艾比湖湿地土壤碱解氮的空间变异性分析

选择艾比湖湿地的博尔塔拉河、精河下游河岸带为研究区域,针对土壤中的碱解氮进行定量测定,采用描述性统计法、地统计学方法和空间分析法,讨论研究区土壤碱解氮的空间变异及分布特征。结果表明:在0~20、20~40和60~80 cm土层碱解氮含量的块金值与基台值之比分别为47.60%、49.98%和58.21%,具有中等的空间相关性。在40~60 cm和80~100 cm土层块金值与基台值之比分别为3.64%和22.69%,具有较强的空间相关性。研究区0~100 cm各层土壤碱解氮含量平均值分别为49.16、37.26、30.22、20.35和17.80 mg/kg,经统计分析15~20 mg/kg的样本频数最多,表明研究区碱解氮含量整体偏低,属于极缺乏性。土壤碱解氮垂直分异规律为:随土层深度的增加而递减;碱解氮含量水平分异规律为:博河区域精河及精河东部区域博、精河间的中部区域。     

外源氮输入对黄河口碱蓬湿地土壤碳氮含量动态的影响

2014年4—11月,选择黄河入海口北部滨岸高潮滩的碱蓬湿地为研究对象,基于野外原位氮输入模拟试验,研究了不同氮输入梯度下(N0,无氮输入;N1,低氮输入;N2,中氮输入;N3,高氮输入)湿地土壤碳氮含量动态特征及其差异。结果表明,不同氮输入处理下土壤的SOC、TN、NH_4~+—N和NO_3~-—N含量整体上均随着土层深度的增加而逐渐降低,各土层的SOC和NO_3~-—N含量在N2处理最高,而TN和NH_4~+—N含量在N3处理最高。尽管不同氮输入处理并未改变湿地土壤中TN和NH_4~+—N含量的动态变化模式,但随氮负荷增强二者含量均呈增加趋势。不同的氮输入处理明显改变了土壤中SOC和NO_3~-—N的动态变化模式,适量氮输入(N1和N2)明显提高了土壤中的NO_3~-—N含量,过量氮输入(N3)则不利于NO_3~-—N的累积;不同氮输入处理下(特别是N2和N3处理)湿地表层土壤(0—20cm)的SOC含量在7月中旬后远大于N0处理(P0.05),说明持续的氮输入可能不利于表层土壤中SOC的转化。研究发现,当未来黄河口湿地氮养分达到N1和N2水平时将有利于土壤氮矿化,而这将使得土壤氮养分的供给更为充足;但氮负荷持续增强可能使土壤表层的SOC转化受到抑制,而这将有助于提升土壤的储碳功能。     

土壤碱解氮测定中固定态铵的释放

对采自江苏省镇江市的下蜀黄土母质发育的土样进行氢氧化钠和氢氧化钾碱解氮的测定比较，土壤固定太铵的测定，以及玉米幼苗盆栽试验，得到如下结果；碱解氮不仅包括水溶性氮，交换性氮和易水解性有机氮，还庆包括部分固定态铵，作物生长过程中氮素营养包括碱解中来自固定态铵的部分，尤其在土壤碱解氮被大量耗蝎后这部分太铵的释放意义更大。     

湿地植物对土壤生态系统中氮含量变化的响应

氮是植物生长必需的生源要素之一,湿地生态系统中土壤氮转化过程直接影响着湿地植物可吸收利用的有效氮含量的多寡,对植物的生长、演替和初级生产力具有明显的制约作用;湿地植物在富氮土壤中生长能够获得较高的生产力;灰色关联分析表明湿地植物氮含量主要受土壤中铵态氮和硝态氮含量变化的制约;建坝、农耕、放牧、排水等人类干扰活动也可通过改变湿地土壤氮含量而对湿地植物的生长产生影响.     

