Soil microorganisms alleviate the allelopathic effect of Eucalyptus grandis × E. urophylla leachates on Brassica chinensis

Soil microbes may be critical players in determining the allelopathic potential of some plants. Low levels of plant community biodiversity in Eucalyptus plantations have been attributed to the allelopathic potential of these tree species. The role of soil microbes in the allelopathic effect of leaf leachates of the hybrid tree Eucalyptus grandis x E. urophylla, was tested in Petri dish assays with Brassica chinensis as a receiver plant. Soils were collected from either a local garden (soil A) or a Eucalyptus plantation (soil B) and half of each soil was sterilized to remove microbes. These soils were then treated with E. grandis x E. urophylla leachates for 0-72 h. Seed germination of B. chinensis was significantly inhibited in soils treated with leaf leachates relative to untreated soils. The inhibitory effect of the leaf leachates was more pronounced in sterilized soils. Total phenolic content was obvious lower in nonsterile leachate-treated soils than in sterile soils. Biomass of B. chinensis was negatively correlated with the total phenolic content in soils. Our findings suggest that soil microbes can alleviate the allelopathic potential of Eucalyptus and thereby its negative impact on plant growth.

Comparative microsporogenesis and flower development in Eucalyptus urophylla×E.grandis

Microsporogenesis and flower development in Eucalyptus urophylla × E. grandis were examined using chromosome tableting to provide a method to predict the meiotic stages in this species. Although microsporogenesis was normal, cytokinesis during meiosis of pollen mother cells occurred simultaneously, with strong asynchronism observed in the two different lengths of stamens in a flower bud. In a single flower, the developmental period of microsporogenesis in anthers on the longer stamens was always ahead of those on the shorter stamens. Flower development was also asynchronous at different locations on a branch. Flower buds on the upper side of the branch were larger in diameter than those on the lower side. In addition, a correlation was observed between microsporogenesis development and flower bud diameter growth. The pachy- tene stage was first observed when the diameter of the flower buds increased to 3.0 mm, and the majority of the meiotic stages were observed when bud diameters ranged from 3.5 to 5.0 mm. This study showed that the developmental stages of microsporogenesis in Eucalyptus urophylla × E. grandis could be distinguished readily, which may be applicable to future breeding studies.

Monoterpene hydrocarbons,major components of the dried leaves essential oils of five species of the genus Eucalyptus from Cote d’Ivoire

The chemical composition of the essential oils obtained from the dried leaves of five species of the genus Eucalyptus (E. camaldulensis, E. de-glupta, E. grandis, E. torelliana, E. urophylla) growing in C?te d’Ivoire, was analyzed by means of GC and GC/MS. The density and the refractive index were measured. The major components of all these oils are: α-pinene, β-pinene, α-phellandrene, limonene, γ-terpinene, p-cymene and β-caryo-phyllene. The particularity of these oils is their monoterpene hydrocarbons major components.

Study on Machining Properties of Eucalyptus urophylla×E. grandis:I. Planing and Sanding Properties

The research method in this paper is based on the standard of American Society for Testing andMaterials (ASTM). Planing and sanding are selected to study the machining properties of E. urophylla × E.grandis plantation wood. Moreover, the reasons for machining defects are analyzed. The results show E.urophylla × E. grandis planted in south China is a good species with a great potential for solid woodutilization.

Influence of Planting Spacing on Mechanical Properties of Eucalyptus grandis × E. urophylla Planted in China

The objective of this study was to understand influence of planting spacing on mechanical properties of Eucalyptus grandis × E. urophylla planted as a potential species for solid wood products in China. Four trees at age of 13 were selected from each of 6 groups of planting spacing and a total of 24 sampling trees were selected from the Dongmen Forestry Center of Guangxi Province in China. Furthermore, a one-meter-long log from each tree was cut into small blocks for wood properties testing. MOE, MOR and compression strength parallel to wood grain were determined in accordance with Chinese standards. In addition, wood density and shrinkage properties were measured. Statistical analysis by SAS software indicated significant differences among the 6 groups of planting spacings on the air-dried density, radial shrinkage and bending MOR properties at the 0.05 level, and also on the compression strength at the 0.10 level. However, it was observed that there is no significant differences among shrinkages in tangential and volume, and MOE.

