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1.
Purpose
Input of N as NH4 + is known to stimulate nitrification and to enhance the risk of N losses through NO3 ? leaching in humid subtropical soils. However, the mechanisms responsible for this stimulation effect have not been fully addressed.Materials and methods
In this study, an acid subtropical forest soil amended with urea at rates of 0, 20, 50, 100 mg N kg?1 was pre-incubated at 25 °C and 60 % water-holding capacity (WHC) for 60 days. Gross N transformation rates were then measured using a 15N tracing methodology.Results and discussion
Gross rates of mineralization and nitrification of NH4 +-N increased (P?<?0.05), while gross rate of NO3 ? immobilization significantly decreased with increasing N input rates (P?<?0.001). A significant relationship was established between the gross nitrification rate of NH4 + and the gross mineralization rate (R 2?=?0.991, P?<?0.01), so was between net nitrification rate of NH4 + and the net mineralization rate (R 2?=?0.973, P?<?0.05).Conclusions
Stimulation effect of N input on the gross rate of nitrification of NH4 +-N in the acid soil, partially, resulted from stimulation effect of N input on organic N mineralization, which provides pH-favorable microsites for the nitrification of NH4 + in acid soils (De Boer et al., Soil Biol Biochem 20:845–850, 1988; Prosser, Advan Microb Physiol 30:125–181, 1989). The stimulated gross nitrification rate with the decreased gross NO3 ? immobilization rate under the elevated N inputs could lead to accumulation of NO3 ? and to enhance the risk of NO3 ? loss from humid forest soils.2.
Bangliang Deng Zhenzhen Li Ling Zhang Yingchao Ma Zhi Li Wenyuan Zhang Xiaomin Guo Dekui Niu Evan Siemann 《Journal of Soils and Sediments》2016,16(3):777-784
Purpose
Ecosystem restorations can impact carbon dioxide (CO2) and nitrous oxide (N2O) emissions which are important greenhouse gasses. Alpine meadows are degraded worldwide, but restorations are increasing. Because their soils represent large carbon (C) and nitrogen (N) pools, they may produce significant amounts of CO2 and N2O depending on the plant species used in restorations. In addition, warming and N deposition may impact soil CO2 and N2O emissions from restored meadows.Materials and methods
We collected soils from degraded meadows and plots restored using three different plant species at Wugong Mountain (Jiangxi, China). We measured CO2 and N2O emissions when soils were incubated at different temperatures (15, 25 or 35 °C) and levels of N addition (control vs. 4 g m?2) to understand their responses to warming and N deposition.Results and discussion
Dissolved organic C was higher in restored plots (especially with Fimbristylis dichotoma) compared to non-restored bare soils, and their soil inorganic N was lower. CO2 emission rates were increased by vegetation restorations, decreased by N deposition, and increased by warming. CO2 emission rates were similar for the three grass species at 15 and 25 °C, but they were lower with Miscanthus floridulus at 35 °C. Soils from F. dichotoma and Carex chinensis plots had higher N2O emissions than degraded or M. floridulus plots, especially at 25 °C.Conclusions
These results show that the effects of restorations on soil greenhouse gas emissions depended on plant species. In addition, these differences varied with temperature suggesting that future climate should be considered when choosing plant species in restorations to predict soil CO2 and N2O emissions and global warming potential.3.
Yaling Zhang Carl Menke Barbara Drigo Shahla Hosseini Bai Ian Anderson Zhihong Xu Hong Chen Manyun Zhang 《Journal of Soils and Sediments》2017,17(10):2410-2419
Purpose
Re-establishment of soil nitrogen (N) capital is a priority in mine rehabilitation. We aimed to evaluate the effects of biochar addition on improving mine spoil N pools and the influence of elevated CO2 concentration on mine rehabilitation.Materials and methods
We assessed the effects of pinewood biochar, produced at three temperatures (650, 750 and 850 °C, referred as B650, B750 and B850, respectively), on mine spoil total N concentrations with five different plant species, including a tree species (Eucalyptus crebra), N-fixing shrubs (Acacia floribunda and Allocasuarina littoralis) and C3 and C4 grasses (Austrodanthonia tenuior and Themeda australis) incubated at ambient (400 μL L?1) and elevated (700 μL L?1) atmospheric CO2 concentrations, as well as the effects of elevated CO2 on mine rehabilitation.Results and discussion
Soil total N significantly improved following biochar incorporation under all plant species (P < 0.05) except for T. Australis. E. crebra had the highest soil total N (0.197%, 0.198% and 0.212% for B650, B750 and B850, respectively). Different from the negligible influence of elevated CO2 on soil properties under the grasses and the N-fixing shrubs, elevated CO2 significantly increased soil water and hot water extractable organic C (WEOC and HWEOC, respectively) and decreased total C under E. crebra, indicating that the nutrient demands were not met.Conclusions
Biochar addition showed the potential in mine rehabilitation in terms of improving soil N pool, especially with E. crebra. However, it would be more difficulty to rehabilitate mine spoils in future with the rising atmospheric CO2 concentration.4.
