Relationships between tree-ring width index and NDVI of grassland in Delingha

The responses of terrestrial ecosystem to and their impacts on global climate change are key issues in global change research. More studies on vegetationmonitoring and land cover change have been performed by using remote sensing data recently, which bene…     

沿空巷道煤柱宽度参数的研究与应用

通过对我矿3246沿空机巷煤柱宽度参数的研究,确定了类似地质条件下的煤柱宽度参数,为今后的采区设计提供了理论依据。     

沿气温梯度中国森林生物量分布特征

基于长期定位监测的森林生物量数据以及气象数据,利用生物量加权计算法和空间关联法,研究气温梯度下中国森林生物量分布特征.结果表明:1)森林总生物量和地下生物量随着温度梯度变化趋势一致,表现为随着气温的增加而持续升高,当气温达到一定值,森林总生物量出现先上升后下降,继而又逐渐上升最后下降趋势.地上生物量随着温度梯度变化有微小差别,随着气温的增加而直接下降,继而又逐渐上升,最后呈下降趋势,在低温前期没有上升的趋势. 2)植物地上生长与地下生长对温度有不同的响应机制,具有滞后效应. 3)对森林生物量总贡献,地上生物量比地下生物量贡献大,茎生物量比枝叶生物量贡献大.以上结果表明了我国森林生物量随着气温的变化有明显规律可循,气温对生 产力具有极其重要的影响作用.      

武夷山不同海拔植被土壤细根比根长季节动态

对位于中亚热带的武夷山不同海拔植被土壤的细根生物量及长度进行了测定,分析了细根比根长的垂直分布及季节动态。结果表明:(1)在0～10 cm和10～25 cm土层,活细根比根长都是高山草甸>矮林>针叶林>常绿阔叶林(p<0.01);(2)常绿阔叶林、针叶林0～10 cm土层内活细根比根长高于10～25 cm土层内活细根比根长,矮林、高山草甸却是在10～25 cm土层内活细根比根长较高。各林分活细根比根长和死细根比根长在两土层间都无显著差异;(3)4种林分两土层内活细根比根长和死细根比根长都表现出一定的季节变化动态,但是季节间均无显著性差异。     

黄土高原植被生长期降水对全球气候变化的响应

利用黄土高原区域40a的降水资料，研究植被生长期降水变化，检测降水突变，分析降水异常的分布和振荡特征，并对千年和湿年进行比较．结果表明：近40a采黄土高原植被生长期降水在1985年左右发生突变，由历史上的多雨转为少雨。根据降水异常响应的敏感程度划分了3个敏感区，即北部、东部和西部；在各区的降水变化存在3a～5a、8a左右的年际振荡和16a～20a左右的年代际振荡，3a～5a的周期明显；划分了千年和湿年，干湿年降水相差大，特别是高原中部相差120mm以上，湿年比千年多40％以上；千年相对变率明显大于湿年．     

Rapid assessment and explanation of tree species abundance along the elevation gradient in Gaoligong Mountains,Yunnan, China

This article presents an analysis of tree species abundance and its association with climatic variables along elevation gradient in the Gaoligong Mountains in west Yunnan, China. Data from scientific papers and books in the Gaoligong Mountains area were collected and extrapolated to elucidate a mechanistic understanding of elevation patterns and the relationship between the elevation range and elevation mid-point of tree species along the gradient by examining climatic variables. Tree species abundance showed a unimodal pattern with a peak at mid-elevation (about 2000 m) and species with a narrow elevation range occurred at higher or lower elevation, while a wider elevation range was found at the middle of the gradient. Tree species abundance was the highest where both temperature and water availability were moderate. The relationship between the climatic variables affecting species appear to be due to both direct and indirect factors, and the effect of these effects varied at different gradients.

