Global Change Biology Bioenergy最新文献

Bioenergy and bioproduct markets are expanding to meet demand for climate-friendly goods and services. Perennial biomass crops are particularly well suited for this goal because of their high yields, low input requirements, and potential to increase soil carbon (C). However, it is unclear how much C is allocated into belowground pools by perennial bioenergy crops and whether the belowground benefits vary with nitrogen (N) fertilizer inputs. Using in situ ¹³C pulse-chase labeling, we tested whether the sterile perennial grass Miscanthus × giganteus (miscanthus) or annual maize transfers more photosynthetic C to belowground pools. The experiment took place at two sites in Central and Northwest (NW) Iowa with different management histories and two nitrogen (N) fertilizer rates (0 and 224 kg N ha⁻¹ year⁻¹) to determine if the fate of plant-derived soil C depends on soil fertility and crop type (perennial or annual). Maize allocated a greater percentage of total new ¹³C to roots than miscanthus, but miscanthus had greater new ¹³C in total and belowground plant biomass. We found strong interactions between site and most soil measurements—including new ¹³C in mineral and particulate soil organic matter (SOM) pools—which appears to be driven by differences in historical fertilizer management. The NW Iowa site, with a history of manure inputs, had greater plant-available nutrients (phosphorus, potassium, and ammonium) in soils, and resulted in less ¹³C from miscanthus in SOM pools compared to maize (approximately 64% less in POM and 70% less in MAOM). In more nutrient-limited soils (Central site), miscanthus transferred 4.5 times more ¹³C than maize to the more stable mineral-associated SOM pool. Our results suggest that past management, including historical manure inputs that affect a site's soil fertility, can influence the net C benefits of bioenergy crops.

The expansion of sugarcane onto land currently occupied by improved (IMP) and semi-native (SN) pastures will reshape the U.S. bioenergy landscape. We combined biometric, ground-based and eddy covariance methods to investigate the impact of sugarcane expansion across subtropical Florida on the carbon (C) budget over a 3-year rotation. With 2.3- and 5.1-fold increase in productivity over IMP and SN pastures, sugarcane displayed a C use efficiency (CUE; i.e., fraction of gross C uptake allocated to plant growth) of 0.59, well above that of pastures (0.31–0.23). Sugarcane also had greater C allocation to aboveground productivity and hence, harvestable biomass relative to IMP and SN. Cane heterotrophic respiration over the 3-year rotation (903 ± 335 gC m⁻² year⁻¹) was 1% and 14% higher than IMP and SN pastures, respectively. These soil C losses responded largely to disturbance over the first year after conversion (1510 ± 227 gC m⁻² year⁻¹) but declined in subsequent years to an average 599 ± 90 gC m⁻² year⁻¹—well below those of IMP (933 ± 140 gC m⁻² year⁻¹) and SN (759 ± 114 gC m⁻² year⁻¹) pastures—despite a significant 40%–61% increase in soil C inputs. Soil C inputs, however, shifted from root-dominated in pastures to litter-dominated in sugarcane, with only 5% C allocation to roots. Reduced decomposition rates in sugarcane were likely driven by changes in the recalcitrance and distribution rather than the size of the newly incorporated soil C pool. As a result, we observed a rapid shift in the net ecosystem C balance (NECB) of sugarcane from a large source immediately following conversion to approaching the net C losses of IMP pastures only 2 years after conversion. The environmental cost of converting pasture to sugarcane underscores the importance of implementing management practices to harness the soil C storage potential of sugarcane in advancing a sustainable bioeconomy in Southeastern United States.

