Influence of Evaporating Under the Clouds on the Precipitation Stable Isotope in the Transition Zone Between Tibetan Plateau and Arid Region of China

Consideration of stable isotopes in precipitation is valuable for investigating hydrological processes.Therefore,correcting the measured isotopic composition of precipitation under below-cloud evaporation is necessary.An accurate description of the underlying processes affecting stable isotopic composition of precipitation could help improve our understanding of the water cycle.The transitivity between monsoonal and arid climates was reflected by the evaporation rate of falling raindrops in precipitation in the Qilian Mountains,a typical transition zone between Tibetan Plateau and arid region of China.Considering 1310 precipitation event-scale samples,based on stable isotope analysis method,the mean below-cloud evaporation rate(f)in the study area was measured as 12.00%during the summer half-year(May-October).The evaporation rate on the northern slopes(12.70%)of the Qilian Mountains in China was significantly higher than that on the southern slopes(9.98%).The transition between monsoonal and arid climates was reflected in the evaporation rate of falling raindrops during precipitation in the Qilian Mountains of China.Below-cloud evaporation contributed to a noticeable enrichment of stable isotopes in the precipitation in the study area.The monthly precipitationδ^(18)O enrichment rate in the Qilian Mountains of China from May to October was 29.18%,23.35%,25.60%,22.99%,31.64%,and 14.72%,respectively.For every 1.00%increase in the evaporation rate of raindrops in Qilian Mountains of China,the changes in the concentration of oxygen isotopes from the bottom of the clouds to the ground increased by 0.92‰;however,with an evaporation rate of<5.00%,for every 1.00%increase in the evaporation rate of raindrops the changes in the concentration of oxygen isotopes from the bottom of the clouds to the ground increased by 1.00‰could also be observed.Furthermore,altitude was an important factor affecting below-cloud evaporation in the study area.

Driving Analysis on Ecological Security in Vulnerable Transition Areas of Mountain and Plain

[Objective] This study aimed to investigate the driving mechanism of eco- logical security in vulnerable areas in mountain and plain. [Method] The ecological security evaluation index system of Lincheng County was established using PSR model. Driving mechanism was analyzed in total system and subsystems respectively by the principal components. The ecological safety driving factor was calculated through the total system and subsystem respectively. And the intersection was adopt- ed as dominant driving factor. [Result] A total of 10 indices including density index of rivers, land degradation index, farmland drought and flood insurance yield, human in- terference index, population density, the natural population growth rate, per capita GDP, the R＆D funds spending accounts for the proportion of GDP, laborer by edu- cation degree and three industry accounted for the proportion of GDP, are the domi- nant driving factors of the regional ecological security. [Conclusion] This study will pro- vide reasonable and feasible advice for the benign development of the area.

Discussion on position of China’s north-south transitional zone by comparative analysis of mountain altitudinal belts

The Qinling Mountains has always been regarded as an essential dividing line between the warm temperate zone and the subtropical zone in eastern China and plays a vital role in the geoecological pattern of China.However,there is controversy about the specific location of this geographical boundary in the academic community.As a product of the combined effects of zonal and non-zonal factors,the mountain altitudinal belts(MABs)can reflect both the horizontal zonality and the vertical zonality of vegetation distribution.Using the MAB information,we can not only profoundly understand the complex mountain system of QinlingDaba Mountains but can also judge its nature as a geographical boundary more scientifically.Therefore,based on the comparative analysis of basal belt,dominant belt characteristics and belt structure characteristics of the MABs in Qinling-Daba Mountains,subtropical and temperate mountains,this paper analyzed the MAB differences and similarities among Qinling-Daba Mountains,subtropical and temperate typical mountains,to reveal the vegetation distribution characteristics in the north-south transitional zone.The results show that:(1)The MABs of the southern part of QinlingDaba Mountains(southern slope of the Daba Mountains)are the same or similar to those of the Subtropical Mountains,and the MABs of the northern part of Qinling-Daba Mountains(northern slope of the Qinling Mountains)are similar to those of the temperate mountains.While it shows obvious transitional characteristics in the vast area between the northern slope of the Daba Mountains and the southern slope of the Qinling Mountains:the basal belts gradually transit from the evergreen broadleaved forest belt(basal belt in subtropical mountains)to the evergreen and deciduous broad-leaved mixed forest belt,and the dominant belts also transit from the evergreen broad-leaved forest belt to the evergreen and deciduous broad-leaved mixed forest belt or the deciduous broad-leaved forest belt.(2)The transitional zone between the subtropical zone and the warm temperate zone is located between the northern slope of the Daba Mountains and the southern slope of the Qinling Mountains.The southern boundary of the transitional zone is along the northern slope of Shennongjia Mountain-the northern slope of Micang Mountain-Baishuijiang Nature Reserve,and the northern boundary is along the southern slope of Funiu Mountain-the southern slope of Taibai Mountain-Lianhua Mountain.Additionally,in the transitional zone,the average temperature in January is between-5°C and 1°C,the annual average temperature is between 10°C and 13°C except Hanzhong Basin and Hanshui Valley,and the accumulated temperature above 10°C ranges from 2000°C to 4000°C,the annual rainfall is about 800-1000 mm.The results provide a scientific basis for revealing the characteristics of China’s north-south transitional zone and scientific division of the boundary between the subtropical zone and warm temperate zone in China.

