Projected soil organic carbon loss in response to climate warming and soil water content in a loess watershed

Abstract

Background Soil organic carbon (SOC) plays a crucial role in the global carbon cycle and terrestrial ecosystem functions. It is widely known that climate change and soil water content (SWC) could influence the SOC dynamics; however, there are still debates about how climate change, especially climate warming, and SWC impact SOC. We investigated the spatiotemporal changes in SOC and its responses to climate warming and root-zone SWC change using the coupled hydro-biogeochemical model (SWAT-DayCent) and climate scenarios data derived under the three Representative Concentration Pathways (RCPs2.6, 4.5, and 8.5) from five downscaled Global Climate Models (GCMs) in a typical loess watershed––the Jinghe River Basin (JRB) on the Chinese Loess Plateau. Results The air temperature would increase significantly during the future period (2017–2099), while the annual precipitation would increase by 2.0–13.1% relative to the baseline period (1976–2016), indicating a warmer and wetter future in the JRB. Driven by the precipitation variation, the root-zone SWC would also increase (by up to 27.9% relative to the baseline under RCP4.5); however, the SOC was projected to decrease significantly under the future warming climate. The combined effects of climate warming and SWC change could more reasonably explain the SOC loss, and this formed hump-shaped response surfaces between SOC loss and warming-SWC interactions under both RCP2.6 and 8.5, which can help explain diverse warming effects on SOC with changing SWC. Conclusions The study showed a significant potential carbon source under the future warmer and wetter climate in the JRB, and the SOC loss was largely controlled by future climate warming and the root-zone SWC as well. The hump-shaped responses of the SOC loss to climate warming and SWC change demonstrated that the SWC could mediate the warming effects on SOC loss, but this mediation largely depended on the SWC changing magnitude (drier or wetter soil conditions). This mediation mechanism about the effect of SWC on SOC would be valuable for enhancing soil carbon sequestration in a warming climate on the Loess Plateau.

Effects of elevated temperature and abnormal precipitation on soil carbon and nitrogen dynamics in a Pinus densiflora forest

“…Changes in atmospheric temperature could, directly and indirectly, influence the fate of soil organic carbon by regulating soil microbial growth and activity, litterfall, root death, and soil moisture (e.g., Qi et al, 2016;Yan et al, 2017;Hartley et al, 2021). Several studies have explored the effects of climate warming on soil organic carbon in forests over several decades (Kasischeke et al, 1995;Melillo et al, 2011;Zhao et al, 2021;Nottingham et al, 2022). However, there is still no scientific consensus on whether soil organic carbon decreased or increased in forests under climate warming due to the contradictory results under different experimental and numerical conditions (Kirschbaum, 2006;Bao et al, 2016;Kong et al, 2022).…”

Spatiotemporal dynamics of forest ecosystem carbon budget in Guizhou: customisation and application of the CBM-CFS3 model for China

“…As the afforestation period in Guizhou is relatively short, the DOM inputs in some dead wood and litter DOM pools, such as the BG fast DOM and AG very fast DOM pools, obtained from the newly grown forest were less than the DOM decomposed, resulting in decreases in C stocks. In terms of SOM pools, including the BG very fast DOM and BG slow DOM pools, the C stock changes in response to climatic warming depend on how C inputs to soil by NPP and C outputs by SOM decomposition are balanced relative to each other [ 81 – 83 ]. Climatic warming not only promotes photosynthesis and plant growth but also accelerates the respiration and decomposition of SOM, thus having both positive [ 84 – 86 ] and negative effects [ 87 – 89 ] on SOM C stock.…”

Assessment of Land Degradation Factors

“…Soil carbon stores have a major impact on global climate change, and LD due to natural conditions or human activities is one of the leading causes of changes in soil carbon storage [78]. In a study conducted in semi-arid steppe areas [79], it was found that a sudden change in soil moisture due to high inter-annual rainfall variability causes about 65-80% of the total carbon loss in soils with different vegetation [80].…”

“…For example, while an expected 3.3 0 C increase in air temperature will result in a loss of 11-16% SOC in Europe, an average increase of 1°C in surface air temperature will result in a net loss of 5% in the worldwide SOC pool. Temperature increase alone leads to SOC losses in all soil moisture contents [80,83,96,98].…”