Habitat range of two alpine medicinal plants in a trans-Himalayan dry valley, Central Nepal     

Bharat Babu SHRESTHA  Pramod Kumar JHA 《山地科学学报》2009,6(1):66-77

Understanding of the habitat range of threatened Himalayan medicinal plants which are declining in their abundance due to high anthropogenic disturbances is essential for developing conservation strategies and agrotechnologies for cultivation. In this communication, we have discussed the habitat range of two alpine medicinal plants, Aconitum naviculare （Bruehl） Stapf and Neopicrorhiza scrophulariiflora （Pennel） Hong in a trans-Himalayan dry valley of central Nepal, Manang district. They are the most prioritized medicinal plants of the study area in terms of ethnomedicinal uses. A. naviculare occurs on warm and dry south facing slopes between 4090-4650 m asl along with sclerophyllous and thorny alpine scrubs, while N. scrophulariiflora is exclusively found on cool and moist north facing slope between 4000 and 4400 m asl where adequate water is available from snow melt to create a suitable habitat for this wetland dependent species. The soil in rooting zone of the two plants differs significantly in organic carbon （OC）, organic matter （OM）, total nitrogen （N） and carbon to nitrogen （C/N） ratio. Due to cool and moist condition of N. scrophulariiflora habitat, accumulation of soil OC is higher, but soil N content is lower probably due to slow release from litter, higher leaching loss and greater retention in perennial live biomass of the plant. The C/N ratio of soil is more suitable in A. navuculare habitat than that of N scrophulariiflora for N supply. Warm and sunny site with N rich soil can be suitable for cultivation ofA. naviculare, while moist and cool site with organic soil for N. scrophulariiflora. The populations of both the plants are fragmented and small. Due to collection by human and trampling damage by livestock, the population of A. naviculare was found absent in open areas in five of the six sampling sites and it was confined only within the bushes of alpine scrubs. For N. serophulariiflora, high probability of complete receding of small glaeiers may be a new threat in future to its habitat. The information about habitat conditions, together with the information from other areas, ean be useful to identify potential habitats and plan for cultivation or domestication of the two medieinal plants.  相似文献   

滹沱河流域本底状态地表水氮、磷非点源污染评价   总被引：2，自引：0，他引：2  

孟令尧  史密伟  闫新兴  卢虹  朱晓磊 《地理与地理信息科学》2009,25(3)

通过对滹沱河流域各支流源头区地表水中氮、磷浓度监测分析,得出本底状态下总氮浓度为0.223～5.631 mg/L,氨氮浓度范围为未检出～0.634 mg/L,可溶态氮浓度为0.190～5.532 mg/L,总磷浓度为0.024～0.683 mg/L,可溶态磷浓度为0.026～0.220 mg/L.本底状态下各水文期氮的非点源污染形态都以可溶态氮为主;磷的非点源污染形态枯水期以可溶态磷居多,丰水期以颗粒态磷为主.滹沱河流域本底状态下氮、磷非点源污染水平较高.  相似文献   

Lagged response of nutrient leaching to reduced surpluses at the field and catchment scales          下载免费PDF全文

Barbro Ulén  Göran Johansson  Katarina Kyllmar  Lovisa Stjernman Forsberg  Gunnar Torstensson 《水文研究》2015,29(13):3020-3037

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Pre‐ and post‐impoundment nitrogen in the lower Missouri River          下载免费PDF全文

Dale W. Blevins  Donald H. Wilkison  Shelley L. Niesen 《水文研究》2014,28(4):2535-2549