The global demand for biomass-based products, including biofuels and biomaterials, is projected to rise significantly in the coming decades, driven by climate change mitigation and the pursuit of energy independence. Expanding biomass production systems, such as short-rotation plantations and energy grasses, offers a promising option to meet this demand. Although these systems deliver environmental benefits, such as carbon sequestration and water purification, their large-scale implementation may lead to landscape homogenization. Conversely, strategically deployed biomass systems can enhance local land use diversity, support biodiversity, and generate mixed income opportunities for farmers. In this study, we present a harmonized analysis of European biomass production systems using spatial data from over 426,783 fields and stands, covering 2,140,568 ha across 17 countries. By integrating empirical data with landscape metrics, we assess the spatial distribution, scale, and land use context of diverse biomass systems ranging from short-rotation plantations to energy grasses. Our results show that depending on their location, biomass production systems have the potential to enhance local land use diversity and support multifunctional landscapes that mitigate the risks associated with large-scale monocultures. Conversely, poorly integrated systems may lead to landscape homogenization and reduced ecological resilience. These findings provide a baseline for crop species selection and spatial planning, thereby informing land use policies that harmonize bioenergy production with environmental sustainability.

Moso bamboo (Phyllostachys edulis) forests play a significant role in carbon sequestration, but their sustainability is threatened by nutrient depletion and greenhouse gas (GHG) emissions. This study aims to evaluate fertilization strategies that optimize both economic returns and environmental protection in these forests. A 1-year field experiment (three treatments with four replicates) was conducted to examine the effects of biochar and chemical fertilizer application on soil carbon and nitrogen pools, microbial community composition, ecosystem carbon stock, and GHG fluxes in a subtropical Moso bamboo forest. Biochar-based compound fertilizer application increased soil organic carbon (SOC) by 12.6%, reduced microbial residual carbon (MRC) by 8.2%, and enhanced CH₄ absorption by 22.4%. In addition, it decreased N₂O emissions by 16.5%. In contrast, chemical fertilizer increased short-term biomass productivity (24.8%) but resulted in higher CO₂ and N₂O emissions. Neither treatment significantly affected microbial α-diversity, but both altered microbial community composition, particularly fungi, with biochar favoring beneficial fungal species. Biochar-based compound fertilizer is a promising strategy for enhancing carbon sequestration and mitigating GHG emissions in Moso bamboo forests. These findings highlight biochar's potential to improve soil health and contribute to more sustainable bamboo forest management, offering valuable insights for climate change mitigation strategies.

Manure and biochar (BC) based practices influence soil carbon (C) dynamics. However, manure does not enhance soil carbon (C) as quickly as BC does. Data on BC from different feedstocks and their co-application with manure in stabilizing labile manure C fractions in soil systems is still inadequate. We hypothesize that manure-BC co-application will increase soil total C by influencing the microbial community, likely to increase labile and recalcitrant C than manure alone. This study evaluated several stability parameters of manure (swine and dairy) under four rates of different BC (herbaceous corn stover, woody yellow pine, and willow) following 1 month of aging. These aged mixtures were applied to the soil and incubated for 203 days to fit a two-pool model, and the soil labile C residence time was determined. A significant (p < 0.05) positive correlation between ash-free volatile solids: fixed solids and molar H:C_org and O:C_org supports that BC addition generally stabilizes manure C by changing the mixture's physicochemical properties. Hot water extracted C of the fresh and aged mixtures revealed that high BC addition rates and BC produced from wood are significantly (p < 0.05) more efficient in decreasing the labile C pool than untreated manure, low BC application rates, and herbaceous BC. Soil incubation study revealed that BC rate significantly (p < 0.05) reduced ammonium-N availability, labile C release, and respirational C loss, but increased soil recalcitrant-C. This study reports that manure type and BC application rate significantly (p < 0.0001) influence microbial biomass C, and co-application was harmless to microbes, which in turn influences the residence time of labile C. This laboratory-based study suggests that manure-BC addition to soil builds soil total C more consistently than manure alone, supporting our initial hypothesis. However, a field-based study is warranted to evaluate manure's C and N stability and nutrient release performances under dynamic soil conditions.