Nitrogen transformation rates and N<Subscript>2</Subscript>O producing pathways in two pasture soils
Ting Lan Helen Suter Rui Liu Xuesong Gao Deli Chen 《Journal of Soils and Sediments》2018,18(9):2970-2979
Purpose
Better understanding of N transformations and the regulation of N2O-related N transformation processes in pasture soil contributes significantly to N fertilizer management and development of targeted mitigation strategies.Materials and methods
15N tracer technique combined with acetylene (C2H2) method was used to measure gross N transformation rates and to distinguish pathways of N2O production in two Australian pasture soils. The soils were collected from Glenormiston (GN) and Terang (TR), Victoria, Australia, and incubated at a soil moisture content of 60% water-filled pore space (WFPS) and at temperature of 20 °C.Results and discussion
Two tested pasture soils were characterized by high mineralization and immobilization turnover. The average gross N nitrification rate (ntot) was 7.28 mg N kg?1 day?1 in TR soil () and 5.79 mg N kg?1 day?1 in GN soil. Heterotrophic nitrification rates (nh), which accounting for 50.8 and 41.9% of ntot, and 23.4 and 30.1% of N2O emissions in GN and TR soils, respectively, played a role similar with autotrophic nitrification in total nitrification and N2O emission. Denitrification rates in two pasture soils were as low as 0.003–0.004 mg N kg?1 day?1 under selected conditions but contributed more than 30% of N2O emissions.Conclusions
Results demonstrated that two tested pasture soils were characterized by fast N transformation rates of mineralization, immobilization, and nitrification. Heterotrophic nitrification could be an important NO3?–N production transformation process in studied pasture soils. Except for autotrophic nitrification, roles of heterotrophic nitrification and denitrification in N2O emission in two pasture soils should be considered when developing mitigation strategies.5.
Purpose
The objective of the present study was to investigate the interactive effects of nitrogen (N) addition, temperature, and moisture on soil microbial respiration, microbial biomass, and metabolic quotient (qCO2) at different decomposition stages of different tree leaf litters.Materials and methods
A laboratory incubation experiment with and without litter addition was conducted for 80 days at two temperatures (15 and 25 °C), two wetting intensities (35 and 50 % water-filled porosity space (WFPS)) and two doses of N addition (0 and 4.5 g N m?2, as NH4NO3). The tree leaf litters included three types of broadleaf litters, a needle litter, and a mixed litter of them. Soil microbial respiration, microbial biomass, and qCO2 along with other soil properties were measured at two decomposition stages of tree leaf litters.Results and discussion
The increase in soil cumulative carbon dioxide (CO2) flux and microbial biomass during the incubation depended on types of tree leaf litters, N addition, and hydrothermal conditions. Soil microbial biomass carbon (C) and N and qCO2 were significantly greater in all litter-amended than in non-amended soils. However, the difference in the qCO2 became smaller during the late period of incubation, especially at 25 °C. The interactive effect of temperature with soil moisture and N addition was significant for affecting the cumulative litter-derived CO2-C flux at the early and late stages of litter decomposition. Furthermore, the interactive effect of soil moisture and N addition was significant for affecting the cumulative CO2 flux at the late stage of litter decomposition but not early in the experiment.Conclusions
This present study indicated that the effects of addition of N and hydrothermal conditions on soil microbial respiration, qCO2, and concentrations of labile C and N depended on types of tree leaf litters and the development of litter decomposition. The results highlight the importance of N availability and hydrothermal conditions in interactively regulating soil microbial respiration and microbial C utilization during litter decomposition under forest ecosystems.6.
