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Biofertilizers with phosphate-solubilizing microorganism (PSM) inoculations have been suggested to diminish the limitation of phosphorus (P) deficiency in plants. However, their applications in agriculture are restricted due to the inconstant effects of various PSMs. Proper carriers for the inoculations may overcome this shortcoming and improve PSMs' effectiveness. The objective of this study was to investigate whether straw compost, a type of organic material, can act as a carrier for improving the efficiencies of phosphate-solubilizing bacteria and fungi named Acinetobacter sp. and Aspergillus niger, respectively, in soils. We monitored the growth and cellular physiological responses of one type of model plants, named perennial ryegrass (Lolium perenne L.), under four soil treatments, including non-fertilization, PSM inoculation alone, straw compost addition alone, and the combined applications of both PSMs and straw compost. We found the combined treatments significantly improved the growth by 14.7% for shoot height and 79.7% for shoot weight, respectively, on average. P and potassium (K) uptakes of ryegrass were also increased by 102.5% and 65.3%, respectively, after the application of both PSMs and straw compost. Furthermore, physiological properties, such as photosynthetic efficiency and P-transportation capacity, of ryegrass were also significantly improved under combined treatments when compared to other treatments, regardless of the types of PSM included. The piecewise structural equation model further indicated that PSM inoculation and straw compost input are synergistically contributing to the nutrient uptake of ryegrass through many direct and indirect ways. We propose that straw compost is a good carrier material for PSMs' survival and would improve their plant growth promotion ability in soil. Our results provide valuable insights into the exploitation and utilization of P-biofertilizers in agriculture. [ABSTRACT FROM AUTHOR]

To enhance the visual performance of low-illumination images, many low-illumination images are analyzed. Based on this, a low-light image enhancement method based on HSV space and semi-implicit ROF model is proposed. First, the low-illumination image is decomposed into HSV space for saturation denoising and brightness enhancement. Then, the Bayesian rules are applied to fuse the saturation and value. The three components in HSV space are converted to the RGB space and obtain a rough enhanced image. Finally, the semi-implicit ROF model is introduced to denoise the global noise and obtain the enhanced image. Such a comprehensive method can improve the low illumination image more clearly. The experimental results show that the algorithm has a PSNR score of 26.48, 6.29, 0.8947, and 28.4124, and the PSNR score is the highest in the comparison algorithm. The experiments on the Low-Light image data set also show that the proposed method can effectively improve the visibility of low-light images, and can provide a simple and effective method for low-light image enhancement. [ABSTRACT FROM AUTHOR]

Soil diazotrophs convert atmospheric nitrogen (N) into biologically active N, which is an important N source for plants and microbes in many natural ecosystems. However, responses of diazotrophic communities to long-term N and phosphorus (P) inputs and the primary mediators remain unclear, particularly in semi-arid grasslands. Here we show that the abundance and community composition of diazotrophs responded distinctly to gradients of long-term N and P additions in an Inner Mongolia steppe. Our results showed that moderate to high N inputs (105–280 kg N ha−1 yr−1) significantly reduced both diazotrophic abundance and community diversity. In contrast, low to moderate P additions (20–80 kg P 2 O 5 ha−1 yr−1), along with low N input (24 kg N ha−1 yr−1), significantly increased diazotrophic abundance, while having no significant effects on soil diazotrophic diversity and community structure. Also, long-term N and P inputs led to different co-occurrence patterns in the diazotrophic community, although both of them reduced the stability of diazotrophic co-occurrence network. Structural equation modeling (SEM) analysis further revealed that N additions suppressed the diazotrophic abundance and diversity, corresponding to the decreasing stoichiometric ratio of soil available C to N. Together, these results indicate that nutrient-induced changes in the relative availability of C to N in soil primarily drives the impacts of nutrient enrichment on diazotrophs. These findings suggest that management regimes with low nutrient inputs may provide unique opportunities to increase plant productivity, while sustaining or even enhancing the abundance and activity of soil diazotrophs. • Nutrient addition effects on soil diazotrophs were examined in a Mongolian steppe. • Moderate to high N input significantly reduced diazotrophic abundance and diversity. • Low N and P additions enhanced the abundance of diazotrophs and their associations. • High N and P additions reduced the stability of diazotrophic co-occurrence network. • The C:N stoichiometry primarily drove the response of soil diazotrophs to N input. [ABSTRACT FROM AUTHOR]

