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1.
割草干扰对典型草原土壤种子库种子数量与组成的影?…   总被引:1,自引:1,他引:0  
对种子雨的来源及其降落进行了研究,结果表明,种子雨的来源取决于各种植物结实的种子数量,60种植物单株结实的种子数量有很大差异,禾草种子数量相对较少,杂类草较多,一、二年生植物的种子数量亦多,种子雨的降落,是通过独立、风力、附着、动物和原地等获布形式来实现的。单位面积上种子的种量取决于群落的种类组成和有结实能力的植株。通过实则和模拟,单位面积上可能降落的种子数量相差不大,前为16763粒·m^-2  相似文献   

2.
对具有生命力的种子数量及其垂直分布进行了研究,结果表明:刈割对土壤种子库中的种子数量有一定的影响,其中对照具有生命力的种子数量,1997 年和1998 年分别为2415 和2253粒/0.12m 3,割一年休一年的处理分别为对照的93.13% 和78.38% ,一年割一次的处理分别为对照的83.23% 和58.50% .从以上数值可见,同一处理内部种子的数量亦有下降.不同处理种子数量的垂直分布有共同趋势,有75.48% ~87.78% 分布在0~4 cm 土层内,有14.92%~18.42% 分布在4~8 cm 土层内,有0.00% ~6.10% 分布在8~12 cm 土层内.连续刈割45年和46 年的草地,种子数量分别为对照的22.57% 和35.98% .单位面积上具有生命力的种子数量远低于降落下的种子数量,这是由于刈割时尚有大量种子未成熟和其它因素引起的.  相似文献   

3.
割草干扰对典型草原土壤咎子库种子数量与组成的影响   总被引:8,自引:0,他引:8  
对具有生命力的种子数量及其垂直分布进行了研究,结果表明:刈割对土壤种子库中的种子数量有一定的影响,其中对照具有生命力的种子数量,1997年和1998年分别为2415和2253粒/0.12m^3,割一年休一年的处理分别为对照的93.13%和78.38.5,一年割一次的处理分别为对照的83.23%和58.50%,从以上 数值可见同一处理内部种子的数量亦有下降,不同处理种子数量的垂直分布有共同趋势,有7  相似文献   

4.
金平  张著林 《贵州科学》1998,16(3):212-215
用植物激素对贵州特有,稀有植物-青岩油杉种子进行预处理试验,结果表明,以400μg/L的IBA溶液处理种子,出苗率达52.5%比对照高19.5%;用400μg/L的NAA溶液处理种子,一年生苗高12.3cm,地径粗0.19cm,比对照增高4.5cm,增粗0.04cm,2,4-D溶液也可在不同程度上提高种子出苗率及苗木年生长量。  相似文献   

5.
对典型草原群落生物量的组成与种子数量的组成进行了比较研究,主要结果如下;在割草干扰下,割一年休一年和一年割一次的群落生物量分别较对照下降了15.58%和25.31%;具有生命力的种子数量分别较对照下降11.35%和27.33%。种群相对生物量与相对种子数量没有一致的关系,表现为5种形式,即生物量较高而种子数量较低;生物量较低而种子数量较高;生物量与种子数量相近;在生物量而无种子数量和无生物量而有种子数量。不同科植物生物量与种子数量有一定的差异。禾本植物生物量较高,而种子数量较低;菊科植物生物量较低,而种子数量较高,豆科植物生物量一般高于种子数量;其余科植物均有各自的特点。不同生活型植物生物量与种子数量也有差异。多年生草本植物生物量最高,而种子数量较低;一年生、二年生草本植物生物量较低,而种子数量占总量的一半以上;灌木和小半灌生物量和种子数量均较低。  相似文献   

