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51.
Effect of reclamation time and land use on soil properties in Changjiang River Estuary,China 总被引:4,自引:1,他引:3
ülo MANDER 《中国地理科学(英文版)》2011,21(4):403-416
The objective of this study is to analyze soil physical and chemical properties,soil comprehensive functions and impact factors after different years of reclamation.Based on the survey data taken from 216 soil sampling points in the Fengxian Reclamation Area of the Changjiang (Yangtze) River Estuary,China in April 2009 and remotely sensed TM data in 2006,while by virtue of multivariate analysis of variance (MANOVA),geo-statistical analysis (GA),prin-cipal component analysis (PCA) and canonical correspondence analysis (CCA),it was concluded that:1) With the in-crease in reclamation time,soil moisture,soil salinity,soil electric conductivity and soil particle size tended to decline,yet soil organic matter tended to increase.Soil available phosphorous tended to increase in the early reclamation period,yet it tended to decline after about 49 years of reclamation.Soil nitrate nitrogen,soil ammonia nitrogen and pH changed slightly in different reclamation years.Soil physical and chemical properties reached a steady state after about 30 years of reclamation.2) According to the results of PCA analysis,the weighted value (0.97 in total) that represents soil nutrient factors (soil nitrate nitrogen,soil organic matter,soil available phosphorous,soil ammonia nitrogen,pH and soil particle size) were higher than the weighted value (0.48 in total) of soil limiting factors (soil salinity,soil elec-tric conductivity and soil moisture).The higher the F value is,the better the soil quality is.3) Different land use types play different roles in the soil function maturity process,with farmlands providing the best contribution.4) Soil physi-cal and chemical properties in the reclamation area were mainly influenced by reclamation time,and then by land use types.The correlation (0.1905) of the composite index of soil function (F) with reclamation time was greater than that with land use types (-0.1161). 相似文献
52.
多期的遥感数据可以用来分析干旱荒漠区植被的空间分布格局和变化特征。本文以1989、2000和2007年3个不同时相的Landsat TM/ETM+影像为数据源,利用线性光谱混合分析和RGB彩色合成法构建一个研究框架,对古尔班通古特沙漠西缘进行植被信息的提取和变化监测分析。在混合像元分解过程中,通过多种方法选择端元,比较... 相似文献
53.
从徐闻珊瑚保护区的8种珊瑚中分离共附生真菌,以获得珊瑚共附生可培养真菌的多样性信息。选用5种培养基,采用平板涂布法培养分离共附生真菌,并进行形态鉴定。8种珊瑚共分离121株真菌,鉴定了其中97株真菌,分属于14个属,青霉属和枝孢霉为优势种属,其次是曲霉属和木霉属。二异角孔珊瑚上分离出22株,数量最多;盔型珊瑚上分离菌株数量最少仅8株。除优势种属外,不同珊瑚样品上真菌种类分布有较大差异,炭角菌属和葡萄穗霉菌属均来源于盔形珊瑚,镰刀菌属在盔形珊瑚和角孔珊瑚上较为常见,盔形珊瑚样品上还分离出2株散囊菌属,1株节菱孢属,因此盔形珊瑚的种群最为丰富;不同培养基分离真菌的能力不同,淀粉培养基分离的菌株最多占所有分离菌株的30.6%,CDA培养基最少,但种类特异。 相似文献
54.
55.
An abrupt ice and snow storm disaster which occurred in the spring of 2008 se-verely destroyed forests over a surprisingly large portion of southern China.A transect crossing Jinggang Mountain-Jitai Basin-Yushan Mountain-Wuyi Mountain was selected as the study area.The authors integrated field data collected in two field surveys to analyze the impacts of the disturbance on forests.The following results were obtained.(1) The extent of damage to plantations along the transect decreased in the order of slash pine > masson pine > mixed plantation > Chinese fir.Slash pine is an introduced species from southern America which is characterized by fast growth,low wood quality and rich oleoresin,and showed a damage rate of 61.3% of samples,of which 70.4% cannot recover naturally.Masson pine is the native pioneer species of forests with harder wood,and 52.5% were damaged due to turpentine,of which 60.9% cannot recovery naturally.Chinese fir is a local tree species and samples showed a rate of 46% and a relative rate of 32.5%,lower than the mixed plantation.(2) From west to east along the transect,we can see that evergreen broad-leaved forest of the western transect on Jinggang Mountain showed the lightest damage extent,and a Cryp-tomeria plantation at an altitude of 700 m was severely destroyed while Chinese fir showed light damage below 700 m and relatively severe damage above 900 m.Masson pine and slash pine in the central transect in Jitai Basin were damaged severely due to turpentine ac-tivities,and closed natural secondary deciduous broad-leaved forest was damaged severely due to high ice and snow accumulation on intertwined shrubs.Masson pine aerial-seeding plantations below 400 m along the eastern transect in Xingguo and Ningdu counties were nearly undamaged for small tree sizes,and Chinese fir at 500-900 m altitude showed a lighter damage extent.However,masson pine which was distributed above 400 m and planted in the 1960s,was severely damaged due to turpentine. 相似文献
56.