Microbial nitrogen (N) limitation is a common problem in terrestrial ecosystems. Pig manure, a type of solid waste, is increasingly applied to improve soil N availability in agriculture through inputs of organic matter and inorganic N. Pig manure application also introduces a lot of exogenous microorganisms, which have distinctly different N requirements and metabolic properties, into the resident soil microbial community. However, the impacts of these manure-borne microorganisms on soil N cycling have not been well determined. Here, we investigated effects of manure-borne microorganisms on the N limitation of soil microorganisms using an ecoenzymatic stoichiometry analysis. We monitored microbial communities over a 90-day period in a laboratory-controlled experiment with four treatments: (1) non-sterilized soil mixed with non-sterilized manure (S-M), (2) non-sterilized soil mixed with sterilized manure (S-sM), (3) sterilized soil mixed with non-sterilized manure (sS-M), and (4) non-sterilized soil without manure addition (S, the control). The microbial N limitations were significantly mitigated in both S-M and sS-M. By contrast, the S-sM and S showed high levels of microbial N limitation, likely stemming from differences in the microbial functional composition. We found chitin-degrading bacteria were the dominant copiotrophic manure-borne bacteria associated with N mineralization, and they may improve soil N availability. We further identified several copiotrophic manure-borne bacteria in S-M and sS-M, and their abundances had significantly negative correlation with the level of N limitation and significantly positive correlation with the stoichiometric homeostasis. As these copiotrophic taxa can maintain homeostasis through regulating enzymatic activities, our results indicate that copiotrophic taxa in pig manure contribute to the mitigation of soil microbial N limitation. Our study also highlights the invasiveness capacity of manure-borne microorganisms in soil and evaluates the biotic effects of manure application on soil N cycling. [Display omitted] • Manure application mitigates microbial nitrogen limitation in soil. • Manure application improves biomass C:N homeostasis of soil microbial communities. • Diverse copiotrophic taxa were introduced into soil through manure application. • Copiotrophic taxa could contribute to the mitigation of nitrogen limitation. [ABSTRACT FROM AUTHOR]

• Responses of alpine soil N transformations to warming and N input were examined. • Warming alone did not significantly affect soil N transformations. • N input significantly increased AOB and N 2 O emissions in the late growing season. • Warming amplified the effects of N input on nitrification and N 2 O emissions. • Ammonia-oxidizing bacteria dominate alpine soil N transformations and N 2 O emission. Alpine ecosystems worldwide are characterized with high soil organic carbon (C) and low mineral nitrogen (N). Climate warming has been predicted to stimulate microbial decomposition and N mineralization in these systems. However, experimental results are highly variable, and the underlying mechanisms remain unclear. We examined the effects of warming, N input, and their combination on soil N pools and N-cycling microbes in a field manipulation experiment. Special attention was directed to the ammonia-oxidizing bacteria and archaea, and their mediated N-cycling processes (transformation rates and N 2 O emissions) in the third plant growing season after the treatments were initiated. Nitrogen input (12 g m−2 y−1) alone significantly increased soil mineral N pools and plant N uptake, and stimulated the growth of AOB and N 2 O emissions in the late growing season. While warming (by 1.4 °C air temperature) alone did not have significant effects on most parameters, it amplified the effects of N input on soil N concentrations and AOB abundance, eliciting a chain reaction that increased nitrification potential (+83%), soil NO 3 −-N (+200%), and N 2 O emissions (+412%) across the whole season. Also, N input reduced AOB diversity but increased the dominance of genus Nitrosospira within the AOB community, corresponding to the increased N 2 O emissions. These results showed that a small temperature increase in soil may significantly enhance N losses through NO 3 − leaching and N 2 O emissions when mineral N becomes available. These findings suggest that interactions among global change factors may predominantly affect ammonia-oxidizing microbes and their mediated N-cycling processes in alpine ecosystems under future climate change scenarios. [ABSTRACT FROM AUTHOR]

