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271.
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273.
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
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
274.
对具典型三层构造的西太平洋海山群富钴结壳样品进行了钙质超微化石地层学研究,获取了富钴结壳从内层致密层、中间疏松层到外层较致密层的生长时代:CM1D03为晚古新世-早始新世、始新世中期、中中新世-更新世;CM3D06分为晚古新世-早始新世、中始新世-晚中新世、上新世-更新世。对富钴结壳壳层的甾烷系列分子(C27、C28、C29)进行了检测并计算了相对含量,结果表明,两块富钴结壳的甾烷分布构型在结壳生长时代上具有一致性:晚古新世-早始新世,呈反"L"型分布;中始新世呈C27优势的"V"型分布;中新世-更新世呈C29优势的"V"型分布。甾烷分布构型的变化与古海洋环境演化造成的海底甾烷输入波动有关,具有一定的时代特征钙质超微化石和分子化石地层学划分方法在富钴结壳层主要生长时代及生长间断的界定上具有一致性,可以用于富钴结壳的地层划分和对比。 相似文献
275.
Katsumasa Yamada Yasushi Miyamoto Chisato Fujii Keiko Yamaguchi Masami Hamaguchi 《Marine Ecology》2014,35(3):308-318
The Manila clam, Ruditapes philippinarum, has maintained small‐sized populations in a semi‐enclosed brackish lake along the Sea of Japan, the Honjo area of Lake Nakaumi, although the environment and biota of this area have changed dramatically due to a large‐scale reclamation project. There should be underlying processes that enable the restoration of this species from small‐sized populations, such as the existence of source (i.e. reproductive) populations in other areas and depth zones of the lake. However, there has been no robust, properly designed evaluation of the distribution of the Manila clam in the subtidal sand flats. In order to elucidate the possible mechanisms that allow for the persistence of populations of the Manila clam, we examined the spatiotemporal and vertical variation in distributions of 0‐age clams in the subtidal zone of sand flats. Seasonal effects on population variations showed erratic changes among depth zones without a decreasing trend along the depth gradient. Further, many local populations became extinct even in the shallower zones due to seasonal (summer) hypoxia at deeper zones and hypoxia by the accumulation of key benthic species (Asian mussel and decaying macroalgae) in mats at shallower zones. A few surviving local populations were stable with a spatial‐fragmental (patchy) distribution, associated with fragmented accumulations of Asian mussels and macroalgae. Efforts to maintain stable populations and to restore this species in the subtidal area may depend on these small, restricted, patchy local populations. These findings suggest that high fertility and productivity of the Manila clam as well as patchy distribution of small populations may contribute to the maintenance of the population and the avoidance of extinction (by spatially diffusing the risk of extinction) in harsh environments resulting from the reclamation project. 相似文献
276.
Spatial distribution pattern of seafloor hydrothermal vents to the southeastern Kueishan Tao offshore Taiwan Island 总被引:1,自引:0,他引:1
HAN Chenhu YE Ying PAN Yiwen QIN Huawei WU Guanghai CHEN Chen-Tung Arthur 《海洋学报(英文版)》2014,33(4):37-44
Investigations of the diffusion activities both within and outside the seafloor hydrothermal vents, as well as related mineral genesis, have been one of the key focuses of ocean biogeochemistry studies. Many hydrothermal vents are distributed close to the southern Okinawa Trough on the less-than-30-m deep shallow seafloor off Kueishan Tao, northeast of Taiwan Island. Investigations of temperature, pH and Eh at four depths of hydrothermal plume were carried out near Kueishan Tao at the white(24.83°N, 121.96°E) and yellow(24.83°N, 121.96°E) vents. An 87 h of temperature time series observation-undertaken near the white vent showed that tide is the main factor affecting the background environment. Based on the observed data, 3-dimensional sliced diffusion fields were obtained and analyzed. It was concluded that the plume diffused mainly from north to south due to ebb tide. The yellow vent's plume could effect as far as the white vent surface. From the temperature diffusion field, the vortices of the plume were observed. The Eh negative abnormality was a better indicator to search for hydrothermal plumes and locate hydrothermal vents than high temperature and low pH abnormalities. 相似文献
277.
