不同直径伐桩对赤桉萌芽更新影响的初步研究

对速生树种赤桉进行了不同直径伐桩（２．１～６ｃｍ）萌芽更新影响的研究，结果表明：伐桩的萌芽率及平均萌条数随伐桩直径的增大而增大，萌条直径、高度随伐桩直径变化不大．     

试论火与兴安落叶松种子发芽条件的关系

兴安落叶松(Larix gmelinii)自然分布区大兴安岭的立地条件和种子发芽条件的特殊性,导致了兴安落叶松天然更新的特殊性。瘠薄的棕色针叶林土,生长季短、冬季漫长以及土壤表层较厚的死地被物层增加了天然更新的难度。然而兴安落叶松的天然更新效果却是令人满意的。兴安落叶松在母树林冠下更新良好,只是在某些林型如草类落叶松林的成熟林冠下更新不良;而在3—10年的择伐迹地和火烧迹地上平均每公顷有13500株幼树。大兴安岭地区兴安落叶松火烧迹地天然更新良好的奥秘何在?火灾后兴安落叶松的种子发芽条件如何?火灾在这方面的作用是什么?作者从天然更新的关键之一——种子     

A jack pine survival model for spring-lifting and planting delays in Ontario

The general problem of developing a model capable of exploring the survival response of seedlings to tradeoffs in the timing of spring lifting, planting and cold storage was investigated. After the construction of an overall model framework, one general and three specific functions to predict first-year survival for batches of 2 + 0 jack pine seelings were developed. The independent variables required by the functions include: cold storage duration (days), average air and soil temperature during planting (°C), cumulative degree days at time of planting (°C), ratio of terminal-to-top length at time of lifting, and cumulative degree days at time of lifting (°C). A brief example of the type of use to which such functions could be put, and an indication of the expected level of confidence that may be placed in such a prediction, is presented. The survival functions developed in this study were not designed for widespread use throughout the Province of Ontario. At most they should be limited to 2 + 0 jack pine planting stock originating from Swastika Nursery, and planted nearby.Approved for publication as Journal Article No. J-7315 of the Mississippi Agricultural and Forestry Experiment Station, Mississippi State University.     

Overstory and shrub effects on natural regeneration processes in native Pinus radiata stands

Native Monterey pine (Pinus radiata D. Don) stands on the Monterey peninsula have been significantly modified by natural and anthropogenic disturbances. The exclusion of fire and the introduction of pitch canker (caused by Fusarium circinatum Nirenberg & O’Donnell) created a need for the examination of these changing ecosystems with respect to regeneration, especially as these stands reach mature ages. We established 210 plots on 35 transects distributed throughout five stands in order to describe the current stand structure and quantify the extent and condition of regeneration. The results indicated that Monterey pine seedling establishment varies throughout the peninsula depending on percent canopy cover, duff and litter depth, and percent shrub cover while seedling growth is influenced by percent shrub cover. Canopy cover was also found to inversely influence shrub cover. Our study highlights the importance of understory removal to increase Monterey pine regeneration and seedling growth as canopy cover decreases, especially in areas where coast live oak (Quercus agrifolia Nee) and poison-oak (Toxicodendron diversilobum E. Greene) are abundant.     

Effects of pre- and post-planting shading on growth of container Norway spruce seedlings

Norway spruce (Picea abies (L.) Karst.) is shade-tolerant and sensitive to high irradiance, summer frosts and winter desiccation, which can impair its reforestation success. In this study, artificial pre- and post-planting shading was examined to determine their effects on post-planting shoot and root growth as well as the vigor of one- and two-year-old Norway spruce seedlings. Three planting experiments were carried out on open nursery fields (Exp. 1, 2) and on a mounded forest clearcut in central Finland (Exp. 3). Before planting, the seedlings were stored over winter either in a freezer or on open fields under snow cover. For two weeks prior to planting, half of the seedlings were placed in the open and the other half under a horizontal shade netting (light transmittance 56 %) (Exp. 1, 2). All seedlings were planted with or without a vertical post-planting shade, which was located on the southern side. Post-planting shading enhanced shoot growth and reduced damage (better visual vigor and needle color and less pine-weevil damage) on Norway spruce seedlings for at least two years after planting (Exp. 2, 3). Those seedlings, that had been stored over winter in the open and kept in shade prior to planting seemed to benefit most from post-planting shading (Exp. 2). However, post-planting shading may give variable results, depending on the seedling quality and weather conditions after planting, and may even reduce shoot growth if no pre-planting shading is used (Exp. 1). Shoot growth may also be improved at the expense of root growth (Exp. 3). The costs of manufacturing and installing post-planting shades may limit their use in practice, for example, to selected regeneration sites where there is high risk of frost damage but where no alternative silvicultural procedure (shelterwood or nurse crop) has been used.     

