Effects of Nitrogen Addition on Plant Functional Traits in Freshwater Wetland of Sanjiang Plain,Northeast China   总被引：1，自引：0，他引：1  

MAO Rong  ZHANG Xinhou  SONG Changchun 《中国地理科学(英文版)》2014,(6):674-681

To clarify the responses of plant functional traits to nitrogen（N） enrichment, we investigated the whole-plant traits（plant height and aboveground biomass）, leaf morphological（specific leaf area（SLA） and leaf dry mass content（LDMC）） and chemical traits（leaf N concentration（LNC） and leaf phosphorus（P） concentration（LPC）） of Deyeuxia angustifolia and Glyceria spiculosa following seven consecutive years of N addition at four rates（0 g N/（m^2·yr）, 6 g N/（m^2·yr）, 12 g N/（m^2·yr） and 24 g N/（m^2·yr）） in a freshwater marsh in the Sanjiang Plain, Northeast China. The results showed that, for both D. angustifolia and G. spiculosa, N addition generally increased plant height, leaf, stem and total aboveground biomass, but did not cause changes in SLA and LDMC. Moreover, increased N availability caused an increase in LNC, and did not affect LPC. Thus, N addition decreased leaf C∶N ratio, but caused an increase in leaf N∶P ratio, and did not affect leaf C∶P ratio. Our results suggest that, in the mid-term, elevated N loading does not alter leaf morphological traits, but causes substantial changes in whole-plant traits and leaf chemical traits in temperate freshwater wetlands. These may help to better understand the effects of N enrichment on plant functional traits and thus ecosystem structure and functioning in freshwater wetlands.  相似文献   

桑沟湾及附近海域表层沉积物碳氮同位素分析及有机质来源   总被引：1，自引：0，他引：1  

夏斌  崔毅  陈碧鹃  崔正国  曲克明  马菲菲 《海洋学报(英文版)》2014,33(12):48-57

Naturally existing stable carbon and nitrogen isotopes are important in the study of sedimentary organic matter sources. To identify the sources of sedimentary organic matter in Sanggou Bay and its adjacent areas, which is characterized by high-density shellfish and seaweed aquaculture, the grain size, organic carbon(OC), total nitrogen(TN), carbon and nitrogen isotopic composition(δ13C and δ15N) of organic matter in the surface sediment were determined. The results showed that, in August, sedimentary OC and TN ranged from 0.17% to 0.76% and 0.04% to 0.14%, respectively. In November, OC and TN ranged from 0.23% to 0.87% and 0.05% to 0.14%, respectively. There was a significant positive correlation between OC and TN(R=0.98, P0.0001), indicating that OC and TN were homologous. In August, the δ13C and δ15N of organic matter varied from-23.06‰ to-21.59‰ and 5.10‰ to 6.31‰, respectively. In November, δ13C and δ15N ranged from-22.87‰ to-21.34‰ and 5.13‰ to 7.31‰, respectively. This study found that the major sources of sedimentary organic matter were marine shellfish biodeposition, seaweed farming, and soil organic matter. Using a three-end-member mixed model, we estimated that the dominant source of sedimentary organic matter was shellfish biodeposition, with an average contribution rate of 65.53% in August and 43.00% in November. Thus, shellfish farming had a significant influence on the coastal carbon cycle.  相似文献   

Food choices,health and environment: Effects of cutting Europe's meat and dairy intake     

《Global Environmental Change》2014

Western diets are characterised by a high intake of meat, dairy products and eggs, causing an intake of saturated fat and red meat in quantities that exceed dietary recommendations. The associated livestock production requires large areas of land and lead to high nitrogen and greenhouse gas emission levels. Although several studies have examined the potential impact of dietary changes on greenhouse gas emissions and land use, those on health, the agricultural system and other environmental aspects (such as nitrogen emissions) have only been studied to a limited extent. By using biophysical models and methods, we examined the large-scale consequences in the European Union of replacing 25–50% of animal-derived foods with plant-based foods on a dietary energy basis, assuming corresponding changes in production. We tested the effects of these alternative diets and found that halving the consumption of meat, dairy products and eggs in the European Union would achieve a 40% reduction in nitrogen emissions, 25–40% reduction in greenhouse gas emissions and 23% per capita less use of cropland for food production. In addition, the dietary changes would also lower health risks. The European Union would become a net exporter of cereals, while the use of soymeal would be reduced by 75%. The nitrogen use efficiency (NUE) of the food system would increase from the current 18% to between 41% and 47%, depending on choices made regarding land use. As agriculture is the major source of nitrogen pollution, this is expected to result in a significant improvement in both air and water quality in the EU. The resulting 40% reduction in the intake of saturated fat would lead to a reduction in cardiovascular mortality. These diet-led changes in food production patterns would have a large economic impact on livestock farmers and associated supply-chain actors, such as the feed industry and meat-processing sector.  相似文献   

