Initial soil organic carbon stocks govern changes in soil carbon: Reality or artifact?. Issue 5 (31st October 2022)

• Record Type: Journal Article
• Authors: Slessarev, Eric W.; Mayer, Allegra; Kelly, Courtland; Georgiou, Katerina; Pett‐Ridge, Jennifer; Nuccio, Erin E.
• Is Part Of: Global change biology. Volume 29:Issue 5(2023)
• Page Start: 1239
• Page End: 1247
• Publication Date: 2022-10-31
• Subjects: carbon cycle -- meta‐analysis -- regression to the mean -- soil -- soil organic matter -- statistical artifact; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.16491
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: Changes in soil organic carbon (SOC) storage have the potential to affect global climate; hence identifying environments with a high capacity to gain or lose SOC is of broad interest. Many cross‐site studies have found that SOC‐poor soils tend to gain or retain carbon more readily than SOC‐rich soils. While this pattern may partly reflect reality, here we argue that it can also be created by a pair of statistical artifacts. First, soils that appear SOC‐poor purely due to random variation will tend to yield more moderate SOC estimates upon resampling and hence will appear to accrue or retain more SOC than SOC‐rich soils. This phenomenon is an example of regression to the mean. Second, normalized metrics of SOC change—such as relative rates and response ratios—will by definition show larger changes in SOC at lower initial SOC levels, even when the absolute change in SOC does not depend on initial SOC. These two artifacts create an exaggerated impression that initial SOC stocks are a major control on SOC dynamics. To address this problem, we recommend applying statistical corrections to eliminate the effect of regression to the mean, and avoiding normalized metrics when testing relationships between SOC change and initial SOC. Careful consideration of these issues in future cross‐site studies will support clearer scientific inference that can better inform environmental management. Abstract : Changes in soil organic carbon (SOC) storage have the potential to affect global climate. Many studies have found that SOC‐poor soils tend to gain or retain carbon more readily than SOC‐rich soils, which implies that SOC‐poor soils should be ideal targets for carbon sequestration. While this pattern may partly reflect reality, its importance can also be exaggerated by several common statistical artifacts, such as spurious correlations caused by regression to the mean. To eliminate these artifacts, we recommend applying statistical corrections and avoiding specific data analysis approaches. Careful consideration of these issues will lead to more effective management of SOC.