Climate exerts stronger control on topsoil carbon persistence than plant input in alpine grasslands

Abstract

Chen et al. (2021) concluded that plant input governs topsoil carbon persistence in alpine grasslands. We demonstrated that the excluded direct effect of precipitation on topsoil Δ14C in their analysis was in fact significant and strong. Our results provide an alternative viewpoint on the drivers of soil carbon turnover.

Response to Comment on ‘Soil carbon persistence governed by plant input and mineral protection at regional and global scales’

“…Thus, to consider these non‐linear relationships, we used log‐transformed plant variables in the subsequent SEM and partial correlation analysis. The comparison showed that if the non‐linear relationship was ignored, similar statistical results with Wu et al (2021) would be generated, that is, precipitation acted as the most important factor on topsoil Δ 14 C (Figure 1a). By contrast, if this non‐linear relationship was considered, the direct effect of climate on Δ 14 C would be removed during model optimisation, and our original result would be obtained, that is, plant input was more important than the climate in regulating the topsoil Δ 14 C (Figure 1b).…”

“…The real reason for the discrepancy between Wu et al ’s (2021) analysis and ours is that they did not consider the non‐linear relationship between plant C input variables and topsoil Δ 14 C, where logarithm transformation was only performed for mineral variables in their analysis. However, as depicted in Figure 1g in Chen et al (2021), the relationship between Δ 14 C and plant input was also non‐linear.…”

“…Consistent with these results over regional scale, plant C input was still the most important factor in regulating topsoil C turnover over global scale after considering this non‐linear relationship (Figure 2b). These results demonstrated that ignoring the non‐linear relationship between plant input variables and Δ 14 C in Wu et al ’s (2021) analysis led to the underestimation of the contribution of plant input on soil C turnover in their analysis. This was the fundamental reason why they came to a different conclusion.…”

“…Similarly, overlooking the non‐linear relationship in Wu et al ’s (2021) analysis was also the reason for the discrepant results of partial correlation analysis between the two research groups. The results showed that when the non‐linear relationship between plant input and Δ 14 C was considered, plant input replaced precipitation as the most important factor affecting the topsoil Δ 14 C (Figure 2a).…”

“…Lastly, in contrast to the argument by Wu et al (2021), we did not treat the amount of plant input as a proxy for priming effects. The priming effect was only one possible reason we proposed for the observed correlation between plant C input and Δ 14 C (Chen et al, 2021).…”