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Chinese fir (Cunninghamia lanceolata) plantation is a dominant forest type and carbon sink in the subtropical region in China. An experiment with simulated nitrogen deposition (addition of 40 kg N ⋅ hm-2 ⋅ a-1) and drought (50% of precipitation exclusion, PE) was established in Chinese fir plantation in 2018. Soil samples (0-15 cm) were collected in summer (July 2020) and winter (January 2021). Soil microbial biomass, colony forming units (CFUs) and carbon source utilization were determined through phospholipid fatty acids (PLFAs), plate count, and Biolog methods, respectively. The results showed significant seasonal variations of PLFAs-related microbial biomass and composition. Soil bacterial and fungal CFUs tended to be decreased by nitrogen addition or precipitation exclusion treatment, and bacterial CFUs were more sensitive to the two treatments than fungal CFUs. Soil microbial function (i. e. carbon source utilization) was not affected by nitrogen addition, but significantly decreased by precipitation exclusion. There was a significant positive correlation between bacterial CFUs and microbial function, indicating the crucial roles of culturable bacteria in microbial carbon transformation. Our results highlight the critical effects of nitrogen deposition and 50% reduced precipitation on microbes in topsoil of fir plantation, with implications for unraveling soil microbial ecological function of subtropical forest ecosystem under global changes in future. [ABSTRACT FROM AUTHOR]

The low utilization efficiency of nitrogen fertilizer in agricultural ecosystem has caused serious economic and environmental issues. Dicyandiamide (DCD) is a widely used nitrification inhibitor, which can inhibit nitrification via affecting ammonia oxidizing microorganisms with minimal influence on other soil microorganisms, thereby reducing the leaching of nitrate and emission of greenhouse gases. The factors influencing the efficiency of DCD in soil include soil temperature, pH, texture, organic matter, moisture, etc. Recently, the application of molecular methods in agricultural systems has shed new light on the microbial mechanism underlying nitrification inhibition by DCD. In this review, the enzymatic inhibition mechanism, the application effects and their influence factors of DCD were summarized, and the prospects of its application were discussed as well. [ABSTRACT FROM AUTHOR]

Archaea, as the third life form distinct from bacteria and eukaryota, widely distribute in various kinds of habitats, and play important roles in the biogeochemical cycles of carbon and nitrogen and in ecosystem functioning. As the biomarker of archaea, archaeal membrane lipids can be used to investigate the archaeal community composition and its responses to the environment. This paper introduced the structural characteristics of archaeal membrane lipids and the differences in the membrane lipids composition among different archaeal communities, and discussed the feasibility of using archeal membrane lipids in depicting archaeal community composition. The abundance of archaeal membrane lipids in the environment could be used to characterize the biomass of archaea, and the related results could complement and ascertain each other with the DNA-based biomolecular approaches on the accuracy, analysis efficiency, and cost. Based on the description of the difficulties and importance of using archaeal membrane lipids to analyze the composition and abundance of archaeal communities, and by linking to the environmental factors such as temperature and pH that affected the archaeal community composition, the relationships between archaea and their habitats were further expatiated, and the evolution process of archaeal communities and its application prospects in the studies of geochemistry and geological events were analyzed. [ABSTRACT FROM AUTHOR]

Eukaryota, bacteria and archaea are the three domains of life. As the third domain of life, archaea has been found not only in extreme environments such as high-temperature, high-saline, and extremely acid habitats, but also in moderate environments including ocean, lake and soil, which implies that archaea may contribute greatly to various ecosystems. By targeting the 16S rRNA gene with real-time PCR approaches, this paper studied the abundance of archaea, crenarchaea and bacteria from two agricultural soil profiles and two long-term fertilization stations Qiyang (QY) and Fengqiu (FQ). The 16S rRNA gene copy number of crenarchaea was 1-2 orders of magnitude lower than that of archaea, and the order of these three groups was crenarchaea < archaea < bacteria. The ratios of both archaea and crenarchaea to bacteria increased with soil depth. The abundance of archaea and crenarchaea had significantly different responses to different fertilization treatments. In QY station, the copy numbers of archaeal and bacterial 16S rRNA gene had significant positive correlations with soil pH (r=0.850, P<0.01 and r=0.676, P<0.05, respectively); in FQ station, all the 16S rRNA gene copy numbers of archaea, crenarchaea and bacteria had no significant correlations with soil pH, but significantly correlated with soil organic matter (r=0.783, P<0.05;r=0.827,P<0.05;r=0.767, P<0.05, respectively). To understand the distribution of archaea and crenarchaea in agricultural soil could provide important information to evaluate their ecological functions in soil ecosystem and element cycling. [ABSTRACT FROM AUTHOR]

