Effects of Regulation of C/N Ratio Wheat Straw Application on Nitrogen,Phosphorus and Potassium Uptake in Tobacco

[Objective]The aim was to study the effects of regulation of C/N ratio wheat straw application on tobacco nitrogen,phosphorus and potassium uptake. [Method]Effects of regulation C/N ratio wheat straw application on the flue-cured tobacco yield,output value,nitrogen,phosphorus and potassium content and cumulative uptake of the upper,middle and bottom leaf were studied by using the field plot experiments at Banqiao town,Qujing city,Yunnan Province during the 2008-2009 summer growing seasons. [Result]The results showed that the application of wheat straw alone or after C/N regulation,could significantly increase tobacco production,potassium content,the potassium and nitrogen accumulation amount of leaf,and was more conducive to the potassium uptake of tobacco leaf with wheat straw application after C/N regulation. Compared with non-straw application,the yield of tobacco increased by 6.59%,3.58%,5.98%,8.80% with application of wheat straw alone,wheat straw and vetch,wheat straw and oilseed cake,wheat straw and urea nitrogen,the potassium content in tobacco leaf increased by 3.85%,7.76%,8.82%,11.21%,respectively,the total potassium cumulative amount of leaf increased by 10.71%,11.62%,15.32% ,21.01% and the total nitrogen cumulative amount increased by 9.76%,1.22%,8.14%,14.00%. However,the differences of tobacco leaf nitrogen content among the different treatments were not significant,the phosphorus uptake of tobacco leaf decreased. [Conclusion]application of high C/N ratio wheat straw in flue-cured tobacco production,which should be concerned not only to adjust C/N ratio by adding nitrogen,but also considering additional phosphorus application.

Relationship Between Leaf C/N Ratio and Insecticidal Protein Expression in Bt Cotton as Affected by High Temperature and N Rate

Expression of insecticidal protein for transgenic Bacillus thuringiensis （Bt） cotton is unstable and related to nitrogen metabolism. The objective of this study was to investigate the relationship between leaf carbon nitrogen ratio （C/N） and insecticidal efficacy of two Bt cotton cultivars. C/N ratio and Bt protein content were both measured at peak square period and peak boll period respectively under 5-7 d high temperature and different nitrogen fertilizer rates on the Yangzhou University Farm and the Ludong Cotton Farm, China. All plants were grown in field. The results showed that the C/N ratio enhanced slightly and the Bt protein content remained stable at peak square period, but significant increases for the C/N ratio and decreases markedly for the leaf Bt protein concentration were detected at the peak boll period. The similar patterns at the two growth periods were found for the leaf C/N ratio and Bt protein content by different N fertilizer treatments. When nitrogen rate was from 0 to 600 kg ha-l, the C/N ratio was reduced by 0.017 and 0.006 for Sikang 1 and Sikang 3 at peak square period, compared to the 1.350 to 1.143 reduction for Sikang 1 and Sikang 3 at peak boll period, respectively. Correspondingly, the leaf Bt protein contents were bolstered by 2.6-11.8 and 26.9-36.9% at the two different growth periods, respectively. The results suggested that enhanced C/N ratio by high temperature and nitrogen application may result in the reduction of inseetiocidal efficacy in Bt cotton, especially in peak boll period.

Biological Nutrient Removal in a Full Scale Anoxic/Anaerobic/Aerobic/ Pre-anoxic-MBR Plant for Low C/N Ratio Municipal Wastewater Treatment

A novel full scale modified A2O （anoxic/anaerobic/aerobic/pre-anoxic）-membrane bioreactor （MBR） plant combined with the step feed strategy was operated to improve the biological nutrient removal （BNR） from low C/N ratio municipal wastewater in Southern China. Transformation of organic carbon, nitrogen and phosphorus, and membrane fouling were investigated. Experimental results for over four months demonstrated good efficiencies for chemical oxygen demand （COD） and NH4^＋-N removal, with average values higher than 84.5%and 98.1%, re-spectively. A relatively higher total nitrogen （TN） removal efficiency （52.1%） was also obtained at low C/N ratio of 3.82, contributed by the configuration modification （anoxic zone before anaerobic zone） and the step feed with a distribution ratio of 1：1. Addition of sodium acetate into the anoxic zone as the external carbon source, with a theoretical amount of 31.3 mg COD per liter in influent, enhanced denitrification and the TN removal efficiency in-creased to 74.9%. Moreover, the total phosphate （TP） removal efficiency increased by 18.0%. It is suggested that the external carbon source is needed to improve the BNR performance in treating low C/N ratio municipal waste-water in the modified A^2O-MBR process.

