西藏地区旱涝等级划分及时空分布特征

利用西藏22个站点1969-1998年逐日降水资料，采用d指数旱涝等级方法。按夏季（5-9月），初夏（5-6月），盛夏（7-8月）时段进行了旱涝等级划分。采用EOF分析方法对全区22个站点旱涝等级展开分解，得出西藏地区的旱涝时空分布特征，主要类型和周期，而且对西藏地区夏季（5-9月）的旱涝做了预测。     

西藏自治区的土壤理化特性探讨

通过对西藏自治区主要土壤类型的实地踏勘和采样分析,并结合全国土壤普查资料的结果进行分析,揭示了本区土壤具有4点特性:即多砾石性、砂质性、成土幼年性和低矿化的富有机质性。因此,在改良本区土壤时,应重视去石与防治沙漠化措施,加强矿质养分肥料的施用,稳定有机肥的投入。     

西藏自治区土壤侵蚀特点及现状

西藏自治区地域辽阔,土壤侵蚀复杂多样。本文在野外调查的基础上,对西藏自治区土壤侵蚀特点作了全面论述,并对西藏自治区不同类型土壤侵蚀区的土壤侵蚀现状做了较全面的分区评价。同时取雅江中游地区19个县作为典型区域,利用1999年1:20万TM遥感图像土壤侵蚀解译结果,对该典型区域的土壤侵蚀现状作了定量评价。最后根据评价结果,对西藏自治区土壤侵蚀的发展趋势做了预测。     

西藏尼玛砂金矿中金和银的提纯与精炼

为提纯与精炼西藏尼玛砂金矿中的金和银，在王水介质中制作供还原的Au液，选择草酸作为还原剂很容易将Au还原，而且不与其他金属离子反应。砂金的提纯与精炼要经还原Au液、排除HNO3和砂金的2次溶解及Au的还原。尾渣以NaCO3、硼砂、KNO3为配料在焦炭炉中进行熔炼和泼珠，进而分离出金、银。在提取银的操作中，采用饱和NaCl水溶液。制定的金、银王水法提纯与精炼流程所产出金锭的成色大于等于99．99％，银锭成色大于等于99．90％。     

西藏南部郎杰学群碎屑物质来源的古水流证据

新近对西藏山南琼果和贡嘎地区(特提斯喜马拉雅北亚带)弱变质的上三叠统深海—半深海沉积地层——郎杰学群地质填图调查,在出露槽模沉积构造的37个古水流点获得了43组数据。赤平投影数据恢复后发现,这一地区主力古水流有南东140°～160°和南西190°～210°两个方向。这一分析结果为郎杰学群沉积物来自北边(未知块体)而非印度次大陆的观点提供了有力证据。     

西藏羌塘地区几个地质构造问题

提出了西藏羌塘地区的六个地质构造问题。包括冈瓦纳与欧亚大陆古特提斯界线；羌塘地区是否存在加里东期或更古老基底；羌塘地区的地层系统及其对比；狮头山、黑熊山一带蓝片岩的地球动力学意义；龙木错─双湖蛇绿岩的性质、成因及年代；羌塘盆地中三叠世以前是一个统一的盆地还是分属两大陆的边缘海盆等。这些问题的解决将有助于更加清楚、完整地认识青藏高原的地质历史过程。     

Reconstruction of atmospheric CO2 from ice-core data and the deep-sea record of ontong Java plateau: the Milankovitch chron

We provide a reconstruction of atmospheric CO₂ from deep-sea sediments, for the past 625000 years (Milankovitch chron). Our database consists of a Milankovitch template of sea-level variation in combination with a unique data set for the deep-sea record for Ontong Java plateau in the western equatorial Pacific. We redate the Vostok ice-core data of Barnola et al. (1987). To make the reconstructions we employ multiple regression between deep-sea data, on one hand, and ice-core CO₂ data in Antarctica, on the other. The patterns of correlation suggest that the main factors controlling atmospheric CO₂ can be described as a combination of sea-level state and sea-level change. For best results squared values of state and change are used. The square-of-sea-level rule agrees with the concept that shelf processes are important modulators of atmospheric CO₂ (e.g., budgets of shelf organic carbon and shelf carbonate, nitrate reduction). The square-of-change rule implies that, on short timescales, any major disturbance of the system results in a temporary rise in atmospheric CO₂.     

青藏高原Pn波研究进展及问题

简要总结了青藏高原地区Pn波速度结构、各向异性研究进展；介绍了Pn波速度结构、各向异性等在岩石圈结构、构造背景反映等方面的应用研究进展。分析了目前青藏高原Pn波研究中存在的一些问题。     

Changes in soil organic carbon and other physical soil properties along adjacent Mediterranean forest, grassland, and cropland ecosystems in Turkey

Cultivation, overgrazing, and overharvesting are seriously degrading forest and grassland ecosystems in the Taurus Mountains of the southern Mediterranean region of Turkey. This study investigated the effects of changes on soil organic carbon (SOC) content and other physical soil properties over a 12-year period in three adjacent ecosystems in a Mediterranean plateau. The ecosystems were cropland (converted from grasslands in 1990), open forest, and grassland. Soil samples from two depths, 0–10 and 10–20 cm, were collected for chemical and physical analyses at each of cropland, open forest, and grassland ecosystems. SOC pools at the 0–20 cm depth of cropland, forest, and grassland ecosystems were estimated at 32,636, 56,480, and 57,317 kg ha⁻¹, respectively. Conversion of grassland into cropland during the 12-year period increased the bulk density by 10.5% and soil erodibility by 46.2%; it decreased SOM by 48.8%, SOC content by 43%, available water capacity (AWC) by 30.5%, and total porosity by 9.1% for the 0–20 cm soil depth (p<0.001). The correlation matrix revealed that SOC content was positively correlated with AWC, total porosity, mean weight diameter (MWD), forest, and grassland, and negatively with bulk density, pH, soil erodibility factor, and cropland. The multiple regression (MLR) models indicated that any two of the three ecosystems and one of the two soil depths accounted for 86.5% of variation in mean SOC values ((p<0.001).