不同树种在落叶松林伐后更新生长情况试验

本文通过落叶松迹地不同树种更新生长情况对比,阐述了落叶松伐后不宜继续更新落叶松,而应更新刺槐的观点,为今后落叶松迹地更新开创了一条新路     

华北落叶松引种试验的探究

华北落叶松和同龄的长白落叶松相比照,无论是平均胸径、平均树高还是平均材积,前者都落后于后者,现已形成低质低效林分,没有实用价值。因此,应尽快伐除华北落叶松,按照适地适树的原则,采取人工更新恢复森林。     

Mangrove community recovery potential after catastrophic disturbances in Bangladesh

The objective of this study was to compare the variation in the soil seed banks and the aboveground vegetation in relation to three habitats, i.e., swamp forests, grassland and sand dunes within the Sundarbans mangrove forests of Bangladesh. We collected vegetation data (species and their percentage cover) by using quadrat sampling: 10 m × 10 m for swamp forests and 5 m × 5 m for grassland and sand dunes. We estimated the density of viable seeds of species in the seed bank by counting germinants from soil cores in a germination chamber. Species richness and composition of both aboveground vegetation and the soil seed banks differed significantly among habitats. We identified a total of 23 species from the soil seed bank. Of these, two were true mangrove species and the remaining were non-mangrove species, including halophytic grasses, herbs and mangrove associate species. Our results confirm that mangrove species do not possess a persistent soil seed bank. The presence of high-density non-mangrove and associated mangrove species in the soil seed bank implies that after frequent catastrophic disturbances which limit incoming propagules from adjacent forest stand, large canopy gaps can easily become invaded by non-mangrove and mangrove associate species. This would result in the formation of a cover of non-mangrove species and cryptic ecological degradation in mangrove habitats. We suggest that forest managers should actively consider gap plantations with mangrove species in the large canopy gaps created after catastrophic disturbances to counteract the invasion of non-mangrove species and cryptic ecological degradation.     

湘南典型残次阔叶林人工促进更新技术研究

于2003年在湖南省汝城县益将国有林场天然残次阔叶林内设置试验样地和对照样地各3个,采用林地清理、补植、补播等手段促进天然更新,并分别于2006年和2011年进行2次人工促进干预;同时,在6个样地内各设置3个样方,共计18个样方,分别于2003、2008、2013年冬,对幼树、幼苗、萌条的数量及地径进行统计,并对样方内胸径≥5 cm的立木进行每木调查。结果表明:种子补播保存率43%,幼苗补植保存率20%,平均保存率32%。树高≤30 cm且地径0.5 cm、31 cm≤树高≤50 cm且0.5 cm地径0.7 cm幼树的数量下降率分别是对照样地的17.5%、21.59%,树高≥51 cm且地径0.7 cm幼树的数量下降率是对照样地的121.66%。2008年单位面积蓄积量是对照样地的2.28倍,2013年达到3.80倍;经过10年更新,单位面积蓄积量是试验前的11.57倍,对照样地单位面积蓄积量仅是试验前的2.55倍;单位面积蓄积量是对照样地的4.54倍。人工促进天然更新所需的人工成本为1 860元/hm2,仅为同期人工营造杉木幼林所需人工成本5 310元/hm2的35%。     

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.     

Deciduous trees affect small-scale floristic diversity and tree regeneration in conifer forests

Abstract

There is a growing interest in the effects of deciduous trees on biodiversity, soil processes and long-term productivity in boreal, conifer-dominated forests. This study investigated whether individual birch trees allowed to grow to maturity in the coniferous forest can have a local effect on floristic richness and regeneration of tree saplings. The ground vegetation was compared in 2?m radius plots around the stem under the canopies of matched conifer–deciduous trees in a mature, conifer-dominated forest, and included in the analysis variables that could potentially mediate the tree effect (soil pH, cover of lichens, bryophytes, leaf and needle litter). The field layer vegetation was more species rich under birch (Betula pendula and B. pubescens) than under conifers (Picea abies and Pinus sylvestris), and several vascular plant species (including saplings of tree species) occurred more often under birch than under conifers. However, when the effect of the number of subordinate trees was taken into account the difference between birch and pine was not significant. The number of tree regenerations (saplings) was lowest under pines, but did not differ between spruce and birch. There were no effects of the canopy species on soil pH or on cover of lichens and bryophytes. The difference in diversity may be caused by the different effects of leaf and needle litter, and it is also likely that canopy structure has an influence via interception and throughfall and by affecting the light and microclimate.     

盐胁迫对‘南林895’杨组培再生芽生根及抗氧化能力的影响

以‘南林895’杨经组培获得的2 cm长再生芽为试验材料,研究不同浓度NaCl处理下再生芽不定根发生能力及其耐盐能力。结果表明:‘南林895’杨再生芽在75 mmol/L以下能够正常产生不定根,100 mmol/L完全抑制不定根的形成。25～50 mmol/L盐处理能够促进‘南林895’杨再生芽不定根的伸长,增加根数,提高叶绿素a及总叶绿素的含量。25 mmol/L处理的SOD、CAT、POD、GR 4种保护酶与对照之间没有显著性差异,MDA含量和电导率也低于对照;而在高浓度盐处理下(75～100 mmol/L),SOD、CAT、GR保护酶活性下降,导致膜透性加大,MDA含量增加,POD和AsA-POD酶活性的提高有助于缓解盐胁迫对‘南林895’杨造成的氧化损伤。     

矮牵牛茎段植株再生体系的建立

将矮牵牛Petunia hybrida Vilm的茎段接种在MS附加不同激素的培养基上进行愈伤组织诱导.结果表明:在MS BA1.0 mol.L-1 NAA1.0 mol.L-1的培养基上可以形成愈伤组织,而且经过继代培养仍可形成愈伤组织;茎段或愈伤组织接种在MS BA1.0 mol.L-1 NAA0.1 mol.L-1的培养基上可以形成不定芽,且诱导率达100%;健壮的高1.5~2.0 cm的不定芽接种在1/2MS IBA0.5 mol.L-1 AC1.0 g.L-1的培养基上,其生长根状况良好,生根率达100%.     

广州火车东站南广场绿地的有机更新实践

对城市已建绿地进行升级改造是城市更新的重要内容。广州火车东站南广场是城市新中轴线上的重要节点,为迎接第16届亚运盛会进行了绿地有机更新,取得了较好的效果。文章以此为例,分析探讨该项目的得与失,并总结阐述了绿地有机更新的一些理念、策略与特点,以期为未来城市绿地的升级改造实践提供有益参考。     

群众杨组培体系的研究

以群众杨(Populus popularis 35-44)为材料建立组织培养再生系统。研究表明，外植体取材部位对不定芽的分化率有非常明显的影响，叶片的再生能力较弱，而幼茎的再生能力很强，叶柄的再生能力介于叶片及幼茎之间。因此，无菌苗幼茎是快繁和基因转化的理想外植体。在组培体系建立过程中发现再生不定芽中存在生长优于对照的个体，是否为体细胞无性系变异有待进一步研究。