A 16 ka climate record deduced from δ^(13)C and C/N ratio in Qinghai Lake sediments, northeastern Tibetan Plateau

On the basis of multi-proxy analysis on TOC, TN, C/N, organic δ^13C and grain size, sediment record from Qinghai Lake provides evidences of stepwise-pattemed climatic change since 16 ka BE Results show that Qinghai Lake underwent six environmental stages. From 16.2 to 14.3 ka BP and from 4.0 to 2.1 ka BP, the organic δ^13C value was controlled by the concentration of atmospheric CO2. Relative higher organic δ^13C values occurred between 14.3 to 10.4 ka BP indicative of water hardness decrease resulted from melting ice water, corresponding to two intervals of C/N peak values to the Boling and AIlerod warm periods in Europe respectively. From 10.4 ka BP, Qinghai Lake entered the Holocene and the climate was warm and a little dry. The Megathermal appeared at about 6.7 ka BP when the vegetation around the lake transformed into a forest. Between 6.3 ka BP and 4.0 ka BP, the temperature decreased and δ^13C value was controlled by the expansion of C3 plants and the retreat of C4 plants in river catchment. Since 4.0 ka BP, the climate gradually became cold and dry. From 2.1 ka BP, the cold-dry climate and human activity resulted in an abrupt increase in C/N with deceased δ^13C value; meanwhile, many coarse grains appeared in sediments.

Effect of C/N Ratio on Nitrogen Removal of A/O-MBBR Process for Treating Mariculture Wastewater

In order to explore the effect of carbon and nitrogen(C/N)ratio on the performance of anoxic/aerobic-moving bed bio-film reactor(A/O-MBBR)process for treating mariculture wastewater,a laboratory-scale A/O-MBBR was conducted.The results showed that the reduction of C/N ratio was conducive to improving the removal efficiency of chemical oxygen demand(COD)and ammonia nitrogen(NH_(4)^(+)-N),while inhibiting that of nitrite nitrogen(NO_(2)^(−)-N)and nitrate nitrogen(NO_(3)^(−)-N).The extracellular polymeric substances(EPS)in anoxic zone were significantly higher in concentration than that in aerobic zone although they both declined with decrease of C/N ratio.The result provides solid support for better controlling the pollution of mariculture wastewater.

Influence of Different C/N Ratios on Aerobic Denitrification Characteristics of the Strain

[ Objective] The research aimed to study influence of different C/N ratios on aerobic denitdfication characteristics of the strain. [ Method] 5 aerobic denitdfying bacteria were isolated from activated sludge at low temperature and low C/N ratio, and their denitdfication capabilities were verified. Influence of different C/N ratios on denitdfication capability of the strain was determined. [ Result] In the five isolated aerobic denitdf- ying bacteria, except HFX08 was G-, HFX00, HFX01, HFX12 and HFX13 were G ＋. HFX08 belonged to Pseudomonas, and other strains be- longed to Acinetobacter. As C/N ratio increased, denitdfication velocity increased, and the highest removal rate of nitrogen for the five strains could reach over 92%. [ Conclusion] The research could provide reference for design and operation of the sewage treatment process with low C/N ratio in winter in the north.