Growth Process of Eucalyptus urophylla × E.grandis Stand Based on Logistic Equation

Eucalyptus is the most valuable cultivated forest genus in the tropical and subtropical areas nowadays. It has been a challenge for foresters to model growth due to the genetic variations, management regimes, and multiple products generated from the plantations. In this paper, Logistic equation was used to study the stock growth process of E. urophylla × E. grandis plantation at age of 14 with 6 spacing treatments. And the biological interpretation of the parameters of Logistic equation was analyzed. The results show that it is flexible, precise and accurate to fit the growth process.

Study on Machining Properties of Eucalyptus urophylla× E.grandis:Ⅱ.Shaping,Boring,Mortising and Turning

The research method of this paper is based on the standards of American Society for Testing and Materials (ASTM). Four items that contain boring, mortising, shaping and turning are selected to study the machining properties of E. urophylla × E. grandis plantation wood. The reasons for machining defects are analyzed. The resultshows thatE. urophylla × E. grandis planted in South China isa good specieswith great potential for solid wood utilization.

Effect of Initial Moisture Content on Solar Drying Ratefor Eucalyptus grandis × E. urophylla

Wood drying is one of the most important process links in wood products processing.However, the existing drying methods mainly depend on heat to desiccate wood, which makes wooddrying consume roughly 40% - 70% of the total energy in the entire wood process. Using solar energyfor drying is greatly significant in two aspects of energy conservation and environment protection. Themoisture content (MC) of lumber affects not only the target value of wood drying, but also the heattransfer properties, moisture rate of expansion, etc., affecting dried lumber quality and drying rate.Eucalyptus grandis × E.urophylla lumbers were collected from Guangdong as test materials and dried inthe solar dryer with low temperature schedule and the effect of initial moisture content were primarystudied on drying rate. Experiments showed that solar drying was suitable for timber with high MC. Interms of drying rate and dried lumber quality, solar drying was as good as traditional steam drying withthe same schedule. And the solar dryer had distinct energy-saving effect.

广林九号桉叶精油的抑菌活性研究

研究了广林九号桉[Eucalyptus urophylla×Eucalyptus grandis(Guanglin 9)]叶精油的抑菌活性。利用气相色谱-质谱联用技术分析桉叶精油的化学成分,采用滤纸片法评价其抑菌活性,以平板稀释法测定了精油的最小抑菌浓度。广林九号桉叶精油的主要成分有:1,8-桉叶油素(40.844%)、α-蒎烯(24.221%)、α-松油醇(4.661%)、反式-松香芹醇(3.735%)、龙脑(2.762%)、乙酸α-松油脂(3.592%)和松香芹酮(1.978%)。广林九号桉叶精油对测试的菌种均有良好的抑菌活性,但对细菌和霉菌的抑菌效果有所差异。对金黄色葡萄球菌(Staphylococus aureus)、枯草芽孢杆菌(Bacillus subtilis)、大肠杆菌(Escherichia coli),黄曲霉(Aspergillus flavus)、黑曲霉(Aspergillus niger)和橘青霉(Penicillum citrinum)的最小抑菌浓度分别为10、20、20、10、10、5 mL/L。

广林九号桉叶挥发油的化学成分分析

目的研究广林九号Eucalyptus urophylla×E.grandis(Guanglin 9)桉叶挥发油中的化学成分。方法采用水蒸气蒸馏法从广林九号桉叶中提取挥发油,通过气相色谱-质谱(GC-MS)联用法分析鉴定挥发油中的化学成分,采用色谱峰面积归一化法计算各成分的相对含量。结果从广林九号桉叶挥发油中鉴定出59种化合物,占挥发油总量的90.966%。挥发油中的主要成份是1,8-桉叶油素(34.659%)、α-蒎烯(10.301%)、α-松油醇(7.638%)、乙酸α-松油酯(7.583%)、龙脑(5.874%)、反式-松香芹醇(2.947%)和葑醇(2.185%)。结论首次研究了广林九号桉叶挥发油的化学成分,为合理开发利用资源提供了科学依据。

