[Characterization of greenhouse gas emissions and stable isotopic composition of ammonia during industrial composting process]. / å·¥åŽ‚åŒ–å †è‚¥æ¸©å®¤æ°”ä½“æŽ’æ”¾å’Œæ°¨æ°”åŒä½ç´ ç‰¹å¾.

Carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4) and ammonia (NH3) emitted during the composting of livestock and poultry waste are important gaseous atmospheric pollutants. However, most previous studies on compost-related anthropogenic emissions of these gases were based on small reactor composting. Our understanding of their in situ emissions during industrial composting remains extremely limited. In order to explore the influence of gas produced by industrial composting on regional environment, we monitored CO2, CH4, N2O and NH3 emissions during industrial composting for 19 days and characterized the isotopic composition of emitted NH3. On average, the emission rates of CO2, CH4, N2O, and NH3 during the composting cycle were 86.8 g CO2-C·d-1·m-2, 9.8 g CH4-C·d-1·m-2, 3.7 mg N2O-N·d-1·m-2 and 736.6 mg NH3-N·d-1·m-2, respectively. The contribution of CH4 to daily global warming potential (GWP) was the highest (65%), followed by CO2, NH3(indirect), and N2O. Moreover, ammonia emitted from industrial compost had a mean δ15N value of -11.6‰±1.2‰ (range: -21.8‰--7.2‰). Overall, this study provided useful information for understanding greenhouse gas emission dynamics and characterizing atmospheric NH3 sources during composting process in livestock and poultry breeding areas.

[Approach and evidence-based study of provincial-level eco-economic development planning]. / çœçº§å°ºåº¦ç”Ÿæ€ç»æµŽå‘å±•è§„åˆ’ç¼–åˆ¶æ–¹æ³•åŠå®žè¯ç ”ç©¶.

The development of ecological economy is one of the core elements of the ecological civilization system and an essential means to optimize the social-ecological systems. The key to developing ecological economy lies in preparing the development plan to realize concrete implementation. Given the objective and realistic demand for the development of ecological economy, it is critically needed to propose the approach of eco-economic planning and conduct empirical research. We sorted out the connotation of ecological economy, proposed the general idea of "object identification-resource evaluation-principal construction-target setting-task content-mechanism guarantee", and proposed three work modules, including "preliminary preparation, content design, review & approval", and finally built a technical system for the preparation of provincial-scale ecological economy planning. We outlined the 14th Five-Year Plan for Eco-Economic Development of Liaoning Province, and discussed critical issues such as the connotation definition and index system establishment for eco-economic development plan. This work provides ideas for the scientific and standardized preparation of ecological economy development plan at the provincial level in China.

[N2O and N2 emission characteristics from maize and greenhouse vegetable soils in Northern China]. / æˆ‘å›½åŒ—æ–¹å‡ ç§çŽ‰ç±³å’Œè®¾æ–½èœåœ°åœŸå£¤çš„N2O和N2排放特征.

To explore N2O and N2 emissions from upland soils after nitrogen fertilizer application, a 60-day aerobic incubation experiment (25 ℃,80% water-filled pore space) using the 15N tracing method was conducted to quantify the N transformation, N2O and N2 emissions from maize soils from four sites (Harbin, Shenyang, Luancheng and Shouguang) and vegetable soils from two sites (Shen-yang and Shouguang), with urea being applied at 167 mg N·kg-1 to simulate the field application rate of 200 kg N·hm-2. The results showed that for the four sites with maize soils, the cumulative emission of N2O was in the order of Shouguang (20 mg N·kg-1) > Luancheng (14 mg N·kg-1) > Shenyang (5 mg N·kg-1) > Harbin (0.5 mg N·kg-1) and the cumulative N2 emission was in the order of Luancheng (176 mg N·kg-1) > Shenyang (106 mg N·kg-1) > Shouguang (75 mg N·kg-1) > Harbin (12 mg N·kg-1). For vegetable soils, the cumulative N2O emission of Shouguang (21 mg N·kg-1) was 10 times of that of Shenyang (2 mg N·kg-1), but without differences in cumulative N2 emissions (28 and 24 mg N·kg-1, respectively). The N2O/(N2O+N2) of the six soils ranged from 5% to 40%. The N2O/(N2O+N2) of the two soils from Shouguang (30%-40%) was significantly higher than other four soils (1%-10%). Soil bulk N pool contributes to 56% of total N2O emission and 61% of total N2 emission, which was higher than the contribution of fertilizer. The cumulative N2O emission was positively correlated with soil background pH, which indicated that soil background pH might be an important factor regulating N2O and N2 emission from upland soils. In the alkaline soil regions of North China Plain (such as Luancheng and Shouguang), mea-sures to reduce soil pH might have great impact on reducing N gaseous emission.

