不同环境因子对辽东栎种子更新影响的研究进展

植物自然更新过程是一个复杂的生态学过程,它对种群的增殖、扩散、延续和群落稳定及演替具有重要的作用。辽东栎通过种子更新可以维持其种群的持久性与遗传多样性。目前国内外对辽东栎种子更新影响的研究主要是从单一环境因子出发,着重分析某一环境因子对其更新的影响。文章主要通过阅读大量文献的方法,从光照、水分、动物搬运、地表覆盖物、林窗几方面对辽东栎种子更新的影响进行总结,并提出今后该领域的研究建议。     

三种生境条件下四合木种群开花结实特性

以鄂托克旗蒙西镇自然分布的四合木种群作为研究对象,采用统计学方法,对不同生境条件下四合木种群的冠幅结构、开花结实量、花果转移率和结籽率进行了研究,以期为探讨种群的更新和濒危机制以及四合木资源保护和利用提供参考依据.结果表明:种群结构与生境条件密切相关,种群A的生境明显优于种群B和种群C,种群A幼龄个体占27.33％,自然更新后备力量充足,属稳定型种群,种群B和种群C缺乏幼龄个体,自然更新不良,属衰退型种群,严酷的生境条件成为限制四合木更新的主要因素之一.单个四合木灌丛的平均开花数为842,平均结实数为388,且开花和结实数量随冠幅级增加呈"山峰"形曲线变化,开花结实高峰期均出现在冠幅级为10～11级时,平均花果转移率为34.48％.试验区四合木结籽率较低,仅为0.87％～2.87％,可能与其胚胎败育率高有关.     

外来树种马占相思主伐后更新与自然繁殖更新研究

对外来树种马占相思自然繁殖特性展开分析发现,保证种子落于裸露地面,才能使种子获得发芽力,实现自然繁殖更新。在炼山被禁止的背景下,人工造林清山成本较高,因此本文对其主伐后更新问题进行了研究,提出采用人为方式对马占相思自然更新进行模仿和控制,促使种子发芽率得到提高,同时对株行距进行规范,达到降低造林成本和保证造林效果的目标。     

不同生境中沙冬青豆荚螟的危害率及空间分布型

豆荚螟(Etiella zinckenella)是沙冬青(Ammopiptanthus mongolicus)种子的主要害虫。在宁夏灵武白芨滩国家自然保护区内选择了沙冬青自然生长(羊场湾样地、枣泉样地)和人工栽植(甜水河样地、马鞍山样地)2类生境的4个试验样地,调查了沙冬青豆荚螟幼虫的危害情况,研究了其空间分布型。结果表明:豆荚螟幼虫数量(2.015只·荚-1)、对豆荚的为害率(82.83%)在马鞍山样地最高,其次是甜水河样地(1.423 3只·荚-1,64.83%)和羊场湾样地(1.218 3只·荚-1,59.83%),枣泉样地最低(0.558 5只·荚-1,32.00%),豆荚螟幼虫的数量和为害率在人工栽植生境显著高于自然散生生境,与沙冬青的种群密度呈正相关。基于频次分布指标、聚集度指标及回归分析显示,不论在人工栽植生境还是自然生长生境中沙冬青豆荚螟幼虫的空间分布型均呈聚集分布。沙冬青豆荚螟幼虫Iwao线性回归方程为M*=1.040 66+0.569 02 M(R=0.925 1),表明沙冬青种子害虫豆荚螟个体间相互吸引,种群分布的基本成分为个体群。     

2012年北京各区县不同寄主上二斑叶螨发生调查

对北京市不同地区及不同寄主上二斑叶螨的种群密度和危害等级进行了比较.结果表明:相同寄主不同地区二斑叶螨种群密度和危害等级各不相同.海淀区辣椒棚该螨种群密度和危害等级显著大于延庆县,昌平区草莓上该螨种群密度和危害等级显著大于房山区,在通州区和密云县的种群密度和危害情况差异不显著.比较二斑叶螨在北京5种常见温室寄主上种群密度,发现其差异显著等级划分为:辣椒＞草莓＞番茄、茄子和人参果.该螨对寄主叶片危害等级与其种群密度不一致,其显著差异等级划分为:人参果、辣椒、番茄、草莓＞茄子.     