海北化工厂已停产15年之久,但Cr6+污染依旧十分严重.调查得知,海北化工厂原生产废液排放及堆存废渣经降水淋滤作用下渗,是造成该区包气带和地下水Cr6+污染的主要原因.采用地下水质量法和污染指数法评价分析该区地下水Cr6+污染范围和污染影响程度.评价结果显示:Cr6+重度污染区面积0.75 km2,厂区包气带Cr6+平均含量67.67×10-6,平均超标指数1691.75,地下水中Cr6+浓度超过Ⅴ类水标准.在分析厂区周边水文地质条件的基础上,提出清除场地废渣废料并置换被污染的包气带、采用抽水法治理被污染的地下水的综合方案. 相似文献
278.
西藏扎西康铅锌多金属矿床是我国首次发现的喷流沉积-热泉水改造型锰铁锑铅锌银矿床,已有研究表明矿床中除了铅锌矿还伴生有银、锑、铜、硫、锰、砷等多种元素。本文在化学多元素分析和光学显微镜镜下鉴定的基础上,结合能谱扫描电子显微镜和X射线衍射分析等手段对扎西康铅锌矿中伴生组分Mn的含量、矿物种类、嵌布和包裹等特性进行了研究。分析结果表明,原生矿石的主要成矿元素Pb和Zn的含量分别为6.00%和4.00%,伴生元素Mn的含量平均达到4.36%;原生矿石中的主要矿物为方铅矿、闪锌矿,其次为黄铁矿、毒砂和菱锰矿等。原生矿石中伴生元素Mn主要以独立的菱锰矿和铁菱锰矿形式存在,与闪锌矿和方铅矿密切共生,是成矿早期重要的载矿矿物,嵌布在石英、黄铁矿、闪锌矿和毒砂的粒间、边部及空隙间,其次以类质同象形式赋存于菱铁矿和菱锌矿中。进一步对扎西康铅锌矿选冶产物中的伴生元素Mn的含量和赋存状态进行研究,研究表明Mn具有较高的综合利用价值,在原生矿石、铅精矿、锌精矿和尾矿中的质量分数分别为4.36%、0.51%、0.95%和5.36%,显示Mn很少一部分进入铅精矿和锌精矿,而绝大部分进入尾矿;Mn在尾矿中仍主要以菱锰矿形式存在,存在形式与原生矿石相比未发生改变,可通过强磁选工艺从铅锌尾矿中综合回收利用Mn。 相似文献
279.
文章以柴达木盆地西部尕斯库勒盐湖沉积物为研究对象,通过对钻孔沉积物和地表沉积物中铀和钍含量的研究,探讨了盐湖沉积物中铀和钍的地球化学特征。分析表明,钻孔沉积物中铀和钍之间存在明显的正相关关系。在横向上,随地表取样点逐渐远离湖表卤水,沉积物中铀和钍的含量先增高后又急剧降低,且受补给水铀含量影响大;在纵向上,同一个晶间卤水层或者碎屑物沉积层内铀含量垂直分异明显,铀含量随深度增加而递增。就沉积物中铀和钍的赋存形式而言,2/3的铀被黏土质点吸附,1/3的铀夹杂在盐类矿物中;而90%以上的钍被黏土质点吸附,10%以下的钍夹杂在盐类矿物中。干盐滩中毛细蒸发和淋滤等化学沉积分异作用造成盐湖沉积中心的沉积物铀含量相对较高。 相似文献
280.
张家洼矽卡岩型铁矿位于华北克拉通东南部,赋存在石炭系本溪组与奥陶系马家沟组之间的假整合面处及闪长岩体与奥陶系马家沟组大理岩的接触带附近,富铁矿石资源量已达大型规模。研究发现矽卡岩矿物种类在内外接触带分布有一定区别,内带为石榴石等钙质矽卡岩矿物,而外带为阳起石、金云母等镁质矽卡岩矿物,整体构成钙镁质矽卡岩。对矽卡岩矿物系统的研究表明,透辉石及石榴石发育有环带,其氧化物含量随矿物环带的形成比例不断变化,暗示酸碱度及氧逸度随着成矿流体的演化而发生相应的变化,即由早期矽卡岩阶段的相对还原的酸性环境演化为退化蚀变阶段相对氧化的碱性环境从而导致铁质逐渐萃取多次富集、沉淀,后期随着磁铁矿的沉淀又逐渐在硫化物阶段转化为还原环境生成金属硫化物。 相似文献