Interdecadal variation of drought patterns and associated influencing factors in the north-south transitional zone of China

In the context of global warming,escalating water cycles have led to a surge in drought frequency and severity.Yet,multidecadal fluctuations in drought and their multifaceted influencing factors remain inadequately understood.This study examined the multidecadal changes in drought characteristics(frequency,duration,and severity)and their geographical focal points within China's north-south transitional zone,the Qinling-Daba Mountains(QDM),from 1960 to 2017 using the Standardized Precipitation Evapotranspiration Index(SPEI).In addition,a suite of eight scenarios,correlation analysis,and wavelet coherence were used to identify the meteorological and circulation factors that influenced drought characteristics.The results indicate the following:(1)From 1960 to 2017,the QDM experienced significant interdecadal variations in drought frequency,duration,and severity,the climate was relatively humid before the 1990s,but drought intensified thereafter.Specifically,the 1990s marked the period of the longest drought duration and greatest severity,while the years spanning 2010 to 2017 experienced the highest frequency of drought events.(2)Spatially,the Qinling Mountains,particularly the western Qinling Mountain,exhibited higher drought frequency,duration,and severity than the Daba Mountains.This disparity can be attributed to higher rates of temperature increase and precipitation decrease in the western Qinling Mountain.(3)Interdecadal variations in droughts in the QDM were directly influenced by the synergistic effects of interdecadal fluctuations in air temperature and precipitation.Circulation factors modulate temperature and precipitation through phase transitions,thereby affecting drought dynamics in the QDM.The Atlantic Multidecadal Oscillation emerges as the primary circulation factors influencing temperature changes,with a mid-1990s shift to a positive phase favoring warming.The East Asian Summer Monsoon and El Ni?o-Southern Oscillation are the main circulation factors affecting precipitation changes,with positive phase transitions associated with reduced precipitation,and vice versa for increased precipitation.

Spatial variations of terrain and their impacts on landscape patterns in the transition zone from mountains to plains—A case study of Qihe River Basin in the Taihang Mountains

Terrain plays a key role in landscape pattern formation, particularly in the transition zones from mountains to plains.Exploring the relationships between terrain characteristics and landscape types in terrain-complex areas can help reveal the mechanisms underlying the relationships. In this study, Qihe River Basin, situated in the transition zone from the Taihang Mountains to the North-China Plain, was selected as a case study area. First, the spatial variations in the relief amplitudes(i.e.,high-amplitude terrain undulations) were analyzed. Second, the effects of relief amplitudes on the landscape patterns were indepth investigated from the perspectives of both landscape types and landscape indices. Finally, a logistic regression model was employed to examine the relationships between the landscape patterns and the influencing factors(natural and human) at different relief amplitudes. The results show that with increasing relief amplitude, anthropogenic landscapes gradually give in to natral landscapes. Specifically, human factors normally dominate the gentle areas(e.g., flat areas) in influencing the distribution of landscape types, and natural factors normally dominate the highly-undulating areas(e.g., moderate relief areas). As for the intermediately undulating areas(i.e.,medium relief amplitudes), a combined influence of natural and human factors result in the highest varieties of landscape types. The results also show that in micro-relief areas and small relief areas where natural factors and human factors are more or less equally active,landscape types are affected by a combination of natural and human factors.The combination leads to a high fragmentation and a high diversity of landscape patterns. It seems that appropriate human interferences in these areas can be conducive to enhancing landscape diversity and that inappropriate human interferences can aggravate the problems of landscape fragmentation.

