Sediment burial stimulates the growth and propagule production of Spartina alterniflora Loisel.     

Zifa Deng  Shuqing An  Congjiao Zhao  Lin Chen  Changfang Zhou  Yingbiao Zhi  Hongli Li 《Estuarine, Coastal and Shelf Science》2008,76(4):818-826

Spartina alterniflora Loisel., an extensively invasive species on the Chinese coast, is a focus of increasing management concern due to its high expansion rate in estuaries and tidal zone, and the significant damage it causes to native ecosystems. In order to understand the processes and mechanisms of invasion of S. alterniflora in China, the impact of three sediment types (sand, sand–loam mixture and loam) and five buried patterns (unburied, 50% burial of initial plant height, 75% burial of initial plant height, complete burial and repeated burial) on the growth of seedlings or ramets was investigated. Results showed that each of the three factors (sediment types, burial pattern and plant materials) and interactions between/among them, significantly affected height and clonal growth, and biomass accumulation and allocation. Plant height, total biomass and number of new vegetative propagules significantly increased with progressive burial treatments. However, the complete burial treatment resulted in the death of all plant materials, and the maximum values of three parameters were found in the 50% burial or repeated burial treatments. Plant responses were determined by the instantaneous thickness of sediment of each time burial rather than by the total quantity of repeated burial. The growth of S. alterniflora was not shown to be dependent on specific types of sediment in sedimentation environment. In contrast to the unburied control, the proportion of primary tillers produced directly from initial individuals and the ratio between the aboveground and belowground biomass were greater under burial treatments. Seedlings produced more new vegetative propagules than vegetative offspring in all experimental treatments, and the former were apt to produce ramets from rhizomes rather than primary tillers. It is concluded that under various sedimentation environments, the clonal spread efficiency of seedlings was higher than that of vegetative offspring, and there is a positive feedback relationship between sedimentation and the growth of S. alterniflora. Thus, moderate sedimentation may stimulate the invasion of exotic species, S. alterniflora in coastal China.  相似文献   

Influence of combined changes in salinity and copper modulation on growth and copper uptake in the tropical green macroalga Ulva reticulata     

Florence Mamboya  Thomas J. Lyimo  Tommy Landberg  Mats Bjrk 《Estuarine, Coastal and Shelf Science》2009,84(3):326-330

The influence of salinity on growth and Cu uptake in the green macroalga Ulva reticulata collected from the intertidal area in the Western Indian Ocean was studied under controlled laboratory conditions. Exposure concentrations ranged from 5 to 500 μg Cu l⁻¹ at five salinities (ranging 20–40). The accumulation of Cu increased with decreasing salinity, so that the uptake at 500 μg Cu l⁻¹ was approximately 2.7, 2.4 and 2.0 times higher at salinities of 20, 25, and 30 respectively, than uptake at salinity of 35, and with uptake being lowest at salinity of 40. Ulva maintained a positive growth rate over the whole salinity range (20–40), with highest rates at salinity of 35. When exposing to Cu at low salinities (20 and 25), the growth rate of Ulva was strongly inhibited suggesting an increase in toxicity of Cu with decreasing salinity. EC50 and NOEC increased with increase in salinity, implying a reduced Cu toxicity at high salinities. It was concluded that salinity needs to be considered when using macroalgae, such as U. reticulata, as a bioindicator of heavy metals in areas with heavy rainfall, underground fresh water intrusion or in estuaries, as they might accumulate more metals and be more negatively affected.  相似文献   

基于GIS的城市空间生长量算研究     

于卓  吴志华  孙玥 《测绘信息与工程》2009,34(6):33-35

分析了城市空间生长影响因素的空间特征差异及对空间操作的影响,探讨了这些影响因素作用强度的主要空间量算途径,给出了GIS功能支持下的城市空间生长量算思路。  相似文献   