Zhijie Chen Heikki Setälä Shicong Geng Shijie Han Shuqi Wang Guanhua Dai Junhui Zhang 《Journal of Soils and Sediments》2017,17(1):23-34
Purpose
Anthropogenic-induced greenhouse gas (GHG) emission rates derived from the soil are influenced by long-term nitrogen (N) deposition and N fertilization. However, our understanding of the interplay between increased N load and GHG emissions among soil aggregates is incomplete.Materials and methods
Here, we conducted an incubation experiment to explore the effects of soil aggregate size and N addition on GHG emissions. The soil aggregate samples (0–10 cm) were collected from two 6-year N addition experiment sites with different vegetation types (mixed Korean pine forest vs. broad-leaved forest) in Northeast China. Carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) production were quantified from the soil samples in the laboratory using gas chromatography with 24-h intervals during the incubation (at 20 °C for 168 h with 80 % field water capacity).Results and discussion
The results showed that the GHG emission/uptake rates were significantly higher in the micro-aggregates than in the macro-aggregates due to the higher concentration of soil bio-chemical properties (DOC, MBC, NO3 ?, NH4 +, SOC and TN) in smaller aggregates. For the N addition treatments, the emission/uptake rates of GHG decreased after N addition across aggregate sizes especially in mixed Korean pine forest where CO2 emission was decreased about 30 %. Similar patterns in GHG emission/uptake rates expressed by per soil organic matter basis were observed in response to N addition treatments, indicating that N addition might decrease the decomposability of SOM in mixed Korean pine forest. The global warming potential (GWP) which was mainly contributed by CO2 emission (>98 %) decreased in mixed Korean pine forest after N addition but no changes in broad-leaved forest.Conclusions
These findings suggest that soil aggregate size is an important factor controlling GHG emissions through mediating the content of substrate resources in temperate forest ecosystems. The inhibitory effect of N addition on the GHG emission/uptake rates depends on the forest type.7.
Lu Yu Xing Lu Yan He Philip C. Brookes Hong Liao Jianming Xu 《Journal of Soils and Sediments》2017,17(3):599-610
Purpose
Soil acidification is universal in soybean-growing fields. The aim of our research was to evaluate the effects of soil additives (N fertilizers and biochar) on crop performance and soil quality with specific emphasis on ameliorating soil acidity.Materials and methods
Four nitrogen treatments were applied as follows: no nitrogen (N0), urea (N1), potassium nitrate (N2), and ammonium sulfate (N3), each providing 30 kg N ha?1. Half plot area of the N1, N2, and N3 treatments was also treated with biochar (19.5 t ha?1) to form N-biochar treatments (N1C, N2C, N3C). Both bulk and rhizosphere soils were sampled separately for the following analyses: pH, exchangeable base cations (EBC), exchangeable acidity (EA), total inorganic N (IN), total N (TN), and microbial phospholipid fatty acids (PLFAs). Soybean biomass and nutrient contents were also determined. Correlation analysis was applied to analyze the relationships between soil chemical properties and soybean plant parameters.Results and discussion
With N-biochar additions (N1C, N2C, N3C), soil chemical properties changed as follows: pH increased by 0.6–1.2 units, EBC, IN, and TN increased by 175–419, 38.5–54.7, and 136–452 mg kg?1, respectively, and PLFAs increased by 23.6–40.9 nmol g?1 compared to the N0 in the rhizosphere. Microbial PLFAs had positive correlations with soil pH; EBC; exchangeable K, Ca, Na, and Mg; TN; IN; NH4 +; and NO3 ? (r?=?0.66–0.84, p?<?0.01). There were negative correlations between PLFAs and EA or exchangeable Al (r?=??0.64, ?0.66, p?<?0.01), which indicated that the additives increased microbial biomass by providing a suitable environment with less acid stress and more nutrients. The additives increased soil NH4 + and NO3 ? by promoting soil organic N mineralization and reducing NH4 + and NO3 ? leaching. Moreover, the soybean seed biomass and the nutrient contents in seeds increased with N-biochar additions, especially in the N3C treatment.Conclusions
N-biochar additions were effective in ameliorating soil acidity, which improved the microenvironment for more microbial survival. N-biochars influenced N transformations at the plant–soil interface by increasing organic N mineralization, reducing N leaching, and promoting N uptake by soybeans. The soil additive ammonium and biochar (N3C) were best in promoting soybean growth.8.