基于贺兰山青海云杉(Picea crassifolia)树轮对过去202a最低气温的重建

在全球变暖的影响下,全球水文气候发生深刻变化,而季风与非季风过渡带地区气候复杂多样,所以摸清该地区过去长期气候变化规律是亟待解决的问题。利用36棵青海云杉(Picea crassifolia)的66个树轮样芯建立了季风与非季风过渡带典型地区(中国贺兰山地区)1798—2016年(219 a)的青海云杉树轮宽度年表,并且通过皮尔逊相关法分析了树轮宽度年表与该地气候因子的相关性。结果表明:(1)青海云杉径向生长与该地的年平均最低温(R2=0.638,P<0.001)关系密切,利用线性回归方程重建贺兰山1815—2016年年平均最低温序列,重建方程的缩减误差和有效系数分别为0.808、0.482。(2)重建的年平均最低温序列在19世纪整体气温偏低,与学术界公认的“小冰期”一致,到19世纪后期,气温逐渐回升,并且气温序列出现了显著的暖期和极暖年,气温在19世纪50和90年代以及20世纪90年代发生3次气温突变。(3)Morlet小波分析显示了6 a、21 a和46~56 a的周期性分布特征。南方涛动、太平洋十年涛动和大西洋多年代际涛动是这种周期性变化的驱动因素。(4)大尺度空间相关分析表明重建的气温序列对大尺度区域的气温变化具有较好的空间表征,如内蒙古大部和宁夏大部。进而重建的季风与非季风过渡带典型地区年平均最低气温序列揭示了该地的气候变化特征,为全球气候变化研究提供参考。

中国南北过渡带油松径向生长对气候因子的响应研究——以鸡公山国家级自然保护区为例

本研究以河南省信阳市鸡公山自然保护区的油松林为研究对象,利用树木年轮学方法建立了油松径向生长宽度年表,其特征值表明,油松标准年表的质量较高,包含较多的气候信息,能反映气候变化对树木生长的影响。标准年表与鸡公山南北气象站(麻城和信阳站)的气象因子相关结果发现:油松生长与鸡公山南侧麻城气象站几乎与所有月份气温都呈负相关,与当年5—7月气温(6月的平均气温,5、6月平均最高气温和6、7月平均最低温度)呈显著负相关,而与几乎所有月份相对湿度都呈正相关,表明过渡带南侧高温带来的土壤水分胁迫对油松生长主要起着限制作用,南侧春末夏初4—6月相对湿度是油松生长的限制因子;鸡公山北侧信阳气象站生长季及生长季后期8—9月气温(8月平均气温、8、9月平均最低气温)对油松生长有明显的促进作用,上年7—8月相对湿度是油松生长的限制因子,北侧生长季后期9月降水对油松生长的促进作用具有滞后效应。滑动相关分析显示出,近几年油松生长对过渡带北侧信阳气象站8—9月平均气温的正响应趋势增强;在气候变暖的情景下,受到高温抑制(亚热带的麻城气温负相关),油松生长南界可能会向北移动。油松响应气候变暖的生长动态研究旨在为过渡带森林管理与更新提供基础数据支持。

THE FEATURE AND EVALUATION OF ECOTONE IN CHINA

Based on explicating the definition of ecotone, this paper discussed emphatically the distribution and features of joint zone between land and water, transition zone between mountains and plains, and intersection zone between agricultural and animal husbandry regions. The geographic environment of the three ecotones were evaluated, their developing tendency predicted and the corresponding measures to be taken in the 21st century pointed out.

