放牧对青藏高原东缘高寒草甸土壤酶活性及土壤养分的影响

对青藏高原四种不同放牧强度(围栏封育、轻牧、中牧和重牧)高寒草甸的土壤酶活性、土壤养分和植被群落特征进行了研究,探讨了不同放牧强度土壤酶活性和土壤养分及植被群落的相关性.结果表明:各样地土壤酶活性、士壤养分和植被群落特征有较大差异.土壤纤维素酶和淀粉酶活性与土壤有机质、速效氮质量分数及地上生物量变化一致,表现为围栏封育>轻牧>中牧>重牧,然而脲酶活性的变化趋势正好与之相反,表现为随着放牧强度的增加而增加.酸性磷酸酶活性和地下生物量变化一致,表现为轻牧>围栏封育>中牧>重牧.经分析,土壤酶活性和土壤养分密切相关,其中土壤淀粉酶和脲酶活性与土壤养分和植被特征的相关性最好,因此这两种酶活性可以作为评价青藏高原高寒草甸土壤质量的指标之一.

亚洲大陆逃逸构造与现今中国地震活动

2008年5月12日汶川地震让中国地学界强烈感受到深入研究地震地质与构造变形的重要性和肩负防震减灾巨大的社会责任。本文作者从构造地质学家的角度对中国大陆地震分布、成因规律以及发展趋势做了一些讨论。按地震分布,中国大陆可以粗分为两个区域,其交界是一条过渡带。该过渡带的东界是郯庐断裂及其和海南岛的连线,西界是齐齐哈尔—北京—邯郸—郑州—宜昌—贵阳—(越南)河内连成的线,后者其实就是松辽盆地的西界(大兴安岭的东界、太行山的东界、大娄山的东界)。我们不妨将上述两线所夹过渡带称之为"地震区分界线"。分界线以西的广大地区,活动断裂、活动褶皱、活动盆地都与印度板块楔入欧亚大陆造成的青藏高原隆升、快速侧向扩展、亚洲大陆逃逸构造活动有关。流变性较好的造山带(如青藏高原和天山)和流变性较差的古老地块(如塔里木、准噶尔、阿拉善、鄂尔多斯、四川盆地等)在其边界强烈对抗,形成强震。地震区分界线以东的中国沿海地区受太平洋和菲律宾海板块运动的影响也会发生地震,但其强度和频度与该线以西的青藏高原周边、天山、鄂尔多斯地块周缘以及张家口-渤海断裂带上地震低得多。由太平洋板块在日本海沟向西深俯冲形成的地震在中国仅分布在吉林省珲春—汪清一带,这些深源地震对地面工程建筑破坏性不大。处于欧亚、菲律宾海和南海3个板块的交汇部位的我国台湾地震不断。受我国台湾地震的影响,闽粤沿海NW和NE向断裂往往被激活,形成地震。总之,虽然中国大陆的现代地震受太平洋、欧亚、印度和菲律宾海四大板块联合作用控制,但最主要、最直接、影响最大的还是印度板块楔入欧亚大陆造成的青藏高原隆升、快速侧向扩展和大陆逃逸。因此,对中国的地震研究不能仅局限于某区域或某条断裂,而应把整个亚洲大陆逃逸构造作为整体的、统一的"一盘棋"看待。

青藏高原植被覆盖变化及其与气候变化的关系

近几十年来,全球气候变化对青藏高原植被覆盖产生了重要影响。基于青藏高原1981—2005年遥感影像及同期气象数据,结合生态学模型,分析了青藏高原植被覆盖度变化趋势及其与气候变化的关系。结果显示,25 a间,青藏高原温度升高、降水量增加,植被覆盖度呈"整体升高、局部退化"趋势;地表植被改善区主要位于植被低覆盖区,退化区主要位于高覆盖区;从不同植被类型看,除针叶林、阔叶林受采伐影响覆盖度下降外,其他植被覆盖度均不同程度的上升;植被覆盖度变化与同期降水量变化、温度变化均呈正相关,且具有明显的区域差异。

