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Renee Sherna LAING Kian Huat ONG Roland Jui Heng KUEH Nixon Girang MANG Patricia Jie Hung KING Muaish SAIT 《山地科学学报》2019,(6)
The mountain ecosystem is a hotspot of biodiversity and provides a significant contribution to the humans' livelihoods. However, there is still a lack of information regarding floral diversity and how it has been affected due to a logging operation in Sarawak. A study was conducted to determine vegetation recovery at the Heart of Borneo conservation area at different elevations: 750–1200 m(S1), 1200–1500 m(S2) and 1500 m(S3). A total of 891 trees were enumerated. The trees comprised 55 families, 98 genera and 203 species. The lowest elevation site, S1, contained the highest number of species(117) and families(42), while the highest elevation site, S3, contained the lowest diversity(25 families and 59 species). A similar forest structure was recorded, whereby diameter at breast height(dbh), basal area and height decreased as elevation increased. The most speciose families in S1 were Dipterocarpaceae(11 species) and Lauraceae(10 species), while Lauraceae and Fagaceae were the dominant tree families at S2 and S3. Secondary tree species are still abundantly found in the logged plots, especially at S2(45.5%), indicating that after 30 years, these stands are still in the recovery stages. The logged plots retained typical secondary forest appearances with lower canopy diameters and heights and dbh than the unlogged forest. Although the species richness approached that of the unlogged plots, especially at S1(90.9%) and S3(94.9%), there were still major differences in the floristic compositions between logged and unlogged plots(35.4%, 21.5% and 44.7% for S1, S2 and S3, respectively). Although potential seed sources were in close proximity, succession at S2 has proceeded much slower than at S1 and S3. Lower concentrations of soil nutrients, especially N, may be the main reason for the slow recovery. In conclusion, the results suggested that the selectively logged forest at the Payeh Maga Highland required more than three decades to recover and achieve a climate forest stage. 相似文献
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应用锆石SHRIMP方法对湖南骑田岭岩体东缘的“印支期”菜岭岩体进行了精确的SHRIMP定年研究。结果表明菜岭花岗岩的形成年龄为(160±2)Ma,从而确证它是燕山期花岗岩,且属于骑田岭岩体主侵入阶段的范畴。少量继承锆石核记录了中元古代的年龄信息,表明前寒武纪岩石可能是区内花岗岩浆熔融源区的重要组成之一。 相似文献
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椭圆型Copulas函数在西安站干旱特征分析中的应用 总被引：5，自引：1，他引：4
本文研究了干旱发生的联合概率、条件概率和重现期等干旱特征.以陕西省西安站月降水为例,应用Meta-Gaussian Copula和Student t Copula构造了干旱历时、干旱烈度和烈度峰值的联合概率分布,并进行了多变量分布拟合优质评价及拟合检验,在此基础上计算了联合分布的重现期以及2变量和3变量情形下的条件概率与条件重现期.研究表明,Meta-Gaussian Copula可以描述干旱历时、干旱烈度和烈度峰值三者的联合分布.由于多元联合分布可以考虑到多个变量之间的不同组合,能够求得不同干旱历时、干旱烈度或烈度峰值下的条件概率和条件重现期,因而能够更加全面客观地反映干旱的特征. 相似文献
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云开造山带强过铝深熔花岗岩地球化学、年代学及构造背景 总被引：15，自引：0，他引：15
云开造山带条带—眼球状(环斑)深熔花岗岩(含紫苏花岗岩)地球化学和年代学的研究表明,绝大多数花岗岩的A／ CNK>1．1,CaO／Na2O=0．62-1．61(平均0．94,大于0．3),Al2O3／TiO=16．6-60．6(平均23．68),高场强元素Ta、Nb、Zr 亏损,具大陆边缘俯冲-碰撞造山带后碰撞构造环境强过铝(SP)高钾钙碱性-钙碱性花岗岩的特征,紫苏花岗岩和片麻状含榴黑云二长花岗岩Al2O3／TiO(平均17．82)明显低于条带-眼球状(环斑)黑云二长花岗岩Al2O3／TiO(平均29．55),显示其形成温度更高,并具A型花岗岩的演化特征．而且从高钾钙碱性条带-眼球状(环斑)黑云二长花岗岩到钙碱性紫苏花岗岩、片麻状含榴黑云二长花岗岩,形成时代由(465±10)Ma、(467±10)Ma变为(435±11)Ma、(413±8)Ma,表明扬子板块与华夏板块在加里东期发生了洋—陆俯冲—碰撞造山和后碰撞的伸展—拆沉—底侵岩浆岩作用,并且后期又经历了海西—印支期挤压抬升和伸展揭顶作用的改造,这也为华南存在加里东期扬子板块向华夏板块的洋-陆俯冲-碰撞造山提供了重要证据． 相似文献
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ＣｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｆａｕｌｔｒｏｃｋｓａｎｄｐａｌｅｏｅａｒｔｈｑｕａｋｅｓｏｕｒｃｅａｌｏｎｇｔｈｅＫｏｋｔｏｋａｙＥｒｔａｉｆａｕｌｔｚｏｎｅ，Ｘｉｎｊｉａｎｇ，ＣｈｉｎａＬＡＮＢＩＮＳＨＩ１）（史兰斌）ＣＨＵＡＮＹＯＮ... 相似文献
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福建马坑矿区水化学微量组分的指示作用 总被引：1，自引：1，他引：0
通过对区域地质背景调查分析、现场取样和室内测试,研究了马坑矿区地下水水化学特征,确定不同类型地下水的特征鉴别离子,分析地下水中微量元素含量异常原因所在,并通过研究地下水中稀土元素的水文地球化学特征,判断矿区地下水径流交替的强弱和稀土元素富集特征,为判别矿坑主要涌水水源提供确切依据。 相似文献
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Experimental study on the bank erosion and interaction with near-bank bed evolution due to fluvial hydraulic force 总被引：1，自引：0，他引：1
