[Advances in the research of transformation and stabilization of soil organic carbon from plant and microbe]. / æ¤ç‰©æºå’Œå¾®ç”Ÿç‰©æºåœŸå£¤æœ‰æœºç¢³è½¬åŒ–ä¸Žç¨³å®šç ”ç©¶è¿›å±•.

Soil organic carbon (SOC) is the core component of terrestrial carbon (C) sink. Exploring the transformation and stabilization mechanism of SOC is key to understand the function of terrestrial C sink which copes with climate change. The traditional perspective is that plant residues are the initial source of SOC. The new concept of "soil microbial C pump" emphasizes that the synthesized products of soil microbial assimilation are important contributors to the stable SOC. This provides a new insight to the sequestration mechanism of SOC. Due to the complex and variable decomposition process of plant residues and the high heterogeneity of microbial residues, the transformation and stabilization mechanism of plant residues and microbial residues into SOC is still unclear. We reviewed research progress in plant and microbial residues, and introduced the characterization methods of quantification and transformation of plant residues and microbial residues, and also summarized the new findings on the transformation of plant and microbial residues into SOC. We further discussed the contribution and driving factors of microbial and plant-derived C to SOC. Finally, we prospected the future development direction and research focus in this field. This review would provide the scientific reference for the research of soil C sequestration in terrestrial ecosystem.

Contribution of microbial necromass to soil organic carbon formation during litter decomposition under incubation conditions.

We conducted a 512-day incubation experiment to study the dynamics of microbial necromass and soil carbon fraction in the 'litter-soil' transformation interface soil layer (TIS) during litter decomposition, using a perennial C3 herb, Stipa bungeana, in the loess hills. The results showed that soil microbial necromass was dominated by fungi in the early and middle stages, and by bacteria in the late stage. The contribution of fungal necromass C to mineral-associated organic C (MAOC) was significantly higher (38.7%-75.8%) than that of bacteria (9.2%-22.5%) and 2-3 times more than the contribution rate of bacterial necromass. Soil organic C (SOC) content was decreasing during litter decomposition. The input of plant C resources stimulated microbial utilization of soil C fractions. The continuous decrease in particulate organic C during the early and late stages of decomposition was directly responsible for the decrease in SOC content. In contrast, the fluctuating changes in microbial necromass C and MAOC played an indirect role in the reduction of SOC. The increase in soil microbial necromass C caused by a single exogenous addition of litter did not directly contribute to SOC accumulation.

[Effects of vegetation restoration on nutrient and microbial properties of soil aggregates with different particle sizes in the loess hilly regions of Ningxia, Northwest China]. / å®å—å±±åŒºæ¤è¢«æ¢å¤å¯¹åœŸå£¤å›¢èšä½“å »åˆ†ç‰¹å¾åŠå¾®ç”Ÿç‰©ç‰¹æ€§çš„å½±å“.

We explored the effects of vegetation restoration on the soil nutrients and microbial pro-perties of soil aggregates with different particle size by comparing soils in a natural grassland which had been restored for nearly 30 years and in cropland in the loess hilly regions of Ningxia. We analyzed the soil organic carbon (SOC), total nitrogen (TN), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), soil basal respiration (CO2-C) and respiratory quotient (qCO2) of different particle size soil aggregates collected from cropland and natural grassland. The results showed that soil aggregates of natural grassland had more micro-aggregates (particle size <0.25 mm), higher nutrient concentrations (SOC, TN and available K) and C/N than that of cropland. The highest concentrations of SOC and TN in 1-2 mm aggregates and higher C/N in natural grassland and cropland suggested that vegetation restoration could improve the capacity of soil aggregates to reduce nutrient loss and accumulate organic matter, with the highest nutrient accumulation in 1-2 mm aggregates. Microbial biomass (MBC, MBN) and CO2-C in natural grassland were higher than in cropland, but the qCO2 was significantly lower, suggesting that vegetation restoration could effectively improve soil microbial biomass and activity, and make soil habitats more stable. The magnitude of responses of the microbial characteristics of different particle aggregates to vegetation restoration varied due to the differences in nutrient characteristics. The MBC of 1-2 mm aggregates, the MBN of <0.25 mm, 0.25-1 mm and 1-2 mm aggregates, the microbial activity of 1-2 mm and >5 mm aggregates were more sensitive than the rest of the particle aggregates of vegetation restoration. In conclusion, vegetation restoration could effectively improve the fertility and structural characteristics of soil aggregates, and the most prominent improvement was in 1-2 mm particle size aggregates.

[Concentrations of different carbon and nitrogen fractions in rhizosphere and non-rhizosphere soils of typical plant species in mountainous area of southern Ningxia, Northwest China].

Taking the rhizosphere and non-rhizosphere soils of five typical plants Agropyron cristatum, Artemisia frigida, Pseudoraphis bungeana, Thymus mongolicus, and Artemisia sacrorum in a mountainous area of southern Ningxia as test objects, this paper studied their C and N forms contents. The C and N forms contents in the rhizosphere and non-rhizosphere soils differed with plant species. In the rhizosphere soil of A. sacrorum, the C content was the highest, with the total soil organic C (TOC), light fraction organic C (LFOC), and heavy fraction organic C contents being 22.94, 1.95, and 20. 88 g kg-1, respectively. In the rhizosphere soil of P. bungeana, the N content was the highest, with the total N (TN), mineralizable N (MN), and available N contents being 2.05 g kg-1 , 23.73 mg kg-1, and 11.99 mg kg-1 , respectively. In the rhizosphere soil of A. frigida, the LFOC/TOC and MN/TN ratios were the highest, which benefited the C and N transformed into more active forms. Light fraction organic C and mineralizable N could be used as the sensitive indicators of plant habitat change. For the five plant species, the contents of different C and N forms in the rhizosphere soil were generally higher than those in the non-rhizosphere soil.