尾叶桉的组织培养及植株再生

研究了以尾叶桉(Eucalyptusurophylla)优树(U6无性系)无菌苗的叶子和茎段作为外植体诱导愈伤组织、丛生芽发生以及植株再生的过程。通过多种生长调节剂不同浓度组合的对比试验,确定了U6快繁体系的最适宜培养条件:(1)愈伤组织诱导培养基:MS 1-2mg/L2,4-D;(2)芽增殖培养基:MS 0.5mg/L6-BA;(3)生根培养基:1/2MS 2.0mg/LNAA。     

厚朴矮林经营技术的初步研究

厚朴伐桩有很强的萌蘖能力，在生长季节采伐也能得到满意的萌芽更新效果，每个伐桩可萌发1－7个萌芽条，7年生厚朴矮林的树干与树枝鲜重达60.2t.hm^-2，平均净生产量为8.6t.hm^-2.a^-1，表明厚朴完全适宜矮林经营，伐桩高度对萌芽条数量，矮林生长影响不大；伐桩萌芽条数量越多，矮林生长越好。     

Effects of a severe typhoon on forest dynamics in a warm-temperate evergreen broad-leaved forest in southwestern Japan

The effects of a typhoon on forest dynamics and the response of major tree species were studied in a warm-temperate evergreen broad-leaved forest in southwestern Japan. The strongest typhoon on record (T9313) passed through this region in 1993. Return periods of typhoons over 30 ms⁻¹ in instantaneous wind velocity and T9313 were estimated to be 2.2 and 104.5 years, respectively. Approximately 10% of all stems suffered some damage from T9313 and annual stem mortality rose from 1.3 to 2.7%. The estimated period that the number of stems would fall below 10% of the initial was four years shorter with T9313-class typhoons than without them. Thus, the disturbance by T9313 was not catastrophic at the site although T9313 was an episodic typhoon. The short-term responses of major tree species to T9313 were classified into four types: 1) blunt-response type with little decrease and recruitment of stems in the DBH ≥ 5 cm class (Distylium racemosum), 2) retreat type with larger decrease than recruitment (e.g. Quercus acuta), 3) sharp-response type with a large decrease and much recruitment (e.g. Cinnamomum japonicum), and 4) advance type with less decrease than recruitment (Eurya japonica). Among the four regeneration types classified by previous studies (climax, light-demanding, subcanopy, and few-sapling), the climax and few-sapling types each showed a specific short-term response, the blunt-response and retreat types, respectively, that explains one aspect of the regeneration strategies of each type. On the other hand, the light-demanding or sub-canopy type showed multiple short-term responses, indicating that each regeneration type contains species with various regeneration strategies. In this paper, I analyzed data from the database that was compiled by the Aya Research Team.     

人为干扰对额济纳胡杨林群落组成及更新的影响

额济纳绿洲是我国西北干旱地区的一道强大的生态防线。但由于水资源匮乏和人为干扰影响,绿洲中胡杨林已严重退化。我们认为人为干扰会对胡杨群落的组成和更新造成影响。应用双向指示种分析法(TWINSPAN)和典范对应分析(CCA),从人为干扰角度对额济纳不同地区胡杨群落进行了分类和排序。结果表明:人为干扰会影响群落林下物种多样性和根孽幼苗生长情况;林下物种多样性主要受旅游干扰影响,并与总干扰强度的关系遵循"中度干扰假说";根孽幼苗生长情况与放牧干扰呈负相关,当根孽幼苗数多的时候,一定程度上能够抵御外界干扰对其生长状况的影响;适度的人为干扰可以增加物种多样性,但要保证胡杨林的繁殖更新,需要以消除放牧干扰影响为前提。     

杉木人工林采伐迹地更新群落结构特征的研究

从杉木人工林科学经营和自然资源管理保护出发，根据定位研究和群落样地调查结果，分析和比较了湖南杉木中心产区会同杉木人工林不同采伐方式迹地上更新群落的组成结构和数量特征．结果表明：迹地群落中共有维管植物85科164属254种，其中乔木、灌木、藤本和草本分别为53种、85种、39种和77种；皆伐和间伐后物种多样性指数高；皆伐8a后迹地群落与皆伐2a后群落相似性较小，而与间伐8a后群落相似性较大；杉木人工林采伐迹地种类成分变更快．提出了合理经营和保护杉木林生态系统多样性和稳定性的措施．