Chemical and Biological Evaluation of Maturity of Pig Manure Compost at Different C/N Ratios

Aerobic static pile composting (mechanical turning every 3 days) of pig manure was prepared at & m3 windrow heaps. Sawdust was used as the bulking agent to provide additional carbon and to increase the porosity of the substrate. Two treatments at initial C/N ratios of 30 and 15, respectively, were designed in the study. Dissolved organic carbon (DOC), soluble NH+4-N, C/N ratios in solid and aqueous phases, E4/E6 ratios, and seed germination index (GI) were determined to evaluate the maturity of the co-composts. Seed germination index, a biological parameter, was suggested as one of the most reliable maturity indicators for organic compost. The results showed that the treatment at the initial C/N ratio of 30 reached maturity after 49 days of composting; however, the treatment at the initial C/N ratio of 15 should require composting time of longer than 63 days to obtain maturation. Chemical multi-indicator evaluation was necessary, and the GI measurement was the recommended approach for maturity evaluation in the study.

Effect of C/N Ratio on DHA Production by Schizochytrium sp.JN-3 and Its Pilot-scale Fermentation

[ Objective] This study aimed to explore the effect of C/N ratio on DHA production by Schizochytrium sp. , and the results were verified by pilot-scale fermentation. [ Method] Effect of C/N ratio on DHA production by Schizochytrium sp. JN-3 was explored. The industrial fermentation potential of Schizochytrium sp. JN-3 was investigated by pilot-scale fermentation in a 200 L fermentation tank. [ Result] Results of fermentation in a 7 L fermentation tank showed that the maximum biomass and total lipid content were 34.3 and 20.1 g/L, respectively, when C/N ratio was 10 ; the maximum DHA yield was 46.9% when C/N ratio was 20. When pilot-scale fermentation was conducted in a 200 L fermentation tank, the biomass was 30. 2 g/L, total lipid content was 18.4 g/L, accounting for 63.2% of the dry weight of cells; DHA content was 7.4 g/L, accounting for 40. 2% of the total lipid content. [ Condasion ] Schizochytrlum sp. JN-3 has good industrial fermentation notential.

Characteristics of Soil Organic Carbon, Total Nitrogen, and C/N Ratio in Chinese Apple Orchards

Soil organic carbon and nitrogen are used as indexes of soil quality assessment and sustainable land use management. At the same time, soil C/N ratio is a sensitive indicator of soil quality and for assessing the carbon and nitrogen nutrition balance of soils. We studied the characteristics of soil organic carbon and total nitrogen by investigating a large number of apple orchards in major apple production areas in China. High apple orchard soil organic carbon content was observed in the provinces of Heilongjiang, Xinjiang, and Yunnan, whereas low content was found in the provinces of Shandong, Henan, Hebei, and Shaanxi, with the values ranging between 6.44 and 7.76 g·kg-1. Similar to soil organic carbon, soil total nitrogen content also exhibited obvious differences in the 12 major apple producing provinces. Shandong apple orchard soil had the highest total nitrogen content (1.26 g·kg-1), followed by Beijing (1.23 g·kg-1). No significant difference was noted between these two regions, but their total nitrogen content was significantly higher than the other nine provinces, excluding Yunnan. The soil total nitrogen content for Xinjiang, Heilongjiang, Hebei, Henan, and Gansu was between 0.87 and 1.03 g·kg-1, which was significantly lower than that in Shandong and Beijing, but significantly higher than that in Liaoning, Shanxi, and Shaanxi. Six provinces exhibited apple orchard soil C/N ratio higher than 10, including Heilongjiang (15.42), Xinjiang (13.38), Ningxia (14.45), Liaoning (12.24), Yunnan (11.03), and Gansu (10.63). The soil C/N ratio was below 10 in the remaining six provinces, in which the highest was found in Shaanxi (9.47), followed by Beijing (8.98), Henan (7.99), and Shanxi (7.62), and the lowest was found in Hebei (6.80) and Shandong (6.05). Therefore, the improvement of soil organic carbon should be given more attention to increase the steady growth of soil C/N ratio.