     

全球变暖背景下江苏气候局地响应的基本特征

在全球变暖背景下,通过对1961-2000年江苏地区13个国家基本基准站地面资料的分析发现,江苏地区气候的响应存在两个基本特征.其一表现为该区域气候年代际变异存在着明显的3个阶段,1968年左右前的降温期,伴随着总云量(低云量)的增加、总辐射减少和大气水汽表征量的减少;在谮1968-1986年左右的转型耦合期,气候变异不明显;1986年以及其后的增温期,伴随着总云量(低云量)的减少、总辐射增加以及大气水汽表征量的增加.第二个基本特征则为,在上述降温-减湿/增温-增湿期,明显对应着降水减少/增加时期,从理论上论证了这种对应关系是由于湿热涡旋效应增强所致.     

芦芽山白杄非结构性碳水化合物和氮含量随海拔梯度的变化?

选择山西省吕梁山脉北端芦芽山沿7个海拔梯度测定了林线树种白杄(Picea meyeri)各组织非结构性碳水化合物(NSC)及其组分含量和全氮含量.结果表明:白杄各组织氮含量均表现出随海拔升高而增加的趋势(茎干除外);NSC含量均随海拔升高而增加,木质化组织中的可溶性糖与淀粉质量比也表现林线高于中低海拔;除茎干外,各组织NSC-N质量比则表现出随海拔升高先减小后增加的趋势.研究表明,氮含量和NSC含量没有限制芦芽山林线树木的生长和发展,即林线树木不存在氮受限和碳限制.     

高速公路标志植物对视觉反应特性的影响

采用简单随机取样法，研究了高速公路匝道入口前的标志植物对驾驶员反应时间的影响。测试结果表明，在匝道入口区域选择红色叶或者红色枝干、单一种类、较大空间体积的标志植物，能够缩短驾驶员对入口识别的反应时间。     

降雨模式对树坪滑坡稳定性影响分析

降雨是诱发滑坡失稳的重要因素,依据饱和-非饱和及斜坡稳定性分析理论,基于等量的降雨量和降雨时间,按照实际库水位调度和降雨集中时间分为三种工况:工况一,稳定水位145 m;工况二,175 m水位线经150 d降到145 m水位线;工况三,145 m水位线经60 d升到175 m水位线,采用Geo-studio软件模拟三峡库区树坪滑坡在不同工况中减弱型、增强型、集中型、平均型4种降雨模式下的降雨入渗过程和稳定性。探讨了树坪滑坡孔隙水压力随时间的变化规律,以及树坪滑坡稳定系数与时间的变化关系。结果表明:降雨模式对树坪滑坡降雨入渗和稳定性有明显的影响,除工况二下水位继续降低作用外,其他二种工况下减弱型降雨模式水位线变化早于其他三种模式,库水位的变动能改变降雨模式对滑坡水位线的影响;降雨模式和库水位变动的双重作用下降雨入渗也发生了明显的变化;滑坡的初始安全系数都在1.2以上,而在工况二下滑坡的安全系数都降到1.2以下,尤其是减弱型模式下滑坡安全系数降幅最大。     

近56年来中国四季降雨事件演变特征的空间差异分析

全球气候变化背景下不同季节降雨及其贡献率的空间分异特征是学界关注的焦点问题之一。本文采用535个站点的日值降水数据分析了1961-2016年中国四季降雨的空间差异性。结果表明：①中国四季降雨雨量和雨日具有明显的“东南高-西北低”的空间分异特征,而中国四季降雨雨量和雨日贡献率的空间格局相比前者差异较大。②在变化趋势上,中国四季降雨雨量和雨日及其贡献率在冬季增加趋势最明显,夏季减少趋势最明显。在波动特征上,中国四季降雨雨量和雨日及其贡献率波动特征在冬季最大,夏季最小。③不同季节降雨雨量和雨日的差异表明季风边缘区是中国四降雨的重要分界线。四季降雨雨量和雨日贡献率的差异特征与前者相比差异较大。降雨贡献率有助于深化认识全球气候变暖背景下的降雨变化特征。     

