温度对兰州市南北两山5种典型人工林土壤氮素硝化潜力的影响

【目的】旨在探究随着温度的变化,土壤氮素硝化量和硝化速率的变化机理。【方法】以兰州市南北两山5种典型人工林(新疆杨林、侧柏林、刺槐林、新疆杨-刺槐混交林、侧柏-刺槐混交林)土壤为研究对象,通过间歇性好氧淋洗法在室内培养,研究在不同温度(15、25、35℃)下,5种典型人工林土壤的氮素硝化特征。【结果】在前期培养内(0~7 d),在同一温度下(35℃),侧柏刺槐混交林的土壤氮素硝化速率最大,分别比新疆杨刺槐混交林、新疆杨林、侧柏林和刺槐林高8.8%、62.6%、64.8%、77.0%。在15~35℃温度范围内,随着温度的升高,5种林分的硝化速率和硝化量均增加;在整个培养期(84 d)内,5种林分的硝化量在35℃达到最大,在0~20 cm和20~40 cm土层,五种林分的硝化量均值表现为35℃>25℃>15℃,且侧柏刺槐混交林的土壤氮素硝化量最大,分别比新疆杨刺槐混交林、刺槐林、新疆杨林和侧柏林高2.5%、13.2%、28.7%、40.8%。【结论】在所有土层中新疆杨-刺槐混交林的土壤硝态氮含量最高,5种林分土壤硝态氮含量和硝化速率随着温度的增加而增加,随土层的加深而降低,且混交林的硝化量和硝化速率均显著高于纯林;各林分敏感性均表现为25℃/15℃>35℃/25℃。

苏打盐碱化稻田土壤氮素矿化和硝化特征及其影响因子

【目的】为探明土壤盐碱化对氮素转化的影响,研究了不同盐碱化条件下氮素的矿化和硝化特征以及这些特征与土壤盐分、养分含量的关系,为盐碱化土壤养分的科学管理提供理论依据和数据支撑。【方法】随机采集了30个不同盐碱化程度的稻田土壤(0—20 cm)样品,根据盐碱化程度将采集的土壤样品划分为轻度(含盐量0.1%~0.3%,碱化度5%~15%)、中度(含盐量0.3%~0.5%,碱化度15%~30%)和重度(含盐量0.5%~0.7%,碱化度30%~45%)盐碱土3类,每个类别中依据最小归类样品数选取盐碱化程度接近的3个土样作为3次重复,进行氮素矿化和硝化室内培养试验(25℃,24 h光照)。于培养的第0、3、6、9、15、21天取样测定土壤铵态氮、硝态氮含量及脲酶和碱性蛋白酶活性。通过相关性分析研究土壤各指标与氮素矿化、硝化过程间的相关关系,采用逐步回归分析筛选影响氮素矿化和硝化过程的主要因子。【结果】随着土壤盐碱化程度的加剧,氮素矿化和硝化作用显著下降(P<0.05)。与轻度盐碱土相比,中度和重度盐碱土的氮素最大净矿化速率分别低12.7%和29.8%,累积矿化氮量分别低15.7%和25.2%,最大净硝化速率分别低15.4%和23.1%,累积硝化氮量分别低15.4%和23.1%,最大脲酶活性分别低16.0%和34.8%,最大碱性蛋白酶活性分别低6.0%和15.6%。逐步回归分析表明,土壤电导率(EC)、pH、CO_(3)^(2-)、Na^(+)、全氮和有机质是影响土壤氮素矿化作用的主要因子,EC、pH、CO_(3)^(2-)、Na^(+)和有机质是影响土壤氮素硝化作用的主要因子。【结论】随着土壤盐碱化程度的增加,土壤氮素净矿化速率、净硝化速率、累积矿化氮量、累积硝化氮量、脲酶和碱性蛋白酶活性不断下降,土壤盐碱化显著抑制了氮素的矿化和硝化作用。

