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Vegetation, microclimate, seedling frequency, freezing tolerance, and cold acclimation were compared for seedlings of Artemisia tridentata collected from 1775, 2175, and 2575 m elevation in the eastern Sierra Nevada, California. Data were used to test the hypothesis that ecotypic differences in stress physiology are important for seedling survival along gradients from desert to montane ecosystems. The vegetation canopy cover and A. tridentata seedling frequency were greatest at 2575 m, compared to 1775 and 2175 m. Snow cover ameliorated temperatures near the soil surface for part of the winter and depth varied across elevations. Freezing tolerance was compared for seedlings maintained in growth chambers at day/night air temperatures of 25°C/15°C. The temperature at which electrolyte leakage and Photosystem II function (FV/FM) from leaves were half-maximum was approximately −13·5°C for leaves of seedlings from all three elevations. Shifting day/night air temperatures from 25°C/15°C to 15°C/5°C initiated about 1·5° of acclimation by plants from all three altitudes, with seedlings from the highest elevation exhibiting the greatest acclimation change. Measurements of ambient air and canopy temperatures at the three elevations indicated that wintertime average low temperatures were consistent with the measured degree of freezing tolerance. At small spatial scales used in this study, pollen and seed dispersal between study sites may have precluded resolution of ecotypic differences. Patterns of freezing tolerance and cold acclimation may depend on a combination of mesoclimate and microclimate temperatures, canopy cover, snow depth, and snow melt patterns. 相似文献
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禾青井动水位对断层蠕动与慢地震过程的响应初析 总被引:3,自引:1,他引:3
以湖南禾青井深井水位观测的异常图象为例进行定性分析,发现动水位观测有可能直接反映出断层的滑动或断层的慢地震过程,前者可能为地下水物理参量的观测与研究提供亲折思路,后者则可能对震源物理学的发展和地震预报水平的提高具有特殊的意义。 相似文献
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介绍一种利用双频仪解决矿区井巷巷道中漏水水力联系的原理和方法。双频梯度测量法有抗干扰能力强、分辨率高、仪器轻便等特点,实践证明应用效果很好。 相似文献
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H. J. Nijhuis 《International Journal of Earth Sciences》1997,86(2):322-331
The prediction of the hydrocarbon potential of a specific trap or of a number of specific traps (venture), referred to herein
as prospect appraisal, concerns a probabilistic exercise based on the quantification of geology in terms of structural closure,
reservoir quality, hydrocarbon charge, and the retention potential of the seal. Its objectives include: (a) prediction of
the hydrocarbon volumes that could be present in the trap from an analysis of its geologic attributes; (b) the amount of uncertainty
introduced in the volumetric prediction by the uncertainties in the subsurface geology; (c) the risk that one or more of the
essential attributes of the prospect are underdeveloped and recoverable reserves are absent. The uncertainty of the geologic
input requires a probabilistic approach, for which the Monte Carlo procedure is well suited.
Prospect appraisal forms the basis for decision-making in oil exploration and development and, therefore, should be reliable,
consistent, and auditable. This requires the use of a consistent methodology, the development of reliable models to quantify
the geologic processes involved, and the collection of comprehensive and relational databases for the many geologic variables.
As a result of data availability, uncertainty and risk tend to increase strongly from mature, producing basins to areas of
frontier exploration. This may complicate management of exploration portfolios.
Received: 1 July 1996/Accepted: 25 November 1996 相似文献