毛竹实生苗物理力学性质的研究

以材性优异且同样条件下种植的当地鞭生毛竹为参比,研究了毛竹实生苗竹材的物理力学性能。结果表明,毛竹实生苗竹材的气干密度为0.617 g/cm~3,小于鞭生竹的气干密度(0.662 g/cm~3);全干密度为0.562 g/cm~3,小于鞭生竹的全干密度(0.607 g/cm~3);气干或全干时,毛竹实生苗的干缩率均小于鞭生竹;除顺纹抗拉强度外,毛竹实生苗的顺纹抗压强度、顺纹抗剪强度、抗弯强度均低于鞭生竹。因此,毛竹实生苗具有较高的强重比,相比鞭生竹材,具有密度较低、干缩率较小、力学强度性能良好的特点。     

4种大径丛生竹材的密度和干缩性研究

对油簕竹(Bambusa lapidea)、车筒竹(B.sinospinosa)、越南巨竹(Dendrocalamus yunnanicus)和麻竹(D.latiflorus)4种大径丛生竹竹材不同部位的密度和干缩性进行了测定和分析。结果表明,4种竹材的基本密度分别为0.742、0.678、0.761和0.601g·cm-3。气干体积干缩性分别为4.61%、3.82%、3.28%和3.66%。各竹种竹材的密度和全干缩性有显著差异,而竹材的气干干缩率没有显著差异。竹材的气干、全干和基本密度均与竹秆高度呈正相关,干缩性则相反。与常见的板材原料毛竹相比,4种竹材的密度和干缩性均可达到板材原料的要求。     

薄壁型巨龙竹物理性质研究

以薄壁型巨龙竹为研究对象,对3~5年生薄壁型巨龙竹秆材的梢部、中部和基部进行物理性质研究。结果表明:薄壁型巨龙竹的基本密度、气干密度和全干密度分别为0.682 g/cm3、0.756 g/cm3、0.711 g/cm3,大于云南甜竹和油簕竹的相应值,略小于毛竹;吸水率为62.68%,显著高于毛竹的吸水率;径向气干干缩率为3.920%,大于毛竹相应值。就物理性质而言,薄壁型巨龙竹适合作为竹板材原料加以开发利用。     

不同竹龄毛竹材物理性质的差异分析

以我国传统竹种——毛竹(Phyllostachy pubescens)为研究对象,在5个竹龄(0.5、1、2、4、6年生)和3个纵向高度水平对其壁厚、基本密度及干缩性(径向干缩率、弦向干缩率和体积干缩率)等主要物理指标进行对比研究。结果表明,毛竹材壁厚6.698-7.875mm,基本密度0.494-0.728g·cm-3,全干、气干体积干缩率分别为10.204%-17.412%、7.881%-14.914%,全干时弦、径向干缩率分别为5.131%-6.119%、4.919%-5.826%,气干时弦、径向干缩率分别为3.953%-5.264%、3.663%-4.612%。壁厚和基本密度随竹龄增加呈增加趋势,干缩率呈减小趋势,2a后干缩率保持在稳定水平。沿纵向高度从基部到梢部,壁厚逐渐减小,基本密度、全干和气干径向干缩率呈增加趋势。双因素方差分析表明:毛竹壁厚、基本密度、体积干缩率和径向线干缩率随竹龄变化在0.001水平显著;竹壁厚度和基本密度随竹秆纵向高度变化在0.001水平显著。     

红壳竹人工林竹材物理力学性质的研究

测试了红壳竹人工林竹材的物理力学性质。结果表明：竹龄对红壳竹竹材的物理力学性质有显著的影响；竹材的径向、弦向、体积全干缩率随竹龄增加逐渐减少；基本密度、顺纹抗压强度、顺纹抗拉强度和抗弯强度都随竹龄增加而提高，至5－6年生强度稳定在较高的水平上，竹午由下至上，含水率、体积全干缩率逐渐减少；维管束密度、基本密度及力学强度相应提高。     

