Effects of whole-soil warming on ecosystem carbon fluxes in an alpine grassland

Background: Global warming impacts ecosystem carbon exchange, thus altering the carbon sink capacity of terrestrial ecosystems. However, the response of ecosystem carbon fluxes to whole-soil-profile warming remains unclear. Methods: We first investigated the effect of whole-soil warming on ecosystem carbon fluxes in an alpine grassland ecosystem on the Qinghai-Tibet Plateau. We also compiled a database of 48 articles to examine the general patterns of experimental warming effects on these fluxes using a global meta-analysis. Results: Our results showed that whole-soil warming elevated gross ecosystem productivity (GEP) by 14% and ecosystem respiration (ER) by 11%, but had a minor impact on net ecosystem carbon exchange (NEE) in the alpine grassland. In the meta-analysis, warming also enhanced GEP (10%–11%) and ER (13%), but did not alter NEE. Warming-induced shifts in plant community and extension of growing season may be the main reasons for the higher GEP and ER under warming, and the offset of both fluxes likely caused the minor response of NEE to warming. Conclusions: More attention should be paid to the long-term response of ecosystem carbon fluxes to whole-soil or whole-ecosystem warming throughout the year. These novel findings may help us better predict and mitigate future climate-carbon feedback under realistic warming scenarios.