极端降雨对黄土沟壑区隧洞施工力学效应影响分析

黄土地区输水隧洞的建设中,降雨入渗极大影响着输水隧洞围岩稳定性。本文利用非饱和渗流理论和数值模拟方法研究了极端降雨条件入渗与黄土沟壑区隧洞的开挖扰动耦合影响下围岩的变形和渗流场演变规律,通过Plaxis3D模型对降雨入渗下新奥法施工过程中围岩力学特性、初期支护过程进行流固耦合分析。结果显示,降雨等级越高,围岩孔隙水压力变化幅度越大,对围岩的稳定性越不利;降雨入渗与开挖扰动会加速土层中渗流场和应力场的重分布过程;基于沟道的汇水特性,隧洞围岩含水率在最初5~10 d呈台阶式增长,拱顶、拱腰和拱趾处的最大变形为17.8 mm、28.2 mm、24.6 mm,最大剪切应力为175.3 kPa、182.5 kPa、150.6 kPa,降雨结束约15~20 d围岩变形速率逐渐减小收敛至特定值,但围岩的应力持续增加,为避免围岩发生塑性变形,故可在15~20 d进行二次衬砌支护。本次研究结果可对极端降雨期黄土沟壑地区隧洞施工安全控制提供参考。     

Application of the moist vorticity vector in the analysis of a heavy rainfall event in North China

The moist vorticity vector (MVV), defined as (ζa×qv)/ρ introduced by Gao et al. is used to study a heavy rainfall event in North China. The MVV has zonal, meridional and vertical components in a three-dimensional framework. Analysis of domain-mean and mass-integrated quantities shows that the variation of the vertical component of the MVV closely follows the variation of the cloud hydrometeors, with a linear correlation coefficient of 0.95, indicating that the vertical component of the MVV is strongly associated with midlatitude convection. Further analysis shows that the vertical component of the MVV reflects the interaction between the horizontal vorticity and the horizontal specific humidity gradient, which can associate dynamic and thermodynamic processes with cloud microphysical processes. Thus, this study can help to understand how the interaction between circulations and clouds aids the development of convection, and the MVV can be used to trace the development and evolution of heavy rainfall.     

Application of the moist vorticity vector in the analysis of a heavy rainfall event in North China

The moist vorticity vector (MVV), defined as (ζa×▽qv)/ρ introduced by Gao et al. is used to study a heavy rainfall event in North China. The MVV has zonal, meridional and vertical components in a three-dimensional framework. Analysis of domain-mean and mass-integrated quantities shows that the variation of the vertical component of the MVV closely follows the variation of the cloud hydrometeors, with a linear correlation coefficient of 0.95, indicating that the vertical component of the MVV is strongly associated with midlatitude convection. Further analysis shows that the vertical component of the MVV reflects the interaction between the horizontal vorticity and the horizontal specific humidity gradient, which can associate dynamic and thermodynamic processes with cloud microphysical processes. Thus, this study can help to understand how the interaction between circulations and clouds aids the development of convection, and the MVV can be used to trace the development and evolution of heavy rainfall.     

煤炭型城市工业碳排放对驱动因素的响应研究

以平顶山市为例,探讨了煤炭型城市工业碳排放的影响因素,及工业碳排放对其影响因素地动态响应特征.根据扩展的Kaya恒等式将影响工业碳排放地因素分为能源碳强度、能源利用效率、产业结构和经济发展四个因素.用脉冲响应函数分析工业碳排放对自身及四个影响因素冲击地动态响应,用方差分解模型定量分析工业碳排放自身和四种影响因素地贡献度.结果显示,能源碳强度和能源利用效率的冲击效应值为负,工业产值占比地冲击效应类似于正弦曲线,GDP和工业碳排放自身的冲击效应为正.工业产值占比对工业碳排放的推动作用最大,接下来依次为工业碳排放自身因素、能源强度、GDP、碳排放系数.     