Copper (Cu) is massively used as feed additives in intensive farms, and the discharge and utilization of livestock wastes may cause certain environmental problems. In this paper, a cultivated black soil in Northeast China was sampled, and added with pig manures that contained different concentration of Cu to simulate the vegetable soil under different years of pig manure fertilization. With this soil, a pot experiment was conducted to study the effects of soil Cu accumulation via the application of the pig manures on the aboveground biomass and its Cu concentration of pakchoi (Brassica chinensis L.), soil microbial biomass carbon, and soil enzymes (dehydrogenase, urease, and acid phosphatase) activities. The results showed that pig manure application increased the aboveground biomass of pakchoi significantly, but had no significant effects on the aboveground biomass Cu concentration. Under the application of pig manure, soil dehydrogenase and urease activities increased in a definite period of time, but their activities as well as soil acid phosphatase activity were depressed gradually with the increase of soil Cu concentration. When the soil total Cu concentration reached 301.3 mg·kg-1, the aboveground biomass of pakchoi, soil microbial biomass carbon, and the activities of dehydrogenase, urease, and acid phosphatase were greatly reducd. The aboveground biomass Cu concentration of pakchoi had significant positive correlations with the concentration of soil total and water soluble Cu (P<0.01), while the aboveground biomass was negatively correlated with soil total Cu concentration (P<0.05). It was suggested that the threshold value of Cu in black soil under vegetable cultivation should be less than 301.3 mg·kg-1. [ABSTRACT FROM AUTHOR]

Microorganisms produce extracellular enzymes to meet elemental requirements and cope with stoichiometric imbalances of resources. To gain insights into the cycling of C, N, and P, the activities of the C∶N∶P acquisition enzymes have been extensively investigated. To detect the effects of long-term fertilization practices on soil nutrient balance and characteristics of soil enzymatic stoichiometry in black soil, four different fertilization treatments were selected： no fertilization （CK）, nitrogen fertilizer （N）, phosphorus fertilizer （P）, and combination of nitrogen and phosphorus fertilizers （NP）. Soil samples were collected in both April 2021 and April 2022 to determine soil enzyme activities and their stoichiometric characteristics. The results showed that soil acid phosphatase and β -D-glucosidase activities were significantly higher in the N and NP treatments than in CK by 68%-158% and 26%-222%, respectively. Soil β -N-acetylaminoglucosidase activities were significantly higher in the P and NP treatments, with the highest around 75.48 nmol·（g·h） -1 and 106.81 nmol·（g·h） -1 , respectively. Two-way ANOVA analysis showed that N and P inputs had a great impact on soil enzyme activities. Redundancy analysis showed that the main factors controlling enzyme activities were soil pH, microbial biomass phosphorus, and soil available P content. It was found that N inputs significantly increased enzyme vector length, which was ranged from 1.32 to 1.52, and the enzyme vector angles were all larger than 45°, suggesting C and P co-limited in the black soils. These findings suggest that 40 years of fertilization have had a great impact on soil enzymes and the related resource use strategy, which provides great implications for assessing soil nutrients balance and soil sustainability.

The reactive nitrogen deposition in subtropical region of China has been increasing annually, which affects biogeochemical processes in forest soils. In this study, three treatments were established, including control (no N addition, CK), low nitrogen deposition (40 kg·hm -2 ·a -1 , LN), and high nitrogen deposition (80 kg·hm -2 ·a -1 , HN) to study the response of denitrifying functional genes and potential N 2 O emissions to simulated nitrogen deposition in the soils of a natural Castanopsis carlesii forest. Results showed that HN significantly decreased soil potential N 2 O emission, while 8-year nitrogen deposition did not affect the abundances of nirS , nirK , nosZ Ⅰ and nosZ Ⅱ. However, the abundance of nosZ Ⅰwas significantly higher than nosZ Ⅱ in all the treatments, indicating that nosZ Ⅰ dominated over nosZ Ⅱ in the acidic soils. HN significantly decreased the ratio of ( nirK+nirS )/( nosZ Ⅰ +nosZ Ⅱ), which was positively correlated with soil pH. The results suggested that long-term high nitrogen deposition reduced soil pH and the abundance ratio of ( nirK+nirS )/( nosZ Ⅰ +nosZ Ⅱ), which subsequently reduced the potential N 2 O emission.