Anchor ice formation in streams: a field study     

Morten Stickler  Knut T. Alfredsen 《水文研究》2009,23(16):2307-2315

In northern steep streams anchor ice is commonly observed during winter, and plays a key role when considering in‐stream conditions. The understanding, however, of the nature of anchor ice formation is less understood, in particular, under natural conditions. In the following, observations of anchor ice formation in three stream environments with different physical characteristics are presented. Results demonstrate that anchor ice not only form in riffle areas, but also in shallow and slow running stream sections. No linkage between spatial distribution of anchor ice and calculated dimensionless numbers (Froude and Reynolds number) was found. Furthermore, analyses on growth and density showed that anchor ice may be distinguished by two main types. (1) Type I: Lower density forming on top of substrata. (2) Type II: Higher density forming between the substrata filling interstitial spaces. Distribution of anchor ice Types I and II suggests a relation between intensity of turbulence expressed by the Reynolds number, growth pattern and density. As anchor ice has both physical and biological implications on in‐stream environments, findings from the present study may be of particular interest to cold region freshwater stream management. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Effects of algal concentration and initial density on the population growth of Diaphanosoma celebensis Stingelin （Crustacea, Cladocera）   总被引：1，自引：0，他引：1  

王岩  谢宁峡  王伟良 《中国海洋湖沼学报》2009,27(3):480-486

The effects of algal concentration and initial density on the population growth of the estuarine cladocera,Diaphanosoma celebensis Stingelin,were evaluated in an indoor experiment.A 2 × 4 layout that included two algal concentrations(Chlorella pyrenoidosa,1 × 106 and 3 × 106 cell/mL) and four inoculation densities(100,200,300 and 400 ind./L) were established.Diaphanosoma celebensis were reared in 150 mL flasks containing 50 mL of algal medium at 22°C,under salinity of 10 and a photoperiod of 12 h L:12 h D.T...  相似文献   

Size-Dependent Growth Rate of Nitzschia closterium at Different Concentrations of Petroleum Hydrocarbon     

YANG Rujun  TANG Hongjie  XIN Yu    WANG XiulinCollege of Chemistry  Chemical Engineering  Ocean University of China  Qingdao  P. R. China 《中国海洋大学学报(英文版)》2009,8(1)

  相似文献   

Growth of white anglerfish (Lophius piscatorius) tagged in the Northeast Atlantic, and a review of age studies on anglerfish     

Landa  Jorge; Duarte  Rafael; Quincoces  Inaki 《ICES Journal of Marine Science》2008,65(1):72-80

  相似文献   

����Delaunay�������Ĵ��ģCORS��׼վ���������о�   总被引：1，自引：0，他引：1  

梅生强  宫煦利  姚宜斌  王泽民  黄石磊 《大地测量与地球动力学》2008,28(1):131-135

???????вο???(CORS)????????????GPS???????????λ(RTK)??????????GPS??????λ?????????????? ??λ???????????????????????????????????????????е?Delaunay?????????????????????CORS????????????????????????????????????????????????ο??????????????????????????????????????????Ч???????????  相似文献   

Age and growth characteristics of crimson sea bream <Emphasis Type="Italic">Paragyrops edita</Emphasis> Tanaka in Beibu Gulf     

Gang Hou  Bo Feng  Huosheng Lu  Junfeng Zhu 《中国海洋大学学报(英文版)》2008,7(4):457-465

Abstact  Age and growth characteristics of crimson sea bream Paragyrops edita Tanaka in Beibu Gulf were studied through bottom trawling and gillnet fleets fishing from July 2006 to December 2007. A total number of 1155 individuals, ranging from 49 to 249 mm in standard length was examined. The age of the fish was determined from sagittal otoliths. One year growth was made up of one translucent and one opaque zone. A maximum likelihood estimation procedure was used to fit the Von Bertalanffy, Logistic and Gompertz growth functions to the length-at-age data. ARSS indicated that there were no significant differences in growth between sexes in the three growth models (P>0.05), and the Von Bertalanffy growth function L _t =292.8{1−exp [−0.167(t+1.116)]} was selected as the most appropriate growth model according to Akaike’s information criterion (AIC).  相似文献   

同步卫星短弧定轨     

尹冬梅  赵有  李志刚 《天文学报》2007,48(2):248-255

同步卫星受到摄动力的影响,它的实际轨道有一点漂移．卫星需要不断的调轨调姿,以保证其正常运行．为了研究卫星在几小时,甚至更短的时间内的轨迹情况,采用短弧段定轨法．用动力学方法进行短弧定轨,分别研究1小时和15分钟定轨并进行比较,目的是为了在同步轨道卫星变轨后,能尽快地为卫星提供精密的预报轨道．此外,在系列短弧定轨后,得到精密轨道系列,为研究轨道变化的力学因素及研究短弧中卫星转发器时延变化规律等提供依据．  相似文献