不同地位级雷竹竹材的物理力学性质比较

测定了不同地位级不同竹龄雷竹竹材的物理力学性质,结果表明:不同地位级雷竹竹材的基本密度和力学性质都随竹龄的增大而提高;径向、弦向和体积全干缩率随竹龄增大而减少,地位级Ⅱ的竹材的基本密度和力学性质高于地位级Ⅰ的,径向、弦向和体积全干缩系数小于地位级Ⅰ;不同地位级的竹材基本密度、顺纹抗压强度、顺纹抗拉强度和弦向抗弯强度有显著差异.     

慈竹材物理力学性质研究

对四川江油1～3年生慈竹材主要物理力学性质进行了测定与分析,结果显示:竹材气千密度,全干密度,基本密度,顺纹抗压强度,顺纹抗剪强度随竹龄和竹秆高度的增加而增加:径、弦向全干缩率随竹龄和竹秆高度的增加而减小:径向全千缩率大于弦向:竹壁厚度随竹龄的增加而增厚,随竹秆高度的增加而减小.方差分析表明,竹材全干密度,基本密度,径、弦向全干缩率,顺纹抗压强度随竹龄变化在0.001水平显著;全千密度,竹壁厚度,顺纹抗剪强度随竹秆高度变化在0.001水平显著.     

毛竹竹材物理力学性能研究

为了解不同竹龄毛竹生材含水率、线性干缩率、气干密度、抗弯强度、抗弯弹性模量和顺纹抗压强度等物理性能,对其加工应用的影响,笔者以2-7年生毛竹为材料进行研究,结果表明：竹材的生材含水率、气干干缩率（弦向、径向、纵向）和全干缩率（弦向、径向、纵向）随着竹龄的增加呈减小的趋势;从基部到梢部竹材的生材含水率、线性干缩率均减小;竹材线性干缩率弦向＞径向＞纵向.竹材气干密度、抗弯强度、抗弯弹性模量和顺纹抗压强度均随着竹龄的增加呈增大的趋势,尤其是3年生竹材的这些物理力学性能与2年生差异显著,但3年后生竹材差异不大;从基部到梢部竹材的气干密度、抗弯强度、抗弯弹性模量和顺纹抗压强度逐渐增加.综合考虑毛竹的物理力学性能和竹林的经济效益,适合采伐的是3年后生竹材,锯截之后的竹材也应根据部位不同进行区分,以便于加工应用过程中合理利用,提高产品的理化性能和质量的稳定性.     

苦绿竹、椽竹、橄榄竹物理力学性质及其在人造板上的应用分析

测定了2-5年生的苦绿竹、椽竹、橄榄竹的物理力学性质和外形尺寸,并对其在人造板上的应用进行初步分析。结果表明:与毛竹相比,绿竹各项力学性能均较低;椽竹和橄榄竹,除了顺纹抗剪偏小外,横纹抗弯、顺纹抗拉、顺纹抗压与毛竹相当。3个竹种的壁厚和直径较小,均不适合于普通竹地板生产;苦绿竹和橄榄竹可用于制作竹材胶合板、碎料板等人造板产品,椽竹因直径较小,只适用于碎料板生产。     

大木竹纤维形态与组织比量的研究

通过对浙江南部大木竹的纤维形态和组织比量测定,并与造纸性能良好的青皮竹和当地分布较广的绿竹进行比较,结果表明：大木竹竹材属于长纤维原料,纤维长2．2,4mm,比青皮竹(2．29m)略小,而比绿竹(1．87mm)为大;纤维长宽比达166,较青皮竹和绿竹的相应值147和131均大,其中与绿竹的差异达显著水平;壁腔比为3．5;纤维组织比量达48．68％,比青皮竹(50．19％)略小,而比绿竹(45．78％)为大。大木竹纤维形态和组织比量各指标在竹秆的纵向和径向均有一定变异,主要表现为,纤维壁腔比和纤维组织比量随秆的高度增加而增大;在径向部位,纤维长度和长宽比均为竹壁中部较大,而壁腔比则为竹壁外侧较大。竹龄主要对壁腔比产生影响,1年生、3年生大木竹的壁腔比明显大于当年生竹。     

