不同种肥施用水平对大果沙棘苗期生长的影响

在西宁地区采用裂区设计将不同品种沙棘种植于不同种肥用量下进行实验结果表明：中华沙棘在其株高、根长、根茎、干重四项指标的测定中均高于向阳、楚伊两个大果沙棘品种。在300 kg/hm^2的施肥水平下,大果沙棘的苗期株高、根长、根茎、干重生长量最大。品种和不同磷酸二氨的施肥量的互作显著,中华沙棘在低肥条件下的生长量大,在高肥条件下向阳、楚伊的生长量大。     

Effect of board density on bending properties and dimensional stabilities of MDF-reinforced corrugated particleboard

We investigated the bending properties of composite boards produced by reinforcing both sides of corrugated particleboard with medium-density fiberboard (MDF). Thickness swelling and linear expansion (LE) were measured to assess the dimensional stabilities of the composite board. Although the apparent density of the composite board was 0.48g/cm³, its strength was found to be equivalent to that of 18-type particleboard as described in JIS A 5908. The boards parallel/perpendicular anisotropy in strength was 0.9. The modulus of rupture (MOR) of the composite board increased with board density only up to a certain density, beyond which the MOR was constant. On the other hand, the thickness swelling of both corrugated particleboard and the composite board was smaller than that of flat-type particleboard, satisfying the JIS A 5908 standard of 12%. Linear expansion (soaking in water of ordinary temperature for 24h) of corrugated particleboard was 0.7%–0.9% in the parallel direction and 2.1%–3.1% in the perpendicular direction; hence, anisotropy in linear expansion existed in the corrugated particleboard. The linear expansion of the composite board was 0.6%–0.9% in the parallel direction and 1.8%–2.5% in the perpendicular direction. Although the LE of the composite board was lower than that of corrugated particleboard, it is necessary to improve the LE of composite board for practical use.     

Performance and nutrient dynamics of holm oak (<Emphasis Type="Italic">Quercus ilex</Emphasis> L.) seedlings in relation to nursery nutrient loading and post-transplant fertility

Holm oak (Quercus ilex L.) seedlings were exponentially (E) nutrient loaded using incremental increases in fertilizer addition or conventionally (C) fertilized using a constant fertilizer rate during nursery culture. The fertility treatments (mg N plant⁻¹) were control (0), 25E, 100E, and 100C. Subsequently, 1-year-old plants were transplanted under simulated soil fertility gradients in a greenhouse to evaluate effects of nutrient loading and post-transplant fertility on seedling performance. Post-transplant fertility consisted of fertilizing plants at two rates (0 vs. 200 mg N plant⁻¹). A water-soluble fertilizer 20-20-20 was supplied in both nursery and post-transplant experiments. Nutrient loading increased plant N content by 73% in 100E and by 75% in 100C relative to controls, although no significant differences were detected between constant and exponential fertilization regimes at the 100 mg N plant⁻¹ rate. When transplanted, nutrient loading promoted post-transplant root growth relative to shoot, implicating potential to confer competitive advantage to loaded holm oak seedlings after trans-planting. In contrast, post-transplant fertility increased new shoot dry mass by 140% as well as N, P and K content relative to controls. Results suggest that holm oak seedlings can be successfully nutrient loaded in the nursery at higher fertility rates, improving its potential to extend new roots, but alternative fertilization regimes and schedules that better fit nutrient availability to the growth rhythm and conservative strategy of this species must be tested.     

尾叶桉MLA无性系林分不同施肥处理经济效益分析

对雷州林业局7种施肥处理的尾叶桉MLA无性系7年生与3年生林分进行经济效益分析，结果表明：最佳处理6(P300g/株 K300g/株 N150g/株)7年生时年均利润1528．1元41m2，比处理7(常规施肥，滤泥5000g/株 P250g/株 K100g/株 N100g/株，年均利润1452．6hm2)提高5．2％，比对照(不施肥，年均利润630．3元/hm^2)提高142．4％；3年生时处理6的年均利润为1605．5元/hm2，比处理7(年均利润1406．8hm2)提高14．1％，比对照(年均利润408．3元/hm2)提高293．2％；处理6的年均利润3年生时采伐比7年生时采伐提高5．1％；处理6和处理7在7年生时采伐，投资回收期均为10．3年，在3年生时采伐分别为8.0年与8．3年，3年生时采伐比7年生时采伐的投资回收期分别缩短2．3年与2．0年。     