Peng Su Philip C. Brookes Yan He Jianjun Wu Jianming Xu 《Journal of Soils and Sediments》2016,16(6):1776-1786
Purpose
Impacts of a commercially available decay-facilitating microbial inoculum on carbon (C) and nitrogen (N) mineralization were evaluated during decomposition of rice straw in a paddy soil.Materials and methods
Two incubation experiments were conducted for 105 days with a typical low-yield high-clay soil in central China to monitor effects of straw and the inoculum on CO2 evolution, as well as dissolved organic C (DOC), NH4 +, NO3 ?, and pH under conditions of 15 °C 70 %, 25 °C 40 %, 25 °C 70 %, 25 °C 100 %, and 35 °C 70 % of water-holding capacity (WHC) with adequate N, supplied as urea or manure, respectively.Results and discussion
Treatments of 25 °C 70 % WHC, 25 °C 100 % WHC, and 35 °C 70 % WHC generally achieved significant higher CO2 evolution while treatment of 25 °C 40 % WHC had least. This was more evident with added manure compared to urea (P?<?0.05). The inoculum generally increased the decomposition of C inputs and the largest increases were in the initial 28 day in treatments 25 °C 70 % WHC, 25 °C 100 % WHC, and 35 °C 70 % WHC; only the 25 °C 40 % WHC actually immobilized C. The CO2 release rates were positively correlated with DOC, but with different slopes within treatments. Despite equivalent N application rates, manure treatments had significantly less N (including NO3 ?, NH4 +, and total dissolved N) than those with urea. Incubation of 25 °C 40 % WHC decreased soil pH the least, probably due to relative low moisture causing delayed nitrification.Conclusions
The results implied that the inoculum, especially fungi, would adjust to edaphic and N fertilization in regulating organic C mineralization, during which water potential would exhibit a great role in regulating substrate and nutrient availability.9.
Guopeng Liang Huijun Wu Albert A. Houssou Dianxiong Cai Xueping Wu Lili Gao Bisheng Wang Shengping Li 《Journal of Soils and Sediments》2018,18(3):697-707
Purpose
Straw residue has been widely applied in the North China Plain agroecosystems due to their positive roles in soil fertility improvement, sustainable production, and climate change mitigation. However, little is known about how straw application alters soil respiration by influencing soil biochemical properties in this region. This is the first study to evaluate the role of soil enzyme activity and glomalin content in the response of soil respiration to straw application at different growth stages in a wheat-maize rotation system.Materials and methods
Field experiment was conducted in a wheat-maize rotation system and it contained two treatments: straw residue removal (CK) and straw residues application (SR). Soil respiration, moisture, and temperature were measured using LI-8100 at different growth stages during wheat and maize (2013–2015) growing seasons. From 2013 to 2014, soil sample (0–20 cm) was collected at different growth stages during wheat and maize growing seasons and transported to the laboratory. Glomalin content and soil enzyme activity were analyzed by using Bradford and enzyme-labeled meter method, respectively. In addition, we determined soil chemical properties such as soil organic carbon (SOC), soil total N content (TN), ammonium N (NH4 +-N), and nitrate N (NO3 ?-N) concentrations.Results and discussion
SR significantly increased soil respiration and this promotion effect became more significant after 4-year straw application. Soil respiration exhibited significant seasonal variation and was significantly increased by soil temperature with Q 10 ranging from 1.73 to 2.14 for CK and from 1.51 to 2.28 for SR. Both soil temperature and moisture accounted for 70–72% of the seasonal variation in soil respiration. SR significantly increased easily extractable glomalin-related soil protein during 2013–2014 wheat growing season except jointing stage. In addition, positive and significant effect of SR on activities of β-glucosidase and cellobiohydrolase was observed at initial and vigorous growth stages. Straw application significantly increased TN, but did not significantly influence SOC, NH4 +-N, and NO3 ?-N concentrations.Conclusions
Our study demonstrated that straw application increased soil respiration by stimulating soil enzyme activities and improving easily extractable glomalin-related soil protein. Straw application is recommended as an agricultural management in the North China Plain because of its role in improving biochemical properties. To improve soil biochemical parameters with a relative low soil respiration rate, further information is necessary about the optimum amount of straw application.10.
