Spatial variability and temporal stability of throughfall water under a dominant beech (Fagus sylvatica L.) tree in relationship to canopy cover     

Jeroen Staelens  An De Schrijver  Kris Verheyen  Niko E.C. Verhoest 《Journal of Hydrology》2006,330(3-4):651-662

Although the spatial heterogeneity of throughfall water (TF) under forest canopies has been related to vegetation structure in several forest types, few reports have been made of the driving factors of small-scale TF variability in deciduous stands. Therefore, the spatial variability of the amount of TF water under one dominant beech (Fagus sylvatica L.) tree was quantified in high temporal and spatial resolution over a 2-year period to examine the temporal stability of spatial TF variability and to relate spatial TF patterns to canopy cover determined photographically above each TF collector (n = 48). The spatial variability of TF was significantly higher during the leafed periods (coefficient of variation (CV) = 18%) than during the leafless periods (CV = 8%), and a strong negative relationship was observed between the CV of event TF and the TF fraction of rainfall in the open field. Geostatistical analysis showed that the cumulative TF water during the leafed periods was spatially correlated up to a distance of 3–4 m. There was a significant temporal stability of spatial TF patterns in the growing periods and in the dormant periods, but patterns differed largely between the two periods of the year. TF water during the growing periods significantly decreased with increasing canopy cover above the sampling locations (r = −0.54, p = 0.014, n = 20), but was more closely correlated with branch cover (r = −0.77, p < 0.001). However, the spatial pattern of TF during defoliated conditions was not related to the measured variation in branch cover.  相似文献   

Particulate matter fluxes in the southern and central Kara Sea compared to sediments: Bulk fluxes, amino acids, stable carbon and nitrogen isotopes, sterols and fatty acids     

Birgit Gaye  Kirsten Fahl  Lyudmila A. Kodina  Niko Lahajnar  Birgit Nagel  Daniela Unger  A. Catalina Gebhardt 《Continental Shelf Research》2007,27(20):2570-2594

The Kara Sea is one of the arctic marginal seas strongly influenced by fresh water and river suspension. The highly seasonal discharge by the two major rivers Yenisei and Ob induces seasonal changes in hydrography, sea surface temperature, ice cover, primary production and sedimentation. In order to obtain a seasonal pattern of sedimentation in the Kara Sea, sediment traps were deployed near the river mouth of the Yenisei (Yen) as well as in the central Kara Sea (Kara) within the framework of the German–Russian project “Siberian River run-off; SIRRO”. Two and a half years of time-series flux data were obtained between September 2000 and April 2003 and were analyzed for bulk components, amino acids, stable carbon and nitrogen isotopes as well as sterols and fatty acids.Sediment trap data show that much of the annual deposition occurred under ice cover, possibly enhanced by zooplanktonic activity and sediment resuspension. An early bloom of ice-associated algae in April/May occurred in the polynya area and may have been very important to sustain the life cycles of higher organisms after the light limitation of the winter months due to no/low insolation and ice cover. The strong river input dominated the months June–August in the southern part of the Kara Sea. The central Kara Sea had a much shorter productive period starting in August and was less affected by the river plumes. Despite different time-scales of sampling and trapping biases, total annual fluxes from traps were in the same order of magnitude as accumulation rates in surface sediments. Terrestrial organic carbon accumulation decreased from 10.7 to 0.3 g C m⁻² a⁻¹ from the riverine source to the central Kara Sea. Parallel to this, preservation of marine organic matter decreased from 10% to 2% of primary productivity which was probably related to decreasing rates of sedimentation.  相似文献   

天山南北麓新生代地理环境演变   总被引：8，自引：0，他引：8  

王树基  阎顺 《地理学报》1987,(3)

本文阐明了晚第三纪以来天山的大幅度隆起及南北麓沉积过程,着重从古植被变化论述了区内新生代的环境演变,并对天山南北麓的沉积环境异同作了对比。文章中首次提出天山地区第三纪以来可分为两个湿润期(古新世-始新世,渐新世晚期-中新世)和三个干旱期(渐新世早中期、上新世、第四纪)。  相似文献   

Semi-empirical estimation of ground motion using observed records at a site in Shikoku, Japan     

Yoshimitsu Fukushima  Masafumi Mori  Shin'ichi Matsuzaki  Shuji Kobayashi  Yuki Ohno 《Journal of Seismology》2001,5(1):63-72

A semi-empirical approach using fore- or after-shockrecords as Green's functions is applicable to thesimulation of strong ground motion, however suchrecords are obviously not available for predictionpurposes. Thus we have predicted ground motion fora hypothetical large earthquake from other minorevents by adopting a distance correction based ongeometrical spreading. Another difficulty inprediction is fault modeling. Surface traces weresimplified as fault models 27, 46, 55, and 77 km inlength. Further, the actual fault rupture may beinhomogeneous, so an asperity distribution isassumed. This asperity model assumes thatdislocation and stress drop are double than theaverage values. Although, the near field term isneglected in our simulation, no significantdifference was seen in the motions estimated byindividual models for periods up to 2.0 seconds. This indicates that the dependence of source size issmall for strong motion, perhaps as a result of therandom summation of high-frequency phases.  相似文献   

