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绿盲蝽蟓在树冠内的空间分布及第1代若虫对枣股的危害规律 总被引：1，自引：0，他引：1
为有效控制绿盲蝽蟓Lygus lucorum Meyer-Dür的危害,在河北沧州金丝小枣产区对绿盲蝽蟓在树冠内的空间分布及第1代若虫对不同年龄枣股的危害规律进行了研究。结果表明:第1代若虫主要危害枣股,8~15 a生枣树的多年生枣股受害占受害枣股的40%以上。绿盲蝽蟓在树冠不同高度层对枣果造成的危害没有显著差异。在不同管理方式下绿盲蝽蟓对枣果造成的危害差异极显著,精细管理、粗放管理和对照的枣果受害率分别为13.96%,23.25%和41.68%。 相似文献
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枣淡缘厚盲蝽(Eurystylu costalis Stal)属半翅目盲蝽科害虫。皖南枣区均有分布。我国著名金丝小枣产区的河北沦州也曾证实有此害虫危害,估计实际分布更为普遍。枣淡缘厚盲蝽以成虫、若虫刺吸枣树花和初座果,引起枣花、果蕾凋萎脱落;刺吸的伤口还能诱发花、果炭疽病、造成“花而不实”,对枣产量影响很大。此外,该 相似文献
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绿盲蝽蟓又称牧草盲蝽,能危害多种果树、蔬菜、棉花、苜蓿等经济作物。
1危害特点及发生情况
1.1形态特征
绿盲蝽蟓属半翅目,盲蝽科。若虫体呈绿色,有黑色细毛,翅芽端部黑色;成虫体长约5毫米,呈绿色,前胸背板为深绿色,有许多小黑点。前翅基部为绿色,端部为灰色。 相似文献
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报道了2007～2010年间采自甘肃南部的半翅目盲蝽科昆虫,经鉴定共有21属42种.本次调查所得的种类中,以东亚分布型为最多,约占全部种属的23.8％,东洋分布型约占21.4％,古北分布型最少,只占16.7％左右.说明甘肃南部具有较强的东亚区系特色,反映了此地区地处在生物地理学中极具中国固有特色的东亚区系发祥地——中国中部和中西部地区的地理特点.其中有甘肃省新纪录8种,分别是远东直头盲蝽、黑角齿爪盲蝽、山地狭盲蝽、横断苜蓿盲蝽、狭领纹唇盲蝽、东亚丽盲蝽、东亚草盲蝽、微小跳盲蝽. 相似文献
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绿盲蝽在葡萄上的发生规律及防治技术 总被引：2，自引：0，他引：2
绿盲蝽学名LygusLucorumMeyer -Dtiro ,又名小臭虫、花叶虫 ,属半翅目 ,盲蝽科 ,杂食性害虫 ,为害多种果树、蔬菜、棉花、苜蓿等经济作物。近年来 ,随着农业产业结构的调整 ,葡萄种植面积的扩大 ,绿盲蝽在葡萄上的危害日益严重 ,并有逐年加重的趋势 ,直接影响到葡萄的产量和品质 ,造成很大的经济损失。下面结合近几年生产实践 ,就绿盲蝽在葡萄上的发生及防治情况介绍如下 :1 为害症状绿盲蝽主要以成虫、若虫的刺吸式口器为害葡萄的幼芽、嫩叶、花蕾和幼果 ,造成细胞坏死或促使其畸形生长。被害嫩叶先出现枯死小点 ,随叶芽伸展 ,小点变成… 相似文献
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A silvopastoral agroforestry system involving sheep is an important silvicultural issue. We examined the factors that affect
the continuation or discontinuation of sheep vegetation management (SVM) in British Columbia. A questionnaire was used to
conduct interviews with a randomly selected sample of contractors and farmers who were involved in SVM in British Columbia
(BC). Based on a stepwise discriminant analysis, we found that the profitability of SVM, and the practitioners' commitment
(number of ewes owned by the farmer or contractor), experience (number of years the farmer or contractor has practiced SVM
on public lands in BC) and trust or confidence (number of years the farmer or contractor has consistently worked for the landlord)
contributed to the farmer's or contractor's continuation or discontinuation of SVM practice. The factors we defined seemed
to be validated (corroborated) by a complex of determinants voiced by various experts concerning the relationship between
SVM and the forestry economy in BC, the scale of sheep farming in BC, the relative absence of an agricultural infrastructure
to support sheep farming in BC, and the continuity of SVM from year to year. Further investigation into these factors and
others is required to advance our understanding of SVM in British Columbia.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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M. P. Coutts 《Forest Pathology》1977,7(1):6-12
Dry zones in conifer wood, characterised by gas filled tracheids, were induced by the injection of dilute solutions of various toxic chemicals followed by incubation at 10 or 20°C. The development of dry zones did not occur at lower temperatures nor with concentrated solutions and was prevented or retarded in an atmosphere of nitrogen. These results are discussed in relation to the development of dry zones in infections by Fomes annosus and other fungi and in the formation of heartwood. It is postulated that the gradual death of ray cells alters their metabolism in such a way that gas emboli are evolved in adjacent tracheids; this can occur at sites of infection or at a distance under the influence of transportable or diffusible toxins. 相似文献
