Globally altitudinal trends in soil carbon and nitrogen storages

Mountainous regions, covering ~20% of the earth's land surface, are particularly vulnerable to climate warming as they combine a steep climatic gradient. The elevational gradient is widely used to investigate the potential impacts of warming on soil carbon (C) cycling. Here, we synthesized 62 altitudinal transects to explore the globally elevational patterns in soil C and N storages and the potential drivers. We found that the altitudinal trends in soil C and N storages were substantially inconsistent, meanwhile, the most important predictor for these variations was mean annual temperature. In specific, low latitudes with warm climate had an increase in the soil C and N storages along increased elevation, while high latitudes with cold climate showed a decreased or unchanged C and N storages along elevation increasing. The altitudinal trend in soil C:N ratio was relatively stable and independent of all the candidate predictors, implying a high stoichiometric homeostasis. No general patterns in profile distribution of soil C along elevation were detected. Overall, our findings imply that decrease in elevation, i.e., increase in temperature, may result in decrease in C storage in low latitudes, but may result in increase in C storage in high latitudes.

Automated summary

Mountainous regions are vulnerable to climate warming, with the elevational gradient playing an important role in soil C and N storage patterns. Mean annual temperature was found to be the most significant driver of these variations. Low latitudes showed an increase in soil C and N storage with increasing elevation, while high latitudes exhibited a decrease or no change in C and N storage. The stable C:N ratio suggests high stoichiometric homeostasis. Decreasing elevation, or increasing temperature, may result in decreased C storage in low latitudes, but increased C storage in high latitudes.