• Responses of alpine N 2 O emission and its Q 10 to warming and N inputs were examined. • Warming or N inputs alone did not affect soil N 2 O emission and its Q 10. • Warming and N combination significantly increased soil N 2 O emission and its Q 10. • Ammonia-oxidizing bacteria predominantly affected the Q 10 of N 2 O emission. • Nitrification process was a dominant source of soil N 2 O emission. Many high-elevation alpine ecosystems have been experiencing significant increases in air temperature and, to a lesser extent, nitrogen (N) deposition. These changes may affect N-cycling microbes and enhance emissions of nitrous oxide (N 2 O, a potent greenhouse gas) from soil. However, few studies have investigated whether and how the resulting changes in N-cycling microbes may affect the temperature sensitivity (Q 10) of N 2 O emission and in turn feed back to N 2 O emissions. We conducted two incubation experiments to examine N 2 O emissions and their temperature sensitivities in soils that had experienced 3-yr field treatments of warming, N inputs and their combination in a Tibetan alpine meadow. Our results showed that neither N inputs nor warming alone affected the rate or Q 10 of soil N 2 O emission, but combining the two significantly increased both parameters. Also, combined N and warming significantly increased the abundance of ammonia-oxidizing bacteria (AOB), corresponding with high soil N 2 O emission. In addition, N 2 O emission from nitrification accounted for 60–80% of total emissions in all soils, indicating that nitrifying microbes dominated the N 2 O production and its temperature sensitivity. Using random forest (RF) and structural equation model (SEM) analyses, we further evaluated the effects of various soil characteristics on soil N 2 O emissions and Q 10. We identified soil moisture, pH, N mineralization and AOB abundance as the main predictors of the Q 10 of N 2 O emissions. Together, these findings suggest that alterations in soil moisture, pH and ammonia-oxidizing bacteria induced by long-term N inputs and warming may increase temperature sensitivity of soil N 2 O emissions, leading to a positive climate feedback in this high-altitude alpine ecosystem. [ABSTRACT FROM AUTHOR]

Polyploidization (i.e., multiplication of genome size) is a major driver of plant evolution and is believed to play a significant role in plant invasion. One hypothesis states that polyploids possess larger root systems with increased root exudation and thus, induce a greater effect on the rhizosphere compared to their diploids counterparts. Few experiments, however, have explicitly tested the impacts of the polyploidy of plants on soil organisms in the field. Using a common garden approach, we examined the impacts of native and introduced populations of Solidago canadensis with differing ploids (diploid, tetraploid and hexaploid) on soil microbes, nematodes, and carbon (C) - nitrogen (N) turnover. Polyploidy generally increased microbial biomass in soil: while the biomass of all microbial groups was significantly higher under introduced than native tetra- and hexa-ploids, there was no significant difference in soil bacteria, fungi, and actinomycetes between diploids of the native and introduced populations. The effect of polyploids on soil microbial biomass was greater in November than July, suggesting that the effect becomes stronger later in the growing season. The impact of polyploidy on nematodes was largely dependent on trophic status; polyploids did not significantly affect bacterivores or omnivores + carnivores, but tended to increase the abundance of fungivores, and significantly increased the number of herbivores. Extraradical biomass of arbuscular mycorrhizal fungi was significantly higher, but NO 3 −-N and the net nitrification rate were significantly lower under tetra- and hexa-ploids than diploids. Together, these results suggest that polyploidization induces rhizosphere processes that improve plant nutrition and contribute to plant invasiveness through stimulation of soil microbial biomass and increased biological activity. Different trophic interactions in the rhizosphere of diploid and polyploids Solidago canadensis. Compared to diploid plants (a), polyploid plants (b) possess larger root systems associated with more arbuscular mycorrhizal fungi (AMF), bacteria and fungi. Higher resource availability subsequently increases fungi-feeding nematodes and plant-feeding nematodes, leading to more N release and plant N uptake through roots and AMF (i.e., a positive plant-soil feedback). (BF: bacterivorous; FF: fungivorous; HE: herbivorous; OM + CA: omnivorous-carnivorous nematodes.). Image 1 • Ploidy effects of Solidago canadensis on plant-microbe interactions were studied. • Mycorrhizal root infection and plant N uptake were higher in poly-than di-ploids. • Polyploids enhanced soil microbial biomass, respiration and N mineralization. • Fungal- and root-feeding nematodes were more abundant under poly-than di-ploids. [ABSTRACT FROM AUTHOR]