Xi-En Long Ju-Pei Shen Jun-Tao Wang Li-Mei Zhang Hongjie Di Ji-Zheng He 《Journal of Soils and Sediments》2017,17(2):384-392
Purpose
Nitrification and denitrification processes dominate nitrous oxide (N2O) emission in grassland ecosystems, but their relative contribution as well as the abiotic factors are still not well understood.Materials and methods
Two grassland soils from Duolun in Inner Mongolia, China, and Canterbury in New Zealand were used to quantitatively compare N2O production and the abundance of bacterial and archaeal amoA, denitrifying nirK and nirS genes in response to N additions (0 and 100 μg NH4 +–N g?1 dry soil) and two soil moisture levels (40 and 80 % water holding capacity) using microcosms.Results and discussion
Soil moisture rather than N availability significantly increased the nitrification rate in the Duolun soil but not in the Canterbury soil. Moreover, N addition promoted denitrification enzyme activities in the Canterbury soil but not in the Duolun soil. The abundance of bacterial and archaeal amoA genes significantly increased as soil moisture increased in the Duolun soil, whereas in the Canterbury soil, only the abundance of bacterial amoA gene increased. The increase in N2O flux induced by N addition was significantly greater in the Duolun soil than in the Canterbury soil, suggesting that nitrification may have a dominant role in N2O emission for the Duolun soil, while denitrification for the Canterbury soil.Conclusions
Microbial processes controlling N2O emission differed in grassland soils, thus providing important baseline data in terms of global change.11.
pH change, carbon and nitrogen mineralization in paddy soils as affected by Chinese milk vetch addition and soil water regime 总被引：1，自引：0，他引：1
Yunfeng Wang Xingmei Liu Clayton Butterly Caixian Tang Jianming Xu 《Journal of Soils and Sediments》2013,13(4):654-663
Purpose
The aim of the research was to explore the effect of Chinese milk vetch (CM vetch) addition and different water management practices on soil pH change, C and N mineralization in acid paddy soils.Materials and methods
Psammaquent and Plinthudult paddy soils amended with Chinese milk vetch at a rate of 12 g?kg?1 soil were incubated at 25 °C under three different water treatments (45 % field capacity, CW; alternating 1-week wetting and 2-week drying cycles, drying rewetting (DRW) and waterlogging (WL). Soil pH, dissolved organic carbon, dissolved organic nitrogen (DON), CO2 escaped, microbial biomass carbon, ammonium (NH4 +) and nitrate (NO3 ?) during the incubation period were dynamically determined.Results and discussion
The addition of CM vetch increased soil microbial biomass concentrations in all treatments. The CM vetch addition also enhanced dissolved organic N concentrations in all treatments. The NO3–N concentrations were lower than NH4–N concentrations in DRW and WL. The pH increase after CM vetch addition was 0.2 units greater during WL than DRW, and greater in the low pH Plinthudult (4.59) than higher pH Paleudalfs (6.11) soil. Nitrogen mineralization was higher in the DRW than WL treatment, and frequent DRW cycles favored N mineralization in the Plinthudult soil.Conclusions
The addition of CM vetch increased soil pH, both under waterlogging and alternating wet–dry conditions. Waterlogging decreased C mineralization in both soils amended with CM vetch. Nitrogen mineralization increased in the soils subjected to DRW, which was associated with the higher DON concentrations in DRW than in WL in the acid soil. Frequent drying–wetting cycles increase N mineralization in acid paddy soils. 相似文献12.
Purpose
This study investigated how nitrogen (N) nutrition and key physiological processes varied under changed water and nitrogen competition resulting from different weed control and fertilisation treatments in a 2-year-old F1 hybrid (Pinus elliottii Engelm var. elliottii?×?P. caribaea var. hondurensis Barr. ex Golf.) plantation on a grey podzolic soil type, in Southeast Queensland.Materials and methods
The study integrated a range of measures including growth variables (diameter at ground level (DGL), diameter at breast height (DBH) and height (H)), foliar variables (including foliar N concentration, foliar δ13C and δ15N) and physiological variables (including photosynthesis (An), stomatal conductance (gs), transpiration (E), intrinsic water use efficiency (WUEi) (A/gs) and xylem pressure potential (ΨXPP)) to better understand the mechanisms influencing growth under different weed control and fertilisation treatments. Five levels of weed control were applied: standard (routine), luxury, intermediate, mechanical and nil weed control, all with routine fertilisation plus an additional treatment, routine weed control and luxury fertilisation. Relative weed cover was assessed at 0.8, 1.1 and 1.6 years after plantation establishment to monitor the effectiveness of weed control treatments. Soil investigation included soil ammonium (NH4 +-N), nitrate (NO3 ?-N), potentially mineralizable N (PMN), gravimetric soil moisture content (MC), hot water extractable organic carbon (HWETC), hot water extractable total N (HWETN), total C, total N, stable C isotope composition (δ13C), stable N isotope composition (δ15N), total P and extractable K.Results and discussion
There were significant relationships between foliar N concentrations and relative weed cover and between tree growth and foliar N concentration or foliar δ15N, but initial site preparation practices also increased soil N transformations in the planting rows reducing the observable effects of weed control on foliar δ15N. A positive relationship between foliar N concentration and foliar δ13C or photosynthesis indicated that increased N availability to trees positively influenced non-stomatal limitations to photosynthesis. However, trees with increased foliar N concentrations and photosynthesis were negatively related to xylem pressure potential in the afternoons which enhanced stomatal limitations to photosynthesis and WUEi.Conclusions
Luxury and intermediate weed control and luxury fertilisation positively influenced growth at early establishment by reducing the competition for water and N resources. This influenced fundamental key physiological processes such as the relationships between foliar N concentration, A n, E, gs and ΨXPP. Results also confirmed that time from cultivation is an important factor influencing the effectiveness of using foliar δ15N as an indicator of soil N transformations.13.