模拟酸雨对桉树苗木生长及生理的影响

采用盆栽法,研究4个不同pH(3.0、4.0、5.0、5.6)的模拟酸雨对巨尾桉9号苗木叶片苗高、地径、生物量、叶绿素含量、细胞膜透性、丙二醛含量、抗氧化物酶活性的影响。以探讨不同pH的模拟酸雨对桉树苗木生长及生理的影响。研究结果表明,随着模拟酸雨pH值的降低,巨尾桉9号苗木苗高相对生长量及地径相对生长量总体呈下降趋势,且分别在pH 3.0、pH 4.0时达到最小;不同pH的酸雨处理下,生物量变化不明显;叶绿素a、叶绿素b、叶绿素总含量及叶绿素a/b、相对电导率、丙二醛含量随着酸雨pH值的降低总体呈上升趋势,在pH 3.0时,达到最大;随着模拟酸雨的pH的降低,巨尾桉9号叶片内超氧化物歧化酶、过氧化氢酶活性呈先上升再下降趋势,均在pH4.0时达到最高,过氧化物酶活性随着模拟酸雨pH值的降低逐渐上升;苗高相对生长量与相对电导率、丙二醛含量间存在显著负相关关系;地径相对生长量与相对电导率间呈显著负相关。轻度模拟酸雨可促进巨尾桉9号生物量及叶绿素含量的积累,pH 4.0时,其相对电导率和丙二醛含量均显著高于对照,多种抗氧化酶活性达到最高,模拟酸雨对细胞膜产生了一定伤害,但对其生长影响不明显,说明巨尾桉9号对酸雨具有较强的抵抗能力。

尾巨桉愈伤组织蛋白质含量和氧化酶活性比较

以尾巨桉(Eucalyptus urophylla×E.grandis)无性系DH32-29无菌苗的茎段为外植体,优化的激素组合的愈伤组织诱导率高,随后培养中愈伤组织分化出绿色、黄绿色、白色和褐色4种类型,绿色和部分黄绿色的为胚性愈伤组织,后两种为非胚性愈伤组织。分别测定不同类型愈伤组织的蛋白质含量以及超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)的活性,结果表明,愈伤组织蛋白质含量从高到低为绿色、黄绿色、白色、褐色;胚性愈伤组织的SOD、POD和CAT活性显著高于非胚性愈伤组织,并且绿色愈伤组织3种酶活性均高于其他愈伤组织。

尾巨桉DH_(32-26)组培快繁技术

[目的]探索尾巨桉DH_(32-26)组培快繁技术,为其规模化生产提供参考。[方法]采用组织培养手段,以尾巨桉DH_(32-26)半木质化萌发茎段为材料,对外植体诱导及无菌组织培养体系进行研究。[结果]最佳外植体诱导培养基为改良MS+6-BA 1.0 mg/L+NAA 0.5mg/L,发芽率为92.3%;最佳增殖培养基为改良MS+6-BA 0.4 mg/L+NAA 0.2 mg/L,增殖个数为3.7;最佳生根培养基为改良1/2MS+IBA 0.2 mg/L+ABT 0.3 mg/L,生根率可达98.3%。[结论]该研究获得了尾巨桉初代诱导、增殖和生根适宜培养基和培养条件,初步达到工厂化生产要求。

冷处理对尾巨桉几种生理指标和POD基因转录的影响

6℃冷处理尾巨桉(Eucalyptus urophylla×E.grandis)半年龄树苗24 h后,检测叶片电导率、叶绿素含量、丙二醛含量、可溶性蛋白质含量、SOD活性、POD活性等生理指标的变化,进行POD同工酶电泳,并用实时定量PCR(Real-time quantitative PCR,q PCR)检测了4个POD基因的转录变化。结果表明,与常温相比,冷处理后尾巨桉的叶绿素含量、可溶性蛋白质含量和SOD活性无明显变化;但相对电导率、丙二醛含量和POD活性都有升高,且与常温下有显著差异。POD同工酶电泳结果显示,冷处理后,L1、L2、L8、L9和L10共5个酶带表达增强;L3、L4、L5、L6、L7共5个酶带的表达明显受到抑制。实时定量PCR检测POD1、POD2、POD3、POD4基因的转录变化发现,低温处理后4个基因的转录明显被抑制,其转录水平分别是常温下的0.21、0.41、0.40和0.21倍。上述结果表明,低温胁迫对尾巨桉的相对电导率、丙二醛含量、POD活性、POD同工酶表达变化和POD基因的转录水平等指标有显著影响,低温下这几个指标的变化幅度可作为筛选耐寒性较强尾巨桉株系的参考。

Effects of Forest Types and Environmental Factors on Soil Microbial Biomass in a Coastal Sand Dune of Subtropical China