Effects of Soil C/N Ratio on Apple Growth and Nitrogen Utilization,Residue and Loss

Soil C /N ratio is an important influencing factor in soil nitrogen cycling. Two-year old apple trees( Borkh. cv. ‘Fuji'/Malus hupehensis) were used to understand the effect of soil C/N ratio [6. 52( CK),10,15,20,25,30,35 and 40]on apple growth and nitrogen utilization and loss by using15N trace technique. The results showed that,with the increasing of soil C/N ratio,apple shoot length and fresh weight increased at first,and then decreased; the higher apple shoot length and fresh weight appeared in C/N = 15,20 and 25 treatments,and there were no significant differences among these three treatments,but significantly higher than the other treatments. Statistical analysis revealed that there was significant difference in nitrogen utilization rate between the different treatments,the highest N utilization rate was occurred in soil C/N = 25 treatment which value was 22. 87%,and there was no significant difference between soil C/N = 25 and C/N = 20 treatments,but both the two treatments were significantly higher than the other treatments; Soil C/N = 40 had the lowest N utilization rate which value was 15. 43%,and this value was less than CK( 16. 65%). The proportion of plant absorption nitrogen from fertilizer was much higher when the value of soil C/N ratio in the range of 15- 25,but the percentage of plant absorption nitrogen from soil was much higher when the soil C/N ratio was too low( < 15) or high( < 25). Amount of residual nitrogen in soil increased gradually with the soil C/N ratio increasing,the amount of residual nitrogen in C/N = 40 treatment was 1. 32 times than that in CK. With the increasing of soil C/N ratio,fertilizer nitrogen loss decreased at first,and then increased,fertilizer nitrogen loss was the minimum in C/N = 25 treatments( 49. 87%) and the maximum were occurred in CK( 61. 54%). Therefore,regarding the apple growth and nitrogen balance situation,the value of soil C/N ratio in the range of 15- 25 would be favorable for apple growth and could increase effectively nitrogen fixed by soil,reduce nitrogen loss,and improve the nitrogen utilization ratio.

藻-菌颗粒污泥处理低C/N生活污水的研究

在光暗交替、零曝气条件下建立两组不同进水C/N(chemical oxygen demand,COD/total nitrogen,TN)(R_(1):10.0,R 2:5.6)的序批式反应器并运行了70 d,研究微藻-细菌颗粒污泥(microalgal-bacterial granular sludge,MBGS)在低C/N进水条件下的污染物去除效果、颗粒组成及稳定性的变化。研究发现,R^(1)组颗粒形态稳定,结构紧密,而R^(2)组颗粒形态出现差异化,结构略松散。R^(2)的COD去除率无显著变化,并且有更好的NH_(4)^(+)-N去除效果(94.68±7.24)%,但其PO_(4)^(3-)-P的去除效果不佳(50.69±13.64)%。通过元素分析进一步发现低C/N条件使MBGS中细菌的比例增加36%,并证明低C/N生活污水中的COD和PO_(4)^(3-)-P主要依靠MBGS的同化作用去除,NH_(4)^(+)-N主要被细菌的硝化作用转化。此外,低C/N组中蛋白质含量显著增加,并分泌更多的松散结合EPS(loosely bound EPS,LB-EPS)来提高颗粒稳定性。

