Exogenous carbon turnover within the soil food web strengthens soil carbon sequestration through microbial necromass accumulation.

Exogenous carbon turnover within soil food web is important in determining the trade-offs between soil organic carbon (SOC) storage and carbon emission. However, it remains largely unknown how soil food web influences carbon sequestration through mediating the dual roles of microbes as decomposers and contributors, hindering our ability to develop policies for soil carbon management. Here, we conducted a 13 C-labeled straw experiment to demonstrate how soil food web regulated the residing microbes to influence the soil carbon transformation and stabilization process after 11 years of no-tillage. Our work demonstrated that soil fauna, as a "temporary storage container," indirectly influenced the SOC transformation processes and mediated the SOC sequestration through feeding on soil microbes. Soil biota communities acted as both drivers of and contributors to SOC cycling, with 32.0% of exogenous carbon being stabilizing in the form of microbial necromass as "new" carbon. Additionally, the proportion of mineral-associated organic carbon and particulate organic carbon showed that the "renewal effect" driven by the soil food web promoted the SOC to be more stable. Our study clearly illustrated that soil food web regulated the turnover of exogenous carbon inputs by and mediated soil carbon sequestration through microbial necromass accumulation.

Effect of row spacings on soil nematode communities and ecosystem multifunctionality at an aggregate scale.

Effect of crop row spacing on the belowground ecosystem, especially at an aggregate scale, remains unexplored. To explore how row spacing influenced nematode community and ecosystem function at the aggregate scale, four row spacings i.e. equidistant-row (ER, 50 cm-inter-row distance, 33 cm-intra-row between plants in each row) and non-equidistant-row including NR1 (100 cm + 50 cm row distance and 22 cm intra-row), NR2 (100 cm + 50 cm inter-row and 25 cm intra-row), and NR3 (60 cm + 40 cm inter-row and 33 cm intra-row) were compared, and four soil aggregate fractions i.e. >2 mm, 1-2 mm, 0.25-1 mm and <0.25 mm were separated. Row spacing did not impact C and N, but significantly influenced P. The regulation effect of acid phosphatase on soil available P was aggregate-scale dependent. Nematode faunal analysis indicated that NR3 within 0.25-1 mm was less disturbed or relatively undisturbed environments. Structural equation model showed row spacing pattern directly affected multifunctionality, while aggregate fractions indirectly contributed to multifunctionality mainly by regulating the richness of total nematodes and trophic groups. It was concluded that NR3 had potential to construct more stable food web, and therefore was possibly the suitable planting pattern.

Effects of Soil Fauna on Cellulose and Lignin Decomposition of Plant Litter in the Changbai Mountain, China.

Cellulose and lignin decomposition is crucial for efficient nutrient cycling, yet few studies have been performed regarding the effects of soil fauna on cellulose and lignin decomposition. This study was conducted to better understand the effects of soil fauna on lignin and cellulose decomposition in the Changbai Mountain. Litterbags of two different mesh sizes were used to examine cellulose and lignin decomposition of 11 species of plant litter in the four vegetation zones of the Changbai Mountain North Slope over a 24-mo period. Cellulose and lignin clearly declined over time for all 11 species of plant litter. Cellulose decomposition rate faster than the rate of lignin decomposition in the majority of plant species. Soil fauna could promote the decomposition of cellulose and lignin. The abundance and richness of soil fauna in coniferous broad-leaved mixed forests were greater than in coniferous forest, Betula ermanii Cham. (Fagales: Betulaceae) forest, and alpine tundra. Soil fauna had a greater effect on Abies nephrolepis Maxim. (Pinales: Pinaceae) cellulose and lignin, whereas contribution rates were relatively lower in the Fraxinus mandshurica Rupr. (Contortae: Oleaceae) and Acer mono Maxim. (Sapindales: Aceraceae) litterbags at the end of the experiment. Litter quality was negatively correlated with the soil faunal contribution to litter decomposition directly. Overall, the findings of this study have implications for the effects of soil fauna on cellulose and lignin decomposition in the alpine ecosystem, and also can provide experimental evidence that soil faunal contribution is affected by soil faunal communities and litter quality.