青藏高原探空大气水汽偏差及订正方法研究

水汽是大气的主要成分和降水的主要物质来源。青藏高原大气水汽分布对区域天气和气候有很大影响,为了探讨探空观测的大气水汽总量(R)资料的可靠性,本文以地基GPS遥感的大气水汽总量(G)为参照标准,对拉萨(1999～2010年)和那曲(2003年)的R进行对比分析和偏差(R-G)订正。结果表明:近10多年拉萨站R比G明显偏小,偏小程度随使用不同的探空仪而异。GZZ-2型机械探空仪和GTS-1型电子探空仪多年平均的PW偏差分别为-8.8%和-3.9%,随机误差分别为17.6%和13.6%。近10多年PW偏差变化呈减少趋势,这与探空仪性能改进有关。分析发现,青藏高原PW偏差具有明显季节变化和日变化特征,夏季比冬季明显,1200UTC比0000UTC明显。拉萨站GZZ-2型和GTS-1型探空仪在1200UTC多年平均的PW偏差分别为-15.8%和-7.3%,在0000UTC分别为-1.6%和-0.4%。那曲站GZZ-2型探空仪在1200UTC和0000UTC的PW偏差分别为-12.4%和-0.3%。分析还表明,太阳辐射加热与气温的日变化和季节变化是造成高原PW偏差日变化和季节变化的重要原因。据此,提出了高原PW偏差的订正方法,并以拉萨和那曲站为例进行PW偏差订正,订正后的PW系统偏差显著减少,随机误差也相应得到了改善。

基于牧户行为的草地管理模式--以西藏自治区为例

本研究利用产量和利润最大化理论,基于随机抽样调查构建多元选择模型,探讨不同类型牧户放牧决策差异及导致牧户过度放牧的内在机制,分析牧民家庭收入、畜牧业科技推广、草地管理投入、牧户兼业行为和风险意识等变量对牧户放牧决策的影响,模拟不同政策组合下过度放牧牧户降低牲畜存栏量的意愿。研究表明,1)牧户生产决策受畜产品价格影响大,然而,不同质量畜产品价格差异小,导致牧民忽略畜产品品质而过度追求存栏量,引致草地禁牧政策失效;2)牦牛饲养比重对牧户减少牲畜存量的边际倾向值最大,比重每增加1单位,牧户意愿降低牲畜存栏量5.684单位,由于牦牛饲养草地需求较多,对是否降低存栏量敏感;3)大部分牧户倾向于选择经济效益,寻找兼顾生态与经济,能够有效提高牧户参与的区域生态经济发展战略是未来西藏牧区生态保护与经济发展策略的核心。

青藏高原大气甲烷浓度时空分布变化特征

利用瓦里关大气本底站甲烷观测数据对美国Aqua卫星的AIRS观测结果进行对比分析,并分析研究了2003~2012年青藏高原对流层大气甲烷的时空分布特征,结果表明:1)AIRS观测结果与近地面观测资料变化趋势一致,存在显著的正相关关系,突变时间比较一致,可以用于青藏高原区域的甲烷浓度特征分析。2)青藏高原对流层甲烷浓度在空间分布上存在显著的西北—东南走向的低值带及其南北侧存在4个固定的高值中心,分别位于阿里、那曲、山南和玉树。3)青藏高原甲烷浓度呈现显著随高度而降低的趋势,年平均甲烷浓度分别为1.810ppm(1 ppm=10-6)、1.797 ppm和1.781 ppm。在对流层中层和中上层,甲烷浓度基本呈现低值带最低、南北侧均高的山谷型分布特征。在对流层层顶,以低值带为分界线,呈现明显的南高北低特征。4)青藏高原甲烷浓度随时间呈缓慢上升趋势,平均速度为0.0018 ppm/a,夏季上升最快,秋季上升最慢。5)青藏高原甲烷存在明显的单峰型季节变化特征,夏秋季高,冬春季低,与东部地区冬、夏双峰型特征不同,随着高度上升季节变化更为明显。