简讯

正英山新发现3株大别山五针松大别山五针松(Pinus dabeshanensis Cheng et Law)俗称青松、果松,是国家公布极度濒危的极小种群物种。该树特点是种鳞鳞盾先端肥厚、有明显反卷,叶型5针一束且短。由于分布种群少,大树不多,结果较少,种子又常受松鼠危害,繁殖出芽率低,1992年10月被列为国家珍稀树种第一批二级保护树种,英山桃花冲是大别山五针松在湖北省唯一的分布地点。近日,湖北大别山国家级自然保护区英山管理局和桃花冲管理站工作人员在自然保护区境内开展巡护     

河南文冠果营造技术及低产林分改造

文冠果为我国重要的生物质能源树种之一,河南具有大面积的自然分布和人工栽培,长期以来,当地林农积累了较丰富的栽培经验.文章主要就该树种在河南的主要营造技术措施及现有低产林分改造进行总结,旨在为文冠果生物质能源林的建设发展提供参考.     

木兰围场天然次生油松林年龄结构及更新动态研究

通过对天然次生油松林下更新状况的调查,编制静态生命表、绘制存活曲线,研究分析河北木兰围场自然保护区内不同立地条件（坡底、坡中、坡顶）下天然油松次生林的年龄结构和更新动态,结果表明：（1）影响天然次生油松林更新的主要因子是郁闭度、灌草盖度。较高郁闭度、较高湿度更利于油松更新,幼苗更新密度最大值达4.192株/m2。（2）该保护区不同立地条件下油松种群年龄结构均为增长型年龄锥体;0~10a生个体数最多,坡中处最多达525株;生命期望最大值集中于10~20a龄级,该龄级属于生理旺盛期,应予以保护。（3）不同立地条件下油松种群的存活曲线变化趋势相似,油松存活率均在10~20a生间急剧下降;在20~60a生间,除坡底30~60a生存活曲线逐渐下降外,坡中和坡顶的存活曲线均大体趋于稳定,但60a生后3块标准地存活曲线均大幅下降,其中坡底处油松种群在70a存活率最小,为0;整体而言,存活率由大到小依次为坡顶、坡底、坡中。     

更新采伐对华北落叶松人工林空间格局的影响

种群空间分布格局是种群个体在水平空间的分布方式,对林分空间格局的研究和分析可以为林业生产提供宝贵资料和实践指导,同时科学地制定抚育经营措施是提高森林质量的关键环节。本试验研究了更新采伐对华北落叶松人工林种群空间分布格局的影响。结果表明,华北落叶松种群的格局强度随研究尺度的不同而不同。通过更新采伐使得原先呈聚集分布的种群空间格局变为随机分布或者使得其聚集强度明显降低。因此在华北落叶松种群生长的整个过程中应定期进行更新采伐,伐除林分中生长落后的林木和有害木,降低林分密度,改善林分结构,保证林分朝着健康稳定的方向发展,实现林分的可持续经营。     

研究杉木种子涩籽的空间特征

杉木是我国南方地区的主要造林树种,具有分布广泛、适应能力强等优点,被广泛应用在南方植树造林中。涩籽一直是影响杉木种子成活率的重要因素,由于杉木分布空间广,不同地区的环境条件也存在明显差异,这就导致杉木种子在不同地区的涩籽概率出现差异。本文结合试验研究,对杉木种子涩籽空间特征的相关问题进行分析。     

Timing of fruit removal affects concurrent vegetative growth and subsequent return bloom and yield in olive (Olea europaea L.)

Olive (Olea europaea) demonstrates a high tendency toward alternate fruit production, with significant negative consequences on the industry. Fruit load is one of the main cause-and-effect factors in the phenomenon of biennial bearing, often disrupting the balance between reproductive and vegetative processes. The objectives of the present study were to identify the time range during which heavy fruit load reversibly interrupts the reproductive processes of the following year. The linkage between timing of fruit removal, vegetative growth, return bloom, and fruit yield was studied. Complete fruit removal in cv. Coratina until about 120 days after full bloom (August 15) caused an immediate resumption of vegetative growth. The new shoots grew to twice the length of those on trees that underwent later fruit removal. Moreover, a full return bloom, corresponding with high subsequent yields, was obtained by early fruit removal, while poor or no bloom developed on late-defruited or control trees. Thus, the critical time to affect flowering and subsequent fruiting in the following year by fruit thinning occurs in olive trees even weeks after pit hardening—much later than previously suggested. Furthermore, the data indicate that flowering-site limitation, due to insufficient or immature vegetative growth during the On-year, is a primary factor inducing alternate bearing in olive.     