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林石 《中南林业科技大学学报(自然科学版)》1996,(4)
静止状态下锯链不垂离导板的临界张力与导板轮廓线圆半径和锯链质量线密度成正比．无缓冲器导板的锯链安装张力应比有缓冲器导板的大．锯链和链轮的制造误差可能引起锯链附加张力或松弛下垂．锯链的松弛程度可用趾部间隙来衡量．锯链与导板的热胀冷缩不同步可能引起热张力或热松弛．文章给出了各种张力和趾部间隙的计算公式． 相似文献
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Invasion of natural ecosystems by exotic plant species is a major threat to biodiversity. Disturbance to native plant communities, whether natural or management induced, is a primary factor contributing to successful invasion by exotic plant species. Herbivory by both wild and domestic ungulates exerts considerable impact on structure and composition of native plant communities. Intensive herbivory by ungulates can enhance exotic plant invasion, establishment, and spread for three reasons: (1) many exotic plants are adapted to ground disturbances such as those caused by ungulate feeding, trampling, and movements; (2) many exotic plants are adapted for easy transport from one area to another by ungulates via endozoochory and epizoochory; (3) many exotic plants are not palatable or are of low palatability to ungulates, and consequently, their survival is favored as ungulates reduce or eliminate palatable, native plants. Ungulate herbivory is a chronic, landscape-scale disturbance capable of influencing plant communities as much as episodic events such as fire. Consequently, ungulate herbivory has the potential to facilitate the invasion and establishment of exotic plants in the interior Pacific Northwest where ungulates occupy nearly every ecosystem. Moreover, ungulate herbivory has intensified in many ecosystems, owing to the addition of domestic ungulates with that of existing, wild ungulates, coupled with the reduction or elimination of migratory movements and predators that previously regulated wild ungulate populations and influenced their distributions. Despite the observational evidence for ungulate herbivory as a strong facilitator of exotic plant invasion and establishment, current knowledge of cause–effect relations is severely limited by a lack of manipulative experiments. Most studies have been observational, unreplicated, and lack the experimental controls needed to eliminate or account for confounding sources of variation. Heightened attention to conservation of biodiversity will increase the importance of managing ungulates in balance with the plant communities that support them. 相似文献
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Christian Andersson 《Forest Ecology and Management》1992,50(3-4):247-251
Oak,Quercus robur, acorns are sometines attacked by a weevil or infested by fungi (Murray, 1974). The number of acorns produced varies greatly from year to year. Acorns produced in the years between mast years may escape these weevil or fungal attacks, be dispersed and germinate.
Acorns were collected annually from 1983 to 1989 from five oak trees in southern Sweden. The percentage of acorns attacked by a weevil or fungi, or both, were monitored and the acorns' ability to germinate was tested.
