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Marginal land conversion to perennial energy crops can provide biomass feedstocks and climate change mitigation. However, the effect of perennial energy crop cultivation on soil organic carbon (SOC) sequestration and its underlying mechanism in marginal land still remains incomplete. Here, SOC turnover, stability, and its potential sequestration were evaluated based on 10 years of land use change from C3 grass‐dominated marginal land to C4 energy crops Miscanthus and switchgrass cultivation. The naturally occurring 13C signature down to 60 cm depth was used to determine the energy crops‐derived C. Compared to reference marginal land, Miscanthus plantation increased the SOC stock at 0–60 cm depth by 17.8% and 64.3% in bulk and root zone, respectively. Similarly, the SOC stock under switchgrass was also 16.5% and 93.0% higher in bulk and root zone than in reference marginal land, respectively. The higher SOC stock in the root zone of switchgrass relative to Miscanthus was supported by the higher contribution of C4‐derived C to SOC (44.5% vs. 32.4%). The mean residence time of old C was higher under switchgrass than Miscanthus in the bulk zone across 0–60 cm (p < 0.05) but remained the same at 0–20 cm in the root zone. Specific SOC mineralization and temperature sensitivity were lower in soils under Miscanthus and switchgrass compared to reference marginal land. The partial least squares path model revealed that perennial energy crop cultivation enhances soil C stock via increased C4‐derived C input and reduced mineralization. In conclusion, marginal land conversion to perennial energy crops is a win–win strategy for C sequestration to mitigate climate change and support the growing bioenergy sector with biomass supply. [ABSTRACT FROM AUTHOR]

Perennial energy crops (PECs) such as Miscanthus spp. and switchgrass (Panicum virgatum L.) may have particular influence on microbial communities and their functions in soil organic carbon (C) utilization and mineralization (Cm). In this study, long‐term effects of PECs on Cm and soil hydrolase activities were examined in bulk and rhizosphere soils of Miscanthus and switchgrass grown on a red soil in South China. Long‐term cultivation (10 years) of PECs led to increases in soil organic C (SOC) and the absolute Cm of bulk and rhizosphere soils. Total Cm was correlated with dissolved organic C and dissolved organic nitrogen (N) in red soils. The specific Cm in bulk soils of switchgrass and Miscanthus were decreased by 11.73% and 20.67% comparing with the control group, respectively. Cultivation of PECs led to a relatively high C/N ratio. There was a difference in priming effect on activities of β‐glucosidase (BG), leucine amin peptidase, N‐acetyl‐β‐glucosaminidase (NAG), and phosphatase between rhizosphere and bulk soils. Compared with the control without PECs, BG activity did not change significantly in bulk soils of PECs, whereas NAG activity decreased significantly. Soil microorganisms were generally limited by soil C and phosphorus (P) in the red soil. The C and P limitations were significantly linearly related with relative Cm (p < 0.05). Phosphorus limitations in microbial communities were lower with PECs than in the control, indicating that cultivation of PECs could provide an optimal nutrient environment for both plants and microorganisms. Thus, long‐term cultivation of PECs increased SOC content but decreased specific Cm rates. However, because C and P limitations remain for plants and soil microbial communities, optimum fertilization is also necessary for sustainable growth of PECs on red soils. [ABSTRACT FROM AUTHOR]

To understand the effects of different marginal land and environments on the growth, biomass yield, quality, and theoretical ethanol yield of different bioenergy grasses, and to compare the adaptability of different bioenergy grasses. This study was conducted in four representative marginal lands located in Chongqing, Liuyang, Nanyang, and Beijing. The agronomic traits, cell wall compositions, and theoretical alcohol yield of nine energy grasses containing 22 accessions were compared. The effects of environmental factors on biomass yield, quality, and theoretical ethanol yield of different accessions were evaluated via parametric and non-parametric statistics and AMMI analysis, and the stability and adaptability of all accessions were also compared. The results revealed that there were significant differences in biomass yield, quality, and theoretical alcohol yield among different species at the same trial site, and the same species also showed large differences between trial sites. Grasses exhibited divergent adaptability across trial sites, such as Saccharum arundinaceum and Miscanthus floridulus were sensitive to low temperatures and could not overwinter normally in Beijing. The biomass yield of Miscanthus sacchariflorus declined as the latitude decreased. Miscanthus × giganteus , Miscanthus lutarioriparius × sinensis , and Panicum virgatum exhibited greater resistance to environmental changes, indicating superior stability and environmental adaptability. [Display omitted] • Grass biomass and quality are significantly influenced by environmental factors. • Significant environmental adaptations are observed in different grass species. • Theoretical alcohol yield of grasses varies significantly between environments. • Unperturbed field trials were conducted on 4 marginal lands and climatic conditions. [ABSTRACT FROM AUTHOR]