6.
食果鸟类通过取食果实,消化果肉后散布种子,从而存在潜在的种子传播作用。樟树(Cinnamomum camphora)是亚热带地区广泛分布的一种常绿阔叶树种,有关其肉质果实传播模式的研究还鲜见报道。本研究调查了江西师范大学瑶湖校区1 100余株樟树的结实量、树冠下以及空地中食果鸟类散布的种子量,研究了食果鸟类对樟树果实的空间散布模式。共调查6 000余个小样方,面积达40 000 m~2,共收集樟树果实和种子20万多粒,40余kg。结果表明:樟树平均结实量为110.00±3.84粒/m~2。取食樟树果实的食果鸟类主要有丝光椋鸟(Sturnus sericeus),乌鸫(Turdus merula),珠颈斑鸠(Streptopelia chinensis),白头鹎(Pycnonotus sinensis),绿翅短脚鹎(Hypsipetes mcclellandii)等。这些食果鸟类均以直接吞食樟树成熟果实,并经一段时间消化后通过呕吐或排泄的方式在空间上散布樟树的种子。经食果鸟类消化后被散布至樟树树冠下的种子量为148.71±7.41粒/m~2,但非结实的樟树下也发现较多被消化排出的种子(37.93±7.60粒/m~2)。另外,在无樟树分布的空地中发现的种子量高达15.93±2.80粒/m~2左右。食果鸟类通过散布樟树种子,对樟树种子传播和幼苗建成有潜在促进作用。  相似文献   

7.
外源Ca~(2 )对水稻幼苗生长的影响   总被引:1,自引:0,他引:1  
用不同浓度外源Ca2+ 对水稻种子进行处理,探讨钙对水稻幼苗生长的影响. 结果表明:低浓度(0.25~0.5 m m ol·L- 1)Ca2+ 处理的水稻幼苗干物质重及健壮度均高于对照,其中以0.5 m m ol·L- 1 Ca2+ 处理效果最显著,水稻幼苗干物重及健壮度分别比对照高9.7% 和8% ;0.25 m m ol·L- 1Ca2+ 处理的叶绿素含量均略高于对照;加钙处理水稻幼苗根系活力高于对照,过氧化氢酶活性也高于对照.  相似文献   

8.
通过研究提出北疆棉花公顷产2250kg皮棉的栽培生理模式,模式包括叶面积指数、光合势、净同化率、群体光合速率、群体呼吸速率、干物质积累与分配等各项生理指标。叶面积指数在开花、盛花、盛铃、盛絮期分别为1.30、2.80、3.90、1.80;总光合势231.35×104m2·d,其中盛铃期以后的光合势占总光合势的70.37%;平均净同化率为8.14g·m-2·d-1,盛铃后期至吐絮期为4.05~4.40g·m-2·d-1;群体光合速率的最高值出现在盛铃前期,值为4.05g·CO2·m-2·h-1,全生育期平均为2.65gCO2·m-2·h-1;群体呼吸速率的最高值出现在盛铃后期,值为2.69gCO2·m-2·h-1,平均为1.46gCO2·m-2·h-1;总干物质积累12657.7kg,经济系数47.9%。  相似文献   

9.
栲树种子库及更新   总被引:11,自引:0,他引:11  
栲树种子进入种子库时,其总量在大小年间差异不大,但其组成却有很在差异。大年时有效种子数为72.15-74.32粒/m^2,  相似文献   

10.
纳米α—Fe金属磁粉制备及其磁性能研究   总被引:10,自引:0,他引:10  
探讨了一种新的纳米αFe 金属磁粉制备方法.在乳化剂PG参与下,从铁盐溶液中沉淀析出FeC2O4·2H2O作前驱体,经热分解、氢气还原和表面钝化处理,制备出轴比1~3(长短径比)、长径约50 nm 的椭球或短棒状αFe 金属磁粉.其主要磁性能,比饱和磁化强度σs 在137.3 A·m2·kg-1 ~157.5 A·m2·kg-1(emu·g-1)之间,矫顽力Hc 在31.8 kA·m -1~43.3 kA·m -1(400 Oe~544 Oe)之间.  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.
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   

14.
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   

15.
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   

16.
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   

17.
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   

18.
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   

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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