Zejiang Cai Minggang Xu Boren Wang Lu Zhang Shilin Wen Suduan Gao 《Journal of Soils and Sediments》2018,18(9):2893-2903
Purpose
Crop straws and animal manure have the potential to ameliorate acidic soils, but their effectiveness and the mechanisms involved are not fully understood. The aim of this study was to evaluate the effectiveness of two crop (maize and soybean) straws, swine manure, and their application rates on acidity changes in acidic red soils (Ferralic Cambisol) differing in initial pH.Materials and methods
Two red soils were collected after 21 years of the (1) no fertilization history (CK soil, pH 5.46) and (2) receiving annual chemical nitrogen (N) fertilization (N soil, pH 4.18). The soils were incubated for 105 days at 25 °C after amending the crop straws or manure at 0, 5, 10, 20, and 40 g kg?1 (w/w), and examined for changes in pH, exchangeable acidity, N mineralization, and speciation in 2 M KCl extract as ammonium (NH4+) and nitrate plus nitrite (NO3??+?NO2?).Results and discussion
All three organic materials significantly decreased soil acidity (dominated by aluminum) as the application rate increased. Soybean straw was as effective (sometimes more effective) as swine manure in raising pH in both soils. Soybean straw and swine manure both significantly reduced exchangeable acidity at amendment rate as low as 10 g kg?1 in the highly acidic N soil, but swine manure was more effective in reducing the total acidity especially exchangeable aluminum (e.g., in the N soil from initial 5.79 to 0.50 cmol(+) kg?1 compared to 2.82 and 4.19 cmol(+) kg?1 by soybean straw and maize straw, respectively). Maize straw was less effective than soybean straw in affecting soil pH and the acidity. The exchangeable aluminum decreased at a rate of 4.48 cmol(+) kg?1 per pH unit increase for both straws compared to 6.25 cmol(+) kg?1 per pH unit from the manure. The NO3??+?NO2? concentration in soil increased significantly for swine manure amendment, but decreased markedly for straw treatments. The high C/N ratio in the straws led to N immobilization and pH increase.Conclusions
While swine manure continues to be effective for ameliorating soil acidity, crop straw amendment has also shown a good potential to ameliorate the acidity of the red soil. Thus, after harvest, straws should preferably not be removed from the field, but mixed with the soil to decelerate acidification. The long-term effect of straw return on soil acidity management warrants further determination under field conditions.14.
Purpose
Carbon (C) flux is largely controlled by the highly bio-reactive labile C (LC) pool, while long-term C storage is determined by the recalcitrant C (RC) pool. Soil nitrogen (N) availability may considerably affect changes of these pools. The aim of this study was to investigate the effects of N treatments on soil LC and RC pools.Materials and methods
A field experiment was conducted in a city lawn soil for 600 days with three N treatments, i.e., the control (0 kg N ha?1 year?1), low-N (100 kg N ha?1 year?1), and high-N (200 kg N ha?1 year?1) treatments. As the N source, NH4NO3 solution was added to soil surface monthly. Measurements of LC, RC, and other soil biochemical properties, including pH, soil respiration rates, microbial biomass, and enzymes activities, were taken during the experiment period.Results and discussion
The low-N and high-N treatments increased 6.3 and 13% of the LC pool, respectively, which was caused by decreased microbial biomass and soil respiration rates under the N treatments. By contrary, the low-N and high-N treatments decreased 5.9 and 12% of the RC pool, respectively. The N addition treatments enhanced phenol oxidase activities. The enhanced oxidase activities decreased new RC input and the increased dissolved organic C stimulated RC pool decomposition. The LC and RC pools were highly influenced by the N treatments, whereas effect of the N treatments on soil organic C was not significant. The N addition treatments also caused soil acidification and reduced bacterial biomass proportion in the soil microbial composition.Conclusions
The N addition increased the LC pool but decreased the RC pool in the soil. These changes should greatly impact soil long-term C storage. 相似文献15.
