Human impacts to mountain streams

Mountain streams are here defined as channel networks within mountainous regions of the world. This definition encompasses tremendous diversity of physical and biological conditions, as well as history of land use. Human effects on mountain streams may result from activities undertaken within the stream channel that directly alter channel geometry, the dynamics of water and sediment movement, contaminants in the stream, or aquatic and riparian communities. Examples include channelization, construction of grade-control structures or check dams, removal of beavers, and placer mining. Human effects can also result from activities within the watershed that indirectly affect streams by altering the movement of water, sediment, and contaminants into the channel. Deforestation, cropping, grazing, land drainage, and urbanization are among the land uses that indirectly alter stream processes. An overview of the relative intensity of human impacts to mountain streams is provided by a table summarizing human effects on each of the major mountainous regions with respect to five categories: flow regulation, biotic integrity, water pollution, channel alteration, and land use. This table indicates that very few mountains have streams not at least moderately affected by land use. The least affected mountainous regions are those at very high or very low latitudes, although our scientific ignorance of conditions in low-latitude mountains in particular means that streams in these mountains might be more altered than is widely recognized. Four case studies from northern Sweden (arctic region), Colorado Front Range (semiarid temperate region), Swiss Alps (humid temperate region), and Papua New Guinea (humid tropics) are also used to explore in detail the history and effects on rivers of human activities in mountainous regions. The overview and case studies indicate that mountain streams must be managed with particular attention to upstream/downstream connections, hillslope/channel connections, process domains, physical and ecological roles of disturbance, and stream resilience.     

Delineation of a large ultramafic massif embedded within a major SW Pacific suture using gravity methods

Gravity studies have delineated the largest ultramafic massif in New Zealand, embedded within a buried major SW Pacific crustal suture zone. This suture records terrane collision onto the Gondwana margin during the Mesozoic and separates a forearc terrane from an outboard accretionary prism terrane. It can be traced throughout the length of New Zealand as the Junction Magnetic Anomaly and contains the Permian Dun Mountain Ophiolite Belt, which in the South Island of New Zealand is characterized by a string of isolated ultramafic massifs in a sheared matrix of serpentinite and sediment. Our analysis reveals a steep gravity gradient at the suture boundary which is attributed to a newly recognised density contrast (0.1 Mg m^− 3) between terranes of the forearc and the accretionary prism. The massif itself is marked by the occurrence of a strong, elongate residual gravity anomaly (+ 120 g.u.) extending 50 km along the suture and coincident with the Junction Magnetic Anomaly. It is modelled, at its southern end, as a dense, 15 km wide source body, extending to at least 6 km in depth. In conjunction with detailed aeromagnetic data, this modeling indicates the presence of a spindle-shaped ultramafic massif, analogous to, but larger than similar bodies found within the Dun Mountain Ophiolite Belt elsewhere. This fabric of sheared serpentinites enclosing ultramafic massifs therefore extends at least the length of New Zealand and probably beyond. In part it may result from accretion of asperities in the subducting plate, but it is also due to disruption of larger ultramafic bodies during subsequent strike-slip motion, which caused the remarkable linearity of the Dun Mountain Belt. Given the common occurrence of the plate tectonic processes involved, it is likely that such structures can be found in other regions around the world using similar geophysical potential field methods.     

西昆仑提孜那甫河与喀拉喀什河山前河谷地貌对比及构造-气候意义

通过对部署在西昆仑新疆叶城县南提孜那甫河与和田市南喀拉喀什河山前3条河谷阶地横剖面所提供的实际资料和ESR、14C年代测试数据的分析,结果表明:①西昆仑这两条相距250km河流属于同一个山前地貌单元;②剖面Ⅰ、剖面Ⅲ的T4、T3、T2、T1分别形成于约100kaB.P.、80kaB.P.、50kaB.P.、30kaB.P.;③依据形成时代,剖面Ⅰ的T3、T2、T1分别对应剖面Ⅱ的T4、T3、T2,剖面Ⅱ的T1形成于8.5kaB.P..对横剖面的对比并结合纵剖面,认为该地区100kaB.P.以来山前河谷地貌的形成,气候作用大于新构造作用;8.5kaB.P.前后发生过一次新构造的抬升作用.     