IL-6、CRP、NLR和NT-proBNP对老年心力衰竭合并肺炎的诊断价值

目的探讨白细胞介素-6(IL-6)、C-反应蛋白(CRP)、中性粒细胞与淋巴细胞比值(NLR)和N末端前脑钠肽前体(NT-proBNP)对老年心力衰竭(以下简称心衰)合并肺炎的诊断价值。方法选取2022年4月至2023年4月该院收治的165例老年心衰患者作为研究对象,根据是否合并肺炎分为心衰合并肺炎组(78例)和单纯心衰组(87例),根据美国纽约心脏病协会(NYHA)心功能分级标准分为Ⅱ级组(59例)和Ⅲ级+Ⅳ级组(106例)。比较各组IL-6、CRP、NT-proBNP水平和NLR;采用Spearman相关分析IL-6、CRP、NLR与NT-proBNP水平的相关性;采用受试者工作特征(ROC)曲线评估IL-6、CRP、NLR、NT-proBNP单独及联合检测对心衰患者合并肺炎的诊断效能。结果心衰合并肺炎组IL-6、CRP、NT-proBNP水平及NLR明显高于单纯心衰组(P<0.05),Ⅲ级+Ⅳ级组IL-6、CRP、NT-proBNP水平及NLR明显高于Ⅱ级组(P<0.05)。Spearman相关性分析结果显示,NT-proBNP水平与IL-6、CRP、NLR水平呈正相关(r=0.263、0.419、0.468,P<0.001)。IL-6、CRP、NLR和NTproBNP联合诊断心衰合并肺炎的曲线下面积(AUC)为0.726(95%CI:0.650~0.803),灵敏度为67.9%,特异度为71.3%。结论心衰合并肺炎患者IL-6、CRP、NT-proBNP水平和NLR明显高于单纯心衰患者,上述4项指标联合检测对心衰合并肺炎患者有一定的诊断效能。

不同调理剂对尾菜低C/N堆肥腐殖化效果的影响

针对尾菜碳氮比(C/N)低自身无法堆肥,现有好氧堆肥工艺下尾菜堆肥需要大量调理剂,不同调理剂组分对尾菜堆肥过程的腐殖化进程影响差异不清的问题,本研究以番茄藤蔓尾菜为主要原料,选用小麦秸秆、椰糠和蘑菇渣三种不同的调理剂进行好氧堆肥,明确不同调理剂添加情况下,尾菜低碳氮比(C/N=14)好氧堆肥过程中腐殖质的产生与变化趋势。采用温度、pH、电导率(EC)和发芽指数(GI)进行堆肥腐熟度评判,通过腐殖质组分的变化,明确不同调理剂添加情况下的尾菜堆肥腐殖化效果及变化规律。结果表明,相较于尾菜无法自身堆肥完成腐殖化,添加不同调理剂均能使尾菜发生腐殖化,且不同处理腐殖化程度相似,堆肥结束腐殖质含量均在28%左右,但不同处理堆肥产物的胡敏酸含量差异较大,蘑菇渣处理(T3)含量最高达到11.9%,添加椰糠处理(T2)最少仅为4.8%;对不同处理堆肥产物红外光谱分析表明,相较于其他两个处理,添加椰糠处理的芳香族伸缩振动改变量最少,腐殖化程度较低。堆肥结果表明,小麦秸秆、椰糠和蘑菇渣三种调理剂均能使尾菜在低C/N条件下进行好氧堆肥,温度、pH、EC和GI值都能达到相关有机肥标准。添加小麦秸秆更易促进腐植酸产生,促进腐殖质的形成;添加椰糠处理,腐殖化效果较差。

低C/N比污水脱氮除磷技术应用研究进展

人类的生存依赖水资源,工业的快速进步发展对水体产生负面影响,氮、磷过度排放使得水体持续恶化,随之而来的水污染成为不可小觑的重大环境问题,干扰人类正常生命活动,毁坏生态平衡,是国民经济绿色长远发展停滞的根源。现已通过多种技术对水环境进行改善修复,其中低C/N比污水脱氮除磷是解决环境问题的重要方法和研究热点。以传统工艺和新型工艺为切入点,以应用型和改进型为分类方法,对现今低C/N比污水脱氮除磷处理工艺进行总结,旨在为低C/N比污水脱氮除磷技术的发展提供新参考和新思路。

Effects of C/N ratio on nitrate removal and floc morphology of autohydrogenotrophic bacteria in a nitrate-containing wastewater treatment process

The effects of C/N ratio of a nitrate-containing wastewater on nitrate removal performed by autohydrogenotrophic bacteria as well as on the morphological parameters of floc such as floc morphology, floc number distribution, mean particle size（MPS）, aspect ratio and transparency were examined in this study. The results showed that the nitrate reduction rate increased with increasing C/N ratio from 0.5 to 10 and that the nitrogen removal of up to 95% was found at the C/N ratios of higher than 5（between 0.5–10）. Besides, high C/N ratio values reflected a corresponding high nitrite accumulation after 12-hr operation, and a fast decreasing rate of nitrite in the rest of operational time. The final p H values increased with the C/N ratio increasing from 0.5 to 2.5, but decreased with the C/N ratio increasing from2.5 to 10. There were no significant changes in floc morphology with the MPSs ranging from35 to 40 μm. Small and medium-sized flocs were dominant in the sludge suspension, and the number of flocs increased with the increasing C/N ratios. Furthermore, the highest apparent frequency of 10% was observed at aspect ratios of 0.5 and 0.6, while the transparency of flocs changed from 0.1 to 0.7.

