Responses of River Terraces to the Activity Variation of the Active Faults in the Eastern Tibetan Plateau     

CHEN Guihu  AN Yanfen  GAO Mingxing  LI Kang  SUN Xiezhe  TAN Xibin 《《地质学报》英文版》2013,87(Z1):339-339

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Experimental investigation on soil carbon, nitrogen, and their components under grazing and livestock exclusion in steppe and desert steppe grasslands, Northwestern China     

Haiyan Wen  Decao Niu  Hua Fu  Jian Kang 《Environmental Earth Sciences》2013,70(7):3131-3141

Livestock grazing is one of the main causes for the change of soil organic carbon (SOC) and total nitrogen (TN) in the arid and semi-arid parts in northern China. This paper examined the SOC, TN, and their components of the local steppe and desert steppe, considering continuous grazing and 4-year livestock exclusion, respectively. In steppe where livestock is excluded, both SOC and TN in the topsoil (0–0.20 m) are found to remain unchanged; however, significant growths are found in microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), particulate organic carbon (POC), and particulate organic nitrogen (PON). On the contrary, both POC and PON progressively decrease at the continuous grazing sites, attributed to the reduction of the mass proportions of soil particulate fraction in the top 0.10 m soil. In the desert steppe where grazing is excluded, the SOC, TN, and their components of the topsoil increase. However, at the continuous grazing sites, POC and PON in the 0.10 m topsoil are reduced, caused by the decrease of C and N content in soil particulate fraction. Besides, microbial quotients were lower in the continuous grazing sites in the two grasslands. It is also found that both MBC and POC are more sensitive to human-induced activities than SOC, and thus could serve as earlier indicators of the soil-fertility variation caused by short-period grazing management.  相似文献   

Soil erosion monitoring and its implication in a limestone land suffering from rocky desertification in the Huajiang Canyon, Guizhou, Southwest China     

Jian Peng  Yue Qing Xu  Ren Zhang  Kang Ning Xiong  An Jun Lan 《Environmental Earth Sciences》2013,69(3):831-841

Over the past decades, the vast limestone mountain areas in southwestern China have suffered greatly from karst rocky desertification (KRD), which is a unique type of desertification caused by irrational land-use practices and has drawn increasing attention of international academic community. Characterizing soil erosion in this region is the key to understanding the escalating KRD problem and finding solution to it. The authors applied leveling method to study soil erosion process in the Huajiang Karst Canyon area between 1999 and 2003, and tried to relate it to KRD expansion. The monitoring data indicate that soil in the study area was losing at an alarming rate, which is much higher than soil formation rate and has already resulted in severe KRD problem. Soil loss under different land-use conditions varied greatly during the monitoring period. The highest soil erosion rate occurred in bare and newly abandoned cropland, followed by sparse grass land, forest land, and dense grass land. In addition, soil erosion could be significantly different under different micro-topographic conditions. Because soil erosion rate in the studied karst mountain areas is surprisingly high, it is urgent to take quick actions to fight against the ongoing KRD problems in Southwest China before an irreversible situation occurs. However, the traditional way to combat KRD by abandoning current cropland needs to be carefully reconsidered, since a bare newly abandoned cropland may suffer more from rapid soil loss than before.  相似文献   

Estimation of N2O emission from tea garden soils, their adjacent vegetable garden and forest soils in eastern China     

Wenyan Han  Jianming Xu  Kang Wei  Yuanzhi Shi  Lifeng Ma 《Environmental Earth Sciences》2013,70(6):2495-2500

The objective of this study was to investigate nitrous oxide (N₂O) emissions from different land-use types in eastern China. The dynamic changes of N₂O emissions were investigated in tea gardens with different nitrogen application rates, their adjacent vegetable garden and forest soils from June 2009 to May 2010. The results showed that high nitrogen application in a tea garden significantly increased soil N₂O emissions. Lower N₂O emission and percentage of N₂O–N to the applied N were observed in a tea garden with low N application than that from vegetable garden, indicating reasonable control of N application can efficiently decrease N₂O pollution in tea gardens. Both air and soil temperature had significant and positive impact on N₂O emissions, but little effect of precipitation was observed. Therefore, N application rate and environmental temperature are the most essential factors in influencing N₂O emission and should be taken into consideration in the field management of tea production.  相似文献   