巨桉人工林下土壤团聚体分形特征及碱解氮分布研究

了解川中丘陵区巨桉林土壤团聚体分形特征及碱解氮含量状况对于掌握该地区巨桉种植对土壤稳定性及土壤养分的影响十分必要。该研究以典型川中丘陵区3.5a生巨桉纯林、巨桉+果树、巨桉+粮食作物土壤为研究对象,以弃耕地土壤为对照,应用分形模型,分析了土壤团聚体分形特征及不同粒径团聚体对土壤碱解氮分布的影响。结果表明:土壤团聚体数量随着粒径的增大呈现出先减少再增加后减少的趋势,其中2~5mm粒径团聚体在土壤结构中占有重要地位;土壤分形维数排序为:弃耕地纯林林果林粮;土壤碱解氮含量排序为:弃耕地林粮林果纯林,巨桉林地较弃耕地土壤分形维数和碱解氮含量低,说明巨桉的栽培在有利于保持土壤水土流失的同时却造成了土壤养分流失和地力衰退;巨桉林地土壤碱解氮集中分布在0.25mm和0.25~0.5mm粒径的细砂和中砂砾中;相关分析表明,土壤碱解氮含量与0.25~0.5mm团聚体碱解氮含量呈负相关,与2~5mm团聚体碱解氮含量呈显著正相关。该研究结果科学评价了巨桉种植对土壤结构和养分的影响,为川中丘陵区土壤的水土保持和肥力维护工作提供了合理的经营模式。     

土壤碱解氮空间变异与合理采样点数量研究

掌握土壤碱解氮变异特征是合理施肥与精准农业发展的前提,而合理采样点数量的确定是高效获取土壤碱解氮空间变异特征的基础。本研究基于江苏省沛县内约38 km²的区域中148个均匀分布的土壤采样点,分析了土壤碱解氮的空间变异特征,并通过区域随机抽样理论,计算了不同置信水平和误差等级的合理采样点数量。研究表明,沛县土壤碱解氮的平均含量为109.97 mg/kg,变异系数为0.29,其在空间分布上以中部和东南部局部地区土壤碱解氮含量较高,而东北部地区含量较缺乏;在95%置信水平上,当误差为5%和10%时的合理土壤采样点的数量分别为69个和27个;而在90%置信水平上,两误差等级所需合理采样点的数量分别为56个和20个。研究结果可为该地区土壤养分调查时高效采样方案的制定提供参考。     

尕海湿地区沼泽草甸生长季土壤碳氮组分对增温施氮的响应

[目的] 为探究高寒湿地土壤碳氮组分对气候变暖和氮沉降的响应特征。[方法] 以尕海湿地沼泽草甸为研究对象,采用开顶箱增温(OTC)和外源氮素(NH₄NO₃)添加模拟未来气候变暖及氮沉降试验,分别设置对照(CK)、增温(W)、施氮(N)和增温施氮(WN)4种处理。在试验进行1.5年后对土壤碳氮组分含量进行测定。[结果] (1)开顶箱增温装置提高0—20 cm土层平均温度1.126℃,显著降低0—10 cm土层土壤含水量(SMC)、pH、全氮(TN)、微生物量氮(MBN)、铵态氮(NH₄⁺—N)、有机碳(SOC)和可溶性有机碳(DOC)含量,提高硝态氮(NO₃^-—N)含量。(2)施氮显著降低NH₄⁺—N、SOC和10—20 cm土层微生物生物量碳(MBC)及DOC含量,增加土壤TN、MBN和NO₃^-—N含量。(3)增温施氮显著增加土壤SMC、TN、NO₃^-—N和MBC含量,降低MBN、NH₄⁺—N和DOC含量。(4)相关分析显示,土壤水分与各理化因子均存在正相关性,土壤碳氮组分间均呈正相关性。[结论] 模拟增温施氮缓解尕海湿地植物生长的温度和氮的限制,促进TN的积累,对土壤微生物量碳氮影响较大,导致土壤微生物量碳氮及分布特征发生转换。     

兰州碱性土壤与农产品中硒分布及形态研究

通过对兰州市主要农业区表层土壤总硒有效硒调查和部分农产品总硒有机硒测定,研究了兰州市碱性农田土壤与农产品中硒的积累特征和分布规律。结果表明,兰州市农田表层土壤pH 8.39±0.26,总硒含量为(0.179±0.066)mg/kg(n=473),处于全国中等水平。全市土壤总硒含量区域性差别较大,市辖区明显低于三县,榆中县居全市之首。土壤有效硒与总硒含量显著正相关,有效硒占比为4.63%～15.8%,平均8.27%。农产品中玫瑰(Rosa rugosa),部分西兰花(Brassicaoleracea var.italica)和芹菜(Apium graveolens)样品硒含量高于0.015 mg/kg,为该市天然富硒农产品。农产品中有机硒占总硒比例较高,均值为73.4%。从区域整体来看,土壤硒含量较高的县区农产品硒含量相对也较高,适合富有机硒优质农产品开发。     