大兴安岭北部扎兰屯脉岩群的地球化学特征及其地质意义

在内蒙古扎兰屯东侧出露一群中性岩脉,产在晚石炭世扎兰屯花岗岩体中,脉岩岩性为闪长玢岩,似斑状结构,斑晶为斜长石、碱性长石、角闪石、辉石和石英,基质为细粒状的上述矿物及玻璃质。其锆石 U-Ph LA-ICP-MS 谐和年龄为120.6±4.7Ma,基质~(40)Ar/~(39)Ar 坪年龄为122.2±0.6Ma,侵位时代可确定为早白垩世。脉岩的 SiO_2含量为56.88%～61.69%,Al_2O_3含量为15.83%～19.29%,全碱含量较高,为5.32%～8.37%。稀土元素总量为121.4×10~(-6)～144.1×10~(-6),轻重稀土分馏系数较大,(La/Yh)_N 值为6.24～10.40。富集大离子亲石元素(LILE),亏损重稀土元素(HREE)。δEu 表现为弱的负异常(0.92～0.79)。在同位素地球化学方面,具有正的ε_(Nd)(t)值( 3.06)和较低的初始~(87)Sr/56 Sr 值(0.7047～0.7053);岩石铅同位素均一,具幔源特征。综合考虑脉岩年代学和地球化学研究结果,本文认为研究的脉岩形成于伸展背景下重熔的新底侵玄武质下地壳的岩浆侵入作用。     

国道317线鹧鸪山隧道工程引道生态护坡方案设计

鹧鸪山隧道地处高海拔的国家天然林保护区，引道边坡裸露面与周围自然环境极不协调，边坡绿化势在必行。本考在详细调查引道边坡情况的基础上，按照边坡的坡度、高度和物质组成，对边坡进行了分类。结合当地气象水文等条件．针对不同类型边坡拟定采用生态基材、三维网客土绿化、植生穴等绿化工法，提出了适宜于不同绿化地段的乔灌草配置模式和耀草配置模式，并进行了相应的物种选择。     

对崀山丹霞地貌旅游开发的几点思考

随着旅游业的蓬勃发展，丹霞地貌的旅游开发已成为旅游开发的一个重要方面。运用对比分析法．通过与国内丹霞地貌旅游开发较好的广东丹霞山、福建武夷山进行比较，分析了新宁崀山丹霞地貌旅游开发的特点和制约因素。崀山丹霞地貌旅游业的开发，要积极发挥资源优势、加强区域合作．同时借鉴其它旅游区特别是丹霞地貌区旅游开发的经验和教训，加强丹霞地貌景观的保护，促进崀山旅游业持续、快速、健康的发展。     

天目山柳杉树轮δ13C方位变化及成因探讨

对天目山两株柳杉(分别简称CF-1与CF-3),分别测定了不同方位上的树轮δ13C年序列。方差分析表明:天目山柳杉树轮δ13C值存在显著的方位差异和年际变化。不同方位上δ13C序列年际变化趋势基本一致,但极值出现的方位存在明显的年际漂移。同一树体各方位之间及两树体对应方位之间δ13C值均存在较好的相关性,表明区域环境背景条件对树轮δ13C值方位变化及年际变化趋势的影响是共同的。重点分析了局部环境差异对树轮δ13C方位变化的影响。不同坡向及树冠不同方位光照条件的差异是造成树轮δ13C值方位变化的主要原因。     

长白山圆池泥炭常量和微量元素分布特征及其环境意义

探讨了长白山圆池泥炭常量和微量元素的分布规律。利用荷兰W ardenaar泥炭采样器野外采取四个新鲜泥炭剖面,现场用不锈钢面包刀从上至下按1~2 cm间隔准确分层取样。针对圆池特殊的自然地理条件,应用澳大利亚产型号为GBC-906原子吸收分光光度计分析了A l、Ti、Mn、Fe、Pb、Zn、Cu;应用日本岛津产型号为7500 ICP等离子体发射光谱仪分析了Ca、Mg、Na、K等元素在不同类型泥炭剖面的积累。研究分析了不同泥炭剖面所测元素的分布趋势及富集状况,结果表明:高位泥炭剖面Mn、Zn和Pb由下层至上层含量有明显增高的特点,其在表层的富集,表明该地区大气污染的环境问题有加重的趋势。     

利用MODIS和ASAR资料估算青藏高原念青唐古拉山脉地区冰雪范围及厚度

利用可见光和微波卫星遥感资料分析了青藏高原念青唐古拉山脉地区冰雪范围和厚度的季节变化.结果表明:青藏高原念青唐古拉山脉地区冰雪范围的季节变化非常明显,2003年4月上旬、5月中旬、7月下旬和9月下旬的冰雪范围分别占选定研究区域的28.9%、69.9%、11.6%和14.7%.在选定的西布冰川区域,由微波遥感得到的冰雪厚度季节变化也非常明显,5月份厚度的数值最大,7月份最小.由于主动微波观测受地面高程、地形和夏季冰雪融化等因素的影响比较大,主动微波遥感在大面积估算冰雪厚度还有一定困难,有待将来作进一步的深入研究.