青藏高原东北缘寺口子剖面碎屑锆石示踪及其构造意义

位于青藏高原东北缘的寺口子剖面发育巨厚的新生代沉积地层,分析这些沉积物的碎屑来源能够为高原东北缘构造变形过程提供重要证据。本文在寺口子剖面磁性地层年代的约束下,对该剖面27~4 Ma的砂岩样品进行了碎屑锆石示踪研究。研究结果显示27~12 Ma的砂岩样品中锆石U-Pb年龄主要分布在200~470Ma(以230Ma、440Ma为峰值年龄)、1600~1890Ma、2100~2450Ma,与>12 Ma的砂岩样品相比,7 Ma的砂岩样品中新增了锆石U-Pb年龄为720~980Ma的年龄峰值;4Ma的砂岩样品中锆石U-Pb年龄谱主要为200~490Ma。这些样品中,1600~1890Ma与2100~2450Ma的锆石εHf(t)值偏负(-31.1~5.1),720~980Ma的锆石具有负的εHf(t)值为-15.1^-1.7,200~470Ma的锆石εHf(t)值范围较宽为-11.2~12.5。通过与周围构造单元对比,发现1600~1890Ma与2100~2450Ma的锆石可能源于与鄂尔多斯地块西缘,720~980 Ma的锆石与宁夏中部的南华山、西华山岩石具有亲缘性,U-Pb年龄为200~470Ma的锆石则与六盘山南部岩浆岩的锆石U-Pb年龄一致。寺口子剖面碎屑锆石示踪与半定量估算表明:六盘山南部可能在27Ma已隆升、变形,成为宁夏南部盆地的物源区,而宁夏南部盆地晚中新世的物源变迁可能反映了海原-六盘山断裂带强烈的构造变形。

青藏高原昆仑山求勉雷克塔格冰川春季表面温度空间变化特征及其影响因素

通过对2013年春季在青藏高原昆仑山求勉雷克塔格冰川上取得的冰川表面温度资料的分析,研究了该冰川表面温度空间变化特征及其影响因素.结果表明:该冰川表面(粒雪)温度在晴天时较多云或阴雪天时偏低,这可能与晴天时冰川表面吸收的部分热量用于粒雪消融而不是粒雪层升温有关;晴天时该冰川表面温度随海拔的升高而降低,其递减率值为0.58℃·(100m)-1,较自由大气的气温递减率值略偏低;晴天时,冰川表层粒雪层厚度对其表面温度具有重要的影响,二者之间呈显著的正相关关系,并且粒雪层厚度每增加10cm,其冰川表面温度会升高约0.46℃.结合青藏高原其他冰川表面温度的观测结果,揭示出当冰川表面存在消融时其表面温度日变化幅度较小,一般只有几度.

Magnetostratigraphy and Anisotropy of Magnetic Susceptibility of the Lulehe Formation in the Northeastern Qaidam Basin

The timing of onset of deposition of the Lulehe Formation is a significant factor in understanding the genesis of the Qaidam basin and the evolution of the Tibetan Plateau. Here, we describe a detailed magnetostratigraphic and magnetic fabric study of the middle and lower parts of the Lulehe Formation. A total of 234 samples were collected from 117 sites throughout a thickness of almost 460 m of fluvial and lacustrine deposits at the Xitieshan section in the northeastern Qaidam basin. Out of these sites, 94 sites yielded well-defined characteristic remanent magnetization components by stepwise thermal demagnetization and were used to establish the magnetostratigraphy of the studied section. Based on correlation with the geomagnetic polarity timescale, the studied section spans the period from 53.8 Ma to 50.7 Ma. Our results show a three-fold decrease in sedimentation rates as well as marked change in facies from braided river to delta and shore-shallow lake around 52.6 Ma, which suggests tectonic uplift of the northeastern Qaidam basin margin ridge was rapid at the onset of formation of the Qaidam basin and subsequently weakened after 52.6 Ma. The anisotropy of magnetic susceptibility results indicate that tectonic compression stress had reached the northeastern Tibetan Plateau by the early stages of Indo-Eurasian plate collision and that the direction of stress in the study area was NE-SW. Furthermore, a weakening of tectonic compression stress around 52.6 Ma is consistent with sedimentary records. The age of initial deposition of the Qaidam basin （around 53.8 Ma） was almost synchronous with that of the Qiangtang, Hoh Xil, Xining, and Lanzhou basins, which implies that stress was transferred rapidly through the Tibetan Plateau during or immediately after the onset of Indo-Eurasian collision.