The sustainability of bioenergy cropping systems hinges on the dynamics of soil organic carbon (SOC). Switchgrass and Miscanthus , as the two leading perennial energy crops, have been extensively cultivated on marginal land for bioenergy production. However, the effects of their cultivation on SOC sequestration and its underlying mechanisms remain unclear. Herein, we quantified the contributions of plant– and microbial–derived C to SOC accumulation by tracing 13C natural abundance and amino sugars on switchgrass- and Miscanthus -planted lands (i.e. belongs to poor acidic red soil) experienced 10 years of C 3 –C 4 vegetation conversion. The results showed Miscanthus cultivation induced an approximately 6.3 times greater improvement in SOC compared to switchgrass. However, the organic C stability in Miscanthus -planted soil was comparatively lower than that of switchgrass. This was consistent with our global meta-analysis, whereby Miscanthus and switchgrass cultivation were observed to increase SOC by 16.0% and 7.1%, respectively. Miscanthus –cultivated soil was more replenished by plant–derived C stored in particulate organic C, owing to the greater biomass and lower root quality (reflected by the high ratio of lignin to nitrogen). In contrast, switchgrass–cultivated soil was enriched with more microbial–derived C, as its greater root quality induced a more efficient C utilization by the microbes. This was preferentially associated with the soil minerals. In conclusion, perennial energy crops cultivation on marginal land substantially enhances SOC sequestration, whereas the stability of SOC is dependent on the root traits. • Switchgrass and Miscanthus cultivation enhance SOC sequestration on marginal land. • Switchgrass cultivation stimulates more microbial-derived C accumulation. • Miscanthus -cultivated soils store more C 4 -derived C. • The SOC accrual contrasting pathway is dependent on root biomass and quality. [ABSTRACT FROM AUTHOR]

• Biomass yield of M. lutarioriparius was higher than that of switchgrass. • Hybrids and M. lutarioriparius were more sensitive to rainfall than switchgrass. • Ash content of M. lutarioriparius and switchgrass was not significantly different. • The highest potential ethanol production of Miscanthus genotype was 14,600 L/ha. The lignocellulosic biomass derived from Miscanthus Anderss. and switchgrass (Panicum virgatum L.) has been widely investigated; however, large−scale production is obstructed by the lack of suitable genotypes for their growth on marginal land. To breed new varieties that can adapt to specific marginal lands, a four-year (2014−2017) field experiment was conducted using switchgrass and 12 Miscanthus genotypes on marginal land in the Yellow River Delta (YRD). The performances of Miscanthus and switchgrass were evaluated and climatic factors limiting their biomass yield were identified. During each year of the trial, 13 genotypes were harvested in winter and their biometric characteristics (biomass yield, plant height, stem diameter, and tiller number) were measured. Quality parameters (cellulose, hemicellulose, lignin, and ash) were determined in the third growing season. The three-year average biomass yield of switchgrass was 5.66 Mg/ha. The three-year average biomass yield of the 12 Miscanthus genotypes ranged from 1.99 to 32.09 Mg/ha. The biomass yields of M. lutarioriparius and hybrids were significantly higher than that of switchgrass, however, these were more sensitive to rainfall than switchgrass. No significant difference was found between the ash contents of M. lutarioripariu s, M. sacchariflorus , and switchgrass. The contents of hemicellulose, cellulose, and lignin were 377.69, 526.10, and 109.33 g/kg, respectively for switchgrass, and 247.56−391.28 g/kg, 473.52−619.85 g/kg, and 83.03−132.88 g/kg, respectively, for Miscanthus. Combining biomass yield and quality, the potential ethanol productions of M. lutarioriparius and Miscanthus hybrids were higher than that of switchgrass, and the Miscanthus hybrid h1 reached 14,600 L/ha. The results of this study provide fundamental information for the development and utilization of biomass crops on marginal land in the YRD. [ABSTRACT FROM AUTHOR]