Growth of Emerald Crystals by Evaporation of Na2O—MoO3 Flux     

Oishi ShujiDepartment of Environmental Science  Technology  Faculty of Engineering  Shinshu University  Wakasato  Nagano -  JapanYamamoto HirofumiDepartment of Chemistry  Material Engineering  Faculty of Engineering  Shinshu University 《中国地质大学学报(英文版)》2002,13(1):35-39

Well-formed crystals of emerald, Be3AI2Si6O18:Cr, were easily grown from an Na2O-MoO3 flux by an isothermal technique. The crystal growth was conducted by heating a mixture of solute and flux at 1 100 ℃ for 24 h. The evaporation loss of flux depended on the amount of Na2O added to MoO3. Emerald crystals of lengths up to 2.1 mm and widths of 1. 4 mm were grown. The crystal sizes were dependent on the evaporation loss of the flux. The obtained crystals were transparent and exhibited the typical emerald-green color. The form of the emerald crystals was a twelve-sided prism bounded by well-developed faces. The aspect ratios were in the region of 1. 4 to 2. 3. The density was (2. 64±0.02) g/cm3. The IR absorption bands were in good agreement with the literature data.  相似文献   

昆仑山西段与东段地貌景观差异性探讨     

王树基 《干旱区地理》1993,16(2):7-8

昆仑山是青藏高原北部一个高寒干旱的自然地理单元。它是亚洲中部高峻挺拔的巨型山系之一,跨经度16°以上。山地东段与西段的自然状况明显不同。本文主要论述东、西段地貌景观的差异性:山地西段呈现横向岭谷相间的形态,处于青壮年地貌发展阶段;山地东段以纵向低山与高位山间盆地为特点,高原地貌特征明显,属老年地貌发展阶段。  相似文献   

论天山山麓带第四纪的重大事件及其深入研究的必要性     

王树基 《干旱区地理》1992,15(3):1-8

本文简要论述了天山南北山麓地带第四纪的重大事件。它们是强烈的第四纪构造活动、黄土堆积、山麓冰川作用以及古人类活动等。指出这些事件中诸多问题需要深入研究的必要性。  相似文献   

Diagnosing drought using the downstreamness concept: the effect of reservoir networks on drought evolution     

Pieter R. van Oel  Eduardo S. P. R. Martins  Alexandre C. Costa  Niko Wanders  Henny A. J. van Lanen 《水文科学杂志》2020,65(Z1):979-990

ABSTRACT

To effectively manage hydrological drought, there is an urgent need to better understand and evaluate its human drivers. Using the “downstreamness” concept, we assess the role of a reservoir network in the emergence and evolution of droughts in a river basin in Brazil. In our case study, the downstreamness concept shows the effect of a network of reservoirs on the spatial distribution of stored surface water volumes over time. We demonstrate that, as a consequence of meteorological drought and recovery, the distribution of stored volumes became spatially skewed towards upstream locations, which affected the duration and magnitude of hydrological drought both upstream (where drought was alleviated) and downstream (where drought was aggravated). The downstreamness concept thus appears to be a useful entry point for spatiotemporally explicit assessments of hydrological drought and for determining the likelihood of progression from meteorological drought to a human-modified hydrological drought in a basin.  相似文献   

西昆仑山大红柳滩断裂一线的新生代熔岩被及其地质意义   总被引：1，自引：0，他引：1  

漆树基 《新疆地质》1989,(2)

沿西昆仑山大红柳滩断裂有三处新生代溶岩被,其岩性主要为中—基性喷出岩,形成时代分别为上新世及晚更新世.火山机体呈串珠状沿断裂展布,属陆相中心式喷发类型.各处的喷发次数、喷发强度、喷发性质、岩石化学特征既有共同的特点,也有明显的差异.这些特征与康西瓦深断裂东段的乌鲁克库勒地区及东昆仑南缘深断裂的黑石湖、鲸鱼湖地区的新生代火山活动特征完全可以对比.新生代以来,由于印度板块与欧亚板块强烈碰撞,使青藏高原急剧抬升,高原内部构造进一步复杂化,同时,使大红柳滩断裂产生了近50km的水平位移,形成当今的状况.  相似文献   

新亚欧大陆桥新疆段沿线人类农业化过程对区域环境演变的影响   总被引：1，自引：0，他引：1  

王树基 《干旱区地理》1996,19(1):4-9

本文主要论述了新亚欧大型桥新疆段线人类农业化过程对区域环境演变的影响。指出绿洲内部的环境得到明显改善，而绿洲外部的环境则在不断恶化、必须引起重视。  相似文献