中国南北过渡带地理结构与范围研究

东西向横穿中国中部的昆仑—秦岭巨型构造系使得我国自然环境产生了巨大的南北分异,但目前对于中国南北分界线的位置和南北过渡带范围的划分仍存在争议。本文对秦巴山地和江淮地区的自然地理结构与范围进行了深入的分析,从而确定了中国南北过渡带的范围和性质。研究表明,中国南北过渡带由西部的秦岭—大巴山系和东部的江淮低山平原两部分组成,以地带性的常绿落叶阔叶混交林为主要标志,与之对应的主要气候指标是最冷月均温0~4℃、极端最低气温为-10~-20℃;秦岭南坡下部常绿阔叶树种的出现不是亚热带开始的标志,而是南北植物交错区的开始或者严格意义上南北过渡的开始;江淮地区具有明显的夏季高温、冬季低温的特点,冬季气候指标比夏季温度指标更具控制作用;秦巴山地的存在和江淮地区冬季低温是我国南北过渡带形成的主要原因,从而发育了长约1750 km、平均宽度400 km、面积约70万km2的中国南北过渡带。南北过渡带的概念比南北分界线和北亚热带的提法更能够反映秦巴山地和江淮地区的自然地理特点,也更能体现我国自然地理格局的独特性质,对于认识中国地域系统结构与功能具有更重要的科学意义。

准噶尔盆地南缘中段第一、二排构造演化与油气成藏

盆-山转换带一直是构造地质研究的重点及难点,开展其构造样式、形成演化及成藏过程解析,对揭示山前复杂构造的控藏作用、指导盆-山转换带的油气勘探均具有重要意义.综合运用地震资料解释、断层活动定量分析、流体包裹体均一温度测定等手段,结合构造物理模拟实验,对准噶尔盆地南缘中段第一、二排构造特征、演化过程、形成机制及控藏机理进行了综合研究.结果表明:南缘中段第一、二排构造主要发育基底卷入与盖层滑脱断层控制的双重构造样式.侏罗纪末期,齐古-昌吉褶皱带初具雏形;古近纪末期,霍玛吐褶皱带开始形成;第四纪,褶皱带被断裂强烈改造,形成断褶带,滑脱层对应力向盆内传递起重要作用.南缘中段发育多套烃源岩,形成了多期差异性的以“自生自储”和“古生新储”为主要组合模式的成藏过程.

中国南北过渡带常绿落叶阔叶混交林的地域分异与地带性问题

中国南北过渡带主要的自然地理属性之一就是发育了常绿落叶阔叶混交林,但对于该类混交林的内部结构及地理地带性的认识一直存在较多分歧。根据国家科技基础资源调查专项“中国南北过渡带综合科学考察”获取的野外植被样地调查数据,分析了秦岭—大巴山地区1条东西向样线及3条南北向样线(三门峡—神农架;西安—达州;天水—广元)木本植物的组成结构变化。结果表明:东西方向上,秦岭南麓仅在旬阳段常绿阔叶成分比较多(重要值27.57%),其余各段都很低,尤其是最西端的迭部—白龙江段以及人类活动集中的汉中—洋县段,常绿阔叶成分重要值几乎为零;南北方向上,常绿阔叶木本植物的物种数、多度比例和重要值3个指标自北向南都具有缓慢增加的趋势。总体上,秦巴山地的落叶阔叶树种占据绝对优势,常绿阔叶树种仅在大巴山南部出现较多,但重要值在20%以下。因而,从植被组成结构来看,秦巴山地植被呈现强烈的过渡性质,且树种组成成分更偏向于暖温带属性。秦巴山地以东的淮河两岸广大区域,更容易受到冬季低温的影响,致使在中国大陆中部形成内部结构复杂、过渡性非常强烈的宽大的气候-植被过渡带,明显区别于暖温带落叶阔叶林地带和亚热带常绿阔叶林地带,具有最高级自然地带的属性特征。