Coastal sand dune ecosystems generally have infertile soil with low water-holding capacity and high salinity. However, many plant species have adapted to the harsh sand environment along the southeastern coast of China. Studying the microbial biomass in such an ecosystem can improve our understanding of the roles that microbes play in soil fertility and nutrient cycling. We investigated the differences in soil microbial biomass carbon(MBC) and nitrogen(MBN) contents and their seasonal dynamics in five forest types(a secondary forest and plantations of Casuarinas, Pine, Acacia, and Eucalyptus). The results indicated that the seasonal variations of soil MBC and MBN contents in all five forest stands were higher in spring and winter, but lower in summer and autumn. The MBC content was lower in the Casuarinas plantation than in the other plantations in the same soil layer. However, no significant differences were observed in MBN contents among the different forest types. The MBC and MBN concentrations were positively correlated with soil moisture, but negatively correlated with soil temperature. The MBC and MBN contents also decreased with increasing soil depth. Across all soil layers, secondary forest had the highest MBC and MBN concentrations. Our study also showed that the MBC and MBN contents were positively affected by total soil carbon(TC), pH, and litter N content, but were negatively impacted by soil bulk density and litter C content. Moreover, the MBN content was positively correlated with root N content. In summary, environmental factors and the differences in litter and fine roots, soil nutrient contents, as well as the soil physical and chemical properties caused by different tree species collectively affected the concentrations of the soil MBC and MBN.

Use of Near Infrared Spectroscopy to Measure Mechanical Properties of Solid Wood

The visible and near infrared(NIR)(350-2500 nm)spectra and the MOE of 438 small clear wood samples from Chinese fir,eucalyptus and poplar 72 were measured.Using partial least-square(PLS)modeling,the NIR spectra could be used to predict MOE and MOR of the clear-wood samples from Chinese fir and eucalyptus solid wood.NIR spectra could only be used to predict MOE but not MOR of poplar clear-wood samples.With the exception of MOR of poplar clear-wood samples,the correlations between NIR and the mechanical properties are very strong,and the calibration and test correlation coefficients are both above 0.80.

不同坡向对尾巨桉人工林林下草本植物多样性的影响

为了解不同坡向对尾巨桉(Eucalyptus urophylla×E.grandis)人工林林下草本植物多样性(Margalef指数dMa、Simpson指数D、Shannon-wiener指数H、Pielou指数J)的影响,以云南省临沧市双江县忙安林场8年生人工林为研究对象,设置不同坡向(阳坡、半阳坡、阴坡、半阴坡)的12个样地进行调查。研究结果显示:1)尾巨桉人工林共调查统计到林下草本植物30种,隶属16科28属,草本层植物物种数在阴坡、半阴坡相同且均高于阳坡、半阳坡。2)不同坡向尾巨桉人工林林下草本物种主要以禾本科的芭茅、菊科的紫茎泽兰为优势物种,占据主导地位。3)不同坡向尾巨桉人工林林下草本层植物在半阴坡的dMa、D、H、J值最大,阳坡最小。综合不同坡向尾巨桉人工林林下植物多样性指数分析比较,阴坡更有利于林下草本植物的生存。

尾巨桉等桉树无性系生长特性分析及选择

对尾巨桉(Eucalyptus urophylla×E.grandis)、巨尾桉(E.grandis×E.urophylla)、尾叶桉(E.urophylla)无性系试验林生长性状和干形进行了分析,为选择优良无性系提供科学依据。结果表明,不同无性系及同一无性系在不同林龄时的胸径、树高、单株材积生长率均有所不同,总体上QL4、QL7无性系生长率较大,而QL1、QL2无性系的生长率则较小;林龄1.5年及6.5年时无性系间胸径、单株材积均有显著差异,而无性系间树高仅在林龄1.5龄时差异显著;其余林龄无性系间的差异均不显著。用6.5年生参试无性系胸径、树高、单株材积、干形观测值对各无性系进行综合评定,结果QL7无性系的综合评定结果最佳,被评为优良无性系,其6.5年生时平均胸径、树高、单株材积分别是16.83 cm、21.42 m、0.233 1 m^3;而QL1无性系综合评定排最后一位;因此,不同无性系及同一无性系在不同阶段的生长表现均有所不同,无性系间胸径、单株材积在其生长的早期及后期均存在显著差异,而树高则在早期差异显著,所选择的QL7优良无性系可在试验地所在区域推广种植。