Inference of surface concentrations of nitrogen dioxide (NO2) in Colombia from tropospheric columns of the ozone measurement instrument (OMI)     

《Atmósfera》2014,27(2):193-214

For the first time, maps of surface concentration of nitrogen dioxide (NO₂) are presented for the Colombian territory. NO₂ surface concentrations for the year 2007 are inferred based on two sources of tropospheric NO₂ column data: (1) a simulation using a three-dimensional global model (GEOS-Chem) and (2) measurements made by the ozone monitoring instrument (OMI) onboard the NASA Aura satellite. Results show monthly averages between 0.1 and 6 ppbv. We compare these inferred values to corrected ground measurements of NO₂. We find correlation coefficients of up to 0.91 between the inferred data and the corrected observational data. A significant source of NO₂ is biomass burning, which can be diagnosed by data of fire radiative power (FRP) from the Monitoring of Atmospheric Composition and Climate (MACC) reanalysis. We find a close relationship between high values of inferred NO₂ surface concentrations and biomass burning for a large area which encompasses the departments of Caquetá, Meta, Guaviare, Vichada, and Putumayo.  相似文献   

应用响应曲面法优化凯氏定氮法的消解条件   总被引：1，自引：1，他引：0  

杨娜  董迈青  谢海东  邢谦 《岩矿测试》2014,33(1):40-43

经典凯氏定氮法是通过观察消解反应现象来控制温度和时间,对于数量较多的样品同时消解会耗费大量的人力及时间,因此需要采用合理的试验设计方法确定最佳消解温度和时间,以实现批量消解样品,提高分析效率。本文利用响应曲面法对凯氏定氮法中的消解条件进行了优化分析,选择料液比、消解温度和消解时间作为优化因素,研究三因素的不同水平对氮含量测定的影响。通过响应曲面分析得到最优的消解条件为:料液比(g/mL)=0.3∶5,消解温度260℃,消解时间60 min。重复实验结果表明,样品在优化的条件下能够很好地消解,重现性较好;标准物质的氮含量的实验测定值(1310×10-6)与标准值(1300×10-6)基本一致,两者的对数误差绝对值为0.003,方法的准确性高。应用响应曲面试验设计方法,对于评价凯氏定氮法中三个消解条件对氮含量的非线性影响起到了很好的优选作用,能更好地预测实验因素对分析结果的影响趋势,可以准确控制消解温度和消解时间,对于提高分析效率具有实用意义。  相似文献   

中国近海沉积物氮和有机碳标准物质的研制     

白亚之  朱爱美  崔菁菁  施美娟  高晶晶  张俊 《岩矿测试》2014,33(1):74-80

我国海洋沉积物的研究近几年发展较快,但是缺少有定值的氮、有机碳标准物质。本文针对及其匮乏的氮、有机碳国家二级标准物质进行了我国近海沉积物总氮(TN)、总碳(TC)、总有机碳(TOC)含量的分析标准参考物质的研制。研究样品采自"我国近海海洋综合调查与评价"专项提供的表层沉积物,经过冷冻干燥、研磨至74μm,使用元素分析仪和氧化热解-气相色谱法分析总氮和总碳的含量;使用元素分析仪和氧化热解-电位法分析总有机碳的含量,制备了一系列16个有定值的总氮、总碳、总有机碳含量的近海沉积物标准物质。样品在均匀性检验中,F的实测值小于临界值,相对偏差较小,样品的均匀性较好。在稳定性检验方面,两年内多次测定的分析结果无方向性变化,统计计算结果显示稳定性良好。本文研制的这16个近海沉积物标准物质在3家实验室进行了联合定值,按照ISO导则35和国家一级标准物质研制规范,给出了该系列标准物质总氮、总碳、总有机碳含量的标准值和不确定度。这批标准物质分为不同海区,不同海区的标准物质又分为不同的沉积物类型,研制的不同海区不同沉积物类型的标准物质对现有的海洋沉积物标准物质进行了有效的补充。  相似文献   

