Millennial-scale evolution of Hunshandake Desert and climate change during the Holocene in Inner Mongolia,northern China

The Hunshandake Desert is located at the northern edge of the East Asian monsoon region,and its natural environment is sensitive to monsoonal changes.Geologic records suggest that desert evolution corresponding to climate change had experienced several cycles in the Holocene,and the evolutionary process can be distinguished by four dominant stages according to changing trends of the environment and climate.(1) Holocene Ameliorative Period(11.0-8.7 cal ka B.P.),when the desert area gradually shrank following an approaching warm-wet climate and strengthening summer monsoon.(2) Holocene Optimum(8.7-6.0 cal ka B.P.),when the majority of moving sand dunes were stabilized and vegetation coverage quickly expanded in a suitable warm-wet climate and a strong summer monsoon.(3) Holocene Multivariate Period(6.0-3.5 cal ka B.P.),during a low-amplitude desert transformed between moving and stabilized types under alternating functions of cold-dry with warm-wet climate,and winter monsoon with summer monsoon.(4) Holocene Decay Period(since 3.5 cal ka B.P.),when the desert area tended to expand along with a weakened summer monsoon and a dry climate.     

面向未来的海面变化研究

长期以来以地质时期海面变化过程等理论性研究为主要方向的海面变化研究经过７０年代在观念、方法和资料积累方面的突破，自８０年代初期以来进入了以“面向未来”为基调的成熟发展的新阶段，出现了一大批关于未来海面变化幅度及其影响和对策的研究成果，形成了较为完整的研究体系。９０年代初以来的几年间，世界海面研究的活跃领域是地质历史时期（例如ＬＧＭ，５ｅ等阶段）的海面实况、极地冰原对气候变化的反应、海面控制原理、海面模型以及绝对海面的航天测量技术与应用等方面。这一情况在一定程度上体现了“预测热”之后的“冷思考”。中国海面变化研究近年来取得了令世人瞩目的迅速发展，今后应注意引进先进技术方法，加强学科间的交叉合作，发掘自身的优势，向纵深发展     

The consequences of land-cover changes on soil erosion distribution in Slovakia

Soil erosion is a complex process determined by mutual interaction of numerous factors. The aim of erosion research at regional scales is a general evaluation of the landscape susceptibility to soil erosion by water, taking into account the main factors influencing this process. One of the key factors influencing the susceptibility of a region to soil erosion is land cover. Natural as well as human-induced changes of landscape may result in both the diminishment and acceleration of soil erosion. Recent studies of land-cover changes indicate that during the last decade more than 4.11% of Slovak territory has changed. The objective of this study is to assess the influence of land-cover and crop rotation changes over the 1990–2000 period on the intensity and spatial pattern of soil erosion in Slovakia. The assessment is based on principles defined in the Universal Soil Loss Equation (USLE) modified for application at regional scale and the use of the CORINE land cover (CLC) databases for 1990 and 2000. The C factor for arable land has been refined using statistical data on the mean crop rotation and the acreage of particular agricultural crops in the districts of Slovakia. The L factor has been calculated using sample areas with parcels identified by LANDSAT TM data. The results indicate that the land-cover and crop rotation changes had a significant influence on soil erosion pattern predominately in the hilly and mountainous parts of Slovakia. The pattern of soil erosion changes exhibits high spatial variation with overall slightly decreased soil erosion risks. These changes are associated with ongoing land ownership changes, changing structure of crops, deforestation and afforestation.     

1971-2009 年珠穆朗玛峰地区尼泊尔境内气候变化

利用珠穆朗玛峰南坡尼泊尔境内(科西河流域) 的10 个气象站1971-2009 年月平均气温、月平均最高、最低气温和逐月降水资料, 采用线性趋势、Sen 斜率估计、Mann-Kendall 等方法分析区域气候变化状况及其时空特征, 并与珠穆朗玛峰北坡地区气候进行比较, 分析了珠穆朗玛峰地区气候变化的特征与趋势。结果表明:(1) 1971-2009 年间, 珠穆朗玛峰南坡年平均气温为20.0℃, 线性升温率为0.25℃/10a, 与北坡主要受年平均最低气温影响相反, 增幅主要受年平均最高气温升高的影响, 并且在1974 年及1992 年间出现两次显著增温, 增温特别明显的月份为2 月和9 月;(2) 该地区降水变化的局地性较强, 近40 年间年平均降水量为1729.01 mm, 年平均降水量以每年约4.27 mm的线性增幅有所增加, 但并不显著, 且降水月变化和季变化特征均不明显;(3) 由于珠穆朗玛峰南坡受到季风带来暖湿气流和喜马拉雅山阻挡的双重影响, 珠峰南坡的年平均降水量远高于北坡;(4) 珠穆朗玛峰南坡气温变暖的海拔依赖性并不明显, 且南坡地区的变暖趋势并没有北坡变暖趋势明显。     

抗高温泡沫钻井液体系评价研究

高频钻井液压力波信息传输技术传输速率高,是实现自动化、智能化钻井的关键技术之一,由于高频钻井液压力波在传输过程中存在较大的衰减,阻碍了该技术的现场应用,探明其衰减规律对于高速传输技术开发具有重要意义。在假设同一钻柱截面钻井液压力相等且钻井液流速存在径向分布的基础上,基于二维轴对称瞬态流动理论,采用小信号分析方法,综合考虑了压力波信号参数、钻柱尺寸及钻井液参数的影响,建立了高频钻井液压力波衰减模型并给出了适用条件。最后采用地面实验验证了该模型的正确性。随后分析钻井液压力波频率、压力波传输距离、钻井液密度及黏度、钻柱内径对高频压力波衰减的影响。结果表明：高频钻井液压力波幅值衰减量随钻井液压力波频率、压力波传输距离及钻井液黏度的增加而增大,且变化规律为指数型;幅值衰减量受频率影响最大,并随钻井液密度及钻柱内径增加逐渐减小。本研究可为高频钻井液压力波信息传输技术研发提供理论指导。

     

Why is Shirase Glacier turning its flow direction eastward?