The re-emergence of indigenous forest in an urban environment, Christchurch, New Zealand

Christchurch, the second largest city in New Zealand is a planned city on a coastal plain on the east coast of the South Island. The birth of the city and the subsequent century of development was characterised by colonial values and tree and garden planting with familiar European species along with those from Australia, North America, and eventually all other continents. The image of an “English garden city” with classical parks of oaks and willow-lined rivers became the accepted norm and the way in which the city has been promoted to potential tourists. Gardening is one of the top two recreational activities and exotic species greatly outnumber native species in the flora and in gardens. This has had serious consequences for the highly fragmented and degraded indigenous vegetation and its co-adapted wildlife. A few hardy indigenous species continued to regenerate through this period, but since the 1970s, there has been a progressive change of attitude and interest in reclaiming the natural heritage of the city, manifest in widespread private and public planting of indigenous species and active habitat restoration. In this article we examine the indigenous and exotic shrub and tree components of the Christchurch flora as planted street trees, in domestic gardens, and in parks. We also present data on shrub and tree regeneration in parks and domestic gardens in the city. Indications are that the more sensitive, less intrusive management of urban environments, combined with the greater density of indigenous seed sources, has allowed regeneration of a wide range of indigenous species across a broad spectrum of habitats – from neglected gardens to pavement cracks to exotic plantations. This is despite the competition from the prodigious seed banks and density of exotic trees, shrubs, and ground covers and albeit minimal impacts of introduced browsing and seed eating mammals. If the present trends continue through appropriate management and facilitation, these tentative signs of native forest regeneration should eventually proliferate into a sustainable mixed origin urban forest that resurrects and preserves the natural character of the region.     

木本果树遗传转化研究进展

从遗传转化方法和影响遗传转化的因素两方面综述了木本果树遗传转化技术近年来的进展。木本果树遗传转化方法主要有农杆菌介导法和基因枪法;影响转化的因素主要从受体与再生系统、选择标记基因与转化细胞的筛选、培养方法与培养条件等方面进行论述。文章还归纳了导入目的基因并获得再生植株的木本果树种类,并对木本果树基因工程进展及展望进行了讨论。     

蔷薇科果树离体再生与遗传转化研究进展

蔷薇科果树在世界果品生产中占据重要地位。近年来,蔷薇科果树离体再生和遗传转化研究取得了较大进展,在较大的树种上均有报道,但对于离体再生与遗传转化体系的主要影响因素和技术参数细节等缺少系统总结。从离体再生途径、离体再生影响因素、遗传转化概况、农杆菌介导的遗传转化体系影响因素等方面进行了重点总结,对未来研究趋势和热点进行了展望。     

果树体细胞胚胎发生研究进展

近年来有关果树组织培养的研究很多,其中对果树体细胞胚胎发生的研究越来越受到重视。现对近10a来国内外果树通过体细胞胚胎发生途径再生植株的研究现状进行了总结,分析了果树体细胞胚胎在发生途径上的特点,并从发生过程分析了体细胞胚胎发生的影响因素,同时对其生理生化代谢以及实际应用等方面进行综述。提出该领域今后应逐步开展对果树体细胞胚胎发生的生理生化和分子机理研究,促进体细胞胚胎发生研究成果在生产实践中的应用。     

间伐干扰对人工林林木生长、幼苗更新及植被多样性的影响

抚育间伐是森林经营的重要措施之一,合理的间伐可以优化林分结构,改善林下环境,提高森林生产力和稳定性。本研究以河北省塞罕坝机械林场华北落叶松人工林和樟子松人工林为对象,对比分析间伐和未间伐林分（自然保护区）中林木生长、物种多样性和天然更新的差异。结果表明,间伐区华北落叶松人工林胸径年均增长0.72 cm,比未间伐区提高53.2%;间伐区樟子松人工林胸径年均增长0.59 cm,比未间伐区提高25.5%。间伐区内Shannon-Wiener指数、Simpson多样性指数、Pielou均匀度指数和Margalef丰富度指数较未间伐区分别高出159.2%、185.3%、185.9%和108.4%。间伐区幼苗幼树的更新种类和数量明显高于未间伐区,其中,樟子松人工林间伐区幼苗幼树的更新种类和数量均高于华北落叶松人工林。可见,对自然保护区内未经营过的人工林进行适当抚育间伐对提高森林生产力、维持生物多样性和促进森林正向演替有重要作用。     