黄河三角洲内陆到潮滩土壤中碳、氮元素的梯度分布规律   总被引：1，自引：0，他引：1  

李远  章海波  陈小兵  涂晨  骆永明 《地球化学》2014,(4):338-345

黄河三角洲是我国典型的通过黄河冲积泥沙填海造陆形成的近代沉积区。区域受到黄河冲积、沉积等自然过程和农业耕种熟化等人类活动的双重影响。本研究通过在黄河三角洲地区内陆到河口海湾不同距离采集典型土壤类型剖面发生层样品,探讨土壤有机碳、总氮等生源要素的空间分布规律,为阐明我国典型海岸带地区陆源碳、氮的输送及循环特征提供基础依据。研究结果表明,黄河三角洲内陆与河口地区呈现出完全不同的土壤碳、氮分布规律。表层土壤碳、氮含量在黄河沿岸及三角洲南部均表现出由陆向海逐级递减的空间分布特征,而在黄河刁口流路和清水沟流路沿行水方向有梯度升高的趋势。内陆地区土壤碳、氮与盐分呈一定的负相关关系,表明土壤碳、氮主要受到耕作熟化过程的影响;而在河口地区两者呈显著的正相关关系（p〈0.01）,表明靠近海湾地区土壤碳、氮积累可能受到细颗粒泥沙沉积和滩涂湿地厌氧等环境影响。表层土壤碳、氮比变幅在3.6~8.6之间,说明该地区土壤有机质分解较快,不利于有机碳的积累。土壤剖面中,一些特殊发生层如红色夹黏层、黑色泥炭层对土壤碳、氮的富集具有明显的作用,其中红色夹黏层的土壤碳、氮含量接近耕层土壤。总之,黄河三角洲土壤在耕作垦殖、泥沙沉积等综合作用下形成的空间分布格局以及剖面特征发生层是影响碳、氮封存、释放和增汇等循环过程的关键驱动因素。  相似文献   

液氮冻结条件下岩石孔隙结构损伤试验研究   总被引：2，自引：0，他引：2  

蔡承政  李根生  黄中伟 《岩土力学》2014,35(4):965-971

液氮温度极低,约在-195.56^-180.44℃之间,当与岩石接触时会对岩石孔隙结构产生损伤。根据这一特点,低温液氮有望作为压裂流体对储层进行压裂改造。为了研究液氮冻结对岩石孔隙结构损伤的影响,选取两种不同砂岩岩样,分别在不同初始含水饱和度条件下进行液氮冻结处理。对冻结前、后的岩样进行孔隙度以及核磁共振测试,得到岩样在冻结前、后的孔隙度、横向弛豫时间T2分布以及T2谱面积变化情况。试验结果表明:液氮冻结会对岩石的孔隙结构产生损伤,损伤程度受到岩性、孔隙度和岩石含水饱和度等因素影响;岩石含水饱和度越大,损伤就越严重,当岩石含水饱和度达到100%时,岩石表面产生了明显裂纹;岩石在液氮冻结下损伤形式主要是微孔隙的发育和扩展,微孔隙的增加会使岩石孔隙结构的连通性增强,甚至会产生新的大尺寸孔隙,从而对孔隙结构造成严重损伤。  相似文献   

陆生植物氮同位素组成与气候环境变化研究进展   总被引：3，自引：0，他引：3  

刘贤赵  张勇  宿庆  田艳林  王庆  全斌 《地球科学进展》2014,29(2):216-226

近年来,由于植物氮同位素组成(δ15N)记载了气候环境变化的信息,因而被广泛应用于全球变化研究中,成为古气候环境再造和了解现代气候环境变化信息的有力工具。然而,人们对气候环境引起的δ15N变化及其指示的气候环境意义并不完全清楚,这就有可能限制植物δ15N在古气候环境变化等领域研究中的应用。在概述植物氮同位素分馏和植物不同氮源的氮同位素分布的基础上,分析了温度、降水、大气CO2浓度和海拔高度等气候环境因子对陆生植物δ15N的影响以及它们的关系。指出了目前研究中存在的问题及其研究前景,认为在全球变化研究中利用植物氮同位素技术不仅可以重建古气候环境(如重建大气CO2浓度变化),揭示历史时期温度、降水的变化,而且还可以在一定的时间和空间上综合反映生态系统氮循环的特征。  相似文献   

短期增温和降水减少对沙质草地土壤微生物量碳氮和酶活性的影响     

王怀海  黄文达  何远政  牛亚毅  朱远忠 《中国沙漠》2022,42(3):274-281

通过模拟气候变化,探究短期增温和降水减少对沙质草地土壤微生物量碳氮及酶活性的影响,揭示沙质草地土壤微生物量碳氮和酶活性对短期气候变化的响应规律。结果表明：（1）短期增温和降水减少对土壤微生物量碳氮和酶活性均产生显著影响。（2）在自然温度下,与自然降水相比,降水减少40%时土壤微生物量碳（MBC）和微生物氮（MBN）含量最高,增幅分别为87.9%和98.8%;降水减少60%时土壤碱性蛋白酶（S-ALPT）活性最低,降幅达32.8%。（3）在增温条件下,与自然降水相比,降水减少40%时土壤MBC和MBN含量最低,降幅分别为25.67%和48.16%,土壤脲酶（S-UE）活性最高,增幅20.42%。（4）土壤pH与3种土壤酶活性正相关,与土壤微生物量碳氮负相关。土壤微生物量碳氮与土壤纤维素酶（S-CL）活性负相关,与S-UE、S-ALPT活性正相关。  相似文献