Study on formation mechanism of gas tunnel in non-coal strata   总被引：1，自引：0，他引：1  

X. B. Kang  M. Xu  S. Luo  Q. Xia 《Natural Hazards》2013,66(2):291-301

Gases are common constituents of the underground environment, along with soils, rocks, and water. It is widely believed that gases in underground originate from the bacterial decomposition and thermal decomposition of organic and inorganic compounds, and geochemical reactions. Gases are usually widely dispersed in low concentrations, but under some geologic conditions are abundant. Gas can be a hazard to construction of underground civil works such as tunnels and underground chambers. Besides the gas tunnels in coal seam, there are a large number of tunnels with gas in non-coal strata in China, such as the Paotaishan Tunnel, Hongshiyan Tunnel, and Zengjiaping 2# Tunnel. These tunnels do not cross coal strata, but all encountered gas problems during construction. Due to lack of full understanding and thorough preparation, as well as the random non-uniform distribution of gas emission, the gas disasters in these tunnels are usually larger than the traditional ones. Study on the causes of formation has great scientific significance. This paper focuses on a variety of complete gas tunnels, summarized three types of gas tunnel in the non-coal strata, namely the structure-connected gas tunnel, including fracture, fault, and fold three subtypes according to the different geological structures; the second one is gas tunnel with metamorphic wall rock; the third is gas tunnel by composite forming causes.  相似文献   

东天山二叠纪大草滩地区镁铁-超镁铁质岩体的岩浆演化过程和含矿性   总被引：1，自引：1，他引：0  

任明浩  王焰  倪康  孙亚莉 《岩石学报》2013,29(10):3473-3486

大草滩地区位于新疆东天山土墩-黄山-图拉尔根镁铁-超镁铁质岩带西侧,觉罗塔格构造带中段,区域构造环境主要受康古尔塔格-黄山深大断裂控制。本次研究的大草滩地区一、二号岩体形成于早二叠纪, SIMS法锆石U-Pb年龄分别为279±2Ma和278±2Ma。2个岩体主要由橄榄岩和辉长岩组成,全岩稀土总量较低,具LREE轻微亏损至平坦的分配型式。全岩Sr-Nd同位素与微量元素组成显示两个岩体的母岩浆来自软流圈地幔,其成分与N-MORB相似,在上升过程中经历了较低程度(1%~5%)的同生A型花岗岩混染。由于低程度的部分熔融(10%~15%)导致硫化物残留在地幔源区,导致母岩浆强烈亏损铂族元素,因此大草滩地区一、二号岩体可能不具有形成具经济价值铜镍硫化物矿床的潜力。  相似文献   