Cenozoic Stratigraphy Deformation History in the Central and Eastern of Qaidam Basin by the Balance Section Restoration and its Implication

The Qaidam Basin, located in the northern margin of the Qinghai-Tibet Plateau, is a large Mesozoic-Cenozoic basin, and bears huge thick Cenozoic strata. The geologic events of the Indian- Eurasian plate-plate collision since -55 Ma have been well recorded. Based on the latest progress in high-resolution stratigraphy, a technique of balanced section was applied to six pieces of northeast- southwest geologic seismic profiles in the central and eastern of the Qaidam Basin to reconstruct the crustal shortening deformation history during the Cenozoic collision. The results show that the Qaidam Basin began to shorten deformation nearly synchronous to the early collision, manifesting as a weak compression, the deformation increased significantly during the Middle and Late Eocene, and then weakened slightly and began to accelerate rapidly since the Late Miocene, especially since the Quaternary, reflecting this powerful compressional deformation and rapid uplift of the northern Tibetan Plateau around the Qaidam Basin.

Apatite Fission Track Evidence of Uplift Cooling in the Qiangtang Basin and Constraints on the Tibetan Plateau Uplift

The Qiangtang basin is located in the central Tibetan Plateau. This basin has an important structural position, and further study of its tectonic and thermal histories has great significance for understanding the evolution of the Tibetan Plateau and the hydrocarbon potential of marine carbonates in the basin. This study focuses on low temperature thermochronology and in particular conducted apatite fission track analysis. Under constraints provided by the geological background, the thermal history in different tectonic units is characterized by the degree of annealing of samples, and the timing of major （uplift-erosion related） cooling episodes is inferred. The cooling history in the Qiangtang basin can be divided into two distinct episodes. The first stage is mainly from the late Early Cretaceous to the Late Cretaceous （69.8 Ma to 108.7 Ma）, while the second is mainly from the Middle- Late Eocene to the late Miocene （10.3 Ma to 44.4 Ma）. The first cooling episode records the uplift of strata in the central Qiangtang basin caused by continued convergent extrusion after the Bangong- Nujiang ocean closed. The second episode can be further divided into three periods, which are respectively 10.3 Ma, 22.6-26.1 Ma and 30.8-44.4 Ma. The late Oligocene-early Miocene （22.6-26.1 Ma） is the main cooling period. The distribution and times of the earlier uplift-related cooling show that the effect of extrusion after the collision between Eurasian plate and India plate obviously influenced the Qiangtang basin at 44.4 Ma. The Qiangtang basin underwent compression and started to be uplifted from the middle-late Eocene to the early Oligocene （45.0-30.8 Ma）. Subsequently, a large-scale and intensive uplift process occurred during the late Oligocene to early Miocene （26.1-22.6 Ma） and the basin continued to undergo compression and uplift up to the late Miocene （10.3 Ma）. Thus, uplift-erosion in the Qiangtang basin was intensive from 44.5 Ma to about 10 Ma. The timing of cooling in the second episode shows that the uplift of the Qiangtang basin was caused by the strong compression after the collision of the Indian plate and Eurasian plate. On the whole, the new apatite fission-track data from the Qiangtang basin show that the Tibetan Plateau started to extrude and uplift during 45-30.8 Ma. The main period of uplift and formation of the Tibetan Plateau took place about 22.6-26.1 Ma, and uplift and extrusion continued until the late Miocene （10.3 Ma）.

Gravity observations along the eastern margin of the Tibetan Plateau and an application to the Lushan MS 7.0 earthquake

This paper introduces relative and absolute gravity change observations in the eastern portion of the Tibetan Plateau. We analyze and discuss a change that occurred in 2010 in the gravity along the eastern margin of the plateau and the relationship between this change and the 2013 Lushan Ms7.0 earthquake. Our results show that： （1） before the Lushan MsT.0 earthquake, gravity anomalies along the eastern margin of the Tibetan Plateau changed drastically. The Lushan earthquake occurred at the bend of the high gradient zone of gravity var- iation along the southern edge of the Longmenshan fault zone. （2） The 2013 Lushan earthquake occurred less than 100 km away from the epicenter of the 2008 Wenchuan earthquake. Lushan and Wenchuan are located at the center of a four- quadrant section with different gravity anomalies, which may suggest that restoration after the Wenchuan earthquake may have played a role in causing the Lushan earthquake. （3） A medium-term prediction based on changes in gravity anoma- lies was made before the Lushan Ms7.0 earthquake, in par- ticular, a prediction of epicenter location.