复垦土壤净氮矿化、硝化速率及氮相关酶活性对不同有机肥的响应

为研究相同氮素水平下,不同有机肥对复垦土壤氮素矿化及相关酶活性的影响,试验以煤矿复垦土壤为研究对象,采用室内好气培养法,在300 mg/kg氮水平下设置5个处理:不施肥(CK)、化肥、鸡粪、猪粪、牛粪,分析0~126 d不同处理土壤净氮矿化、硝化速率及相关酶活性的变化情况。结果表明,各施肥处理土壤铵态氮含量随着培养时间的延长呈先下降后平稳的趋势,而硝态氮含量随培养时间延长呈先上升后平稳的趋势;不施肥处理土壤的净氮硝化和矿化速率在整个培养期间变化不大,而化肥、鸡粪、猪粪处理土壤的净氮硝化和矿化速率随培养时间延长呈下降趋势,牛粪则呈相反的变化趋势。各处理土壤铵态氮含量、硝态氮含量、氮素净矿化、硝化速率从大到小排序均为:化肥>鸡粪>猪粪>牛粪>不施肥,且各处理间差异显著。与化肥相比,施用有机肥显著提高了土壤脲酶、蛋白酶、天冬酰胺酶活性,对谷氨酰胺酶活性影响不大,但化肥处理抑制了谷氨酰胺酶活性。综上所述,施用化肥和有机肥均能促进土壤中氮素的矿化,有机肥与化肥相比还可以提高土壤中与氮素转化相关酶的活性。

室内模拟氮素沉降对盐渍化土壤氮素矿化和硝化作用

【目的】研究氮素沉降对土壤氮素矿化及硝化作用。【方法】以喀什地区疏附县尔库萨克乡盐渍化土壤为试材,采用室内模拟方法研究了氮素沉降对盐渍化土壤氮素矿化和硝化作用。【结果】表层土壤(0~20 cm)的矿质氮含量最高。氮沉降后其各土层矿质氮含量均高于无氮素沉降的结果,即氮沉降增加了土壤矿质氮的含量。随着培养天数的增加,氮沉降后的土壤氮素净硝化速率逐渐增加,没有氮素沉降的土壤氮素净硝化速率依次减少。【结论】氮素的沉降加速了原有土壤氮素的硝化作用。氮沉降后其氮素的净矿化速率变化规律性不强。

四种典型烟田土壤硝化特征及其氨氧化微生物分析

为揭示不同烟田土壤的硝化特征及氮转化微生物差异,开展4种典型植烟土壤(诸城棕壤、邵武水稻土、湄潭黄壤和宣恩黄棕壤)的室内微宇宙培育试验,以探究不同烟田土壤氮素硝化过程及其氨氧化微生物(氨氧化古菌AOA和氨氧化细菌AOB)特征。结果表明,4种烟田土壤的硝态氮含量和硝化速率差异明显,其硝化速率随培养时间延长呈波动下降趋势,黄壤与黄棕壤的硝态氮含量和硝化速率相对较高;各类型土壤中N_(2)O排放速率起初波动下降,后趋于稳定,其中水稻土排放速率与累积排放量最高。在各土壤的氨氧化过程中AOA均占主导地位,黄壤与水稻土的AOA丰度和AOA/AOB比值显著高于其他土壤。土壤硝化参数与理化性状相关性分析结果显示,土壤pH、有机碳、全氮含量、无机氮含量及碳氮比是导致不同烟田土壤N_(2)O排放和氨氧化微生物多样性差异的关键因素。综上,不同植烟土壤的硝化速率和N_(2)O排放受土壤理化性质影响,其中黄壤和黄棕壤硝化速率较高,水稻土N_(2)O排放量最大,氨氧化古菌AOA普遍占优势。

Effect of Lime Nitrogen on the Transformation of Ureain Soils

Laboratory incubation experiment was conducted to study the effect of lime nitrogen(LN) on transfor-mation of iirea-N in three paddy soils. The results showed that LN had an inhibitory effect on urease activityin these soils especially in the first 5 days, and that in the first 20 days of incubation, the amount of NH-Nderived from urea was lower in the soil with LN than in the soil without LN. While after 30 days the ainountof NH-N was higher in the mature haplic paddy soil developed on Quaternary red clay(MHPS) with LNthan that in the soil without LN. The amonnt of NH_3-N volatilized was decreased in the earlier stage andincreased in the later stage of incubation in the MHPS by the addition of LN.

Transformation of Fertilizer-N in Rhizosphere Soils of Wheat

INTRODUCTION There is a close relationship between the transformation of fertilizer-N and the statusof nitrogen nutrition in rhizosphere soils.Previously,Harmsen and Jager(1962)made ananalysis of N and C contents in the rhizosphere soils of upland crops and found thatclose to the root zone there was an enrichment of these substances.Recently,Qin and Liu(1984;1989)investigated the distribution of nitrogen in the rhizosphere of crops after ap-