Enhancing anoxic denitrification of low C/N ratio wastewater with novel ZVI composite carriers

External organic carbon sources are needed to provide electron donors for the denitrification of wastewater with a low COD/NO_(3)^(-)-N(C/N)ratio,increasing the treatment cost.The economic strategy is to enhance the bioactivity and/or biodiversity of denitrifiers to efficiently utilize organic substances in wastewater.In this study,novel zero-valent iron(ZVI)composite carriers were prepared and implemented in a suspended carrier biofilm reactor to enhance the bioactivity and/or biodiversity of denitrifiers.At the influent C/N ratio of 4(COD was 179.5±5.0 mg/L and TN was 44.2±0.8 mg/L),COD and TN removal efficiencies were 85.1%and 66.4%,respectively,in the reactors filled with 3 wt%ZVI composite carriers.In contrast,COD and TN removal efficiencies were 70.4%and 55.3%,respectively,in the reactor filled with conventional high-density polyethylene(HDPE)biofilm carriers.The biofilm formation on the 3 wt%ZVI composite carriers was optimized due to its higher roughness(surface square roughness increased from 76.0 nm to 93.8 nm)and favorable hydrophilicity(water contact angle dropped to 72.5°±1.4°from 94.3°±3.2°)compared with the HDPE biofilm carriers.In addition,heterotrophic denitrifiers,Thauera and Dechloromonas,were enriched,whereas autotrophic denitrifiers,Raoultella and Thiobacillus,exhibited high relative abundance in the biofilm of ZVI composite carriers.The coexistence of heterotrophic denitrifiers and autotrophic denitrifiers on the surface of ZVI composite carriers provided mixotrophic metabolism of denitrification(including heterotrophic and iron-based autotrophic),thereby ensuring effective denitrification for wastewater with a low C/N ratio without external organic carbon source addition.

The performance of a combined nitritation–anammox reactor treating anaerobic digestion supernatant under various C/N ratios

A combined nitritation–anammox reactor was developed to treat the digestion supernatant under various C/N ratios. Due to the difficulties for heterotroph to utilize the refractory organics, the reactor presented relatively stable performance with increasing supernatant addition. Nevertheless, the adverse effects of supernatant would accumulate during the long-term operation and thus weakened the activity and shock resistance of microbes,which further led to the gradual decrease of reactor performance after 92 days＇ operation.Under this circumstance, supernatant with volatile fatty acids（VFAs） residuals was further introduced into the reactor to investigate the performance of combined nitritation–anammox process with VFA addition. With the appearance of VFAs, the nitrogen removal performance gradually restored and the reactor finally achieved stable and efficient performance with C/N ratio of 0.35. The VFA residuals within 150 mg/L in the supernatant served as the extra electron donors and stimulated the heterotrophic denitrification process, which was vital for the enhancement of reactor. The nitrogen removal rate and total nitrogen removal efficiency reached 0.49 kg N/（m^3·day） and 88.8% after 140 days＇ operation, respectively. The combined nitritation–anammox reactor was proved suitable to treat digestion supernatant.

