Population ecology of the endangered Himalayan Yew in Khokhan Wildlife Sanctuary of North Western Himalaya for conservation management     

Shreekar Pant  S. S. Samant 《山地科学学报》2008,5(3):257-264

The Himalayan Yew （Taxus baccata subsp, wallichiana） is an endangered native high value medicinal plant of the Himalayan Region. The several medicinal properties of the bark and leaves of this species have increased its risk of extinction due to pressures for utilization. It is also subjected to harvest for fuelwood. The species does not regenerate well from seed and that is another risk factor. The objective of this research was to investigate the population ecology of the species as a foundation for its conservation. Six forest communities in the Khokhan Wildlife Sanctuary where the species is present were sampled. The abundance of the species, impacts of harvesting and its current regeneration patterns indicate that it may soon be extirpated from the Sanctuary. A plan for conserving the remaining sub-populations is presented. It could provide a template for conservation in other locations where the species is at risk.  相似文献   

同幅双速跟踪成像CCD相机模拟电路系统设计     

李勇明  李彬华  王慧娟  卢诚 《天文研究与技术》2007,4(4):376-382

讨论了同幅双速跟踪成像技术对CCD相机系统的特殊要求,详细地介绍了该相机前端模拟系统的设计思想、系统结构和主要的电路模块。对系统中一些关键电路模块进行了仿真和测试,并对仿真和测试结果进行比较分析,以检验电路系统设计的合理性。  相似文献   

Testing turbulence model at metric scales with mid-infrared VISIR images at the VLT     

A. Tokovinin  M. Sarazin  A. Smette 《Monthly notices of the Royal Astronomical Society》2007,378(2):701-708

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鄱阳湖流域气候变化事实研究     

占明锦  殷剑敏  孔萍 《气象与减灾研究》2013,(3):18-24

基于江西79个气象站1961-2010年逐日气温和降水观测资料,采用滑动t检验和Mann-kendell法对鄱阳湖流域年平均气温进行突变检验分析,利用线性回归方法分别对鄱阳湖流域气温、降水量、降水日数、降水强度等要素的变化趋势进行了分析。结果表明：（1）1961-2010年鄱阳湖流域年平均气温为18.0℃,升温趋势明显,升温率达0.16℃/（10 a）,在1996年出现显著突变。冬季升温趋势最明显,夏季气温虽呈上升趋势,但不显著。（2）流域平均年降水量为1643 mm,呈略增多趋势。20世纪60-80年代和21世纪00年代降水量偏少,90年代降水量相对偏多。最大年降水量出现在1975年,为2149.6 mm;最小年降水量出现在1963年,为1111.6 mm。（3）流域年降水日数总体呈现下降趋势,下降率约为6.9 d/（10 a）。其中,小雨日数下降最为显著,下降率约为7.1 d/（10 a）;中雨日数呈略下降趋势;大雨和暴雨日数呈现略增加趋势。（4）流域年降水强度总体呈现上升趋势,每10 a上升约0.52 mm/d,说明流域降水集中度增大,强降水事件增多。  相似文献   

1960～2018年中国高温热浪的线性趋势分析方法与变化趋势     

张嘉仪  钱诚 《气候与环境研究》2020,25(3):225-239

高温热浪直接影响人体健康和作物生长。研究全球变暖背景下我国高温热浪发生率的趋势是气候变化研究的基本问题之一,可为人们的生产生活等提供重要的科学信息。目前对于高温热浪趋势的研究大都使用最小二乘（Ordinary Least Squares,OLS）方法估计趋势,结合学生t检验判断趋势的统计显著性。本文审视了以往常用方法在研究我国高温热浪发生率的线性趋势时的适用性。首先,以2018年东北局部地区因当年高温日数异常多而形成离群值的例子展开,说明OLS方法估计趋势时对离群值非常敏感,造成虚假趋势。进一步,通过正态分布检验和自相关计算,发现1960~2018年中国至少有91.14%站点、90.06%格点的高温日数和92.18%站点、87.74%格点的热浪次数的序列不服从正态分布,而且多数存在自相关。采用一种不易受离群值影响并考虑自相关的非参数方法,本文对1960～2018年中国站点和格点、4个典型区域以及全国平均的高温日数和热浪次数的线性趋势做出了更为准确的估计。研究发现,高温日数显著增多的站点主要出现在华南和西北地区,热浪次数呈显著增多趋势的站点目前几乎仅限于华南地区和新疆的个别站点;区域平均而言,仅有华南区域和西北区域的高温日数和热浪次数是显著增多的,华北区域和东北区域趋势并不显著;全国平均的高温日数和热浪次数都是显著增多的。本文对高温热浪的趋势及其显著性估计、统计预测的方法选择上有重要参考价值。  相似文献   