Large water‐sample sets collected from 1899 through 1902, 1907, and in the early 1950s allow comparisons of pre‐impoundment and post‐impoundment (1969 through 2008) nitrogen concentrations in the lower Missouri River. Although urban wastes were not large enough to detectably increase annual loads of total nitrogen at the beginning of the 20^th century, carcass waste, stock‐yard manure, and untreated human wastes measurably increased ammonia and organic‐nitrogen concentrations during low flows. Average total‐nitrogen concentrations in both periods were about 2.5 mg/l, but much of the particulate‐organic nitrogen, which was the dominant form of nitrogen around 1900, has been replaced by nitrate. This change in speciation was caused by the nearly 80% decrease in suspended‐sediment concentrations that occurred after impoundment, modern agriculture, drainage of riparian wetlands, and sewage treatment. Nevertheless, bioavailable nitrogen has not been low enough to limit primary production in the Missouri River since the beginning of the 20^th century. Nitrate concentrations have increased more rapidly from 2000 through 2008 (5 to 12% per year), thus increasing bioavailable nitrogen delivered to the Mississippi River and affecting Gulf Coast hypoxia. The increase in nitrate concentrations with distance downstream is much greater during the post‐impoundment period. If strategies to decrease total‐nitrogen loads focus on particulate N, substantial decreases will be difficult because particulate nitrogen is now only 23% of total nitrogen in the Missouri River. A strategy aimed at decreasing particulates also could further exacerbate land loss along the Gulf of Mexico, which has been sediment starved since Missouri River impoundment. In contrast, strategies or benchmarks aimed at decreasing nitrate loads could substantially decrease nitrogen loadings because nitrates now constitute over half of the Missouri's nitrogen input to the Mississippi. Ongoing restoration and creation of wetlands along the Missouri River could be part of such a nitrate‐reduction strategy. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.  相似文献   

Harmful algal blooms and eutrophication: ��strategies�� for nutrient uptake and growth outside the Redfield comfort zone     

Patricia M. GLIBERT  JoAnn M. BURKHOLDER 《中国海洋湖沼学报》2011,29(4):724-738

While many harmful algal blooms have been associated with increasing eutrophication, not all species respond similarly and the increasing challenge, especially for resource managers, is to determine which blooms are related to eutrophication and to understand why particular species proliferate under specific nutrient conditions. The overall goal of this brief review is to describe why nutrient loads are not changing in stoichiometric proportion to the "Redfield ratio", and why this has important consequences for algal growth. Many types of harmful algae appear to be able to thrive, and/or increase their production of toxins, when nutrient loads are not in proportion classically identified as Redfield ratios. Here we also describe some of the physiological mechanisms of different species to take up nutrients and to thrive under conditions of nutrient imbalance.  相似文献   

Application of stable isotope techniques in studies of carbon and nitrogen biogeochemical cycles of ecosystem   总被引：1，自引：1，他引：0  

Zhigao Sun  Xiaojie Mou  Xinhua Li  Lingling Wang  Hongli Song  Huanhuan Jiang 《中国地理科学(英文版)》2011,21(2):129-148

Stable isotope techniques have been proved useful as tools for studying the carbon (C) and nitrogen (N) biogeochemical cycles of ecosystem. This paper firstly introduced the basic principles and the distribution characteristics of stable isotope, then reviewed the recent advances and applications of stable isotope in the C and N biogeochemical cycles of ecosystem. By applying the 13 C natural abundance technique, ecologists are able to understand the photosynthetic path and CO 2 fixation of plants, the CO 2 exchange and C balance status of ecosystem, the composition, distribution and turnover of soil organic C and the sources of organic matter in food webs, while by using the 13 C labeled technique, the effects of elevated CO 2 on the C processes of ecosystem and the sources and fate of organic matter in ecosystem can be revealed in detail. Differently, by applying the 15 N natural abundance technique, ecologists are able to analyze the biological N 2 -fixation, the N sources of ecosystem, the N transformation processes of ecosystem and the N trophic status in food webs, while by using the 15 N labeled technique, the sources, transformation and fate of N in ecosystem and the effects of N input on the ecosystem can be investigated in depth. The applications of both C and N isotope natural abundance and labeled techniques, combined with the elemental, other isotope ( 34 S) and molecular biomarker information, will be more propitious to the investigation of C and N cycle mechanisms. Finally, this paper concluded the problems existed in current researches, and put forward the perspective of stable isotope techniques in the studies on C and N biogeochemical cycles of ecosystem in the future.  相似文献   

Long-term numerical evolution of the nitrogen bulk content in the Mediterranean Sea     