Global changes have profound impacts on biodiversity and ecological functioning of terrestrial ecosystems. Arbuscular mycorrhizal (AM) fungi can form symbiotic associations with most terrestrial plant species and play an important role in nutrient acquisition of host plants, promotion of plant growth, and maintenance of plant diversity. In this review, we primarily focused on the responses and feedbacks of AM fungal community and functioning to elevated atmospheric CO 2 (eCO 2 ) and warming in forest and grassland ecosystems. eCO 2 influenced AM fungi mainly through indirectly impacting host plants and soil carbon inputs. A majority of previous studies reported that eCO 2 could enhance the abundance and activity of AM fungi, and influence their diversity and community composition. Warming could have direct and indirect (via plant and/or soil pathways) impacts on AM fungi. Warming significantly altered the community compositions of AM fungi in forest soils. But the results from grassland were not consistent. We identified some outstanding problems in current studies and proposed future research topics which deserve more attentions. Our aim was to elucidate the AM fungal responses and adaptation to eCO 2 and warming and to improve our understanding of AM fungal functioning in soil ecological processes. This review could provide insights into the implications of AM fungi to mitigate global change and improve the resilience of soil functions, as well as climate change adaptation of ecosystems.

Subtropical region of China is one of the global hotspots receiving nitrogen deposition. Nitrogen deposition could affect the abundance and community structure of ammonia oxidizers including ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA) and complete ammonia oxidizer (comammox Nitrospira ), with consequences on soil nutrient cycling that are driven by microorganisms. There is limited understanding for the newly discovered comammox Nitrospira in the subtropical forest soils. Here, we investigated the effect of simulated N deposition on abundances of soil ammonia oxidizers in the Castanopsis fargesii Nature Reserve in Xinkou Town, Sanming City, Fujian Province, China. Soil samples were collected from the field plots which received long-term nitrogen deposition with different dosages, including: CK, no additional treatment; LN, low nitrogen deposition treatment, dosage of 40 kg N·hm -2 ·a -1 ; and HN, high nitrogen deposition treatment, dosage of 80 kg N·hm -2 ·a -1 . After 8-year treatment, simulated N deposition decreased soil pH and organic matter content, and increased nitrate content. We failed to amplify the amoA gene of AOB in the tested soils. High nitrogen deposition increased the abundance of AOA, but did not affect the abundance of comammox Nitrospira clade A and clade B. The ratio of comammox Nitrospira to AOA decreased with N addition, indicating that N addition weakened the role of comammox Nitrospira in nitrification in the subtropical forest soils. However, there were strong non-specific amplifications for both comammox Nitrospira clades A and B, highlighting the demand for the development of high coverage and specificity primers for comammox Nitrospira investigations in the future. The abundance of comammox Nitrospira clade A was positively correlated with total nitrogen (TN) and NH 4 + concentration, while that of clade B was positively associated with soil organic carbon (SOC), TN and NH 4 + Concentration. Overall, our findings demonstrated that simulated N deposition increased the relative importance of AOA in nitrification in the natural Castanopsis carlesii forest soil. These findings could provide theoretical support in coping with global change and N deposition in these regions.