[Effects of soil moisture on microbial processes of soil nitrogen gases production under anaerobic conditions]. / 土壤水分对土壤产生气态氮的厌氧微生物过程的影响.

Gaseous nitrogen (N) emission [nitric oxide (NO), nitrous oxide (N2O), and nitrogen (N2)] is an important pathway of soil N loss. Nitrification and denitrification are the main processes of gaseous N production in soil. However, the contribution of heterotrophic nitrification, co-denitrification, and anammox to gaseous N production remains uncertain. In a laboratory soil incubation experiment, we used the 15N labelling and pairing technique, combining the nitrification inhibitor dicyandiamide (DCD), to quantify the contribution of different microbial processes to soil NO, N2O and N2 production under anaerobic conditions. The results showed that after 24 h anaerobic incubation, the highest total 15N recovery of three gases occurred at 65% water filled pore space (WFPS), accounting for 20.0% of total added 15N. Denitrification contributed 49.9%-94.1%, 29.0%-84.7%, and 58.2%-85.8% to the production of NO, N2O and N2 respectively, suggesting that denitrification was the predominant process of those three N gases emission. Heterotrophic nitrification was an important pathway of NO and N2O production, particularly at conditions with low soil water content (10% WFPS), with its contribution to those two N gases production being 50.1% and 42.8%, respectively. Co-denitrification contributed 10.6%-30.7% of N2O production. For N2 production, the total contribution of co-denitrification and anammox was 14.2%-41.8%. The role of co-denitrification can not be ignored for N2O and N2 production. Our results demonstrated that the 15N labelling and pairing technique is a promising tool to quantify the contribution of different microbial processes to gaseous N loss.

Generalist Taxa Shape Fungal Community Structure in Cropping Ecosystems.

Fungi regulate nutrient cycling, decomposition, symbiosis, and pathogenicity in cropland soils. However, the relative importance of generalist and specialist taxa in structuring soil fungal community remains largely unresolved. We hypothesized that generalist fungi, which are adaptable to various environmental conditions, could potentially dominate the community and become the basis for fungal coexisting networks in cropping systems. In this study, we identified the generalist and habitat specialist fungi in cropland soils across a 2,200 kms environmental gradient, including three bioclimatic regions (subtropical, warm temperate, and temperate). A few fungal taxa in our database were classified as generalist taxa (~1%). These generalists accounted for >35% of the relative abundance of all fungal populations, and most of them are Ascomycota and potentially pathotrophic. Compared to the specialist taxa (5-17% of all phylotypes in three regions), generalists had a higher degree of connectivity and were often identified as hub within the network. Structural equation modeling provided further evidence that after accounting for spatial and climatic/edaphic factors, generalists had larger contributions to the fungal coexistence pattern than habitat specialists. Taken together, our study provided evidence that generalist taxa are crucial components for fungal community structure. The knowledge of generalists can provide important implication for understanding the ecological preference of fungal groups in cropland systems.

[Concurrent Collection of Ammonia Gas and Aerosol Ammonium in Urban Beijing During National Celebration Days Utilizing an Acid-Coated Honeycomb Denuder in Combination with a Filter System].