滇南尾巨桉人工林对不同间伐抚育措施的生长响应及其效益分析

本实验旨在揭示不同抚育措施对尾巨桉(Eucalyptus urophylla×E.grandis)人工林生长的影响,为滇南地区尾巨桉人工林的培育提供理论依据。以云南省宁洱市小黑江林区4年生尾巨桉林为研究对象,依立地特征将其划分为Ⅰ、Ⅱ、Ⅲ等3个类型,连续4年对样地进行观测,分别进行每木检尺、树高测量以及林下灌木和草本的统计,通过显著性差异分析、连年增长量分析以及生物多样性指数的比较,评价不同间伐措施的抚育效果。结果表明:在Ⅰ类样地中,间伐处理样地伐后第1年树高和胸径的连年增长量均高于对照YP(树高连年增长量约0.5 m/a,胸径连年增长量约1.28 cm/a),间伐强度为30%样地(BTQ1-30%-1/1、CCD1-30%-1/1和MMH1-30%-1/1等)伐后第1年树高和胸径的连年增长量均高于间伐强度为50%的样地(CCD2-50%-1/1和XSHK-50%-1/1等);同时,经过抚育间伐样地的林下植被多样性指数均高于对照样地,间伐强度为50%样地(MZP2-50%-1/1和BTQ2-50%-3/3)的林下灌木种类在各样地中最多(均达到10种),间伐方式为砍三留三样地比砍一留一样地的植被多样性指数高。在Ⅱ类样地中,间伐强度为50%的情况下,砍三留三样地的树高、胸径连年增长量均高于对照样地和砍一留一样地。在Ⅲ类样地中,仅开展间伐抚育样地的林分伐后第1年胸径连年增长量(0.90 cm/a)同对照样地(0.85 cm/a)并没有较大差别,而间伐抚育+施肥措施结合样地的伐后第1年胸径连年增长量(1.35 cm/a)却明显高于对照。在各立地条件样地中,间伐抚育林地的667 m^2蓄积量和经济总产值均大于对照样地,不同间伐措施样地之间也存在一定的差异;其中,Ⅰ类立地中间伐强度为30%,砍一留一样地的667 m^2产量最高,经济产值也最大;在Ⅱ类立地中,间伐强度为50%,砍三留三样地的产量最高,经济产值也明显高于对照和其他样地。可得出结论,间伐抚育能够提高滇南地区尾巨桉人工林胸径的增长量、667 m^2蓄积量以及经济产值,丰富林下植被多样性。其中,间伐强度为30%更适于Ⅰ类立地,间伐方式为砍三留三更适于Ⅱ类立地(间伐强度为50%的情况下),Ⅲ类立地在间伐的同时应该结合施肥等措施才能有效改善林分的生长。同时,砍三留三的间伐方式比砍一留一的间伐方式更有利于丰富林分的林下植被多样性。此外,样地的立地条件越好,进行间伐抚育所取得的效益一般越高。

巨尾桉人工林林木二元形高模型的研建

为研究巨尾桉(Eucalyptus grandis×E.urophylla)人工林林木二元形高模型,利用编制双江县巨尾桉二元立木材积表的138株造材样木实测数据(随机划分编表样本103株,检验样本35株),使用SPSS 21.0软件非线性回归分析工具对8个常用的二元形高备选模型进行拟合,根据分析计算的相关指数(R2)、均方差(RMSE)、平均绝对偏差(MAD)、总相对误差(RS)、模型预估精度(P)等指标对模型进行统计分析和综合评价,结果表明:模型FH=aHb Dc和FH=aHb/Dc的各项评价指标综合得分并列最高,基于国内外林学界在二元形高模型方面的应用传统,本研究选定FH=aHb/Dc作为巨尾桉人工林林木二元形高的编表模型,代入参数值的模型表达式为FH=0.633358 H^(1.356645)/D^(0.493597)。使用35株检验样本实测数据进行适用性检验的结果表明:模型的相关指数(R2)为0.90480,估计值的均方差(RMSE)为0.61151,平均绝对偏差(MAD)为0.50557,总相对误差(RS)为1.561%,预估精度(P)为98.52%;经残差检验,检验样本残差图以横轴为中轴线分布均匀;经进行F检验,计算得F值为0.96,小于F_(0.05)(1,33)的查表值4.14。生产性检验的结果表明:模型的相关指数(R2)为0.99035,估计值的均方差(RMSE)为3.37780,平均绝对偏差(MAD)为2.85151,总相对误差(RS)为1.836%,预估精度(P)为99.48%。编表样本和检验样本的各项评价指标结果表明,模型FH=0.633358 H^(1.356645)/D^(0.493597)的拟合精度高、误差小,适合作为巨尾桉人工林林木的二元形高模型,以此为基础编制的二元形高表可以在生产实践中应用。