Genesis of the mega-crystal zircons in the dunite veins of North Qaidam Mountains, northwestern China

A megacrystal zircon occurs in serpentinized dunite veins from North Qaidam, northwestern China. It is red-brown and 3―4 mm long and 2 mm wide in size. BSE imaging shows the presence of micro-grains （30―50 μm） of zircon between olivine and serpentine, part of them gathering into clusters （100―300 μm）. Thus we infer that these zircon crystals were precipitated from hydrothermal fluid. Inclusions of baddeleyite （white） in the shape of isolated island locally occur in the large zircon （grey）, implying that the former formed earlier than the latter. The mirco-baddeleyite （50―100 μm） aggregate consists of baddeleyite （3―5 μm） and olivine （〈5 μm）, indicating the zircon formation through interaction between baddeleyite and silica-bearing fluid. Therefore, we consider a genetic link between the formation of the large zircon and the serpentinization of dunite. SHIRIMP U-Pb dating of the large zircon gave two groups of concordant ages at 414 ± 13 Ma and 371 ± 9 Ma, respectively. This might reflect two episodes of zircon growth in response to two episodes of fluid action.     

基于零极点分析法的谐振电路的频率响应研究

文章对谐振电路的频率响应用零极点分析法进行了研究,其幅频特性曲线和相频特性曲线用Multisim 7仿真,归纳出了谐振电路的主要指标与零极点的关系,得出了具有一定参考价值的结论.     

秦淮河流域典型排涝泵站前池水质与降雨特征响应关系

为分析排涝泵站前池水质与降雨特征的响应关系,对南京市城区秦淮河沿线2个排涝泵站前池水质以及降水量开展高频在线自动监测,结合回归树方法分析了不同降雨强度、前期干旱时间条件下排涝泵站前池水质变化规律,探讨了不同类型排涝泵站前池水质的主要影响因素。结果表明:晴雨天均有生活污水汇入的A泵站前池氨氮质量浓度在大雨强下降低,中雨强下先升高后降低,小雨强下平缓上升,A泵站前池污染物质量浓度主要受降雨强度和次降水量影响;主要接收降雨径流,雨量大时有生活污水溢流汇入的B泵站,前池污染物质量浓度在大雨强下先升高后逐渐降低,中雨强下降低,小雨强下变化不大,B泵站前池水质主要受次降水量、前期干旱时间和降雨强度影响;2个泵站前池CODMn质量浓度变化与降雨的响应规律相似,但更多受到与前期干旱时间关联的地表径流冲刷作用影响;连续降雨均导致泵站前池氨氮质量浓度和CODMn质量浓度波动变化较大,而前期干旱时间越长,降雨发生后泵站前池水质越差。     

地面交通荷载对浅埋隧道的动力响应分析

为研究地面交通荷载对浅埋隧道的动力响应,建立地面移动荷载作用下隧道数学模型.以济南市顺河快速路南延地下结构工程为背景,将地面交通荷载进行合理近似简化;利用动力方程推导围岩波势函数表达式,结合边界条件确定的波函数展开项系数,得到移动荷载作用下隧道的动力响应,并利用数值模拟的方式对结果进行验证;讨论移动荷载速度及隧道埋深对动力响应的影响.结果表明:径向应力响应在隧道拱顶处引起较大响应;切向应力则在拱顶处和两侧均引起较大响应;车辆速度及隧道埋深是影响动力响应大小的因素.     

Velocity structure of the crust and uppermost mantle in the boundary area of the Tianshan Mountains and the Tarim Basin

A portable 3-component broadband digital seismic array was deployed across the Tianshan orogenic belt (TOB) to investigate the lithospheric structure. Based on receiver function analysis of the teleseismic P-wave data, a 2-D S-wave velocity profile of the boundary area of the TOB and the Tarim Basin was obtained at the depths of 0--80 km.Our results reveal a vertical and lateral inhomogeneity in the crust and uppermost mantle. Four velocity interfaces divide the crystalline crust into the upper, middle and lower crust. A low velocity zone is widely observed in the upper-middle crust. The depth of Moho varies between 42 and 52 km. At the north end of the profile the Moho dips northward with a vertical offset of 4--6 km, which implies a subduction front of the Tarim Basin into the TOB. The Moho generally appears as a velocity transitional zone except beneath two stations in the northern Tarim Basin, where the Moho is characterized by a typical velocity discontinuity. The fine velocity structure and the deep contact deformation of the crust and upper most mantle delineate the north-south lithospheric shortening and thickening in the boundary area of the TOB and the Tarim Basin, which would be helpful to constructing the geodynamical model of the intracontinental mountain-basin-coupling system.