江汉平原过渡带黏性层状土弥散试验与模拟研究

为研究江汉平原—大别山区过渡带黏性层状土中溶质迁移的规律,以保守性阴离子Br-为示踪剂,通过等温吸附试验、一维弥散试验、HYDRUS-1D软件模拟反演手段,研究了Br-在黏性层状土中的吸附参数、迁移规律,模拟反演其弥散参数。结果表明:(1)Freundlich模型和Langmuir模型均能较好的拟合吸附试验结果,随着土壤中黏粒比例的增大,土壤对Br-的饱和吸附量有所增加;(2)层状土中土壤质地与结构均会影响穿透曲线的形状,但一维饱和土柱中的弥散过程主要取决于含水介质系统中黏性颗粒的占比,黏粒的增加会对溶质运移产生阻碍作用;(3)通过HYDRUS-1D软件构建模型反演弥散参数,R2均大于0.991,拟合效果较好,分析发现层状土中无论土壤组成类型还是层厚及排序的影响,其本质都是改变了土壤的平均孔隙流速从而影响弥散作用,平均孔隙流速越小其弥散系数越小;(4)试验中粉质黏土弥散系数约为0.005~0.048 cm^(2)/d,远远小于下部砂土弥散系数0.524~7.477 cm^(2)/d,差值达到了至少两个数量级,表明研究区内厚层黏土为控制地层,会较大程度阻碍地下水中溶质运移,上部含水层中的污染物或有机质很难穿透该层向下迁移,具有良好的截污性能。研究结果对江汉平原过渡带地下水环境保护、水质治理具有重要应用价值。

Latitudinal differentiation and patterns of temperate and subtropical plants in the Qinling-Daba Mountains

Geographically,the Qinling-Daba Mountains serve as the main body of the north-south transitional zone of China.However,the transitional patterns of their plant species still need to be clarified.This study analyzed latitudinal variations of plant species richness,relative importance values(RIV),and plant species abundance based on plant community field survey data for 163 sample sites along three north-south transect lines in the eastern,middle,and western parts of the study areas.The difference in RIV between subtropical and temperate species(SND-RIV)was selected to reveal the latitudinal interlacing pattern of northern and southern plant species.Along the eastern(Sanmenxia-Yichang),middle(Xi’an-Dazhou),and western(Tianshui-Guangyuan)transects,the richness and RIV of subtropical plant species increased while those of temperate plant species decreased from north to south.In the eastern transect,temperate plant species richness and RIV were the highest at Shennongjia and Funiu Mountain,respectively,because of their high elevations.In the middle transect,subtropical plant species richness and RIV were the highest in the Daba Mountains.In the western transect,richness and RIV were higher for subtropical than temperate plant species from the south of Longnan.The crisscrossing areas of northern and southern plant species were∼180 km,∼100 km,and∼60 km wide for the eastern,middle,and western transects,respectively,showing a narrowing trend from east to west.For the eastern and western transects,decreases in subtropical plant species distribution from south to north could be attributed to a decrease in mean annual precipitation in the same direction.However,for the middle transect,mean annual temperature had a slightly greater influence on plant species’latitudinal distribution than the moisture index.This study provides a more solid scientific basis for future investigations of this key geographical boundary in China.

江西省河长制效能分级分区评价体系构建

为实现河长制分级分区评价,提出行政分级和地形地貌分区相结合的矩阵化效能评价模式,从河长制的六大任务和社会公众等7个方面分别构建市县(18个指标)、乡村(16个指标)2个级别的河长制效能评价指标体系,利用层次分析法得出山丘区、平原和滨湖区2个区域不同特性的指标权重,建立二级模糊综合评价模型对江西省赣州市、南昌市、上犹县、樟树市、梅水乡和张家山街道等典型区域进行评价,评价结果分别为好、中、好、好、中、好。结果表明:在山丘区,水资源保护是影响各级河长制效能的主要因素,水生态修复影响了赣州市、上犹县效能,水污染防治影响了上犹县、梅水乡效能,而在平原和滨湖区水污染防治是影响各级河长制效能的主要因素,此外水资源保护影响了南昌市、樟树市效能,水生态修复影响了樟树市效能。结果与实际情况基本一致,表明该评价体系适用于河长制效能分级分区评价。