DYNAMIC CHANGES OF INORGANIC NITROGEN AND ASTAXANTHIN ACCUMULATION IN HAEMATOCOCCUS PLUVIALIS

This study on dynamic changes of culture color, astaxanthin and chlorophylls, inorganic N including N NO - 3, N NO - 2 and N NH + 4 in batch culture of Haematococcus pluvialis exposed to different additive nitrate concentration showed (1) ast/chl ratio was over 0.8 for brown and red algae, but was usually less than 0.5 for green and yellow algae; (2) N NO - 3, in general, was unstable and decreased, except for a small unexpected increase in nitrate enriched treatment groups; (3) measurable amounts of N NO - 2 and N NH + 4 were observed respectively with three change modes although no external nitrite and ammonia were added into the culture; (4) a non linear correlation between ast/chl ratio (or color) changes and the levels of N NO - 3 , N NO - 2 , N NH + 4 in H. pluvialis culture; (5) up and down variation of the ast/chl ratio occurred simultaneously with a perceptible color change from yellow to brown (or red) when N NO - 3, N NO - 2 and N NH + 4 fluctuated around 30, 5, 5 μmol/L respectively; (6) existence of three dynamic modes of N NO - 3, N NO - 2 and N NH + 4 changes, obviously associated with initial external nitrate; (7) the key level of total inorganic N concentration regulating the above physiological changes during indoor cultivation was about 50 μmol/L; and (8) 0.5-10 mmol/L of nitrate was theoretically conducive to cell growth in batch culture.

Characterization of the start-up period of single-step autotrophic nitrogen removal in a sequencing batch reactor

The characteristics of the start-up period of single-step autotrophic nitrogen removal process were investigated. The autotrophic nitrogen removal process used a sequencing batch reactor to treat wastewater of medium to low ammonia-nitrogen concentration, with dissolved oxygen （DO）, hydraulic retention time （HRT） and temperature controlled. The experimental conditions were temperature at （30±2） ℃, ammonia concentration of （60 to 120） mg/L, DO of （0.8 to 1.0） mg/L, pH from 7.8 to 8.5 and HRT of 24 h. The rates of nitrification and nitrogen removal turn out to be 77% and 40%, respectively, after a start up period going through three stages divided according to nitrite accumulation： sludge domestication, nitrifying bacteria selection and sludge adaptation, It is demonstrated that dissolved oxygen is critical to nitrite accumulation and elastic YJZH soft compound packing is superior to polyhedral hollow balls in helping the bacteria adhere to the membrane.

Spatial Distribution and Environmental Determinants of Denitrification Enzyme Activity in Reed-Dominated Raised Fields

Denitrification is an important process of nitrogen removal in lake ecosystems.However,the importance of denitrification across the entire soil-depth gradients including subsurface layers remains poorly understood.This study aims to determine the spatial pattern of soil denitrification enzyme activity(DEA) and its environmental determinants across the entire soil depth gradients in the raised fields in Baiyang Lake,North China.In two different zones of the raised fields(i.e.,water boundary vs.main body of the raised fields),the soil samples from 1.0 m to 1.1 m depth were collected,and the DEA and following environmental determinants were quantified:soil moisture,p H,total nitrogen(TN),ammonia nitrogen(NH4+-N),nitrate nitrogen(NO3–-N),total organic carbon(TOC),and rhizome biomass of Phragmites australis.The results showed that the soil DEA and environmental factors had a striking zonal distribution across the entire soil depth gradients.The soil DEA reached two peak values in the upper and middle soil layers,indicating that denitrification are important in both topsoil and subsurface of the raised fields.The correlation analysis showed that the DEA is negatively correlated with the soil depth(p < 0.05).However,this phenomenon did not occur in the distance to the water edge,except in the upper layers(from 0.2 m to 0.7 m) of the boundary zone of the raised fields.In the main body of the raised fields,the DEA level remained high;however,it showed no significant relationship with the distance to the water edge.The linear regression analysis showed significant positive correlation of the DEA with the soil TN,NO3–-N,NH4+-N,and TOC;whereas it showed negative correlation with soil p H.No significant correlations with soil moisture and temperature were observed.A positive correlation was also found between the DEA and rhizome biomass of P.australis.

氮素调控剂对不同类型土壤氮素转化的影响

采用室内培养试验方法,比较了硝化抑制剂双氰胺（DCD）和3,5-二甲基吡唑（DMP）对华北平原两种主要土壤类型潮褐土和潮土中氮素转化的调控效果,并进一步研究了DMP与脲酶抑制剂氢醌（HQ）的配合施用对潮土中氮素转化的影响.结果表明：在两种供试类型土壤上DMP对尿素氮的硝化抑制作用均强于DCD.与单施尿素相比,在氮素转化高峰时,DMP可使土壤中NH4＋-N含量显著提高149.5%-387.2%,NO3--N含量降低22.3%-55.3%;同一抑制剂对潮土中氮素转化的调控效应较潮褐土更为明显;与DMP单施相比,DMP和HQ配施表现出明显的对氮素转化的协同抑制效果。