Improving agricultural productivity to meet the growing food and feed demand via nitrogen fertilization comes with trade-offs such as environmental pollution and biodiversity loss. Biogas residues (BRs) being a relatively new biofertilizer aiming at substituting chemical nitrogen fertilizers, have raised questions regarding their biosecurity and environmental footprint. In this study, we explored and compared the effect of repeated application of different nitrogen fertilizers on the bacterial and fungal α-diversity, relative abundance, β-diversity, and taxonomic composition in grassland soils over a period of two years. Given the paramount importance of arbuscular mycorrhizal fungi in sustainable agriculture and climate change, we examined the relative abundance of Glomeromycota and their response to the different nitrogen fertilizers. Finally, the soil microbial community was scanned for the most prominent pathogens that are often detected in BRs and are the main concern related to their application on agricultural soils. Microbial communities in the soil were identified and quantified via high-throughput sequencing of the 16S rDNA marker gene for bacteria, and the ribosomal DNA Internal Transcribed Spacer (ITS2) region for fungi. Overall, the results suggest that the soil bacteriome is more sensitive than the mycobiome to nitrogen fertilization. Specifically, ammonium sulfate application appears to negatively impact bacterial alpha-diversity, while also altering the relative abundance of Glomeromycota, prompting us to question the potential involvement of the sulfammox process in the loss of soil microbial diversity. Notably, the application of biogas residues did not alter the diversity or abundance of soil microbial communities, nor harbored any significant pathogens; therefore, advocating for their safety and encouraging further research to validate their safe nature and beneficial properties.

A significant land use change from cropland to short rotation forestry (SRF) has taken place in the northwestern (NW) Ethiopian highlands where a fast-growing tree species, Acacia mearnsii, is cultivated to produce charcoal for urban markets. We investigated the extent of this land use change, its impact on the landscape carbon (C) budget, and its implications for climate change mitigation by combining field studies with remote sensing. We analyzed land use and land cover changes between 2005 and 2022 using Google Earth Pro imagery and validated the result with ground truthing through field observations. We estimated C stocks using soil and biomass samples collected from A. mearnsii plantation fields managed by smallholder farmers across three rotations and stand ages, as well as from cropland and other major land use types. Between 2005 and 2022, 60% of the cropland in the studied district was converted to A. mearnsii plantations. Our analysis showed that A. mearnsii cultivation had the highest spatial cover in 2017. However, a disease outbreak in 2020 resulted in a 40% reduction in cultivated area by 2022 compared to 2017 levels. The expansion of A. mearnsii cultivation increased total landscape C stocks by 21%, equivalent to a net sequestration of 0.3 Mt CO₂ year⁻¹ in the study district. This corresponded to 2.3% of Ethiopia's total annual fossil fuel emissions in 2021. The observed gain was due to C accumulation in standing biomass. In contrast, soil C stock showed a declining trend with successive rotations, though this change was not statistically significant. The main contribution of A. mearnsii based SRF in NW Ethiopia to the C budget is its potential to reduce dependence on natural forest for charcoal and firewood production.

Metabolic engineering of Saccharomyces cerevisiae has enabled xylose-fermenting yeast strains. However, the bioavailability dilemma of xylose has become the core bottleneck restricting the economy of lignocellulose. This study investigates the overexpression of the transketolase gene (TKL1) in the pentose phosphate pathway to enhance xylose utilization efficiency during mixed sugar fermentation. We initially characterized the effects of different carbon and nitrogen sources on xylose consumption and ethanol production. The recombinant yeast strain INVSc-xylA-Xltr1p-TKL1 demonstrated significant improvements in xylose utilization. In a xylose-only medium (SCX) with organic nitrogen, the strain consumed 1.54 g/L of xylose over 120 h, while in a mixed glucose and xylose medium, xylose consumption reached 3.01 g/L, reflecting increases of 52.4% and 16.2% compared with the control, respectively. With inorganic nitrogen, the strain consumed 1.3 g/L of xylose in a SCX medium and 2.69 g/L in a mixed glucose-xylose medium, corresponding to increases of 13% and 24.5% compared with the control group, respectively. Under optimal conditions, the recombinant strain achieved a sugar-to-ethanol conversion rate of 0.43 g/g, yielding 84.3% and 93.5% of the theoretical ethanol production for glucose and xylose, respectively. Furthermore, qPCR analysis revealed that the expression level of the xylose isomerase (xylA) gene in INVSc-xylA-Xltr1p-TKL1 was significantly upregulated, doubling that of the control. This enhanced expression correlated with reduced xylulose accumulation, suggesting alleviation of xylA repression. These findings demonstrate that transketolase overexpression enhances the co-utilization of glucose and xylose, improving bioethanol production efficiency.

