

Grid cells with fewer than three soil C estimates or fewer than four R_H estimates were assigned NA values. Land and water grid cells were automatically distinguished by combining multiple datasets containing soil C and R_H information over land.

Soil carbon turnover time (years), denoted as τ, was calculated under the assumption of a quasi-equilibrium state using the formula:

τ = C_S / R_H

where C_S is soil carbon stock and R_H is the heterotrophic respiration rate. The uncertainty range of τ was estimated for each grid cell using:

τ_max = C_S⁺ / R_H⁻  τ_min = C_S⁻ / R_H⁺

where C_S⁺ and C_S⁻ are the maximum and minimum soil C values, and R_H⁺ and R_H⁻ are the maximum and minimum R_H values, respectively.

To calculate the temperature sensitivity of decomposition (Q₁₀)—the factor by which decomposition rates increase with a 10 °C rise in temperature—we followed the method described in Koven et al. (2017). The uncertainty of Q₁₀ (maximum and minimum values) was derived using τ_max and τ_min, respectively.  

The harmonized dataset files available in the repository are as follows:

·       harmonized-RH-hdg.nc: global soil heterotrophic respiration map

·       harmonized-SOC100-hdg.nc: global soil C map for 0–100 cm

·       harmonized-SOC30-hdg.nc: global soil C map for 0–30 cm

·       Q10.nc: global Q10 map

·       Turnover-time_max.nc: global soil C turnover time estimated using maximum soil C and minimum R_H

·       Turnover-time_min.nc: global soil C turnover time estimated using minimum soil C and maximum R_H

·       Turnover-time_mean.nc: global soil C turnover time estimated using mean soil C and R_H

·       Turnover-time30_mean.nc: global soil C turnover time estimated using the soil C map for 0-30 cm

More details are provided in:

Shoji Hashimoto, Akihiko Ito, Kazuya Nishina (submitted) 

Reference

Koven, C. D., Hugelius, G., Lawrence, D. M. & Wieder, W. R. Higher climatological temperature sensitivity of soil carbon in cold than warm climates. Nat. Clim. Change 7, 817–822 (2017).

Table1 : List of soil carbon and heterotrophic respiration datasets used in this study.

*The vertical depth intervals did not exactly match 100 cm and 30 cm. Therefore, weighted means were calculated for the 0–100 cm and 0–30 cm depths. **Only the soil C stock data for the 0–30 cm depth is officially provided in the repository. ***IDs for 0–100cm/0–30cm

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