Photosynthetic characteristics of Fagus sylvatica and Quercus robur established for stand conversion from Picea abies

Efforts in Europe to convert Norway spruce (Picea abies) plantations to broadleaf or mixed broadleaf-conifer forests could be bolstered by an increased understanding of how artificial regeneration acclimates and functions under a range of Norway spruce stand conditions. We studied foliage characteristics and leaf-level photosynthesis on 7-year-old European beech (Fagus sylvatica) and pedunculate oak (Quercus robur) regeneration established in open patches and shelterwoods of a partially harvested Norway spruce plantation in southwestern Sweden. Both species exhibited morphological plasticity at the leaf level by developing leaf blades in patches with an average mass per unit area (LMA) 54% greater than of those in shelterwoods, and at the plant level by maintaining a leaf area ratio (LAR) in shelterwoods that was 78% greater than in patches. However, we observed interspecific differences in photosynthetic capacity relative to spruce canopy openness. Photosynthetic capacity (A₁₆₀₀, net photosynthesis at a photosynthetic photon flux density of 1600 μmol photons m⁻² s⁻¹) of beech in respect to the canopy gradient was best related to leaf mass, and declined substantially with increasing canopy openness primarily because leaf nitrogen (N) in this species decreased about 0.9 mg g⁻¹ with each 10% rise in canopy openness. In contrast, A₁₆₀₀ of oak showed a weak response to mass-based N, and furthermore the percentage of N remained constant in oak leaf tissues across the canopy gradient. Therefore, oak photosynthetic capacity along the canopy gradient was best related to leaf area, and increased as the spruce canopy thinned primarily because LMA rose 8.6 g m⁻² for each 10% increase in canopy openness. These findings support the premise that spruce stand structure regulates photosynthetic capacity of beech through processes that determine N status of this species; leaf N (mass basis) was greatest under relatively closed spruce canopies where leaves apparently acclimate by enhancing light harvesting mechanisms. Spruce stand structure regulates photosynthetic capacity of oak through processes that control LMA; LMA was greatest under open spruce canopies of high light availability where leaves apparently acclimate by enhancing CO₂ fixation mechanisms.     

广州市南沙红树植物无瓣海桑、木榄人工林生物量的研究

红树林是热带、亚热带海岸潮间带的木本植物群落,它是海湾河口地区生态系统最重要的生产者,对保护海湾河口地区的生态平衡起着十分重要的作用。湿地植物生物量是衡量湿地生态系统健康状况的重要标志。红树林生物量的研究,对于了     

宽叶杜香叶柄再生体系建立及种质离体保存研究

The tender leafstalks of Ledum palustre var.dilatatum were used as explants for the experiment.Uniform design for the most suitable media for shoots regeneration immediately at base of tender leafstalks,rooting and germplasm conservation in vitro was screened.The results showed that N6+ZT 2.65 mg·L-1+IAA 0.05 mg·L-1 was fits for shoots regeneration,the frequency of shoots induction was higher than 92.5%;MS(modified)+IAA 0.1 mg·L-1+Kt 0.75 mg·L-1 for rooting,the rate of rooting was 98%;N-68+B9 2.5 mg·L-1+ Ph...     