Yaling Zhang Hong Chen Shahla Hosseini Bai Carl Menke Manyun Zhang Zhihong Xu 《Journal of Soils and Sediments》2017,17(10):2400-2409
Purpose
This study aimed to assess the effects of biochar on improving nitrogen (N) pools in mine spoil and examine the effects of elevated CO2 on soil carbon (C) storage.Materials and methods
The experiment consisted of three plant species (Austrostipa ramossissima, Dichelachne micrantha, and Lomandra longifolia) planted in the N-poor mine spoil with application of biochar produced at three temperatures (650, 750, and 850 °C) under both ambient (400 μL L?1) and elevated (700 μL L?1) CO2. We assessed mine spoil total C and N concentrations and stable C and N isotope compositions (δ13C and δ15N), as well as hot water extractable organic C (HWEOC) and total N (HWETN) concentrations.Results and discussion
Soil total N significantly increased following biochar application across all species. Elevated CO2 induced soil C loss for A. ramossissima and D. micrantha without biochar application and D. micrantha with the application of biochar produced at 750 °C. In contrast, elevated CO2 exhibited no significant effect on soil total C for A. littoralis, D. micrantha, or L. longifolia under any other biochar treatments.Conclusions
Biochar application is a promising means to improve N retention and thus, reduce environmentally harmful N fluxes in mine spoil. However, elevated CO2 exhibited no significant effects on increasing soil total C, which indicated that mine spoil has limited potential to store rising atmospheric CO2.16.
Purpose
Agricultural practises impact soil properties and N transformation rate, and have a greater effect on N2O production pathways in agricultural soils compared with natural woodland soils. However, whether agricultural land use affects N2O production pathways in acidic soils in subtropical regions remains unknown.Materials and methods
In this study, we collected natural woodland soil (WD) and three types of agricultural soils, namely upland agricultural (UA), tea plantation (TP) and bamboo plantation (BP) soils. We performed paired 15N-tracing experiment to investigate the effects of land use types on N2O production pathways in acidic soils in subtropical regions in China.Results and discussion
The results revealed that heterotrophic nitrification is the dominant pathway of N2O production in WD, accounting for 44.6 % of N2O emissions, whereas heterotrophic nitrification contributed less than 2.7 % in all three agricultural soils, due to a lower organic C content and soil C/N ratio. In contrast, denitrification dominated N2O production in agricultural soils, accounting for 54.5, 72.8 and 77.1 % in UA, TP and BP, respectively. Nitrate (NO3 ?) predominantly affected the contribution from denitrification in soils under different land use types. Autotrophic nitrification increased after the conversion of woodland to agricultural lands, peaking at 42.8 % in UA compared with only 21.5 % in WD, and was positively correlated with soil pH. Our data suggest that pH plays a great role in controlling N2O emissions through autotrophic nitrification following conversion of woodland to agricultural lands.Conclusions
Our results demonstrate the variability in N2O production pathways in soils of different land use types. Soil pH, the quantity and quality of organic C and NO3 ? content primarily determined N2O emissions. These results will likely assist modelling and mitigation of N2O emissions from different land use types in subtropical acidic soils in China and elsewhere.17.