东秦巴山地自然保护地样区植被物候的过渡特性研究

本文选取东秦巴山地神农架样区和伏牛山样区2个自然保护地集中分布地域作为研究区,通过比较分析南、北2个不同地域精细尺度的物候格局,探讨东秦巴山地植被物候的南北过渡特征。基于近20年时序遥感影像信息综合提取植被物候空间格局,从物候总体分布特征、物候与高程关系等多方面分析2个研究区物候特征的联系和差异,并在物候信息高程校正的基础上,对比分析同高程、不同地域物候的南北变化特征及规律。研究结果表明,在不考虑地形高程影响的情况下,神农架样区植被生长季开始期晚于伏牛山样区8.49 d;生长季长度则短于伏牛山样区9.31 d;不同海拔高度对于南、北2个研究区植被物候影响也不一样,海拔每增高100 m,神农架样区生长季开始时间推迟1.97 d,生长季长度缩短2.54 d;伏牛山样区生长季开始时间推迟2.05 d,生长季长度缩短1.56 d。经过高程校正,神农架样区整体植被生长季开始时期比伏牛山样区早2.52 d,植被生长季长度比伏牛山样区植被生长季长度增长了3.91 d。比较2个研究区主要的植被类型落叶阔叶林和常绿针叶林之后可发现,神农架样区的落叶阔叶林生长季开始时间比伏牛山样区早3.25 d;常绿针叶林的生长季开始时间比伏牛山样区早1.78 d,生长季长度长11.96 d。在植被物候信息高程校正前后,2个研究区的植被生长季开始期相对早晚、生长季长度相对大小均发生反转。这种物候格局的复杂分布特征,较好地呈现了多列山地阻隔和分异作用所形成的东秦巴山地植被复杂过渡特征。

Spatial patterns of Pinus tabulaeformis and Pinus massoniana forests in Qinling-Daba Mountains and the boundary of subtropical and warm temperate zones

The Qinling Mountains is not only the geographical boundary between North and South China,but also the boundary between subtropical and warm temperate zones.It plays an important role in the geo-ecological pattern of China.However,there is controversy about the specific location of this geographical boundary in academic community due to the complexity,transition and heterogeneity of the transitional zone,as well as the differences in the delimitation indicators and research purposes.To further reveal the characteristics of the North-South transitional zone and clarify the specific location of the geo-ecological boundary between North and South China,combined with SRTM topographic data,temperature and precipitation data,Pinus massoniana forest and Pinus tabulaeformis forest,which represent subtropical coniferous forest in South China and temperate coniferous forest in North China respectively,were chosen to analyze their spatial distributions in the Qinling-Daba Mountains and the climatic conditions at their boundary with the climatic indexes of annual precipitation,the coldest month(January) average temperature,the warmest month(July) average temperature and the annual average temperature.The results show that:(1) Pinus massoniana and Pinus tabulaeformis forests and the climate indicators of their boundary can be used as one of the vegetation-climate indexes for the delimitation of subtropical and warm temperate zones.The boundary between the subtropical coniferous forest(Pinus massoniana forest) and temperate coniferous forest(Pinus tabulaeformis forest) is located along the south slope of Funiu Mountain to the north edge of Hanzhong Basin(the south slope of Qinling Mountains) at an altitude of 1000–1200 m,where the climatic indictors are stable:the annual precipitation is about 750–1000 mm,the annual average temperature is about 12–14℃,the coldest monthly average temperature is 0–4℃,and the warmest monthly average temperature is about 22–26℃.(2) It can be more scientifically to delimitate the boundary of subtropical and warm temperate zones in China by comprehensively considering the vegetation-climate indicators.Additionally,the boundary between subtropical and warm temperate zones in Qinling-Daba Mountains should be a transitional zone consisting of the boundaries of coniferous forests,broad-leaved forests and shrubs between subtropical and warm temperate zones.The results provide a scientific basis for the selection of delimitation index of subtropical and warm temperate zones.

Distribution patterns of SOC/TN content and their relationship with topography,vegetation and climatic factors in China’s north-south transitional zone