Heterogeneous strain regime in the eastern margin of Tibetan Plateau and its tectonic implications

The eastern margin of Tibetan Plateau is one of the most active zones of tectonic deformation and seismicity in China. To monitor strain buildup and benefit seismic risk assessment, we constructed 14 survey-mode global position system （GPS） stations throughout the northwest of Longmenshan fault. A new GPS field over 1999-2011 is derived from measurements of the newly built and pre-existing stations in this region. Sequentially, two strain rate fields, one preceding and the other following the 2008 MwT.9 Wenchuan earthquake, are obtained using the Gausian weighting approach. Strain field over 1999-2007 shows distinct strain partitioning prior to the 2008 MwT.9 Wenchuan earthquake, with compression spreading over around Longmenshan area. Strain fieldderived from the two measurements in 2009 and 2011 shows that the area around Longmenshan continues to be under striking compression, as the pattern preceding the Wenchuan earthquake, implying a causative factor of the sequent of 2013 Mw6.7 Lushan earthquake. Our GPSderived dilatation shows that both the Wenchuan and Lushan earthquakes occurred within the domain of pro- nounced contraction. The GPS velocities demonstrate that the Longriba fault underwent slight motion with the faultnormal and -parallel rates at 1.0 -4- 2.5 mm and 0.3 4-2.2 mm/a; the Longmenshan fault displayed slow activity, with a fault-normal rate at 0.8 ± 2.5 mm/a, and a fault-parallel rate at 1.8 4- 1.7 mm/a. Longriba fault is on a par with Longmenshan fault in strain partitioning to accommodate the southeastward motion of eastern margin of the Tibetan Plateau. Integrated analysis of principal strain tensors, mean principal stress, and fast directions of mantle anisotropy shows that west of Sichuan is characterized as mechanically strong crust-mantle coupling.

Winter soil CO_2 efflux in two contrasting forest ecosystems on the eastern Tibetan Plateau, China

Significant CO2 fluxes from snow-covered soils occur in cold biomes. However, little is known about winter soil respiration on the eastern Tibetan Plateau of China. We therefore measured winter soil CO2 fluxes and estimated annual soil respiration in two contrasting coniferous forest ecosystems （a Picea asperata plantation and a natural forest）. Mean winter soil CO2 effluxes were 1.08 μmol m-2 s-1 in the plantation and 1.16 μmol m-2 s-1 in the natural forest. These values are higher than most reported winter soil CO2 efflux values for temperate or boreal forest ecosystems. Winter soil respiration rates were similar for our two forest ecosystems but mean soil CO2 efflux over the growing sea- son was higher in the natural forest than in the plantation. The estimated winter and annual soil effluxes for the natural forest were 176.3 and 1070.3 g m-2, respectively, based on the relationship between soil respiration and soil temperature, which were 17.2 and 9.7 % greater than their counterparts in the plantation. The contributions of winter soil respiration toannual soil efflux were 15.4 % tor the plantation and 16.5R for the natural forest and were statistically similar. Our results indicate that winter soil CO2 efflux from frozen soils in the alpine coniferous forest ecosystems of the eastern Tibetan Plateau was considerable and was an important component of annual soil respiration. Moreover, reforesta- tion （natural coniferous forests were deforested and refor- ested with P. asperata plantation） may reduce soil respiration by reducing soil carbon substrate availability and input.

