Asynchronous responses of microbial CAZymes genes and the net CO2 exchange in alpine peatland following 5 years of continuous extreme drought events

Aluminum and microplastic release from reflective agricultural films disrupt microbial communities and functions in soil

Reflective agricultural films are widely used in vegetable production and orchards to repel pests, accelerate fruit ripening, and boost yields. These films, composed of a plastic base metallized with aluminum (Al), degrade over time in soil, releasing Al and microplastics. This study investigated the aging and weathering of Al-coated reflective films (polyethylene terephthalate, PET-based) under UV radiation, simulated rainfall, and soil burial for up to 120 days, assessing the effects of released Al and microplastics on soil chemistry and microbial communities. Weathering was confirmed by the formation of C-O/CO functional groups, an increasing carbonyl index, and the oxidation of Al to Al₂O₃, as shown by Fourier-transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). Faster Al-coated shedding and PET oxidation were observed in the soil environment. Microplastics (0.5 % w/w) from the films reduced soil micronutrient availability (Fe, Mn, Cu), suppressed functional genes involved in carbon, nitrogen, and phosphorus cycling, and shifted microbial communities towards oligotrophic bacteria enrichment (e.g., RB41, Candidatus_Udaeobacter, Gemmatimonadetes, and Chloroflexi) while reducing copiotrophic bacteria (e.g., Sphingomonas, Ellin6067, Dongia, Puia, and Flavisolibacter). Therefore, these findings highlight that reflective film weathering strongly alters soil nutrient content and microbial community composition, with potential implications for soil health and agricultural sustainability.

Flooding episodes and seed treatment influence the microbiome diversity and function in the soybean root and rhizosphere

Climate change-related events such as flooding have threatened crop productivity, agricultural sustainability, and global food security by causing hypoxic conditions. Such conditions impaire root development and nutrient acquisition, and alter root rhizospheric microbial communities that are vital for plant health and productivity. Seed treatment with pathogen protection have been key to maintaining early seed germination and plant productivity in field conditions. Still, their role in flooding stress and microbiome diversity and functionality in soybeans is poorly understood. Here, we performed field-based investigations to understand the impact of flooding episodes (0, 3, and 7 days after floodings; DAF) and seed treatment (Cruiser MAXX) on soybean plant growth and rhizosphere microbiome diversity and functionality. Flooding episodes significantly reduced seed yield (746 kg ha-1) compared to untreated control. However, the seed treatment increased plant height and pods per plant (3-DAF) and reduced flood injury by 33 % (7-DAF). The shotgun metagenomic analysis showed that seed treatment significantly enhanced the microbial community in rhizospheric soil. Flooding episodes impacted the microbial communities with higher abundance at 3-DAF than at 7-DAF. Flooding stress reduced the microbial diversity, although Proteobacteria increased as root endophytes. Seed treatment and flooding combinations decreased microbiome functionality and reduced gene counts for phytohormone biosynthesis, fermentation, nitrogen, symbiosis, and degradation pathways. Similarly, flooding stress shifted the carbohydrate synthesis to a more specialized substrate. These findings enhance understanding of soybean root and rhizosphere microbiome diversity and functionality dynamics during flooding stress and provide a platform to develop sustainable agricultural practices for enhancing soybean stress tolerance to flooding.

Increasing drying changes the relationship between biodiversity and ecosystem multifunctionality

Increased drying of rivers under global climate change is leading to biodiversity loss. However, it is not clear whether biodiversity loss affects river functions. In this study, we investigated the changes in biofilm community diversity and functions in an artificial stream after different drying durations. A critical drying duration of around 60 days was found in the microbial composition and functions. Therefore, different drying durations can be divided into short-term drying (~0-20 days) and long-term drying (~60-130 days) to analyse the effect of biodiversity in terms of ecosystem functions. In summary, the dominant relationship of biodiversity on community stability got uncoupled after long-term drying. Community assembly became dominant in maintaining multifunctionality with increasing drying duration rather than biodiversity as traditionally perceived. This study reveals the importance of community assembly, extending theoretical knowledge of the relationship between biodiversity and ecosystem multifunctionality.