Since 2013, the Chinese government implemented the Air Pollution Prevention and Control Action Plan. As a result, the atmospheric concentrations of sulfate reduced significantly, whereas the nitrate concentrations remain relatively high due to the excess of ammonia (NH3). To date, there is no official observation network monitoring NH3 concentrations in China. Previous studies have focused on NH3 or ammonium (NH4+) separately. These limitations hinder a complete understanding of their dynamic changes due to the rapid gas-to-particle conversion. In this study, the concentrations of NH3 and NH4+ were measured concurrently in urban Beijing during autumn 2019 utilizing an acid-coated denuder-filter combination with a time resolution from 2 h (PM2.5>35 µg·m-3) to 5 h (PM2.5<35 µg·m-3). The mean concentrations of NH3 and NH4+ during the study were (4.1±2.9)µg·m-3 and (1.7±1.4) µg·m-3, respectively. The temporal patterns of NH3 or NH4+ coincided with that of PM2.5, CO, and NO2 throughout the sampling period. The diurnal distributions of NH3 were bimodal, both on polluted (PM2.5>75 µg·m-3) and non-polluted (PM2.5<75 µg·m-3) days, peaking at 21:30-05:30 and 05:30-08:30, respectively. The NH3 concentrations on polluted days were relatively lower during 17:30-21:30, which may be related to higher wind speeds. In contrast to NH3, NH4+ had an obvious peak during 17:30-21:30 due to the formation of ammonium nitrate. The meteorological conditions favor the gas-to-particle conversion on polluted days, resulting in a lower NH3/NH4+ ratio of 0.8. However, this value may reach 2.8 on non-polluted days. The concentrations of NH3, CO, NO2, SO2, and PM2.5 in the emission control period showed a significant increase greater than or comparable to those in the non-control period by 54.2%, 40.4%, 33.3%, 0%, and 49.4%, respectively. This result shows that the stagnant conditions offset the benefit of emission control actions implemented during and before the National Celebration Day.

[Source Apportionment of Atmospheric Ammonia: Sensitivity Test Based on Stable Isotope Analysis in R Language].

Ammonia (NH3) is an important precursor of fine particles and nitrogen deposition. It is critical to identify and quantify the sources of NH3 before the implementation of a mitigation strategy. Stable isotope analysis in R (SIAR) has potential with regard to the source apportionment of NH3, but its reliability is closely related to the signatures (δ15N-NH3) of emission sources. Based on SIAR, we found that the agricultural contribution varied significantly with mean δ15N-NH3 values of endmember input. In contrast, both the contributions of fossil fuel and NH3 slip showed low sensitivity against the change of endmember input. Moreover, the agricultural contribution changed by about 20% due to the variations in agricultural endmember mean values. Such a change is five times that due to the variations in endmember standard deviation values. Notably, regardless of the number of input sources tested, "non-agricultural source" was the dominant source of NH3 during hazy days in January 2013 in Beijing. Since various agricultural sources showed large variations in δ15N-NH3, future studies should focus on the endmember signatures of agricultural sources to further reduce the uncertainty in SIAR-based NH3 source apportionment.

Large-scale patterns of soil antibiotic resistome in Chinese croplands.

Soil is a vital reservoir of antibiotic resistance genes (ARGs), but we still know little about their distribution in cropland soils and the main driving forces. Here we performed an investigation for ARGs patterns in 105 cropland soils (planted with maize, peanut or soybean) along a 2, 200 km transect in China using high-throughput quantitative PCR approaches. Totally, 204 ARGs were detected, with a higher diversity found in central China than that in northeast and south China. The most abundant (top 50%) and highly shared (present in >50% samples) ARGs regarded as core resistome were dominated by multidrug resistance genes such as oprJ, acrA-05 and acrA-04. Regressive analyses revealed that the relative abundance of total ARGs and core resistome both had significant relationships with mobile genetic elements (MGEs). Anthropogenic factors including the consumption of plastic films and soil properties including heavy metals showed good correlations with the diversity of ARGs. Structural equation modelling analysis further explained that anthropogenic factors were the main forces shaping the ARGs patterns. These findings highlight the importance of human activities in shaping soil antibiotic resistome in the croplands, providing potential management strategies to mitigate the dissemination of ARGs to humans via food chain.

