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941.
Following boreal forest ecosystem disturbance,such as fire and clear-cutting, the ericaceousspecies Calluna vulgaris often becomescompletely dominant and may convert forestlandinto heathland. Calluna is known toeffectively exclude other vegetation and causes``growth check' or stagnation of coniferseedlings to result in poor tree regeneration.In this study we investigated the use of steamtreatment as an alternative method forvegetation control of Calluna vulgaris.Scots pine (Pinus sylvestris L.)establishment and growth were recorded in botha planting and a seeding experiment. Steamtreatment was compared with mechanical soilscarification and intact vegetation in theplanting experiment and with intact vegetationin the seeding experiment. The results showthat the vegetation is still strongly reducedfive years after the treatment. The steamtreatment strongly favoured the establishmentand growth of both seeded and planted Scotspine. The planted seedlings grown in the steamtreated plots had a dry weight more than twiceas high when compared to scarified plots.Seedling height and basal diameter were alsohighest for seedlings grown in steamed plots.Seedlings planted in scarified plots did notgrow as well during the first years possiblydue to injuries caused by frost heaving. Theseeding experiment showed an increasedestablishment and growth of Scots pineseedlings in steam treated plots compared to inintact vegetation. 相似文献
942.
943.
《Scandinavian Journal of Forest Research》2012,27(8):710-718
We examined the growth and quality of young oaks in stands established at three different spacings. The three densities were the traditional level, that is, 8000?seedlings?ha?1 (1.5?×?0.85?m) plus two where the initial density was decreased by 50% and 70%, achieved by increasing the distance between the rows from 1.5 to 3 or 4.5?m. The experiment was located in central Poland on a moderately fertile site. In the two wider spacings, the intention was to use natural regeneration occurring between oak rows as a replacement of intraspecific competition for oaks. The mean height was only affected in the third and the fourth year after establishment. Subsequently, the differences between spacings with respect to both growth and quality traits were insignificant and small. At lower densities, natural regeneration of willow and aspen was abundant and inter-species competition replaced intra-species competition, thus explaining the absence of a spacing effect on growth and quality properties. In the study period, the wider spacings were economically beneficial compared to traditional densities. A strong competition affecting height growth caused by natural regeneration necessitated extensive tendings. More tendings are likely to be needed in the future and they might reduce the initial economical superiority of wider spacing. The study indicates that it is possible to decrease the initial spacing in oak plantations and simultaneously support good growing conditions by means of natural processes, for example, natural regeneration. However, economic efficiency of the method has to be studied in a longer perspective. 相似文献
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946.
在泰乐菌素产生菌的原生质体再生中出现有两种不同表型的菌落。一种菌落大,一种菌落小。活性测定结果表明,在185个大菌落中高落性菌株占20.5×10~(-3),而在179个小菌活中仅占1.7×10~(-2);但在小菌落中的无活菌株竟占86.6×10~(-2),大菌落中只占10.3×10~(-2)。说明菌落的表型与产素能力有明显的相关性。实验还表明UV诱变原生质体对形成的大菌落有良好效果,从中筛到一株产量超过出发菌株3倍以上的高产菌株。 相似文献
947.