Effects of N fertilizer treatments on biologically active N pools in soils under plow and no tillage

Studies assessing the effects of different tillage and N fertilizer management practices on distributions and amounts of various C and N pools in soil can provide information about the influence of such management on the quality of organic matter in agricultural soils. To assess the influence of management on soil quality, we characterized the organic matter by measurements of total N, organic C, microbial biomass N and active N in the 0–20cm profiles of soil from long-term field experiments containing plots under treatments of plow or no tillage and 0, 135, or 270kgNha^–1 fertilizer. Previous work had established that on the basis of the crop growth requirement of maize, these application rates of fertilizer N provide amounts of N that are deficient, sufficient, and excessive, respectively. The studies reported provide evidence that the sufficient amount of fertilizer N stimulated formation of the biologically active pools of N (biomass N and active N) in soils under no tillage treatments, but the excessive amount of fertilizer N tended to suppress these pools. The results demonstrated that these influences of excessive N fertilization were not reflected in distributions of total N or total organic C in soil profiles but became evident with the measurements of biologically active N. This suggests that such measurements can provide information related to the influence of different management practices on soil quality. Received: 30 November 1995     

Biochar mitigates N2O emissions by promoting complete denitrification in acidic and alkaline paddy soils

Biochar is an efficacious amendment for mitigating nitrous oxide (N₂O) emissions in soils. Nevertheless, the underlying mechanisms responsible for reduced N₂O emissions by biochar in paddy soils remain inadequately elucidated. Here, using two typical paddy soils with contrasting pH values (5.40 and 7.56), the N₂ and N₂O fluxes and the associated functional genes were investigated in soil amended with varying amounts of biochar (0%, 0.5%, and 5%, weight/weight) via soil slurry incubation integrated with the N₂/Ar technique and qPCR analysis. The results showed that N₂O fluxes were significantly (p < 0.05) reduced by 0.65–3.64 times following biochar amendment, concomitant with a significant (p < 0.05) increase in N₂ fluxes (5.47–46.14%) in both acidic and alkaline paddy soils. As a result, the N₂O/(N₂O + N₂) ratios were significantly (p < 0.05) reduced by 1.53–4.65 fold in both soil types. In acidic paddy soils, the enhanced denitrification rates and the decreased N₂O/(N₂O + N₂) ratios exhibited a strong correlation with increased pH values. In alkaline paddy soil, these changes were ascribed to the enhanced nosZ Clade I gene abundance and nosZ/(nirS + nirK) ratio. Our findings reveal that biochar primarily mitigates N₂O emissions in paddy soils by promoting its reduction to N₂.     

Enzymatic hydrolysis of soil organic phosphorus by immobilized phosphatases

 In order to estimate the role of phosphatases in maintaining the potential bioavailable P pool in soils, water and 0.4 M NaOH soil extracts were incubated with immobilized acid phosphatase, alkaline phosphatase, phospholipase and nuclease, separately, and in combinations. Immobilized nuclease at an optimum pH of 7.0 hydrolyzed the most soluble unreactive P (SUP) both in water and 0.4 M NaOH extracts. The combination of immobilized alkaline phosphatase and nuclease increased the hydrolysis of SUP at pH 7.0 by up to 61% in 0.4 M NaOH extracts relative to that due to immobilized nuclease alone. The combination of immobilized acid phosphatase and nuclease, however, did not increase the hydrolysis of SUP in either extract relative to that due to immobilized nuclease alone. Immobilized alkaline phosphatase and phospholipase increased the hydrolysis of SUP at pH 7.0 by up to 62% in 0.4 M NaOH extracts relative to that due to immobilized phospholipase alone. Similarly, immobilized acid phosphatase and phospholipase increased the hydrolysis of SUP at pH 7.0 by up to 49% in 0.4 M NaOH extracts relative to that due to immobilized phospholipase alone. The similarities in the optimum pH of indigenous phosphatases in soils and the immobilized phosphatases used in this study, immobilized on positively charged supports, suggests that indigenous phosphatases could be immobilized on positively charged surfaces in soils. Received: 17 November 1998     