Multiple factors drive the abundance and diversity of the diazotrophic community in typical farmland soils of China.

Biological nitrogen fixation plays an important role in nitrogen cycling by transferring atmospheric N2 to plant-available N in the soil. However, the diazotrophic activity and distribution in different types of soils remain to be further explored. In this study, 152 upland soils were sampled to examine the diazotrophic abundance, nitrogenase activity, diversity and community composition by quantitative polymerase chain reaction, acetylene reduction assay and the MiSeq sequencing of nifH genes, respectively. The results showed that diazotrophic abundance and nitrogenase activity varied among the three soil types. The diazotrophic community was mainly dominated by Bradyrhizobium, Azospirillum, Myxobacter, Desulfovibrio and Methylobacterium. The symbiotic diazotroph Bradyrhizobium was widely distributed among soils, while the distribution of free-living diazotrophs showed large variation and was greatly affected by multiple factors. Crop type and soil properties directly affected the diazotrophic ɑ-diversity, while soil properties, climatic factors and spatial distance together influenced the diazotrophic community. Network structures were completely different among all three types of soils, with most complex interactions observed in the Red soil. These findings suggest that diazotrophs have various activities and distributions in the three soil types, which played different roles in nitrogen input in agricultural soil in China, being driven by multiple environmental factors.

Protist communities are more sensitive to nitrogen fertilization than other microorganisms in diverse agricultural soils.

BACKGROUND: Agricultural food production is at the base of food and fodder, with fertilization having fundamentally and continuously increased crop yield over the last decades. The performance of crops is intimately tied to their microbiome as they together form holobionts. The importance of the microbiome for plant performance is, however, notoriously ignored in agricultural systems as fertilization disconnects the dependency of plants for often plant-beneficial microbial processes. Moreover, we lack a holistic understanding of how fertilization regimes affect the soil microbiome. Here, we examined the effect of a 2-year fertilization regime (no nitrogen fertilization control, nitrogen fertilization, and nitrogen fertilization plus straw amendment) on entire soil microbiomes (bacteria, fungi, and protist) in three common agricultural soil types cropped with maize in two seasons. RESULTS: We found that the application of nitrogen fertilizers more strongly affected protist than bacterial and fungal communities. Nitrogen fertilization indirectly reduced protist diversity through changing abiotic properties and bacterial and fungal communities which differed between soil types and sampling seasons. Nitrogen fertilizer plus straw amendment had greater effects on soil physicochemical properties and microbiome diversity than nitrogen addition alone. Moreover, nitrogen fertilization, even more together with straw, increased soil microbiome network complexity, suggesting that the application of nitrogen fertilizers tightened soil microbiomes interactions. CONCLUSIONS: Together, our results suggest that protists are the most susceptible microbiome component to the application of nitrogen fertilizers. As protist communities also exhibit the strongest seasonal dynamics, they serve as the most sensitive bioindicators of soil changes. Changes in protist communities might have long-term effects if some of the key protist hubs that govern microbiome complexities as top microbiome predators are altered. This study serves as the stepping stone to promote protists as promising agents in targeted microbiome engineering to help in reducing the dependency on exogenous unsustainably high fertilization and pesticide applications.

Thinning effect on photosynthesis depends on needle ages in a Chinese fir (Cunninghamia lanceolata) plantation.