【目的】研究潮霉素、卡那霉素和头孢霉素对尾巨桉愈伤组织诱导、不定芽分化及生根的影响,确立抑制农杆菌生长的头孢霉素质量浓度。【方法】以尾巨桉无菌苗茎段为外植体,先后接种于添加不同质量浓度抗生素的愈伤组织诱导培养基、不定芽诱导培养基以及生根培养基上,统计愈伤组织诱导率、不定芽诱导率和不定芽生根率,观察头孢霉素对农杆菌生长的影响。【结果】(1)培养基中的潮霉素、卡那霉素、头孢霉素的质量浓度分别为15,25,200 mg/L时,尾巨桉外植体的愈伤组织诱导率分别为6.7%,12.1%和26.7%;(2)潮霉素、卡那霉素、头孢霉素的质量浓度分别为15,25,250 mg/L时,不定芽分化受到明显抑制,不定芽诱导率分别仅有2.6%,10.2%和7.6%;(3)潮霉素、卡那霉素、头孢霉素的质量浓度分别为15,25,250 mg/L时,不定芽生根困难,生根率分别为10.2%,16.2%和10.1%;当头孢霉素质量浓度≥200 mg/L时,农杆菌生长被完全抑制。【结论】尾巨桉对不同抗生素的敏感性存在差异,在尾巨桉遗传转化过程中,抗性愈伤组织与不定芽诱导的潮霉素适宜质量浓度为10 mg/L,卡那霉素为20 mg/L;生根诱导适宜的潮霉素和卡那霉素的质量浓度分别为15 和25 mg/L;抑制农杆菌生长的头孢霉素较适宜的质量浓度为200 mg/L。 相似文献
948.
目的 探讨林分结构与林下更新幼苗之间的关系,为人工促进天然更新提供理论依据。 方法 以辽东山区蒙古栎林为研究对象,采用拟合模型和Pearson相关分析法,研究了林分空间结构对蒙古栎天然更新的影响。 结果 (1)林分断面积对更新幼苗密度影响显著,随林分断面积的增加,幼苗密度呈增加趋势,当断面积达到31 m2·hm−2,幼苗密度增加逐渐放缓;(2)林分断面积与幼苗基径和苗高呈显著负相关关系(P < 0.05);(3)林分竞争指数和密集度均与幼苗密度之间存在典型的抛物线关系,与密集度相比,竞争指数对幼苗密度的影响更显著;(4)林分空间结构对更新幼苗的物种多样性影响显著,林分的混交度越大,垂直结构越复杂,更新幼苗的种类和Shannon-Wiener多样性越高。(5)多元逐步回归分析结果显示:林分断面积、竞争指数和密集度是影响蒙古栎林更新幼苗密度的主要因子。 结论 人工促进蒙古栎林天然更新,改善林下物种多样性,可通过调控林分断面积、竞争指数和密集度的经营方式来实现。 相似文献
949.
《国际水土保持研究(英文)》2020,8(2):124-130
The Brazilian Cerrado has been converted to farmland, and there is little evidence that this expansion will decrease, mainly because agriculture is the country’s main economic sector. However, the impacts of intense modification of land use and land cover on surface runoff and soil erosion are still poorly understood in this region. Here, we assessed surface runoff and soil loss in a woodland Cerrado area under a former pasture area, which was abandoned and has undergone a natural regeneration process for 7 years (RC). Its results were compared with that found in an undisturbed area of woodland Cerrado (CE), 40-month-old eucalyptus (3.0 × 1.8 m) (EU), and pasture under rotational grazing (PA). The study was conducted on Red Acrisol located in the Brazilian Cerrado. We performed rainfall simulations on a plot of 0.7 m2 and using three constant rainfall intensities of 60, 90, and 120 mm h−1 for 1 h. For each rainfall intensity, we carried out four repetitions using different plots in each treatment, i.e. 12 plots per treatment studied and 48 plots in total. We noted that the soil physical properties were improved in RC and, consequently, water infiltration and soil erosion control; RC presented surface runoff and soil loss different from EU and PA (α = 0.05). The macroporosity and soil bulk density affected surface runoff in RC and PA because the RC was used as pasture and is currently regenerating back to the cerrado vegetation. As the rainfall intensity increased, EU became more similar to PA, which showed the highest surface runoff and soil loss. Our findings indicate that natural regeneration processes (pasture to the cerrado vegetation) tend to improve the soil ecosystem services, improving infiltration and reducing surface runoff and soil erosion. 相似文献
950.
本文研究了BA、NAA、AgNO_3、子叶龄、培养密度以及Km对花椰菜子叶再生系统的影响,建立了一个高频再生系统,使再生频率达100%,其最佳各成分的配比是:MS BA4.5mg/L NAA0.1mg/L AgNO_35.0~10.0mg/L. 相似文献