三江平原环型湿地土壤溶解性有机碳的时空变化特征

土壤溶解性有机碳(DOC)是指溶解于土壤水、且能通过0.45 μm微孔滤膜的有机态碳,是土壤有机碳中最活跃的组成部分[1-2].一般认为,土壤DOC的产生源自有机物的不完全降解,因此冷湿或贫营养环境、土壤有机质和C/N摩尔比高的区域有利于DOC的产生[3].自然湿地,尤其是位于中纬度地区的湿地,储存了大量的碳,是重要的DOC库和河流DOC的主要来源[4-5].     

Effect of soil characteristics on N mineralization capacity in 112 native and agricultural soils from the northwest of Spain

N mineralization capacity and its main controlling factors were studied in a large variety (n=112) of native (forest, bush) and agricultural (pasture, cultivated) soils from several climatic zones in Spain. The available inorganic N content, net N mineralization, and net N mineralization rate were determined after 6 weeks of aerobic incubation. NH _inf4 ^sup+ –N largely predominated over NO _inf3 ^sup- -N (ratio near 10:1) except in some agricultural soils. Net N mineralization predominated (83% of soils) over net N immobilization, which was more frequent in agricultural soils (25%) than in native soils (9%). In forest soils, both net N mineralization and the net N mineralization rate were significantly higher than in the other soil groups. The net N mineralization rate of pasture and cultivated soils was similar to that of bush soils, but available inorganic N was lower. The net N mineralization rate decreased in the order: soils over acid rocks>soils over sediments>soils over basic rocks or limestone; moreover, the highest net N mineralization and available inorganic N were found in soils over acid rocks. The highest N mineralization was found in soils with low C and N contents, particularly in the native soils, in which N mineralization increased as the C:N ratio increased. N mineralization was higher in soils with a low pH and base saturation than in soils with high pH and base saturation values, which sometimes favoured N immobilization. Soils with an Al gel content of >1% showed lower net N mineralization rates than soils with Al gel contents of <1%, although net N mineralization and available inorganic N did not differ between these groups. The net N mineralization rate in silty soils was significantly lower than in sandy and clayey soils, although soil texture only explained a low proportion of the differences in N mineralization between soils.     

黑垆土有机氮组分对可矿化氮的关系

Mineralizable N and organic N components in different layers (0-15, 15-30, 30-45, 45-60, 60-80 and 80-100 cm) of six soils with different fertilities sampled from Yongshou County, Shaanxi Province, China,were determined by the aerobic incubation method and the Bremner procedure, respectively. Correlation,multiple regression and path analyses were performed to study the relation of minerallzable N to organic N components. Results of correlation and regression analyses showed that the amounts of the N mineralized were parallel to, and significantly correlated with, the total acid hydrolyzahle N, but was not so with the acid-insoluble N. Of the hydrolyzable N, the amino acid N and the ammonia N had a highly consistent significant correlation with the mineralized N, and their partial regression coefficients were significant in the regression equations, showing their importance in contribution to the mineralizable N. The amino sugar N, on the other hand, had a relatively high correlation with the mineralized N, but their partial regression coefficients were not significant in the regression equations. In contrast, the hydrolyzable unknown N had no such relations.Path analysis further indicated that the amino acid N and ammonia N made great direct contributions to the mineralized N, but the contributions of the amino sugar N were very low. These strongly suggested tha tthe mineralized N in the soils tested was mainly from the hydrolyzable N, particularly the amino acid N and ammonia N which are the major sources for its production.     