Tree age and soil phosphorus conditions influence N2-fixation rates and soil N dynamics in natural populations of Acacia senegal

Acacia senegal, an important leguminous tree in arid and semi-arid environments, has shown promise as a multipurpose species, including gum production and soil fertility improvement, linked with N₂-fixation capabilities. Of particular interest are ontogenetic and edaphic effects on A. senegal performance in natural populations. Our research objectives were to investigate the effect of tree age and site phosphorus conditions on (1) tree N₂-fixation and (2) soil N and C dynamics in natural stands of A. senegal var. senegal, Baringo District, in the Rift Valley, Kenya. Sites consisted of A. senegal saplings (9 months) and mature A. senegal trees (7 years) along an edaphic gradient of soil P availability. A single-tree neighborhood approach was employed using a two by two factorial design: site conditions [high and low soil P contents] and tree age class [juvenile and mature]. Soil (N and C pools and fluxes) and plant metrics were quantified. A soil transfer experiment was also employed to confirm age and site effects on soil N mineralization. On the high soil P site, A. senegal had significantly lower foliar (¹⁵N levels than neighboring non-leguminous species (Balanites aegyptiaca), while foliar δ¹⁵N values in A. senegal on the low P site exhibited no significant difference with our reference plant, B. aegyptiaca. Across P sites, B. aegyptiaca had similar foliar δ¹⁵N values. These results indicate that the rate of N₂-fixation of A. senegal trees, as determined with foliar ¹⁵N natural abundance methodology, increased with increasing soil P availability in these natural populations. However, N₂-fixation rates declined with age. Although soil texture and soil CO₂ efflux did not differ between sites or across ages, soils under mature A. senegal at the high P site exhibited significantly greater total N content and total C content in comparison to soils at the low P site and under juvenile plants. Furthermore, under mature A. senegal trees, soil N mineralization rates were significantly greater as compared to under saplings. Soil transplants confirmed that soil microbial activity may be stimulated under mature trees as N mineralization rates were 2-3 fold greater compared to under A. senegal saplings. Our findings suggest that tree age and soil P availability are important factors in the nitrogen budget of natural populations of A. senegal, determining N₂-fixation rates, and potentially influencing soil total N and C pools and soil mineral N. This study provides information regarding the adaptation of A. senegal under differing edaphic conditions thus increasing accuracy of management support for A. senegal populations as productive agroforests.     

采伐对大兴安岭落叶松-苔草沼泽土壤有机碳储量的影响

对比分析了大兴安岭不同采伐强度(未采伐—对照、轻度择伐—25%、中度择伐—35%、强度择伐—50%)下落叶松-苔草沼泽土壤密度、土壤有机碳含量与土壤有机碳储量的变化,揭示了采伐干扰对森林湿地土壤有机碳储量的影响规律。结果表明:①中度择伐与强度择伐显著提高了其土壤密度,轻度择伐则对土壤密度无显著影响;②轻度择伐显著提高了其表层和深层土壤的有机碳含量,中度择伐与强度择伐显著降低了其各土壤层和中上部土壤层的有机碳含量;③轻度择伐显著提高了其深层土壤有机碳储量,中度择伐和强度择伐则分别显著降低了中下部和中部土壤层的有机碳储量;④轻度择伐样地土壤有机碳储量较对照提高了16.2%(P>0.05),中度择伐和强度择伐样地土壤有机碳储量分别较对照降低了48.5%和30.1%(P<0.05)。     

绿竹造林及丰产培育技术研究

１９９６－１９９７年在福建省福安市对绿竹不同立地造林和竹林结构、留母竹株数、打蔸、扒晒、施肥及切鞭等丰产栽培技术进行了试验研究。绿竹造林以山 下部较河滩地和平地效果好。绿竹竹林结构以保留１－２年生竹和切鞭以竹丛产笋量增产效果显著,绿竹施肥以饼肥最佳,其次是施尿素２次和复合肥。４月份扒晒对产笋有增产效果     

