Xiaolin Yin

Forests and grasslands play an important role in carbon cycling. They not only absorb CO₂ from the air through vegetation biomass and soil carbon sinks, but also reduce and control the horizontal transport of soil carbon (i.e., reinforcing soil carbon storage via soil conservation), thus avoiding erosion-induced CO₂ emissions. In this study, vegetation biomass and soil carbon sinks, soil carbon reinforcement and reduced carbon emissions via soil conservation by forests and grasslands were quantified on the scale of the whole of China. The analysis was based on the distribution of biomass and the soil carbon pool and soil erosion rates derived from national surveys, as well as carbon density values from field surveys and literature. In 2021, forests and grasslands in China generated 394.18 Mt C/year (y) of steady-state carbon sinks through vertical biomass and soil absorption. The biomass carbon sinks of grasslands, and those of leaves, twigs, flowers and fruits of the forests, were not taken into account when quantifying the stable biomass sink, because they can become net producers of CO₂ due to seasonal withering and carryover, or they can form soil organic carbon as potential soil carbon sinks. The amount of horizontal soil carbon reinforcement in China’s forests and grasslands in 2021 was 20.31 Mt C/y, which was positively correlated with the reduction in the water erosion area; consequently, vertical emissions of approximately 14.89–29.78 Mt of CO₂ into the atmosphere were avoided. Overall, in 2021, China’s forests and grasslands absorbed atmospheric CO₂ and reduced emissions by 1.46–1.47 Gt CO₂/y, equivalent to approximately 13% of China’s annual fossil CO₂ emissions. This study demonstrates the fact that the adoption of forest and grassland measures sequesters carbon in soil and biota and reduces the risks of CO₂ emissions by both vertical and horizontal paths, which is important for achieving carbon neutrality and mitigating climate change.

Due to the region’s social economy and historical culture, rough grazing has led to unresolved grassland-based ecological problems in Northern China. Soil microorganisms are essential structural and functional components of underground ecosystems, and the effects of various grazing intensities on the physicochemical properties and bacterial communities of soil are unclear. A stocking density regulation experiment was carried out in the desert steppe of the Inner Mongolia Autonomous Region. In the study area, four grazing intensities were set, namely, the enclosure control group (CK), light grazing, moderate grazing, and heavy grazing. Field investigations and 16S rRNA sequencing were used to compare and analyze the characteristics of soil bacterial community structures and their correlations with soil nutrient factors under different grazing intensities. The experiment showed the following results: (1) The Shannon, Simpson, and Pielou indices of the light grazing group were significantly higher than those of the CK (p < 0.05), and the indices of the moderate and heavy grazing groups were lower than those of the CK, but the difference was not significant, and there were no significant differences in the Chao1 index between each group. (2) Acidobacteria, Actinobacteria, Proteobacteria, and Chloroflexi were the main bacterial phyla. (3) With the exception of soil organic matter and available potassium, which had significant negative correlations with the Shannon index (p < 0.05), other soil factors had no significant correlation with the soil bacterial diversity. (4) The contents of soil organic matter, total phosphorus, alkali-hydrolyzed nitrogen, available phosphorus, and available potassium influenced the differences between soil bacterial communities under different grazing intensities.