CHARACTERISTICS OF UT/LS CARBON MONOXIDE INTRASEASONAL OSCILLATIONS AND THEIR IMPACT FACTORS OVER THE TIBETAN PLATEAU AND ITS ADJACENT AREAS IN SUMMER

The study presented herein investigated the main characteristics of carbon monoxideintraseasonal variability and evaluated its possible impact factors using the upper troposphere and lowerstratosphere (UT/LS) Aura Microwave Limb Sounder (MLS) observations over Tibetan Plateau and itsadjacent areas in summer (June to August) of 2005 and 2006. Observations show a persistent constituentextreme extending up into the UT/LS throughout summer, as well as a temporally reversed phase variationbetween the carbon monoxide and ozone in UT/LS. The intraseasonal oscillations (ISOs) of carbonmonoxide during summer are investigated by using methods of wavelet and band pass filter analysis. It isfound that ISOs over the Tibetan Plateau have periods of 10 to 20 days and 30 to 60 days. The formermainly appeared in upper troposphere while the latter in lower stratosphere. Further analysis shows thatthese two periods of ISOs in UT/LS are mainly in phase to the activities of convection over the south of theplateau and the variation of South Asia High, respectively. The above two factors and their dynamicalcoupling may be responsible for the tracer ISOs at different levels.

青藏高原北缘三危山断裂东北段的古地震事件

三危山断裂位于青藏高原北缘,为阿尔金断裂带的一条重要分支,研究其晚更新世以来的活动特征,可为全面地把握青藏高原北缘的地震活动规律提供基础资料。在对三危山断裂东北段(十工口子西-双塔)进行遥感资料解译、野外地质地貌调查和探槽开挖,并分析探槽内揭露的断层、地层和楔状堆积三者之间关系的基础上,结合相关堆积物的光释光断代研究,最终利用逐次限定法分析了古地震事件发生的年代。研究发现该断裂段上晚更新世以来发生了3次古地震事件:距今最远的一次事件E1发生在约5.3万年前,接近5.3万年;第二次事件E2发生于距今约4万年之前,5.3万年之后,更接近4万年;最近的一次事件E3发生于距今7.42—2.47ka。由于晚更新世以来探槽开挖地点地层沉积的不连续,或地层沉积之后发生的侵蚀作用,导致探槽内揭露出的古地震事件存在严重缺失。但可以确定的是,在晚更新世中晚期和全新世,三危山断裂东北段上确有破裂地表的古地震事件发生。

Response of Lakes to Climate Change in Xainza Basin Tibetan Plateau Using Multi-Mission Satellite Data from 1976 to 2008

Changes in the lake areas of Xainza basin in the past 33 years(1976 to 2008) were studied using Landsat data from Multispectral Scanners(1973-1977), Thematic Mapper(1989-1992, 2007-2009), and Enhanced Thematic Mapper Plus(1999-2002). The results indicated that lakes in the study area evidently expanded from 1976 to 2008, with total expansion of 1512.64 km2. The mean annual air temperature presented an upward trend with certain fluctuations from 1966 to 2008. The air temperature rise rates in the cold season(0.31°C/10a) were higher than those in the hot season(0.24°C/10a), in the Xainza station example. Precipitation exhibited evident seasonal differences. Mean annual precipitation in hot season is 281.48 mm and cold season is 32.66 mm from 1966 to 2008 in study area. Precipitation in the hot season was the major contributor to the increase in annual precipitation. Grey relational analysis(GRA) was used to study the response of lake areas to climatic factors. The mean air temperature and precipitation were selected as compared series, and the lake areas were regarded asthe reference series. The grey relational grade(GRG) between compared series and reference series were calculated through GRA. The results indicated that changes in lake areas were mainly affected by climatic factors in the hot season. Lakes in this region were classified into three grades, namely, Grades I, II, and III according to the recharge source and elevation. The GRGs of each series varied for different grade lakes: the area of Grade III lakes were the most relevant to the hot season factors, the GRGs of precipitation and air temperature were 0.7570 and 0.6606; followed by the Grade II lakes; Grade I lakes were more sensitive to the air temperature.

Response of Biomass Spatial Pattern of Alpine Vegetation to Climate Change in Permafrost Region of the Qinghai-Tibet Plateau,China