接种不同真菌菌株后黄栌生物电指标的变化

以黄栌枯萎病发病植株的根部所分离到的3种优势菌株作为供试菌株,利用新型电感电容表和电导率仪分别测定黄栌的树干电容、电阻和叶片电导率等生物电指标的变化,发现接种不同真菌菌株后黄栌的树干电容均值都呈现逐渐下降的趋势,树干阻抗均值、叶片细胞外渗液的相对电导率和叶片离子外渗百分率则都呈现逐渐增大的趋势。但接种Verticillium dahliae后黄栌出现枯萎病症状,且各项生物电指标均呈现更为显著的变化,其变化幅度较分别接种Fusarium sp.、Cylindrosporium sp.菌株后的电指标变化幅度大,而且树干电容和电阻在接种5 - 7天后表现出显著差异性,比病害症状出现提前7 - 10天;同时,受Verticillium dahliae侵染的植株和未受侵染植株在树体干部电容、阻抗和单位电容指标上差异显著,树干电阻与树干电容在植株受侵染后表现出更为显著的负相关关系。     

地涌金莲及红苞地涌金莲对光和CO2的响应

比较分析了地涌金莲原种及红苞地涌金莲变种的光响应和CO2响应特征以及叶绿素含量等指标.结果表明:(1)在Pn-PAR中,地涌金莲原种的最大光饱和净光合速率、光补偿点和暗呼吸速率分别较红苞变种高20.42％、34.88％、31.95％,而光饱和点却较红苞变种低4.95％;Pn-Ci响应的各参数中,原种的光呼吸速率、CO2饱和最大净光合速率以及羧化效率分别高于红苞变种2.73％、14.79％、21.35％,说明地涌金莲的光合能力要强于红苞地涌金莲;(2)地涌金莲具有典型的C3植物特征;(3)地涌金莲为阳性耐荫植物;(4)地涌金莲的叶绿素a、b以及a/b的含量分别高于红苞地涌金莲22.60％、32.46％、25.06％.     

小陇山不同经营措施下次生锐齿栎天然林物种多样性研究

采用固定样地和样方法调查了小陇山林区百花林场3个实施不同经营措施的锐齿栎天然林林分特征和物种组成,运用4种常用的物种多样性指数对调查林分的乔木层、灌木层和草本层的物种多样性进行对比分析,结果表明:3种类型锐齿天然林的灌木层相对于其乔木层和草本物种组成丰富,多样性高;长期封育后的锐齿栎天然林群落在3种天然林类型中物种组成最丰富,乔木层、灌木层和草本层的Shannon-Wiener指数、Pielou指数和Margalef指数值在3个林分中最高;近自然技术单株经营后的锐齿栎天然林各层次的物种组成相对较少,多样性较低,但其林分中保留的乔木树种个体较大;结构优化抚育后的锐齿栎天然林的物种组成和多样性介于二者之间.抚育经营措施对林分的影响与抚育经营强度密切相关,适当的抚育经营强度能够促进林分多样性提高,否则会带来不利的影响,结构化森林经营技术是一种有效的经营方法.     

第二代桉树人工纯林和混交林土壤呼吸及其组分研究

以广西凭祥中国林业科学研究院热带林业实验中心第二代桉树人工纯林(PP2)及其与降香黄檀混交的混交林(MP2)为研究对象,采用壕沟法,利用LI-8100土壤呼吸测定系统,对两种林分土壤呼吸组分进行分离研究。结果表明:PP2和MP2土壤呼吸速率及其各呼吸组分季节变化与土壤5 cm处的温度季节变化相似,峰值出现在6—8月份,谷值出现在12月底至次年1月初,土壤呼吸速率与土壤含水量无关;PP2全年土壤总呼吸为1 147.41 g·m-2,比MP2(844.07 g·m-2)增加了26.44%,MP2的自养呼吸(RR)累积量(136.87 g·m-2)比PP2(506.72 g·m-2)降低72.99%,而其异养呼吸(RH)累积量(707.21 g·m-2)却比PP2(640.69 g·m-2)增加了10.38%。纯林和混交林的细根生物量差异以及土壤有机质含量、凋落物有机质含量、土壤C/N、凋落物量和凋落物C/N的不同是导致自养呼吸和异养呼吸产生差异的主要原因。