The spatial distributions and variation mechanism of key soil indices in the Qinling-Daba Mountains are important indicators for the identification of the transitional effect and regional characteristics of the north–south transitional zone in China.This manuscript analyzes the spatial variations in soil organic carbon(SOC)and total nitrogen(TN)and corresponding relationships with major geographical factors based on spatial analysis and geostatistics considering data obtained from the Second National Soil Survey.The results indicate that the spatial distributions of the SOC and TN contents are consistent,and three high-content areas,one secondary high-content area and one low-content area are observed.High content values are located in the high-altitude regions of the Qinling-Daba Mountains and mountainous areas to the west of the Jialing River,the low-content area occurs on the north slope of the Qinling Mountains,and the secondary high-content area mainly encompasses both sides of the Hanjiang River and regions in the Qinling-Daba Mountains at altitudes below 1000 m.The SOC and TN contents vary between the above two ranges,with the gradual increase in content revealing a horn-shaped pattern.Considering the spatial variations and functions of vegetation,topography and climate factors,it is found that the SOC/TN range in the secondary high-content area remains consistent along the 1000 m contour line,the upper limit of the transitional mountain altitudinal belt,the 0℃isotherm line in January and the 24℃isotherm line in July.This region constitutes the main body of the transitional zone between the subtropical and warm temperate zones,and the northern boundary is roughly distributed along the Dujiangyan-Maoxian-Pingwu-Wenxian line to the west of the Jialing River and the 1000 m contour line on the southern slope of the Qinling Mountains,while the southern boundary occurs along the Dujiangyan-Beichuan-Qingchuan line to the west of the Jialing River and the 1000 m contour line on the northern slope of the Daba Mountains.SOC/TN spatial variation provides a reference for the demarcation of the subtropical and warm temperate zones,and further identification of the soil processes and ecological effects in typical regions can help reveal multidimensional transitional characteristics and variation mechanisms.

3种地形上高杆塔雷击次数规律的研究

为了更有效地研究电力线路杆塔在不同地形下防雷性能的差异性,笔者针对珠三角地区中的杆塔在3种不同地形下受雷击次数分布差异性问题进行分析。首先建立区域雷击统计模型,研究统计区域雷击次数的方法。然后基于雷电定位系统,对珠三角地区三种地形上10年落雷情况进行统计分析,得出电力杆塔在山区受雷击次数略高于平原建筑区,平原建筑区上的杆塔虽受高层建筑屏蔽保护作用,不易受雷击,但杆塔所处区域受雷击次数高于平原植被区。经过统计得出平原建筑落雷次数增长率明显增大,而山区与平原植被区落雷次数增长率呈下降趋势。最后利用电场仿真软件仿真坐落在3种地形上杆塔周围的电场分布趋势,验证统计出区域雷击次数规律的合理性。

六盘山植物区系基本特征的初步分析

六盘山位于陕甘宁交接地区,属于半湿润气候向半干旱气候的过渡带,是黄土高原生物多样性最丰富的地区之一,有维管植物836种,隶属于93科,359属。本区属于泛北极植物区、中国-日本森林植物亚区、华北植物地区的黄土高原亚地区。全部种子植物可分为13个分布区类型和12个变型,以北温带分布类型为主,与其他植物区系联系广泛,但特有属较贫乏。六盘山与小陇山、太白山和中条山的属相似性系数较高,均达60%以上,表明几座山体处于相似的生物气候背景之下,地理隔离性不明显。与贺兰山的属相似性系数低于60%,因为贺兰山位于干旱的荒漠与半荒漠区,可能有地理隔离作用。

北京南部地壳精细结构深地震反射探测研究

为了研究北京平原区的地壳结构特征、断裂的空间展布、断裂活动性以及深浅构造关系,在北京平原区的南部完成了1条长90km的深地震反射剖面.探测结果表明,该区地壳以双程反射时间(TWT)6～7s的强反射带Tc为界分为上地壳和下地壳,上地壳厚约18～19km,下地壳厚约16～17km,Moho界面深度约为34～35km.该区结晶基底起伏变化较大,上、下地壳分界面和Moho界面都是一个具有一定厚度的过渡带.上地壳反射层位丰富,断裂构造发育,构造形态清晰.在夏垫断裂西北,剖面揭示了4～5组能量较强的反射震相,表现为典型的隆起区特征;在夏垫断裂东南,上部为一套向东南倾伏的密集强反射层,下部为一套形态各异、结构复杂的强反射层,这些反射具有典型的沉积盆地特征,盆地最深处约为11km.剖面揭示的地壳深断裂倾角较陡,向上切穿了上、下地壳分界面,延伸到上地壳沉积盆地的底部,向下切穿了壳幔过渡带,与上部断裂和沉积盆地构成了独特的组合关系.