Carbon input to soil may decrease soil carbon content

TL;DR: Soil carbon sequestration is crucial for limiting global warming, with proven technologies capable of sequestering 500-1000 kg/ha/year in various land types, but uncertainties remain regarding emissions, CO2 fertilization, and long-term carbon storage.

Abstract: Introduction Poplar (Populus spp.) is widely recognized as an ideal model system for studying plant-microbial interactions due to its rapid growth, genetic tractability, and ecological importance in afforestation programs. Leveraging these advantages, we investigated how poplar cultivation reshapes soil microbial communities and their nutrient cycling functions. Although plant roots are known to profoundly influence microbial community structure and functionality, comprehensive studies systematically linking poplar-induced microbiome shifts to nutrient cycling remain limited. Methods Here, we employed an integrative approach combining metagenomic sequencing with soil nutrient analyses to assess poplar-induced changes in microbial community and metabolic activities at the root-soil interface. Results Our analyses revealed three major findings: (1) poplar cultivation significantly altered the composition of microbial communities—including bacteria, fungi, and archaea—and reduced the complexity of microbial interaction networks, as revealed by co-occurrence analysis; (2) poplar cultivation enhanced microbial genetic potential related to degradation pathways for starch, lignin, and aromatic compounds, as well as carbon (C) fixation, while suppressing cellulose/hemicellulose decomposition; and (3) soil nutrient cycling processes involving nitrogen (N), phosphorus (P), and sulfur (S) were reprogrammed through changes in both gene abundance (e.g., nifH, pqqC, aprA) and nutrient availability (e.g., NO3-, P). Moreover, specific microbial taxa showed strong correlations with these functional shifts, i.e., Bacteroidota correlated with P metabolism in roots/soil, Actinobacteria and Firmicutes with organic C turnover, and Gemmatimonadetes and Nitrospirae with nitrate cycling dynamics. Discussion By integrating poplar’s roles as both a model species and a driver of ecological change, this study elucidates how afforestation shapes soil ecosystems through complex plant-microbe-environment interactions. These findings provide critical insights for sustainable land management strategies.

Abstract: Additional file 1: Table S1. Comparison of taxonomic and functional β-diversity between and within treatments. Table S2. Effects of N deposition on microbial taxonomic and functional diversity, as assessed by Shannon index. Table S3. Significantly changed representative OTUs calculated by difference analyses. Table S4. Topological properties of microbial functional gene networks. Table S5. Summary of soil and vegetation attributes in control and N deposited samples. Table S6. Mantel tests for correlations between a range of environmental attributes and quantitative measures of microbial community dissimilarity. Fig. S1. Comparison of the percentage change by N deposition for (a) microbial phyla; (b) N cycling genes; and (c) C cycling genes between using 32 and 4 samples as biological replicates. Fig. S2. The percentage change in relative abundances of microbial class induced by long-term N deposition. Asterisks indicate significant differences. *, P < 0.050; **, P < 0.010. Fig. S3. The percentage change in the relative abundance of major microbial genera induced by long-term N deposition treatment. All selected genera are significantly changed by N deposition treatment as calculated by the response ratio analysis. Fig. S4. The percentage change in the relative abundance of genes associated with C fixation induced by N deposition, calculated as 100*(( mean value in N deposited samples/mean value in control samples) – 1). Mean values and standard deviations are presented. Asterisks indicate significant differences. *, P < 0.050; **, P < 0.010. The numbers in the figure represent the pathways of C fixation. (i) 3-hydroxypropionate bicycle, (ii) Bacterial microcompartments, (iii) Calvin cycle, and (iv) Reductive tricarboxylic acid cycle. Fig. S5. The percentage change in the relative abundance of genes associated with methane and phosphorus cycling genes induced by N deposition, calculated as 100*((mean value in N deposited samples/mean value in control samples) – 1). Mean values and standard deviations are presented. Asterisks indicate significant differences. *, P < 0.050; **, P < 0.010. Fig. S6. N deposition effects on amoA gene. The relative abundance of amoA is presented as the signal intensity difference between control and N deposited samples. Error bars represent standard errors. Blue bars represent genes derived from archaea (AOA), and pink bars represent genes derived from bacteria (AOB). Asterisks indicate significant differences. *, P < 0.050; **, P < 0.010.

TL;DR: In this paper, the authors build a conceptual model of the priming effect based on the contradictory results available in the literature adopting the concept of nutritional competition, and they postulate that priming results from the competition for energy and nutrient acquisition between the microorganisms specialized in the decomposition of fresh organic matter and those feeding on polymerised SOM.

TL;DR: In this article, the authors present an analysis of Soil organic matter storage in Agroecosystems. But their focus is on the storage of organic matter in Soil Fraction and Aggregates.