G. Crispi  M. Pacciaroni 《Estuarine, Coastal and Shelf Science》2009

The behavior of the Mediterranean ecosystem in response to realistic riverine inputs and dissolved matter exchange is investigated. The strategy is to evaluate the stability of the ecosystem subjected to various atmospheric inputs.  相似文献   

南黄海表层沉积物中氮的区域地球化学特征   总被引：5，自引：0，他引：5  

吕晓霞  宋金明 《海洋科学进展》2003,21(2):174-180

通过分级浸取分离的方法获得了南黄海表层沉积物不同形态的氮，首次探讨其分布的区域性特征：南黄海表层沉积物中各形态氮在不同测线上均呈现出波状分布。B测线的基本上呈现出中部海域高，两边海域低，而西部海域又略高于东部海域的趋势，D和E测线的基本上呈现出西高、东低的趋势，C测线的则呈现出西低、东高的趋势，F测线的变化趋势比较平缓，从整体上看，SOEF—N和TN的分布呈现出西部海区比东部海区低的趋势。受各测线上沉积物种类差异的影响，自北向南各形态氮的变化幅度逐渐减小，其中SOEF-N在各测线上的变化幅度最大，且自北向南降幅最大。受水动力及沉积物粒度的影响，不同形态氮在黄海槽内各站位沉积物中的含量较高。沉积物中各形态氮在不同测线上的分布还表明，陆源输入对南黄海沉积物中氮测线分布有较小的影响，海洋自生氮对南黄海表层沉积物中氮的形态、含量与分布具有重要影响。  相似文献   

强水动力湖泊夏季分层期氮的生物地球化学循环初步研究:以贵州红枫湖南湖为例   总被引：10，自引：1，他引：9  

肖化云  刘丛强  李思亮  王仕禄 《地球化学》2002,31(6):571-576

湖泊在夏季由于藻类生长而消耗大量硝酸盐,水体硝酸盐含量一般要低于春季。而红枫湖南湖水体硝酸盐含量却高于春季(比平均含量高0.83mg/L),说明尚有其他重要的硝酸盐来源。据估算,南湖水体硝酸盐含量升高0.83mg/L约需要1.66×105kg硝酸盐,另外有约10.1×105kg硝酸盐随下泻水输出南湖,再加上夏季藻类生长(生产的chla量约为640kg)所消耗的硝酸盐3.52×105kg,共消耗硝酸盐15.28×105kg。扣除河流输入的4.42×105kg硝酸盐,南湖尚存在约10.86×105kg硝酸盐的亏空。利用氮稳定同位素示踪技术,结合硝酸盐及叶绿素a(chla)含量、溶解氧(DO)等的变化,认为这部分硝酸盐来自湖泊中下部(斜温层)有机质的大量矿化(硝化),是水动力驱动高DO的上部水体下沉从而引起下部有机质(硝化)的结果。南湖这种强水动力湖泊整个夏季分层期氮的生物地球化学循环是斜温层有机质矿化(硝化)释放硝酸盐和变温层藻类生长同化硝酸盐为有机质同时发生的特殊类型。  相似文献   

再力花/菖蒲生物湿地床去除河水中氮磷的试验     

王骥  张兰英  卢少勇  甘树  金相灿 《吉林大学学报(地球科学版)》2012,(Z1):408-414

采用再力花和菖蒲构建湿地床,以考察其对污染河水的净化效果。6个月的连续试验表明:在水力负荷为0.24 m3/(m2.d)、植物种植密度大于158株/m2的条件下,2种植物存活率均大于93%,说明植物能适应低污染负荷、高种植密度的无土培养环境;再力花和菖蒲湿地床月均去除率分别为:总氮(TN),48.22%～78.53%和43.23%～72.42%;总磷(TP),77.62%～85.67%和58.07%～80.77%。再力花湿地床对TN、TP的净化效果好于菖蒲湿地床;2种植物吸收N、P含量分别占去除总量的比例:N为44.14%、37.75%,P为73.43%、62.05%。湿地床技术可有效去除来水中的TN、TP,通过植物吸收作用累积N、P含量较高,不同种类的植物构建湿地床对污染河水中N、P去除效果存在显著差异,且硝化反硝化和植物吸收是去除N的主要途径,而植物吸收是去除P的有效手段。  相似文献