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941.
Characteristics and dynamics of the soil seed bank at the north edge of Taklimakan Desert 总被引:3,自引:0,他引:3
In order to understand the potential of revegetation of halophytic community at the north edge of Taklimakan Desert, the species structure, storage capacity, the vertical distribution pattern and seasonal dynamics of soil seed bank and their interrelationship with community structure of above-ground plants were investigated. The results show that (i) 9 species were identified from seed bank in different seasons indicating that plant composition in this area was simple. (ii) The seed density in soil was 222±10.79 grain/m2 on average, and showed a seasonal variation range from 132±8.16 grain/m2 in summer to 303±12.70 grain/m2 in autumn. (iii) The similarity coefficient between soil seed bank and above-ground vegetation was 0.778. (iv) Vertically, seed densities declined with soil depth. 82.4% of total seeds were found in the top 3 cm of soil profile. No active seeds were found in soil profile below 6 cm. It is concluded that the seed bank at the north edge of Taklimakan Desert contains active seeds of all plant species observed on above ground, and is able to supply potential contribution to reconstruction of vegetation. 相似文献
942.
本文描述了在全波实验中所见到的三种现象,即:1.纵横波初至的振幅(绝对值)具有相同的变化规律;2.纵横波初至的相位彼此总是反向的;3.纵横波初至的振幅变化周期为2π。经过充分的分析和解释指出这些现象应该出现在全波测井条件下,从而为利用相位差从全波中提取有用的信息奠定了基础。 相似文献
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提出了一种新型的基于概率的非参数Gibbs模型,并建立了光谱空间-二维影像空间的映射关系,通过多级光谱编码策略实现了多波段遥感影像的纹理分割。 相似文献
947.
Carbon isotopic composition of modern soil and paleosol as a response to vegetation change on the Chinese Loess Plateau 总被引:7,自引:0,他引:7
LIU Weiguo NING Youfeng AN Zhisheng WU Zhenghai LU Huayu & CAO Yunning State Key Laboratory of Loess Quaternary Geology IEE Chinese Academy of Sciences Xi''''an China Northwest Sci-Tech University of Agriculture Forest Yangling China 《中国科学D辑(英文版)》2005,48(1):93-99
The relationship between the carbon isotopic composition of paleosols and pale-ovegetation on the Loess Plateau is still unclear. One of the main reasons is that we are short of knowledge about the characteristics of the carbon isotopic composition of modern soil in this area. A preliminary investigation of the carbon isotopic compositions of the modern soil and the loess/paleosol sequence on the Loess Plateau shows that the carbon isotopic composition of modern soil is consistent with the distribution of modern plants on the Loess Plateau, where the ecosystem is dominated by a mixture of C4 and C3 plants. Comparing the δ13C values of modern soil and loess-paleosol sequences from the Xunyi profile, we conclude that C3 plants dominated the landscape during loess sediment stages, while C4 plants expanded during paleosol stages. 相似文献
948.
Based on the theories of landscape ecology,landscape eco-environment in the coutrol watershed by reser-voir of Erlong Mountain in Heilogjiang Province was analyzed and assessed by using GIS technique and statistical model of Principal Component Analysis and Spatial Cluster Analysis.It is found that 100.08km^2(36%) of the total area is in the state of kilter,85.73km^2(31%) of the total area is in the state of general,and 47.26km^2(17%) and 15.48km^2(16%) is in the relatively poor state and ideal state.According to landscape ecological structure,there are three land-scape function areas being planned and designed.1) Agricultural landscape function area:its developmental direction is tour agriculture and high-benefit agriculture.2)Eco-environment protected function area:the direction of development and utilization of this region is to develop vigorously forest for soil and water conservation ,and try to increase the rate of vegetation cover.3)Forest landscape function area:rational cut and utilization of forest resources,space optimization disposal of category of forest ,foster of forest and protection of wildwood will become the main development directions for this region.This study trys to provide scientific foundation for ecological restoration of the whole valley and its sustain-able development. 相似文献
949.
阐述了“水基”系统概念的内涵,论述了其客观存在与演进特性,构建了水基系统概念模型。在此基础上,从人与自然和谐相处的理念出发,应用系统论的观点,提出了解读和评价水基系统的稳定态、和谐度、演进率等指标的定义,并对水基系统的应用策略进行了讨论,展望了应用水基系统理论解决水问题的前景。 相似文献
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