Assessing the structure and stability of street trees in Lhasa,China

Street trees can provide important environmental services to residents living in high-altitude cities. Nevertheless the performance of street trees in this unique environment is largely unknown. This article examines the impact of high-altitude environments on the growth of street trees through a case study in Lhasa, China. The structure, species composition, and health condition of street trees in Lhasa were surveyed using a representative sampling approach. The history of street tree programs and factors that affect the health of street trees was also analyzed. The results showed that there were 24 species and cultivars in 2032 sampled street trees. The street tree population in Lhasa contained a significant number of small trees, which was due to the large-scale planting program initiated in recent years. The street tree population in Lhasa was not very stable due to the uneven age distribution. The health conditions of street trees were affected by climatic factors as well as by management practices. We concluded that unfavorable environmental conditions in high-altitude cities may affect the sustainability of street tree populations to some degree but that human management of the street tree population is a more significant factor.     

Spread of mistletoes (Amyema preissii) in fragmented Australian woodlands: a simulation study

A simulation model was used to study the interaction between landscape pattern and components of the dispersal strategy of the mistletoe Amyema preissii by mistletoe birds (Dicaeum hirundinaceum). The landscape was modelled as a map of host trees for the mistletoes, characterised by the total density and clumpiness of trees. A landscape was considered as a set of equal sized bird territories, with the majority of seeds produced in such a territory dispersed within that area. Age-specific birth and death rates of mistletoes were measured in the field. Seed dispersal was characterised by four parameters: the fraction of within-tree seed dispersal, the ratio of attractiveness to birds of tree canopy volume over attractiveness of mistletoe fruit number, seed survival, and the fraction of seeds leaving their original territory.A sensitivity analysis was carried out using a factorial design on landscape type and dispersal parameters. General linear modelling of mistletoe population size after 100 years showed that, in a given landscape, seed survival was the strongest determinant. Total mistletoe population also increased exponentially with tree density, but the number of mistletoes per tree decreased. Population size depended on tree clumping as well, with larger mistletoe populations sustained by woodlands with clumped trees.For a given level of seed survival, population size increased when birds were more attracted by canopy volume than by fruit crop. The strongest increase in population size occured for a combination of low tree density with high relative attractiveness. The relative effects of the fraction of within-tree dispersal and tree density depended on seed survival. For lower survival, fraction of within- tree dispersal determined population size more strongly while for higher survival, tree density became the dominant factor. Population size was negatively correlated with the fraction of within-tree dispersal. Finally, population size strongly increased only if dispersal out of a bird's territory represented 10% of the seed crop, a high value which seems unlikely in the field.The results support the hypothesis that woodland fragmentation promotes invasion by mistletoes. Although simulated mistletoe populations deviated from our natural population in having an excess of young individuals, sensitivity analysis produced several non- intuitive results and is thus valuable in focussing further efforts on field data collection. This study also illustrates how a simulation model of population dynamics can help in determining control strategies for an invasive organism. A reduction in seed survival and disinfection of larger trees would appear to be the most efficient strategy.     

不同砧木对苹果树水分状况年变化的影响

苹果树各器官水势的年变化中，大部时间乔砧树高于矮化中间砧树，与半矮化中间砧树差异较小，与矮化中间砧树差异较大。水势较低影响树体营养生长而有利生殖生长。     

Aesthetic growth of a native tree species with desirable characteristics for urban green areas in arid and semiarid environments

Having an aesthetic form is one of the desirable aspects of trees used to create or reforest urban green areas, which is often achieved by procedures that require a great effort. The understanding of factors affecting the architecture of plants in natural conditions may be useful to promote a desirable shape during the growth process. Under the hypothesis that trees in high luminosity conditions have a more aesthetical growth, in this study we explore the relationship between plant shape and photosynthetically active radiation (PAR) in Bursera fagaroides, a characteristic species of the tropical dry forest and xerophytic shrub-lands useful for urban green areas in semiarid environments. To evaluate trees shape we calculate a symmetry index (I_S) by using two diameters of the crown, perpendicular to each other, and the total height. Measurements were made over three periods (before, during and after the growth period); and PAR was also measured for each tree. Linear regressions were used to analyze the relationship between the symmetry of trees and PAR received during the growth period. The post-growth symmetry of trees showed a positive relationship with the PAR received by trees during the growth period, suggesting that PAR effects can be harnessed to develop post-germination strategies for the production of trees with a more aesthetical growth in the studied species. Effect of PAR on the shape of plants may represent a practical option to promote aesthetical growth of trees and shrubs with importance for creation and restoration of urban green areas.