Ti(C,N)基金属陶瓷成分对抗热震性能的影响

制备了不同碳氮比Ti(C,N)固溶体和分别加入NbC、TaC、VC、Cr_(3)C_(2)的Ti(C,N)基金属陶瓷,采用水淬冷热震方法研究了不同成分对Ti(C,N)基金属陶瓷抗热震性能的影响。结果表明:金属陶瓷在热冲击过程中,陶瓷相在热应力的作用下会发生开裂现象,在裂纹扩展路径上产生的微裂纹能促进裂纹扩展;在不同碳氮比的Ti(C_(x),N_(y))固溶体金属陶瓷中,碳氮比7/3的Ti(C_(0.7),N_(0.3))金属陶瓷的抗热震性能最好,本文研究中其热震临界温度为240℃;在添加的四种碳化物(NbC、TaC、VC和Cr_(3)C_(2))中,NbC和TaC能显著提升金属陶瓷的抗热震性,且TaC更优于NbC,而VC和Cr_(3)C_(2)的加入不利于改善金属陶瓷抗热冲击性能。

Effects of Elevated CO_2 Concentration on the Biomasses and Nitrogen Concentrations in the Organs of Sainfoin(Onobrychis viciaefolia Scop.)

In forage grasses, the nitrogen concentration is directly related to the nutritional value. The studies examined the hypothesis that global elevation of CO2 concentration probably affects the biomass, nitrogen （N） concentration, and allocation and distribution patterns in the organs of forage grasses. While sainfoin （Onobrychis viciaefolia Scop.） seedlings grew on a low nutrient soil in closed chambers for 90 days, they were exposed to two CO2 concentrations （ambient or ambient＋350 μmol mol^-1 CO2） without adding nutrients to them. After 90 days exposure to CO2, the biomasses of leaves, stems, and roots, and N concentrations and contents of different parts were measured. Compared with the ambient CO2 concentration, the elevated CO2 concentration increased the total dry matter by 25.07%, mainly due to the root and leaf having positive response to the elevated CO2 concentration. However, the elevated CO2 concentration did not change the proportions of the dry matters in different parts and the total plants compared with the ambient CO2 concentration. The elevated CO2 concentration lowered the N concentrations of the plant parts. Because the dry matter was higher, the elevated CO2 concentration had no effect on the N content in the plants compared to the ambient CO2 concentration. The elevated CO2 concentration promoted N allocations of the different parts significantly and increased N allocation of the underground part. The results have confirmed the previous suggestions that the elevated CO2 concentration stimulates plant biomass production and decreases the N concentrations of the plant parts.

Spatial Variability of Soil Carbon to Nitrogen Ratio and Its Driving Factors in Ili River Valley,Xinjiang,Northwest China

Soil carbon to nitrogen(C/N) ratio is one of the most important variables reflecting soil quality and ecological function,and an indicator for assessing carbon and nitrogen nutrition balance of soils.Its variation reflects the carbon and nitrogen cycling of soils.In order to explore the spatial variability of soil C/N ratio and its controlling factors of the Ili River valley in Xinjiang Uygur Autonomous Region,Northwest China,the traditional statistical methods,including correlation analysis,geostatistic alanalys and multiple regression analysis were used.The statistical results showed that the soil C/N ratio varied from 7.00 to 23.11,with a mean value of 10.92,and the coefficient of variation was 31.3%.Correlation analysis showed that longitude,altitude,precipitation,soil water,organic carbon,and total nitrogen were positively correlated with the soil C/N ratio(P < 0.01),whereas negative correlations were found between the soil C/N ratio and latitude,temperature,soil bulk density and soil p H.Ordinary Cokriging interpolation showed that r and ME were 0.73 and 0.57,respectively,indicating that the prediction accuracy was high.The spatial autocorrelation of the soil C/N ratio was 6.4 km,and the nugget effect of the soil C/N ratio was 10% with a patchy distribution,in which the area with high value(12.00–20.41) accounted for 22.6% of the total area.Land uses changed the soil C/N ratio with the order of cultivated land > grass land > forest land > garden.Multiple regression analysis showed that geographical and climatic factors,and soil physical and chemical properties could independently explain 26.8%and 55.4% of the spatial features of soil C/N ratio,while human activities could independently explain 5.4% of the spatial features only.The spatial distribution of soil C/N ratio in the study has important reference value for managing soil carbon and nitrogen,and for improving ecological function to similar regions.