We applied an image correlation method to Japanese Earth Resources Satellite-1 (JERS-1) synthetic aperture radar (SAR) data obtained from 1996 to 1998 to examine flow velocity within Shirase Glacier, Antarctica. From the grounding line to the downstream region of the glacier, the obtained ice-flow velocity was systematically higher on the western streamline than the eastern. The differences between the two streamlines were 0.31 km/a in 1996 and 0.37 km/a in 1998, significantly larger than the error estimate of 0.03 km/a. The direction of ice flow was about 312° at the grounding line and changed to 327° at 10 km, 346° at 20 km and 2° at 30 km downstream from the grounding line. The total accumulated deflection is 50° to the east. Under the assumption of the conservation of ice mass across the glacier, the observed eastward change in flow direction can be explained by an asymmetric deepening of bedrock topography, that is, across the 8 km width of the glacier, the eastern side is 50 m (10%) deeper than the western side. This eastward turning of flow direction appears to be accelerated by tributary inlets, that flow to the north and northeast at 60–75% of the velocity of inlets on the western streamline.     

生态地理学概念界定及其经典案例分析

对生态地理学的概念进行了详细讨论和辨析,并将它与相近学科如生物地理学、生态地理区划、宏生态学等进行了比较分析,界定了生态地理学的概念。研究认为：生态地理学是生态学和地理学的交叉学科,是研究生态系统各组分关系和生态过程的地理空间分布格局或/和时间演变规律及其与地理环境耦合机制的学科。生态地理学的目的是揭示不同环境梯度下或不同时间尺度上生态系统各组分关系和生态过程的普适性规律及其成因。同时,结合国内外野外实验平台介绍,在全球变化等研究领域列举了经典案例进行分析：① 全球不同气候带森林凋落物分解和碳汇功能的研究;② 中国不同陆地生态系统碳通量和碳汇功能研究;③ 中国东北样带和南北样带陆地生态系统的脆弱性与适应性研究;④ 中国北方草地样带尺度的生态系统生态学研究。主要目的是在辨析生态地理学概念的基础上指出未来发展方向,推动生态地理学的发展。     

基于统计模型识别气候变化对农业产量贡献的研究进展

从统计模型与作物机理模型的区别与联系出发, 介绍了识别气候变化对农业产量贡献的3 种主要统计模型, 即时间序列模型、截面模型和面板模型;综述了前人在站点和区域(全球、国家、省级、地区、县级) 尺度对这一问题的研究进展;总结了应用统计模型识别农业产量对气候变化响应敏感性的4 个主要问题, 包括时空尺度问题、产量的非气候趋势去除问题、气候要素间的自相关问题和忽略适应措施的问题;最后针对以上主要问题, 提出了改进建议及今后研究的发展趋势。     

青藏高原高寒草地净初级生产力(NPP)时空分异

基于1982-2009 年间的遥感数据和野外台站生态实测数据,利用遥感生产力模型(CASA模型) 估算青藏高原高寒草地植被净初级生产力(NPP),分别从地带属性(自然地带、海拔高程、经纬度)、流域、行政区域(县级) 等方面对其时空变化过程进行分析,阐述了1982 年以来青藏高原高寒草地植被NPP的时空格局与变化特征。结果表明:① 青藏高原高寒草地NPP多年均值的空间分布表现为由东南向西北逐渐递减;1982-2009 年间,青藏高原高寒草地的年均总NPP为177.2×10¹² gC·yr^-1,单位面积年均植被NPP为120.8 gC·m^-2yr^-1;② 研究时段内,青藏高原高寒草地年均NPP 在112.6~129.9 gC·m^-2yr^-1 间,呈波动上升的趋势,增幅为13.3%;NPP 增加的草地占草地总面积的32.56%、减少的占5.55%;③ 青藏高原多数自然地带内的NPP呈增加趋势,仅阿里山地半荒漠、荒漠地带NPP呈轻微减低趋势,其中高寒灌丛草甸地带和草原地带的NPP增长幅度明显大于高寒荒漠地带;年均NPP增加面积比随着海拔升高呈现"升高—稳定—降低"的特点,而降低面积比则呈现"降低—稳定—升高"的特征;④ 各主要流域草地年均植被NPP均呈现增长趋势,其中黄河流域增长趋势显著且增幅最大。植被NPP和盖度及生长季时空变化显示,青藏高原高寒草地生态系统健康状况总体改善局部恶化。     

树轮稳定同位素记录:进展、问题及展望

树轮稳定同位素比率(δ13 C、δ18O 和δD)变化与树木生长季的气候和环境条件密切相关。控制实验表明, 树轮稳定同位素比率变化可较好地记录树木叶片气孔活动、水分来源、水分利用效率等相关信息, 已成为古气候和全球变化生态学研究的重要代用指标和手段之一。树轮稳定同位素记录能够较好地保留低频气候环境变化信息, 与年轮宽度相结合, 可有效地进行区域古气候重建和全球变化生态学方面的研究。文章综述了树轮稳定同位素的分馏机理及其发展, 系统阐述和评价了利用树轮稳定同位素指标进行古气候和古环境的相关研究成果, 并指出树轮稳定同位素研究在中国未来亟须着重发展的方向。