Jun Cui Jingjing Wang Jun Xu Chonghua Xu Xiaoniu Xu 《Journal of Soils and Sediments》2017,17(8):2156-2164
Purpose
Evergreen broad-leaved forest ecosystems are common in east China, where they are both ecologically and economically important. However, nitrogen (N) addition over many years has had a detrimental effect on these ecosystems. The objective of this research was to evaluate the effect of 4 years of N addition on microbial communities in an evergreen broad-leaved forest in southern Anhui, China.Materials and methods
Allochthonous N in the form of aqueous NH4NO3 and phosphorus (P) in the form of Ca(H2PO4)2·H2O were applied at three doses with a control (CK, stream water only without fertilizer): low-N (50 kg N ha?1 year?1), high-N (100 kg N ha?1 year?1) and high-N+P (100 kg N ha?1 year?1 + 50 kg P ha?1 year?1). Quantitative PCR analysis of microbial community size and Illumina platform-based sequencing analysis of the V3-V4 16S rRNA gene region were performed to characterize soil bacterial community abundance, structure, and diversity.Results and discussion
Bacterial diversity was increased in low-N and high-N treatments and decreased in the high-N+P treatment, but α-diversity indices were not significantly affected by N additions. Proteobacteria, Acidobacteria, and Actinobacteria were the predominant phyla in all treatments, and the relative abundance of different genera varied among treatments. Only soil pH (P = 0.051) showed a weak correlation with the bacterial community in CK and low-N treatment.Conclusions
The composition of the bacterial community and the abundance of different phyla were significantly altered by N addition. The results of the present study indicate that soil bacterial communities in subtropical evergreen broad-leaved forest are, to a certain extent, resilient to changes derived from N additions.18.
Jianbo Yang Xuechao Li Li Xu Feng Hu Huixin Li Manqiang Liu 《Biology and Fertility of Soils》2013,49(1):23-30
The effect of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on N transformations and composition of ammonia-oxidizing bacteria (AOB) communities was investigated at the centimeter scale in a microcosm experiment under laboratory conditions. After 28 days, samples were collected from soil treated with urea or urea and DMPP at increasing distance from the fertilizer zone; this distance ranged from 0 to 5 cm in both horizontal and vertical directions. The results showed that DMPP application significantly increased soil pH and NH 4 + -N and mineral N (NH 4 + -N, NO 3 ? -N, and NO 2 ? -N) concentrations but decreased (NO 3 ? + NO 2 ? )-N concentration, and such effect was decreased by increasing the distance from the fertilizer zone. Fingerprint profiles of denaturing gradient gel electrophoresis showed that the number of bands decreased by increasing the distance from the fertilizer zone due to decreasing NH 4 + -N concentrations in the urea treatment. Compared to urea applied alone, DMPP application increased NH 4 + -N concentrations and decreased AOB diversity from 0 to 3 cm but promoted diversity from 3 to 5 cm distance from the fertilizer zone. A phylogenetic analysis showed that AOB communities were dominated by Nitrosospira cluster 3. Therefore, the nitrification inhibitor DMPP modified the composition of AOB communities by increasing the distance from the fertilizer zone and this probably was related to the changes in soil pH and inorganic N concentration. 相似文献
19.
Purpose
Alpine ecosystems on the Qinghai-Tibetan Plateau are sensitive to global climatic changes. However, the effects of temperature change resulting from global warming or seasonal variation on soil N availability in those ecosystems are largely unknown.Materials and methods
We therefore conducted a 15N tracing study to investigate the effects of various temperatures (5–35 °C) on soil gross N transformation rates in an alpine meadow (AM) soil on the Qinghai-Tibetan Plateau. A natural secondary coniferous forest (CF) soil from the subtropical region was chosen as a reference to compare the temperature sensitivity of soil gross N transformation rates between alpine meadow and coniferous forest.Results and discussion
Our results showed that increasing temperature increased gross N mineralization and NH4 + immobilization rates and overall enhanced N availability for plants in both soils. However, both rates in the CF soil were less sensitive to a temperature change from 5 to 15 °C compared to the AM soil. In both soils, different N retention mechanisms could have been operating with respect to changing temperatures in the different climatic regions. In the CF soil, the absence of NO3 ? production at all incubation temperatures suggests that in the subtropical soil which is characterized by high rainfall, an increase in N availability due to increasing temperature could be completely retained in soils. In contrast, the AM soil may be vulnerable to N losses with respect to temperature changes, in particular at 35 °C, in which higher nitrification rates were coupled with lower NH4 + and NO3 ? immobilization rates.Conclusions
Our results suggest that increased soil temperature arising from global warming and seasonal variations will most likely enhance soil N availability for plants and probably increase the risk of N losses in the alpine meadow on the Qinghai-Tibetan Plateau.20.
Bing Han Xuhong Ye Wen Li Xichao Zhang Yulong Zhang Xiangui Lin Hongtao Zou 《Journal of Soils and Sediments》2017,17(10):2457-2468