Canopies in evergreen coniferous plantations often consist of various-aged needles. However, the effect of needle age on the photosynthetic responses to thinning remains ambiguous. Photosynthetic responses of different-aged needles to thinning were investigated in a Chinese fir (Cunninghamia lanceolata) plantation. A dual isotope approach [simultaneous measurements of stable carbon (δ13C) and oxygen (δ18O) isotopes] was employed to distinguish between biochemical and stomatal limitations to photosynthesis. Our results showed that increases in net photosynthesis rates upon thinning only occurred in the current-year and one-year-old needles, and not in the two- to four-year-old needles. The increased δ13C and declined δ18O in current year needles of trees from thinned stands indicated that both the photosynthetic capacity and stomatal conductance resulted in increasing photosynthesis. In one-year-old needles of trees from thinned stands, an increased needle δ13C and a constant needle δ18O were observed, indicating the photosynthetic capacity rather than stomatal conductance contributed to the increasing photosynthesis. The higher water-soluble nitrogen content in current-year and one-year-old needles in thinned trees also supported that the photosynthetic capacity plays an important role in the enhancement of photosynthesis. In contrast, the δ13C, δ18O and water-soluble nitrogen in the two- to four-year-old needles were not significantly different between the control and thinned trees. Thus, the thinning effect on photosynthesis depends on needle age in a Chinese fir plantation. Our results highlight that the different responses of different-aged needles to thinning have to be taken into account for understanding and modelling ecosystem responses to management, especially under the expected environmental changes in future.

[Isotope analysis of ammonium and nitrate: A review on measured methods and their application]. / é“µç›å’Œç¡é ¸ç›ç¨³å®šåŒä½ç´ ä¸°åº¦æµ‹å®šæ–¹æ³•åŠå ¶åº”ç”¨æ¡ˆä¾‹.

In the past several decades, a variety of methods have been developed for measuring the isotopic composition of ammonium (δ15N) and nitrate (δ15N and δ18O). This review summarized the advantages and disadvantages of these methods. Nowadays, the most popular method for measu-ring δ15N of ammonium is the combined hypobromite (BrO-) and hydroxylamine (NH2OH) me-thod, while for δ15N and δ18O of nitrate is the denitrifier method and the sodium azide (NaN3) me-thod. These methods convert NH4+ or NO3- into nitrous oxide (N2O) and measure its isotopic compositions, with higher analytical precision because of the lower background concentration of atmospheric N2O. Accordingly, these methods are suitable for the samples with lower N concentration, and normally require 10-60 nmol N. The development of new methods for measuring N isotopic composition has greatly stimulated the studies in nitrogen cycling worldwide.

Variations in nitrogen-15 natural abundance of plant and soil systems in four remote tropical rainforests, southern China.

The foliar stable N isotope ratio (δ(15)N) can provide integrated information on ecosystem N cycling. Here we present the δ(15)N of plant and soil in four remote typical tropical rainforests (one primary and three secondary) of southern China. We aimed to examine if (1) foliar δ(15)N in the study forests is negative, as observed in other tropical and subtropical sites in eastern Asia; (2) variation in δ(15)N among different species is smaller compared to that in many N-limited temperate and boreal ecosystems; and (3) the primary forest is more N rich than the younger secondary forests and therefore is more (15)N enriched. Our results show that foliar δ(15)N ranged from -5.1 to 1.3‰ for 39 collected plant species with different growth strategies and mycorrhizal types, and that for 35 species it was negative. Soil NO3 (-) had low δ(15)N (-11.4 to -3.2‰) and plant NO3 (-) uptake could not explain the negative foliar δ(15)N values (NH4 (+) was dominant in the soil inorganic-N fraction). We suggest that negative values might be caused by isotope fractionation during soil NH4 (+) uptake and mycorrhizal N transfer, and by direct uptake of atmospheric NH3/NH4 (+). The variation in foliar δ(15)N among species (by about 6‰) was smaller than in many N-limited ecosystems, which is typically about or over 10‰. The primary forest had a larger N capital in plants than the secondary forests. Foliar δ(15)N and the enrichment factor (foliar δ(15)N minus soil δ(15)N) were higher in the primary forest than in the secondary forests, albeit differences were small, while there was no consistent pattern in soil δ(15)N between primary and secondary forests.

Mixing effects of understory plant litter on decomposition and nutrient release of tree litter in two plantations in Northeast China.