Alpine ecosystems in permafrost region are extremely sensitive to climate changes.To determine spatial pattern variations in alpine meadow and alpine steppe biomass dynamics in the permafrost region of the Qinghai-Tibet Plateau,China,calibrated with historical datasets of above-ground biomass production within the permafrost region's two main ecosystems,an ecosystem-biomass model was developed by employing empirical spatialdistribution models of the study region's precipitation,air temperature and soil temperature.This model was then successfully used to simulate the spatio-temporal variations in annual alpine ecosystem biomass production under climate change.For a 0.44°C decade-1 rise in air temperature,the model predicted that the biomasses of alpine meadow and alpine steppe remained roughly the same if annual precipitation increased by 8 mm per decade-1,but the biomasses were decreased by 2.7% and 2.4%,respectively if precipitation was constant.For a 2.2°C decade-1 rise in air temperature coupled with a 12 mm decade-1 rise in precipitation,the model predicted that the biomass of alpine meadow was unchanged or slightly increased,while that of alpine steppe was increased by 5.2%.However,in the absence of any rise in precipitation,the model predicted 6.8% and 4.6% declines in alpine meadow and alpine steppe biomasses,respectively.The response of alpine steppe biomass to the rising air temperatures and precipitation was significantly lesser and greater,respectively than that of alpine meadow biomass.A better understanding of the difference in alpine ecosystem biomass production under climate change is greatly significant with respect to the influence of climate change on the carbon and water cycles in the permafrost regions of the Qinghai-Tibet Plateau.

夏季青藏高原附近云顶分布和对流层顶高度的关系（英文）

以CALIPSO卫星观测的云顶高于对流层顶事件为参考,亚洲夏季风区该事件的发生率占北半球的49%,进一步通过对大尺度连续方程的诊断估计,在该区域上升气流的作用下,亚洲季风区在北半球夏季对流层向平流层物质输送总量中贡献远大于50%。南亚高压反气旋对云顶高度的影响体现在:在南侧的高空东风急流核附近(约16.5 km),云顶出现的概率最大,垂直方向达到了10%每500米;北侧的高空西风急流下方,云顶垂直概率大于3%每500米的区域被抑制在11 km以下,远离热力学对流层顶但接近动力学对流层顶。

^(137)Cs tracing of the spatial patterns in soil redistribution,organic carbon and total nitrogen in the southeastern Tibetan Plateau

The southeastern Tibetan Plateau,which profoundly affects East Asia by helping to maintain the stability of climate systems,biological diversity and clean water,is one of the regions most vulnerable to water erosion,wind erosion,tillage erosion,freeze-thaw erosion and overgrazing under global climate changes and intensive human activities.Spatial variations in soil erosion in terraced farmland(TL),sloping farmland(SL)and grassland(GL)were determined by the^(137)Cs tracing method and compared with spatial variations in soil organic carbon(SOC)and total nitrogen(total N).The^(137)Cs concentration in the GL was higher in the 0-0.03 m soil layer than in the other soil layers due to weak migration and diffusion under low precipitation and temperature conditions,while the^(137)Cs concentration in the soil layer of the SL was generally uniform in the 0-0.18 m soil layer due to tillage-induced mixing.Low^(137)Cs inventories appeared at the summit and toe slope positions in the SL due to soil loss by tillage erosion and water erosion,respectively,while the highest^(137)Cs inventories appeared at the middle slope posi-tions due to soil accumulation under relatively flat landform conditions.In the GL,the^(137)Cs data showed that higher soil erosion rates appeared at the summit due to freeze-thaw erosion and steep slope gradients and at the toe slope position due to wind erosion,gully erosion,freeze-thaw erosion and overgrazing.The^(137)Cs inventory generally increased from upper to lower slope positions within each terrace(except the lowest terrace).The^(137)Cs data along the terrace toposequence showed abrupt changes in soil erosion rates between the lower part of the upper terrace and the upper part of the immediate terrace over a short distance and net deposition on the lower and toe terraces.Hence,tillage erosion played an important role in the soil loss at the summit slope positions of each terrace,while water erosion dominantly transported soil from the upper terrace to the lower terrace and resulted in net soil deposition on the flat lower terrace.The SOC inventories showed similar spatial patterns to the^(137)Cs inventories in the SL,TL and GL,and significant correlations were found between the SOC and^(137)Cs inventories in these slope landscapes.The total N inventories showed similar spatial patterns to the inventories of,37Cs and SOC,and significant correlations were also found between the total N and^(137)Cs inventories in the SL,TL and GL Therefore,^(137)Cs can successfully be used for tracing soil,SOC and total N dynamics within slope landscapes in the southeastern Tibetan Plateau.