The abundance of denitrifying functional genes plays a key role in driving the soil nitrous oxide (N 2 O) emission potential. Nitrite reductase genes ( nirK and nirS ) and nitrous oxide reductase genes ( nosZ I and nosZ II ) are the dominant denitrifying funtional genes. In this study, real-time quantitative PCR was conducted to evaluate the effects of 32-year imbalanced fertilization and lime and gypsum additions on the abundances of nirK , nirS , nosZ I and nosZ II genes in an Ultisol at Yingtan, Jiangxi Province. We further explored the underlying driving factors . The results showed that, compared with the balanced fertilization treatment, fertilization without phosphorus (P) signifi-cantly decreased the abundances of nirK , nirS , nosZ I and nosZ II genes. Fertilization without nitrogen (N) significantly reduced the abundances of nirK , nosZ I and nosZ II , but did not affect the abundance of nirS . Fertilization without potassium (K) did not affect the abundances of all denitri-fying functional genes. Results of stepwise regression analysis and random forest analysis showed that soil pH was a key environmental factor affecting the abundances of nosZ I and nosZ II . The application of lime or lime + gypsum significantly increased soil pH, which subsequently increased the abundances of nosZ II and nosZ II / nosZ I by 150%-231% and 127%-155%, respectively. Our results suggested that application of lime or lime + gypsum favored nosZ II more than nosZ I in upland Ultisols, which might enhance the relative importance of nosZ II in N 2 O reduction. Overall, fertilization without P would reduce denitrifying gene abundances, while the application of lime or lime + gypsum enriched nosZ II and increased ratio of nosZ II/nosZ I , which might be beneficial for reducing N 2 O emission potential in the Ultisols.

Fertilization affects soil nitrogen cycling and nitrous oxide (N 2 O) emissions, which are mainly driven by microbes. A 32-year field experiment was conducted to investigate the effects of chemical fertilizers and their combination with organic materials on the abundance of denitrifying functional genes ( nirS , nirK , nosZ I and nosZ II) in Ultisol. The treatments comprised no fertilizer (CK), chemical fertilizer, chemical fertilizer+peanut straw, chemical fertilizer+rice straw, chemical fertilizer+radish and chemical fertilizer+pig manure. Compared with the single chemical fertilizer treatment, soil pH and organic carbon content increased in the chemical fertilizer plus organic material treatments, with chemical fertilizer+pig manure having the strongest effect. Long-term fertilization did not affect the abundance of nirK gene, but significantly altered the nirS gene abundance. Compared to CK, long-term chemical fertilizer application increased the abundance of nirS gene by 426%. However, partial replacement of chemical fertilizer by organic materials decreased the abundance of nirS gene. The abundance of nosZ I gene was one order of magnitude higher than that of nosZ II, indicating the domination of nosZ I in the acidic Ultisol. Long-term fertilization did not affect the abundance of nosZ II, whereas chemical fertilizer+pig manure increased the abundance of nosZ I by 138%. Results of stepwise regression analysis showed that available phosphorus content was the primary factor regulating the abundance of nosZ I gene, whereas the abundance of the nosZ II gene was mainly regulated by nitrate content. Moreover, the lowest ( nirS + nirK )/( nosZ I+ nosZ II) value in the chemical fertilizer+pig manure treatment indicated that long-term manure application might reduce N 2 O emission potential in Ultisols.

Drought and nitrogen input are profoundly influencing most life on Earth and the substance cycling in forest ecosystems in the Anthropocene, with consequences on global carbon balance and feedback on climate changes. Soil microorganisms drive biogeochemical cycling and key ecological processes, with central role and global importance in climate change biology. Here, we reviewed the research in the area of the effects of drought and nitrogen deposition on soil bacteria and mycorrhizal fungi in forest ecosystems. We proposed that future studies should focus on how microbial diversity, activity, and ecological functioning respond to multiple global change factors and their interactions; how subtropical forest ecosystems respond to global changes on the basis of establishment of the long-term field experimental station; the interaction of different soil biological guilds; utilizing microbial big data to construct the relevant mechanistic models. Taken together, based on improved understanding of the responses of soil microbial diversity and community composition to global changes, further research may subsequently focus on manipulating the microbial communities to enhance forest management, ecological resources protection, and environmental sustainability. This review would provide some critical theoretical basis for the microbial strategy in mitigating climate change in future.