Bank erosion is a typical process of lateral channel migration,which is accompanied by vertical bed evolution.As a main sediment source,the failed bank soil may directly cause the increase of sediment concentration and considerable channel evolution in a short time.The paper presents an experimental study on non-cohesive and cohesive homogenous bank failure processes,influence of the failed bank soil on bank re-collapse,as well as the interaction between bank failure and near-bank bed evolution due to fluvial hydraulic force.A series of experiments were carried out in a 180° bend rectangular flume.The results reveal the iteration cycle between bank erosion and bed deformation:undercutting of the riverbank,slip failure of the submerged zone of the bank,as well as cantilever failure of the overhang,failed bank soil staying at bank toe temporarily or hydraulic transportation,exchange between the failed bank soil and bed material,bed material load being re-transported either as bed load or as suspended load,and bed deformation.Same as bank failure,the mixing of failed bank soil and bed material is more severe near the curved flow apex.Moreover,non-cohesive bank failure tends to occur near the water surface while cohesive bank failure near the bank toe.For non-cohesive dense(sandy) soil,the bank erosion amount and residual amount of failed bank soil on the bed increase with the near-bank velocity or bed erodibility.But for cohesive soil,only bank erosion amount follows the above rule.The results are expected to provide theoretical basis for river management and flood prevention. 相似文献
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TAN Hong-bo SHEN Chong-yang XUAN Song-bai WU Gui-ju YANG Guang-liang WANG Jian 《地震地质》2017,39(2):356-373
The main rupture of Ludian MS6.5 earthquake is directed to the northwest, which occurred in the east of Xianshuihe-Xiaojiang fault zone. The epicenter is in the transitional zone of the Sichuan-Yunnan block and the South China block, where there are many slip and nappe structures. Some controversy still remains on the earthquake tectonic environment. So, Bouguer gravity anomalies calculated by EGM2008 were broken down into 1-5 ranks using the way of Discrete Wavelet Transform(DWT), then we get the lateral heterogeneity in different depths of the crust. The distribution characteristics of Bouguer gravity anomaly are analyzed using measured gravity profile data. We also get its normalized full gradient(NFG)picture, and study the differences between different depths in crust. The results show that: (1)the characteristic of Buoguer gravity anomaly in southwest to northeast is high-low-high between the Lianfeng Fault(LFF)and Zhaotong-Ludian Fault(ZLF). The mainshock and aftershocks are distributed in the middle of the low-value zone, which means that the east moving materials of Qinghai-Tibet plateau broke through the southern section of Lianfeng Fault(LFF), moving along the Baogunao-Xiaohe zone(low-value belt)to the southeast, stopped by the Zhaotong-Ludian Fault(ZLF), and then earthquake occurred.(2)The third-order discrete wavelet transform(DWT)details show that: there is a good consistency between the negative gravity anomaly in upper crust and the distribution of major faults, which reflects that the rupture caused by the movements of the faults in crust has reduced gravity anomaly. There is a NW-trending negative anomaly belt near the epicenter, which may has some relationship to the southward development of the Daliangshan Fault(DLSF). So we speculate that the southward movement of Daliangshan Fault is the main direct force source of Ludian earthquake.(3)In the picture of the fourth-order DWT details, there is an obvious positive gravity anomaly under the epicenter of Ludian earthquake, which confirms the presence of a high-density body in the middle crust. While the fifth-order DWT details show that: A positive anomaly belt is below the epicenter too, which may be caused by mantle material intruding to the lower crust. Tensile force in crust caused by mantle uplift and extrusion-torsion force caused by Indian plate push are the main force source in the tensile and strike slip movement of the Ludian earthquake.(4)The normalized total gradient of Bouguer gravity anomalies of Huili-Ludian-Zhaotong profile shows that: there is obvious ‘deformation’ in the Xiaojiang fault zone which dips to the east and controls the local crust movement. There is a local ‘constant body’ at the bottom of the epicenter. The stable constant body in density has limiting effects to the earthquake rupture, which is the reason that the earthquake rupture' scale in strike and in depth are limited.(5)The ability of earthquake preparation in Zhaotong-Ludian Fault is lower than the Xianshuihe-Xiaojiang fault zone, and the maximum earthquake capacity in this area should be around magnitude 7. 相似文献