中更新世以来的哈尔滨黄土物源变化——来自TIMA自动定量矿物的证据北大核心CSCD     

汪进秋  谢远云  康春国  迟云平  孙磊  吴鹏  魏振宇 《中国沙漠》2022,42(5):25-35

黄土隐含丰富的古气候信息,了解其物源变化对理解亚洲内陆干旱化、大气环流模式和亚洲季风演变至关重要。哈尔滨荒山剖面地层出露厚度大,地层连续,保存了松嫩平原最完整的黄土-古土壤序列。此外,重矿物在河流源-汇研究中得到广泛应用,但在风成沉积物中较少。定量矿物学方法分析速度快,能在较短时间内获得大量数据。因此,我们对哈尔滨黄土-古土壤序列进行TIMA(TESCAN Integrated Mineral Analyzer)自动定量矿物分析及年代学(OSL、ESR和14C)测试,以期了解哈尔滨黄土在冰期-间冰期时间尺度上的物源变化。结果表明:TIMA方法鉴别的矿物种类高于传统方法,且TIMA定量的重矿物含量与传统方法相比存在一定的差异,但两者揭示的重矿物组合基本一致。黄土-古土壤序列在15.1 m(234.2 ka)上、下地层的20—63μm组分的铁板钛矿、闪石类、锆石、磷灰石、金红石、钛铁矿、铬铁矿、榍石、辉石以及重矿物特征指数(ZTR和GZi)等存在明显不同的变化特征;然而,除了铁板钛矿和独居石外,<20μm组分并没有表现出如此特征。黄土-古土壤序列上、下地层重矿物组成的差异指示了哈尔滨黄土物源的变化。15.1 m以下,哈尔滨黄土除了接受松嫩沙地的近源粉尘贡献外,也有远源(比如,浑善达克和科尔沁沙地)粉尘的贡献。随着干旱化气候的加剧,松嫩沙地范围扩大,使得15.1 m以上黄土的远源贡献比例减少,近源贡献显著增加。即增强的气候干旱化导致的松嫩沙地粉尘源区范围扩大,是哈尔滨黄土物源发生变化的主要原因。  相似文献   

不同来流条件下四圆柱尾流场试验研究     

高洋洋  蘧鑫晨  杨康  张宝峰 《海洋工程》2018,36(6):84-91

基于粒子图像测速技术(PIV)对小间距比比L/D=1.5工况下方形布置四圆柱在不同来流角角α(α=0°、15°、30°、45°)条件下的尾流流场特性进行了试验研究,分析了不同来流角度条件下四圆柱瞬时和时均尾流流场特征,获得了瞬时和时均速度矢量、涡量等值线、流线拓扑及雷诺应力分布随来流角度变化的规律。试验结果表明,来流角度对方形布置四圆柱尾流形态有显著影响。四圆柱瞬时尾流形态随来流角度增大可分为延伸体流动流态(α=0°)、尾流剪切层附着流态(α=15°、30°)及尾流剪切层共同脱落流态(α=45°)三种流态。当来流角度增大时,四圆柱下游断面平均流向速度分布由"W"形向"U"形转变,时均雷诺正应力及雷诺剪切应力等值线分布特征也会发生明显改变。  相似文献   

GCMs with implicit and explicit representation of cloud microphysics for simulation of extreme precipitation frequency     

In-Sik Kang  Young-Min Yang  Wei-Kuo Tao 《Climate Dynamics》2015,45(1-2):325-335

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An automatic mosaicking method for building facade texture mapping using a monocular close-range image sequence     

Zhizhong Kang  Liqiang Zhang  Sisi Zlatanova  Jonathan Li 《ISPRS Journal of Photogrammetry and Remote Sensing》2010,65(3):282-293

This paper presents an automatic mosaicking method for generating building facade textures from a monocular close-range digital image sequence. The process begins with the computation of the camera parameters (except the coordinates of the projective center), which are determined by combining vanishing point geometry with constraints of a straight line bundle as well as prior information of parallel lines in object space. The raw images are later rectified for the purpose of eliminating their salient geometric distortion. Next, automatic retrieval of the relevant image segment is implemented using the detecting range variance by means of the histogram of projective differences between the corresponding points for each of the facades from the raw image sequence. A strip model of the least-squares adjustment, which is similar to the strip block adjustment in aerial triangulation, is employed to determine the spatial alignment of each of the image segments in order to generate the facade textures from the relevant image segments. Afterwards, the entire building facade texture is mosaicked by ortho-image generation. Two refining strategies are proposed to optimize the mosaic result. One is refining the mosaic region where corresponding points are difficult to match but plenty of horizontal lines are available, and the constraint of corresponding horizontal lines is introduced to implement this process. The other strategy is to refine the unsatisfactory mosaic region by densifying the corresponding points by means of the spatial alignment of the relevant image segment computed by the strip method. The experimental results indicate that this method is widely applicable and compares well with other reported approaches with regard to automation level and applicability, for uncalibrated images as well as images with large geometric distortions.  相似文献