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1.
栓皮栎种群的年龄动态与稳定性研究   总被引:7,自引:0,他引:7  
对河南省内不同干扰程度下栓皮栎种群的年龄动态进行分析,结果表明较大干扰下其幼龄个体数量多,但死亡率较高,为增长型种群;而干扰较小时相反。  相似文献   

2.
【目的】明晰自然演替下枫香(Liquidambar formosana)种群的数量动态特征,为南京紫金山地区森林的可持续经营提供参考。【方法】以南京紫金山南麓受人为干扰较小的固定样地中枫香种群为研究对象,记录样地内所有枫香个体的胸径、树高、冠幅等指标;根据调查样地内枫香个体胸径的大小,划分为9个径级(以0~7.5 cm径阶为径级Ⅰ,后每间隔5 cm划分径级直至径级Ⅸ),用径级来对应种群个体的龄级,绘制枫香种群年龄结构图,并用结构动态指数定量描述种群数量动态。通过编制植物种群静态生命表,绘制种群存活率、死亡率和消失率曲线,利用生存分析函数和线性平稳时间序列对该种群的结构特征现状及未来变化趋势进行分析和预测。【结果】(1)枫香种群个体年龄结构为“金字塔”型,在干扰下种群整体的龄级结构数量变化指数为0.02,表明种群个体数量在当前演替阶段能够维持正增长。(2)种群存活曲线趋于Deevey-Ⅰ型,种群个体生存率逐渐下降,死亡率、消失率、累积死亡率和危险率总体上逐渐上升,死亡密度则趋于稳定。(3)时间序列模型的预测结果表明枫香种群能够在未来较长的演替时间内仍呈增长趋势。(4)枫香树在胸径达到≥3...  相似文献   

3.
朱鹮的环志情况及其生命表的分析研究   总被引:2,自引:1,他引:2  
采用环志的方法,对朱野外种群进行了6年研究,编制了生命表;并对其繁殖地点变动、繁殖情况及各年龄组的存活情况等现状做了分析,发现洋县朱种群中,当年幼鸟死亡率比较高。增加种群数量的关键是保护1龄幼鸟。  相似文献   

4.
在1987 ̄1997年的11年里,采用鸟类环志的方法研究了野生朱Huan的存活和死亡状况编制了动态生命表;并对其繁殖地,繁殖情况及年龄组的存活数量等做了分析,发现洋县野生朱Huan种群中,当年幼鸟死亡率比较高,增加种群数量的关键是保护当年的幼鸟。  相似文献   

5.
朱Huan的环志情况及其生命表的分析研究   总被引:5,自引:0,他引:5  
采用环志的方法,对朱Huan野外种群进行了6年研究,编制了生命表;并对其繁殖地点变动、繁殖情况及各年龄组的存活情况等现状做了分析,发现洋县朱Huan种群中,当年幼鸟死亡率比较高。增加种群数量的关键是保护1龄幼鸟。  相似文献   

6.
斑苦竹无性系种群的数量统计   总被引:11,自引:0,他引:11  
应用生命表和生存曲线对缙云山斑苦竹无性系种群的数量进行统计分析,结果表明,①斑苦竹竹笋-幼竹无性系种群的生存曲线介于B型与C型之间,是一条较为平缓的凹形曲线,其死亡率为40%,②斑苦竹无性系种群的年龄结构比较稳定,但已表现出轻度的衰退迹象。③生存曲线呈波状曲折的C型,各龄级竹子构件的死亡率不同,幼龄和老龄竹死亡率较中龄竹子大.  相似文献   

7.
天然毛竹无性系种群的结构动态与数量统计   总被引:1,自引:0,他引:1  
利用生命表和生存曲线对海子坪天然毛竹无性系种群的结构动态和数量进行统计分析,并对分株年龄的鉴别特征进行了研究。结果表明:(1)天然毛竹无性系种群随分株年龄增加,所占的分株比例逐渐减小;(2)天然毛竹无性系种群动态生命表中的生存曲线介于B型与C型(凹型)之间,是一条较为平缓的凹型曲线,反映出整个同生群幼体的死亡率较高,成体的死亡率降低并且接近于不变;(3)静态生命表中的生存曲线介于B型和C型(凹型)之间,总的趋势反映出B2型生存曲线的特点,说明该种群具有死亡率较恒定的特点。  相似文献   

8.
张林源 《大自然》2010,(2):38-41
麇鹿是中国特产的鹿科动物,从元朝开始,麋鹿就因专供皇帝狩猎之用而被放养在北京南海子皇家猎苑中。19世纪末的战争与自然灾害.使野生麋鹿彻底在中国消失了。一百多年前,中国最后一批圈养麋鹿种群在北京南海子灭绝,仅有被西方列强运到欧洲的部分麋鹿保存下来。为了在中国重新建立麋鹿种群,1985年,我国在麋鹿的最后灭绝地南海子原皇家猎苑的中心区域建立了麋鹿苑。  相似文献   

9.
郭耕 《大自然》2012,(4):40-42
“何日相将去,千山麋鹿群。”2012年初,一批麋鹿被输出到千山国家鹿类辽阳马家庄呈龙鹿业基地(下面简称千山基地),成为再现“千山麋鹿群”意境的希望之种。这一工作的完成标志着一个新的麋鹿迁地种群的建立及辽河平原麋鹿种群恢复的开始。  相似文献   

10.
为掌握稽灵山马尾松次生林种群的数量动态和生存状况,采用“空间取代时间”的分析方法来编制稽灵山马尾松种群静态生命表,并以生存分析为理论基础,对稽灵山马尾松种群动态进行了研究。结果表明:(1)稽灵山马尾松种群结构是纺锤形,幼龄个体和老年个体数量少,中龄个体较多,种群在一定程度上表现为衰退型;(2)种群的死亡率随着龄级的增加而不断增长,死亡率峰值出现在第8龄级;(3)该马尾松种群的存活曲线属于Deevey II 型。马尾松是亚热带次生林的过渡树种,其群落的衰退,有利于其他物种的生长,适当辅以人工抚育,对于丰富该地区树种多样性具有重要意义。  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

13.
王慧 《科技信息》2008,(10):240-240
Wuthering Heights, Emily Bronte's only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.  相似文献   

14.
The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.  相似文献   

15.
There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.  相似文献   

16.
The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3~4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰~ -7.8‰, PDB) and matrix dolomites (-6.6‰~ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084~0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078~0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.  相似文献   

17.
In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.  相似文献   

18.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

19.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

20.
1 Rise of studies on climate change's effects on biodiversity
Until the 1980s, climate change and biodiversity were studied as two independent disciplines for more than a century. In 1992, the Ecological Society of America's annual report named climate change, biodiversity, and the sustainable ecological system as the three major global environmental issues of the twenty-first century [1].  相似文献   

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