Seasonal variation of phosphatase activity in woodland soils

Seasonal variation of phosphatase activity in 0–5 cm soils from 1.6 m² plots in 48 English Lake District woodlands has been studied. Six per cent or 21% of the total variation in phosphatase activity at the assay temperature of 13°C was seasonal if activity was expressed respectively as phenol liberated g^?1 soil or cm^?3 soil. No seasonal pattern of activity at 13°C was detectable within individual plots due to high within-plot spatial variation. By averaging the results of all 48 plots, a seasonal pattern was identified but this did not resemble the seasonal pattern of soil available P content. Two, possibly three, peaks of activity occurred during the year, one in summer, a second after leaf-fall in autumn and possibly a minor peak in spring. The highest activity occurred in mid-winter.When adjusted to field temperature, 19 or 37% of the total variation in phosphatase activity, expressed respectively in terms of g^?1 soil or cm^?3 soil, was seasonal. The same three peaks of activity were still apparent, but their relative heights were altered, with maximum activity occurring in summer. After adjustment to field temperature, the seasonal pattern could be detected in many of the individual plots, if activity was expressed in terms of cm^?3 soil, and reflected the seasonal pattern of soil available P.Soil phosphatase data should be expressed in terms of activity per unit soil volume and adjusted to field temperatures, if the biological significance of the seasonal variation in activity is to be appreciated.     

肉鸭粪便排放特征的季节性变化

本研究旨在探讨肉鸭粪便的特性,并对其不同季节的污染物排放特征进行评价,为肉鸭养殖场废弃物处理和资源化利用提供依据。分4个季节进行了北京Z型肉鸭饲养试验(饲养期37 d),记录采食量、产粪量,并定期测定饲料和粪便中水分和有机质含量及总氮(TN)、P、Cu、Zn含量。结果表明:肉鸭粪便中Zn含量秋季最高, TN、P、Cu含量均为冬季最高;冬季粪便中TN含量极显著高于夏、秋两季(P0.01); P、Cu含量在冬季均极显著高于其余季节(P0.01);粪便中Cu、Zn含量均为春季最低。肉鸭粪便平均含水率为84.61%,夏季最高,春季最低;平均有机质含量为83.38%,表现为冬春秋夏。春夏秋冬四季的粪便产生量分别为338.3g?d~(-1)?只~(-1)、275.9 g?d~(-1)?只~(-1)、317.6 g?d~(-1)?只~(-1)和327.0 g?d~(-1)?只~(-1),夏季最低。TN、P、Cu、Zn的排泄系数分别为2.13 g?d~(-1)?只~(-1)、2.48g?d~(-1)?只~(-1)、2.56 mg?d~(-1)?只~(-1)、21.10 mg?d~(-1)?只~(-1);春冬两季的TN日排泄量显著高于夏秋两季; P的日排泄量表现为冬季极显著高于其余3个季节;夏季Cu的日排泄量与春季差异不显著,极显著低于秋、冬两季(P0.01)。TN在秋季排泄占比最低,春季最高;而P排泄占比为秋季最高,春季最低。肉鸭在饲养期TN、P、Cu、Zn的排泄量与对应元素的摄入量具有极显著的正相关关系(P0.01)。研究表明:季节因素能对肉鸭粪便中含水率、有机质、TN、P、Cu和Zn含量产生显著影响,同时各季节各元素的排泄量与相应元素的摄入量显著相关。     

Seasonal protein dynamics in Alaskan arctic tundra soils

In the arctic tundra of Alaska, plant growth is limited by N supply, especially in tussock tundra. Because proteins are the predominant form of soil organic N, proteolysis is considered to be the rate-limiting step in both the release of amino acids and in N mineralization. To help understand the controls on N availability in tundra soils, and to determine whether proteolysis is controlled by enzyme activity or by substrate availability, we measured soil protein concentrations, and proteolysis rates with and without added protein, every 1-2 weeks through the summer of 2000 and twice in the summer of 2001. Protease activity with added protein (‘potential’) was higher than without added protein (‘actual’). However, differences between the two tended to be driven by relatively brief peaks in potential protease activity. In fact, actual and potential rates were usually similar, suggesting that much of the time proteolysis was not limited by substrate availability, but rather by enzyme activity. Our data suggest that protease activity was actually only substrate limited at the times when it was highest. Potential rates peaked at the same times that soluble proteins were also high. These increases in protease activity and soluble protein concentrations occurred when soil amino acid and NH₄⁺ concentrations were at their lowest, drawn down by the seasonal peaks in root growth. The fact that the peaks in protease activity coincided with the peak in soil amino acid and NH₄⁺ demand strongly suggests that proteolysis was stimulated by high soil amino acid demand, and resulted in increases in soluble protein concentrations caused by the solubilization of larger proteins.