Not all acorns were damaged in low crop years; the proportion of undamaged acorns varied between 33 and 69%. The proportion of weevil-attacked acorns differed significantly between the years. The proportion of acorns that were able to germinate in each category did not vary significantly between years. The germination ability was significantly higher in undamaged or fungi-infested acorns. 相似文献
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Qi-Jing Liu Xuan-Ran Li Ze-Qing Ma Nobuo Takeuchi 《Forest Ecology and Management》2005,210(1-3):25-37
This study intended (1) to develop a quantitative method to describe vegetation succession or change by remote sensing approach, and (2) to test the capability in clarifying the stability or instability of natural forests in landscape scales. With special attention on the coniferous forest, the attempt was conducted on the natural reserve of Changbai mountain in northeast China by using multi-temporal TM images. Two simple parameters were derived to represent succession rate or change extent. One was the mean change of radiance, and another was the number of pixels with changed reflection property. As conclusion, TM imagery is effective for detecting vegetation changes. The results also demonstrated that the so called climax is not a pure stand, which is generally assumed to be exclusively dominated by climax species, but rather a complex of shifting mosaic. The pioneer patches are permanent units in the forest community. This method is considered applicable for assessing the developing status or behavior of plant communities in large scales, like a life zone, under disturbance of global warming, especially for long-time span. 相似文献
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Impact of invasion of pine wood nematode on the growth of dominant shrub Pleioblastus amarus in Pinus massoniana communities 总被引：1，自引：0，他引：1
When pine trees are invaded by pine wilt diseases,the severely infected pine trees will die and fall down,or they will be removed when found to be damaged by the disease.It gives rise to the invasion of other species in these empty niches originally occupied by pine trees,i.e.,competing surrounding trees or understory shrubs will invade the empty niches during the following years.As a result,the spatial distribution and pattern of the main tree species in a pine forest will change,and a niche variety in the... 相似文献
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Soil organic matter in a ponderosa pine forest with varying seasons and intervals of prescribed burn 总被引：1，自引：0，他引：1
Prescribed burning is used to reduce fuel loads and return ponderosa pine forests of the Western U.S. to their historical structure and function. The impact of prescribed burning on soil is dependent on fire severity which is largely managed by burning in the fall or the spring; frequency of fire will also regulate long-term fire impacts. The objective of this study was to determine if soils and soil organic matter (SOM) were affected by prescribed burning in the fall or the spring using singular or multiple prescribed burns. Prescribed burning was initiated in the spring of 1997 and fall of 1997 at 5-year intervals and once during a 15-year period on a study site located within the Malheur National Forest of the southern Blue Mountains of eastern Oregon. Soils were sampled by major genetic horizon in 2004. The 5-year interval plots had burned twice with 1–2 years of recovery while the 15-year interval plots had burned only once with 6–7 years of recovery. Samples were analyzed for pH, carbon (C), nitrogen (N), C/N ratio, cation exchange capacity, base saturation, water repellency, and humic substance composition by alkali extraction. Fall burning decreased C and N capital of the soil (O horizon +30 cm depth mineral soil) by 22–25%. Prescribed burning did not have an effect on fulvic or humic acid C concentration (FA and HA, respectively) of the mineral soil and only a minor effect on FA and HA concentration of the O horizon. One or two fall burns decreased humin and the alkali non-soluble C (NS) content of O horizon by 15 and 30%, respectively. Initiating fall burning in fire-suppressed stands may not preserve soil C, N, humin, and NS content, but may replicate the natural fire regime. Spring burning using a return interval of 5 or more years reduces the fuel load while having little impact on soil C, N, and SOM composition and may be used to prepare a site for subsequent fall burns. 相似文献
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Influencing micropropagation and somatic embryogenesis in mature trees by manipulation of phase change, stress and culture environment 总被引：1，自引：0，他引：1
This review focuses on clonal propagation of mature trees by tissue culture. Most trees have marked phase changes that result in a decline in their potential for somatic embryogenesis or micropropagation. By altering conditions of the source material ex vitro, or by changing in vitro conditions encountered by the explant, rejuvenation and increased propagation can sometimes be accomplished. Various methods of enhancing micropropagation are reviewed, with particular emphasis on manipulations that involve application of osmotic, temperature or hormonal stress. 相似文献
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Catarina Pereira Fernando Caldeira Jorge Mark Irle José Maria Ferreira 《Journal of Wood Science》2006,52(4):311-317
Data are presented on the effects that cork, blue gum, or maritime pine, all grown in Portugal, have on cement setting. These
materials were mixed with cement either without any treatment or after being extracted previously with a range of solvents
(ranging from nonpolar to very polar). Other experiments were carried out in which extractives or calcium chloride were added
to the cement paste. All lignocellulosic substrates have detrimental effects on cement setting, which is mostly seen by a
delay in attaining the maximum temperature in the process. However, the addition of calcium chloride was able to overcome
this disadvantage. Extraction of the substrates with some polar extraction agents before addition to the cement paste only
slightly improved compatibility, and the addition of water-based extractives to a cement paste affects the setting much less
than the lignocellulosic material by itself. Several thermal compatibility indices, including a new index proposed in this
article, were calculated from data taken from temperature profiles, and conclusions are presented on the performance of the
setting systems, as compared with a neat cement paste. In addition, comments are expressed on the level of accuracy offered
by the indices applied in this study, and how such accuracy can be checked or improved by matching them to the physical properties
of the wood-cement composites. 相似文献