钦-杭结合带在中生代构造转折事件以前的板块构造机制 总被引:5,自引:0,他引:5
钦州湾—杭州湾结合带是位于扬子与华夏两大古陆块中间的巨型构造结合带,在演化成西太平洋活动大陆边缘之前,经历了多期次的构造-岩浆事件。扬子和华夏板块于新元古代通过四堡造山运动(1 000~880 Ma)沿江山—绍兴断裂,经赣东北、湘中至钦州湾地区发生碰撞-拼合事件,拼合界线大致位于钦州湾—杭州湾结合带内,形成"两陆夹一盆"的主要格局。后碰撞过程经历了造山后岩浆活动和大陆拉张裂解两个过程,在结合带形成广阔的拉张盆地,加里东期(460~410 Ma)以及印支期(250~200 Ma)发生的碰撞-拼合事件导致扬子和华夏地块多次再造,引发强烈的构造-岩浆活动,并形成了华南统一的沉积环境。受西太平洋板块俯冲影响,华南地区中生代构造转折事件(125~140 Ma)使华南地区主要构造背景由碰撞挤压调整为岩石圈减薄,成为华南最重要的岩浆活动和成矿期。根据内部结构的不均一性和演化历史差异,钦州湾—杭州湾结合带可分为北段、中段和南段3段。其中,中段与传统南岭大体一致;北段为南岭以北地区,即绍兴—江山—萍乡一带;南段为南岭以南地区,大致与云开隆起—十万大山盆地相当。年代学和地球化学研究显示,在云开地块西缘的一系列变质基性岩、超基性岩和变质基性火山岩形成于新元古代洋中脊(MORB)或者岛弧(ITA)特征的构造环境,最近在岑溪一带发现形成于加里东期(441 Ma)的变质火山岩同样具有MORB型地球化学特征。在十万大山两侧发现早中生代的酸性火山岩和流纹岩具有典型岛弧型火山岩地球化学特征。可见结合带南段曾经存在古老洋壳,先后经历了新元古代、加里东期和印支期的碰撞造山事件,与北段演化历史具有一致性。 相似文献
57.
Separation of total nitrogen from sediments into organic and inorganic forms for isotopic analysis 总被引:3,自引:0,他引:3
Nitrogen isotopic (δ15N) analysis is widely applied in palaeoceanography, palaeolimnology and soil science. Most measurements are performed on untreated bulk samples containing both organic and inorganic nitrogen (ON and IN), which could sometimes confound isotopic signals. Here we propose a sample pretreatment method to physically and quantitatively separate the total nitrogen into ON and IN for subsequent concentration and isotopic measurements. In the method, the sediment is first demineralized with HCl and HCl-HF, adsorbed and bound IN being liberated into the acid solutions during the demineralization. Then, organic matter (OM) dissolved in the acid solutions is recovered by a sorbent of styrene divinyl benzene polymer (Bond Elut PPL, Varian) and is then combined with the acid-resistant OM to obtain the total OM. Finally, IN in the acid solutions passing through the PPL sorbent is recovered by way of steam distillation. Total nitrogen recovery with the method is 92.4% and isotopic mass balance calculations show that the δ15N value of total nitrogen can be quantitatively partitioned into the organic and inorganic forms. The δ13C values of the separated OM show a small positive excursion of 0.2‰ relative to those of bulk OM, ruling out significant loss of ON during the pretreatment. By comparison, the KOBr method, widely used to remove ON from bulk samples for isotope measurements, gives lower IN concentration and higher δ15NIN values, attributed to the partial loss of IN and escape of some oxidation-resistant ON. 相似文献
58.
Xianyu HuangPhilip A. Meyers Weichao WuChenglin Jia Shucheng Xie 《Organic Geochemistry》2011,42(2):156-165
The potential significance of the contributions of long chain iso and anteiso monomethyl alkanes (LC MMAs) from plants of the Lamiaceae, a family that includes many culinary and aromatic herbs of cultural value, to sediments and soil has been evaluated by analyzing 21 specimens from 16 species of Lamiaceae from different environmental settings in Hubei Province, central China, and comparing the results with those from tobacco plants, which are established to be rich in these compounds. Odd numbered iso-alkanes (i-C25 to i-C36) and even numbered anteiso-alkanes (a-C25 to a-C36) are abundant in the Lamiaceae (1.9-23.2% and 0.9-23.8% of total alkanes, respectively). The proportions of LC MMAs are relatively high and comparable to those in the tobacco plant. However, chain lengths in the Lamiaceae are longer than those in tobacco plants and compound-specific δ13C values are more negative than in the tobacco plants, potentially allowing distinction of their different origins. The results imply that Lamiaceae, in addition to some other land plants, can be important sources of LC iso- and anteiso-alkanes in sediments and soils. 相似文献
59.
Wei Yang Bai-quan Lin Yong-an Qu Shuai Zhao Cheng Zhai Li-li Jia Wu-qiang Zhao 《International Journal of Coal Geology》2011,85(3-4):300-306
In this paper, an equation correlated with normal stress and permeability was developed and FLAC3D software was used to investigate the rock mass stress evolution and distribution to understand the methane flow characteristics. Research results show that the rock mass under the protective coal seam can be divided into three belts (zones) in the vertical direction, including total de-stressed belt, vertical de-stressed belt and original stress belt. Methane in the total de-stressed belt can flow into the working face of protective coal seam by its own pressure gradient. Methane in the vertical de-stressed belt can only be extracted by boreholes. In the horizontal direction, the rock mass was also divided into five zones, including original zone, compression zone, expansion zone, recovering zone and re-compacted zone, which have been proved correct by the field experiments. The rock mass permeability in the de-stressed belts doesn't increase until stepping into the expansion zone, and from then on higher concentration of methane can be extracted. The methane in original regions is difficult to extract because rock stresses stay the same. The division of “three belts and five zones” reveals the rock mass stress and permeability distribution and evolution and supplies theoretical guidance for relieved methane control. 相似文献
60.