Switchgrass (Panicum virgatum L.) is a native North American grass currently considered a high-potential bioenergy feedstock crop. However, previous reports questioned its effectiveness in generating soil organic carbon (SOC) gains, with resultant uncertainty regarding the monoculture switchgrass's impact on the environmental sustainability of bioenergy agriculture. We hypothesize that the inconsistencies in past SOC accrual results might be due, in part, to differences in prior land management among the systems subsequently planted to switchgrass. To test this hypothesis, we measured SOC and other soil properties, root biomass, and switchgrass growth in an experimental site with a 30-year history of contrasting tillage and N-fertilization treatments, 7 years after switchgrass establishment. We determined switchgrass' monthly gross primary production (GPP) for six consecutive years and conducted deep soil sampling. Nitrogen fertilization expectedly stimulated switchgrass growth; however, a tendency for better plant growth was also observed under unfertilized settings in the former no-till soil. In topsoil, SOC significantly increased from 2007 to 2023 in fertilized treatments of both tillage histories, with the greatest increase observed in fertilized no-till. Fertilized no-till also had the highest particulate organic matter content in the topsoil, with no differences among the treatments observed in deeper soil layers. However, regardless of fertilization, the tillage history had a strong effect on stratification with depth of SOC, total N, and microbial biomass C. Results suggested that historic and ongoing N fertilization had a substantial impact on switchgrass growth and soil characteristics, while tillage legacy had a much weaker, but still discernible, effect.

In many regions of Europe, biogas production is an integral part of farming to generate methane as a sustainable and versatile renewable energy carrier. Besides providing feedstock for ruminants and energy production, grasslands support multiple beneficial ecosystem services, namely diverse flora and habitats that serve as resources for pollinators. The cost-effective utilization of grassland biomass is mainly determined by the biomass quality, which is highly variable and dependent on the management intensities. Besides chemical analyses, biogas models are usually applied to predict the biogas yield of a specific biomass type and quality. However, available models do not apply to mixed grass stands as they primarily refer to individual grass species and/or are just based on single parameters such as lignin. In this work, we evaluated flower-rich extensive fen grassland for its biogas yield using a newly created model based on common chemical parameters. Therefore, flower-rich biomass from a cultivation experiment (n = 48) was analyzed for its biomass yield (average 9.43 ± 1.26 t_VS × ha⁻¹), chemical composition by wet chemical analysis and near-infrared spectroscopy (NIRS), specific methane yield (SMY) potential via batch tests, and methane hectare yield (1505.62 ± 282.86 m³_N × ha⁻¹). In the results obtained, we found flower-rich grassland biomass characterized by high fiber (30.1% ± 1.7%) and high protein content (11.3% ± 1.3%) with reliable determinability of chemical composition by NIRS. The most important predictors on SMY assessed by multiple linear regression were crude ash (XA), crude protein (XP), amylase neutral detergent fiber (aNDF_vs), acid detergent fiber (ADF_vs), and enzyme-resistant organic matter (EROM). We conclude that extensive flower-rich grassland biomass composed of diverse species and different growth and ripening stages provides a suitable feedstock for biogas production despite late harvest dates. NIRS proved capable of analyzing the biomass quality of flower-rich grassland and thus contributes to optimizing grassland management strategies and provision of demand-driven feedstock qualities.