With the development of economics, the deposition of available nitrogen in the terrestrial ecosystem is increasing dramatically due to anthropic activities, which negatively impacts the sustainability of the ecosystem ecology. In this study, the effect of long-term stimulated nitrogen deposition[with nitrogen addition of 0, 1, 4, 8, and 32 g·(m 2 ·a) -1 ] on the microbial community structure of soil was investigated in a temperate steppe in Inner Mongolia using a pyrosequencing technique targeting the bacterial 16S rRNA gene. The results show that the available nitrogen in soil increases with increasing nitrogen addition, resulting in the decrease of the soil pH. The results of pyrosequencing indicate that soil bacterial OTU (operational taxonomy unit) numbers increase with increasing nitrogen deposition, while bacterial α diversity indices show an initial increase and subsequent decrease. Non-metric multidimensional scaling (NMDS) analysis indicates that the bacterial community structure significantly varies among treatments, which can be largely attributed to the changes in the soil pH and nitrogen content due to nitrogen deposition. At the class level, the relative abundance of different bacterial groups shows a varying trend depending on the nitrogen deposition. This study indicates that long-term nitrogen deposition significantly impacts the bacterial community by changing the soil properties.

Nitrogen is the main limiting factor in the productivity of ecological system, and biological nitrogen fixation is the main nitrogen source in the natural ecosystem. Biological nitrogen fixation includes 3 types: symbiotic, associate and free-living nitrogen fixation. Associate and free-living nitrogen fixations are collectively called asymbiotic nitrogen fixation. Compared with symbiotic system, asymbiotic nitrogen fixation rate is lower, but asymbiotic nitrogen fixation microorganisms can survive and fix nitrogen without forming symbiotic structure with plants, therefore play an important role in nitrogen cycling, especially nitrogen input in ecosystems, due to their wide distribution and high adaptability to different environments. In this review, we mainly introduced the research progress of asymbiotic nitrogen fixation microorganisms in terms of diversity, distribution characteristics, the factors influencing asymbiotic nitrogen fixation efficiencies in soils and phyllosphere, and also highlighted the existing problems and future perspectives in this research field.

Soil ammonia oxidizers, as key players for the ammonia oxidation process in soil N cycling, could respond, adapt, and give feedback to global change. In this research, soil samples were collected from a long-term field experiment with increased precipitation and warming in a temperate steppe of Inner Mongolia. We analyzed the responses of the abundance, diversity, and community structure of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) to warming and increased precipitation using quantitative real-time PCR, terminal restriction fragment length polymorphism (T-RFLP), and clone library. The results showed that increased precipitation significantly stimulated soil pH and warming significantly reduced soil respiration (SR). No significant difference was detected regarding the abundances of amoA genes across all treatments, whereas increased precipitation significantly affected the community structure of soil AOB. However, the interactive effect between warming and increased precipitation had no significant influence on the community structure of soil ammonia oxidizers. The result of the structural equation model indicated that the plant diversity and community structures of soil ammonia oxidizers were significantly correlated, suggesting that there were certain relationships among climate change, microbes, and plants. In conclusion, this study confirmed that soil microorganisms had the ability to adapt to climate change, which could provide important information for predicting future changes in ecosystems.

In recent decades, global climate change is one of the main concerns around the world. Land use change and the high demand for fossil fuel have caused severe consequences of climate change, such as elevated greenhouse gases, warming, and altering precipitation pattern. These combined factors have substantial impacts on ecosystem processes, especially carbon and nitrogen cycles in terrestrial ecosystems. Since the 1970s, a series of field manipulative experiments had been set up to stimulate the influences of monofactorial and/or multifactorial climate changes, improving our understanding of ecosystem response and feedback to global change. In this review, we summarized the development history of global change experiments, and discussed the main issues of using field manipulative experiments in simulating global change. The application of multifactorial experiments, such as CO 2 enrichment, warming, precipitation and nitrogen deposition, were highlighted in the research of soil microbial ecology. Moreover, the response and feedback of soil biota as well as the biogeochemical processes that they mediated were further addressed. We also proposed the prospects of their application in global change research to explore the impact of global change on terrestrial ecosystems.