A new methodology for building local climate change scenarios: A case study of monthly temperature projections for Mexico City     

《Atmósfera》2014,27(4):429-449

This paper proposes a new methodology for generating climate change scenarios at the local scale based on multivariate time series models and restricted forecasting techniques. This methodology offers considerable advantages over the current statistical downscaling techniques such as: (i) it provides a better representation of climate at the local scale; (ii) it avoids the occurrence of spurious relationships between the large and local scale variables; (iii) it offers a more appropriate representation of variability in the downscaled scenarios; and (iv) it allows for compatibility assessment and combination of the information contained in both observed and simulated climate variables. Furthermore, this methodology is useful for integrating scenarios of local scale factors that affect local climate. As such, the convenience of different public policies regarding, for example, land use change or atmospheric pollution control can be evaluated in terms of their effects for amplifying or reducing climate change impacts.  相似文献   

Sedimentary stylolite networks and connectivity in limestone: Large-scale field observations and implications for structure evolution     

《Journal of Structural Geology》2014

Stylolites are rough surfaces, formed by localized rock dissolution, and prevalent in carbonates and other sedimentary rocks. Their impact on porosity and permeability, and capacity to accommodate compactive strain, are well documented. This paper presents a meso-scale field study on sedimentary stylolites in carbonates, characterizing large-scale distributions of stylolites, including measurements conducted on longer than kilometer-long stylolites. Our field study suggests that on large scales connections between stylolites become important. Since connectivity, and also lack of connectivity, are expected to play a significant role in strain accommodation and hydraulic rock properties, we suggest that large-scale analysis may require a new characterization scheme for “stylolite populations”, based on their connectivity. We therefore divide sedimentary stylolite populations into three end-member types, which are correlated with the three possibilities for percolation of such systems: isolated stylolites (with zero percolation/connectivity), long-parallel stylolites (with 2-dimensional percolation/connectivity), and interconnected stylolite networks (with 3-dimensional percolation/connectivity). New statistical parameters and measures are devised and used to quantitatively characterize the different population types. Schematic mechanistic models are then offered to explain the evolution of the three end-member connectivity-classes. In addition we discuss the effect on fluid flow of the different population types.  相似文献   

王坡井田煤层气井部署方法研究     

杜志强  吴艳  张妙逢 《中国煤炭地质》2014,(9):24-26

王坡煤矿是高瓦斯矿井,已有的井下瓦斯抽排不能满足矿井安全生产的要求,迫切需要通过地面抽采来缓解。在已有地质成果基础上,采用煤层气藏数值模拟方法,对王坡井田地面煤层气抽采工程部署方案进行优化。结果表明:A区块是井田煤层气开发试验首选区,以梅花形井网作为试验井网,井间距300m×250m,井网长轴方向60°。这种布井方式在工程实践中取得了较好效果,具有较大的推广价值。  相似文献   

Model of optical turbulence profile at Cerro Pachón     

A. Tokovinin  T. Travouillon 《Monthly notices of the Royal Astronomical Society》2006,365(4):1235-1242

New measurements of optical turbulence profile at the Cerro Pachón observatory in Chile are analysed jointly with previously published data to model the variations of the intensity and thickness of the ground layer and free atmosphere under a variety of observing conditions. This work is motivated by the need to predict statistically the performance of ground-layer adaptice optics. We find that the ground-layer profile can be represented by a decaying exponent with a scale height of 20–40 m, increasing to 100 m under bad conditions. The zone from 6 to 500 m contributes typically about 61 per cent to the total integral, the latter causing a median seeing of 0.77 arcsec. Turbulence integrals in the ground layer and in free atmosphere vary independently of each other, in 50 per cent of cases they deviate by less than 1.8 times from their respective median values. The existence of periods with low turbulence in the free atmosphere and their importance for adaptive optics is stressed.  相似文献   

Estimation of anisoplanatism in adaptive optics by generalized SCIDAR profiling     

R. W. Wilson  N. J. Wooder  F. Rigal  J. C. Dainty 《Monthly notices of the Royal Astronomical Society》2003,339(2):491-494

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