Understory vegetation plays a crucial role in carbon and nutrient cycling in forest ecosystems; however, it is not clear how understory species affect tree litter decomposition and nutrient dynamics. In this study, we examined the impacts of understory litter on the decomposition and nutrient release of tree litter both in a pine (Pinus sylvestris var. mongolica) and a poplar (Populus × xiaozhuanica) plantation in Northeast China. Leaf litter of tree species, and senesced aboveground materials from two dominant understory species, Artemisia scoparia and Setaria viridis in the pine stand and Elymus villifer and A. sieversiana in the poplar stand, were collected. Mass loss and N and P fluxes of single-species litter and three-species mixtures in each of the two forests were quantified. Data from single-species litterbags were used to generate predicted mass loss and N and P fluxes for the mixed-species litterbags. In the mixture from the pine stand, the observed mass loss and N release did not differ from the predicted value, whereas the observed P release was greater than the predicted value. However, the presence of understory litter decelerated the mass loss and did not affect N and P releases from the pine litter. In the poplar stand, litter mixture presented a positive non-additive effect on litter mass loss and P release, but an addition effect on N release. The presence of understory species accelerated only N release of poplar litter. Moreover, the responses of mass loss and N and P releases of understory litter in the mixtures varied with species in both pine and poplar plantations. Our results suggest that the effects of understory species on tree litter decomposition vary with tree species, and also highlight the importance of understory species in litter decomposition and nutrient cycles in forest ecosystems.

Preliminary insights into δ15N and δ18O of nitrate in natural mosses: a new application of the denitrifier method.

Natural mosses have been employed as reactive and accumulative indicators of atmospheric pollutants. Using the denitrifier method, the concentration, δ(15)N and δ(18)O of moss nitrate (NO(3)(-)) were measured to elucidate the sources of NO(3)(-) trapped in natural mosses. Oven drying at 55-70 °C, not lyophilization, was recommended to dry mosses for NO(3)(-) analyses. An investigation from urban to mountain sites in western Tokyo suggested that moss [NO(3)(-)] can respond to NO(3)(-) availability in different habitats. NO(3)(-) in terricolous mosses showed isotopic ratios as close to those of soil NO(3)(-), reflecting the utilization of soil NO(3)(-). Isotopic signatures of NO(3)(-) in corticolous and epilithic mosses elucidated atmospheric NO(3)(-) sources and strength from the urban (vehicle NO(x) emission) to mountain area (wet-deposition NO(3)(-)). However, mechanisms and isotopic effects of moss NO(3)(-) utilization must be further verified to enable the application of moss NO(3)(-) isotopes for source identification.

Dynamics of soil inorganic nitrogen and their responses to nitrogen additions in three subtropical forests, south China.

Three forests with different historical land-use, forest age, and species assemblages in subtropical China were selected to evaluate current soil N status and investigate the responses of soil inorganic N dynamics to monthly ammonium nitrate additions. Results showed that the mature monsoon evergreen broadleaved forest that has been protected for more than 400 years exhibited an advanced soil N status than the pine (Pinus massoniana) and pine-broadleaf mixed forests, both originated from the 1930's clear-cut and pine plantation. Mature forests had greater extractable inorganic N pool, lower N retention capacity, higher inorganic N leaching, and higher soil C/N ratios. Mineral soil extractable NH4(+)-N and NO3(-)-N concentrations were significantly increased by experimental N additions on several sampling dates, but repeated ANOVA showed that the effect was not significant over the whole year except NH4(+)-N in the mature forest. In contrast, inorganic N (both NH4(+)-N and NO3(-)-N) in soil 20-cm below the surface was significantly elevated by the N additions. From 42% to 74% of N added was retained by the upper 20 cm soils in the pine and mixed forests, while 0%-70% was retained in the mature forest. Our results suggest that land-use history, forest age and species composition were likely to be some of the important factors that determine differing forest N retention responses to elevated N deposition in the study region.