To investigate the effect of moisture change on nitrification and denitrification and their corresponding functional microbes, an acidic paddy soil from Taoyuan, Hunan Province was selected as the study object, and soil microcosm experiment containing 4 different water holding capacity (WHC) levels (30% WHC, 60% WHC, 90% WHC, and waterlog) was set up in this study. Results showed that no active nitrification and denitrification occurred in 30% WHC treatment as there were no obvious ammonia consumption and nitrate accumulation, while nitrification was active in 60% WHC and 90% WHC treatments as indicated by the obvious accumulation of nitrate in those two treatments. Meanwhile, significant ammonia consumption and N2O emission were only observed in 90% WHC treatment, implying that a much stronger nitrification in 90% WHC treatment than in 60% WHC treatment and the co-occurrence of nitrification and denitrification in 90% WHC treatment. In waterlog treatment, relatively lower N2O emission was detected and no obvious nitrification was detected, corresponding to a significant lower soil Eh in this treatment than in the other three non-waterlog treatments. Except the early stage of incubation (7 d), the abundance of nirS, nirK and ammonia-oxidizing bacteria (AOB) amoA genes showed similar responses to soil moisture change over time. Except the slight decrease in waterlog treatment, the abundances of the three genes increased significantly as the soil moisture increased, and the highest abundances of nirS, nirK, and amoA gene were observed in 90% WHC treatment in which the highest nitrification and denitrification activity was detected. T-RFLP analysis showed that the community composition of nirS gene-containing denitrifiers changed significantly in response to soil moisture change after two weeks, and soil Eh and C(w) were the main factors affecting the community composition of denitrifiers.

Super absorbent polymers (SAPs), a new water retention material, have a potential for application in water-saving agricultural production. In this study, we investigated the effects of SAPs, synthesized from natural plant extracts, on Chinese cabbage fresh weight, soil water content, soil water stable aggregates, soil microbial biomass (carbon) and soil microbial respiration under three water conditions (excessive, normal and deficient) and two SAPs application strategies (bulk treatment and spraying treatment). The results showed that the SAPs significantly promoted the soil water content, water-stable aggregates (> 0.25 mm) and the soil microbial activities, especially under the water deficient conditions. Meanwhile, SAP application strategy was of great significance to the effects on Chinese cabbage and soil properties. Compared with the control treatment under normal water condition, spraying treatment of Jaguar C (S-JC) could reduce irrigation water amount by about 25% without reducing the crop production. Furthermore, compared with the control treatment under the same water condition with S-JC (deficient), it could increase Chinese cabbage production by 287%. Thus, SAPs is an environmental friendly water-saving technique in agricultural production.

Super absorbent polymers (SAPs) are compounds that can absorb a lot of water which can be several folds of their original size and weight. They can increase soil water content and aggregates, promote fertilizer utilization efficiency, and stimulate crop growth. Therefore, SAPs have been widely regarded as a potential agent for water-saving agriculture. In this paper, we reviewed the advances of SAPs in materials, properties and applications in agriculture and pointed out that the absence of influences of SAPs on soil microbial ecology was the main issue in current studies. In regard to the adverse effects on soil environment caused by misuse of SAPs, we should address the systematic safety assessment of SAPs application in the soil, especially the effects on the soil microorganisms, which should be an important part of chemicals risk assessment in the soil application.

Manganese (Mn) oxides are common minerals in natural environments that may play an important role in the biogeochemical cycles of heavy metals. Increasing evidences have shown that Mn (II) oxidation is a microbially-mediated process, and the Mn oxidizing microorganisms are thus recognized as the major drivers of the global Mn cycle. The major pathway for bacterial Mn (II) oxidation is catalysed by a multicopper oxidizing enzyme family. The primary Mn (IV) biooxides are phyllomanganate-like minerals most similar to delta-MnO2 or acid birnessite. Manganese oxides are known to have high sorption capacities for a wide variety of metal ions and considered to be the important environmental oxidant to many metal ions. This paper reviewed the mechanisms of biogenic manganese oxides formation and their reactions with heavy metal ions in environment.

Culturable microorganisms provide very limited information on soil microbial diversity, because only 0.1%-10% of soil microorganisms can be cultured under conventional laboratory conditions. A novel culture-independent approach, i.e., metagenomic methodology, has been developed as an effective tool for the discovery of new natural products and microbial functions. Soil metagenomic methods, comprising isolation of soil DNA and construction and screening of clone libraries, enable to peep at more complete scenario of soil microbial communities, and thus, to better understand their interactions. This methodology is of great potential for use in the studies of soil microbial communities and their functional genes, and in the discovery of new biocatalysts for industry and pharmacy. This review summarized some advances of soil metagenomic study.