Microplastics from polyvinyl chloride agricultural plastic films do not change nitrogenous gas emission but enhance denitrification potential

The effects of microplastics (MPs) from agricultural plastic films on soil nitrogen transformation, especially denitrification, are still obscure. Here, using a robotized flow-through system, we incubated vegetable upland soil cores for 66 days with MPs from PE mulching film (F-PE) and PVC greenhouse film (F-PVC) and directly quantified the emissions of nitrogenous gases from denitrification under oxic conditions, as well as the denitrification potential under anoxic conditions. The impact of MPs on soil nitrogen transformation was largely determined by the concentration of the additive phthalate esters (PAEs) containing in the MPs. The F-PE MPs with low level of PAEs (about 0.006 %) had no significant effect on soil mineral nitrogen content and nitrogenous gas emissions under oxic conditions. In contrast, the F-PVC MPs with high levels of PAEs (about 11 %) reduced soil nitrate content under oxic conditions, probably owing to promoted microbial assimilation of nitrogen, as the emissions of denitrification products (N2, NO, and N2O) was not affected. However, the F-PVC MPs significantly enhanced the denitrification potential of the soil due to the increased abundance of denitrifiers under anoxic conditions. These findings highlight the disturbance of MPs from agricultural films, particularly the additive PAEs on nitrogen transformation in soil ecosystems.

Role of genes encoding microbial carbohydrate-active enzymes in the accumulation and dynamics of organic carbon in subtropical forest soils

Microbial anabolism and catabolism regulate the accumulation and dynamics of soil organic carbon (SOC). However, very little attention has been paid to the role of microbial functional traits in the accumulation and dynamics of SOC in forest soils. In this study, nine forest soils were selected at three altitudes (600 m, 1200 m, and 1500 m) and three soil depths (0-15 cm, 15-30 cm, and 30-45 cm) located in Jiugong Mountain. Vertical traits of functional genes encoding microbial carbohydrate-active enzymes (CAZymes) were observed using metagenomic sequencing. Soil amino sugars were used as biomarkers to indicate microbial residue carbon (MRC). The results showed that GH1 (β-glucosidase: 147.49 TPM) and GH3 (β-glucosidase: 109.09 TPM) were the dominant genes for plant residue decomposition, and their abundance increased with soil depth and peaked in the deep soil at 600 m (GH1: 147.89 TPM; GH3: 109.59 TPM). The highest abundance of CAZymes for fungal and bacterial residue decomposition were GH18 (chitinase: 30.81 TPM) and GH23 (lysozyme: 58.02 TPM), respectively. The abundance of GH18 increased with soil depth, while GH23 showed the opposite trend. Moreover, MRC accumulation was significantly positively correlated with CAZymes involved in the degradation of hemicellulose (r = 0.577, p = 0.002). Compared with the soil before incubation, MRC in the topsoil at the low and middle altitudes after incubation increased by 4 % and 8 %, respectively, while MRC in the soils at 1500 m tended to decrease (p > 0.05). The mineralization capacity of SOC at 1500 m was significantly higher than that at 1200 m and 600 m (p < 0.05). Our results suggested that microbial function for degrading plant residue components, especially hemicellulose and lignin, contributed greatly to SOC accumulation and dynamics. These results were vital for understanding the roles of microbial functional traits in C cycling in forest.

Effects of microplastics on carbon release and microbial community in mangrove soil systems

Mangrove ecosystems are major carbon sink biomes and also a sink of microplastics (MPs). The final enrichment of MPs in sediments may have a significant impact on the microbial community and carbon turnover in the soil. However, the effects of MP pollution on the mangrove soil microbial communities and carbon release remain unknown. Here, we conducted a manipulative incubation experiment by adding MPs to soil at different soil depths to examine the effect of enriched MPs on soil microorganisms and its function (i.e., decomposition of soil carbon). The results showed that the addition of MPs had no significant effect on the microbial diversity and CO2 cumulative emission in the topsoil but significantly increased CO2 release from the subsoil. The promoting effect of polylactide (PLA) on the release of CO2 from the subsoil was stronger than that of polyethylene (PE) and aging PE. In the subsoil, the activity of soil extracellular enzymes related to N acquisition increased with the MP addition, indicating an increase in microbial N deficiency. The subsoil was more sensitive to MPs because of the exacerbated nitrogen limitation. MP addition reduced the microbial diversity of the subsoil and altered soil microbial interactions. The increasing abundance of some microbial taxa, especially bacteria related to the sulfur cycle, indicated more active electron transfer and organic carbon mineralization in the subsoil. Our findings suggest that MP contamination has potential effects on microbial communities, nutrient cycling, and carbon release in mangrove soils that vary depending on soil depth.