大叶栎容器苗育苗期的施肥试验

在大叶栎容器苗的育苗期进行了氮、磷、钾3种元素不同配比的施肥试验,研究不同施肥配比处理对其苗木生长量、叶面积、叶绿素含量、生物量以及苗木质量指数的影响。结果表明:不同配比施肥处理的大叶栎容器苗苗木各项指标均存在显著性差异。氮、磷、钾3种元素的平衡施用对大叶栎容器苗生长的促进作用最大,为最优施肥配比,经过4次施肥后苗木的苗高、地径、叶面积、叶绿素含量、地上干重、地下干重分别是不施肥(对照)的205.2%、122.7%、375.3%、148.3%、240.7%、124.7%。     

太行山片麻岩区村级景观特征对比分析

运用景观生态学原理，选取景观多样性、景观优势度和均匀度等指标，对比分析了具有相似地貌类型的太行山片麻岩区村级景观特征的差异，探讨了人类活动与景观稳定性之间的关系。结果表明，在人为将大面积灌草丛、耕地改造成经济林，将退化灌木林地恢复为乔木林的情况下，景观多样性、景观均匀度下降，景观优势度、景观破碎度提高，景观异质性提高，景观稳定件增强。     

木材及木基材料吸湿尺寸稳定性检测方法研究

为实现木材及木基材料吸湿尺寸稳定性横向比较,规范其检测方法,依据现有相关检测标准,借鉴日本工业木材吸湿尺寸稳定性检测方法,结合木质材料特性以及我国的具体情况,提出一种木材及木基材料吸湿尺寸稳定性的检测方法,即以温度20℃、相对湿度65%条件下的材料尺寸为基准,测定在温度40℃、相对湿度为75%和90%的两种吸湿环境条件下的材料尺寸变化。通过该方法对柚木、印茄木、朴木3种不同尺寸的木材和对多层材料、高密度纤维板、普通刨花板3种木基材料的吸湿尺寸稳定性进行测定,以评价该方法的适用性和可行性。结果表明:木材与木基材料试样不超过12 d即可达到吸湿平衡,不同材料尺寸变化率、湿胀系数的大小关系也与实际情况一致。因此木材与木基材料试样均适于用该方法。     

油松谷胱苷肽转移酶Tau1单体结构稳定性研究

[目的]探究油松PtGSTU1结构与功能的关系,探讨油松PtGSTU1蛋白的单体稳定性。[方法]利用同源建模模拟PtGSTU1的三维结构,推测其N末端18位精氨酸(Arg18)和C末端103位天冬氨酸(Asp103)能够形成氢键来稳定蛋白单体结构。利用定点突变,分别将Arg18和Asp103突变为具有不同极性和构象的氨基酸残基,检测其蛋白的催化活性及结构稳定性。[结果]6个Arg18突变体均无法获得高纯度的具有正确折叠的可溶蛋白,而Asp103突变体可以表达为可溶蛋白,Asp103突变体对不同底物的催化活性和亲和力明显低于野生型,对经典底物CDNB和GSH反应的催化速率(Vmax)降低了至少9倍,对底物的催化效率(kcat/Km)也明显降低。[结论]Arg18和Asp103之间形成的氢键对稳定PtGSTU1单体结构具有重要作用,由于植物GST蛋白N端的保守性和C端结构域的多变性,Arg18的突变对结构和活性的影响大于Asp103,同时预示着C端结构域中可能存在其他氨基酸位点能够与18位精氨酸形成氢键,从而稳定蛋白单体折叠结构。     

Seasonal changes of understorey herbage yield in relation to light intensity and soil moisture content in a Pinus pinaster plantation

The relationship of understorey herbage yield with light intensity and soil moisture content was investigated in a 20-year-old Pinus pinaster plantation in Kilkis of Macedonia, northern Greece, in three seasons (fall, winter and spring). The plantation was thinned at three density levels, high, medium and low (2500, 1750 and 1000 trees/ha respectively) and it was seeded with Dactylis glomerata. In addition, two fertilization levels (0 and 110 N+150 P₂O₅ kg/ha) and grazing intensity levels (0 and 0.8 sheep/ha/yr) were applied in a split-split plot experimental design. It was found that herbage yield was highest in the ungrazed and fertilized low tree density stands in all seasons. In the medium tree density stand, although light was lacking, fertilized plots produced higher herbage yield as compared to unfertilized low tree density stands while fertilization is of no use in close stands if herbage production is the goal. Animals seemed to prefer fertilized and medium density stands. Third degree polynomial equations were the best to explain herbage variation through the seasons both in fertilized and unfertilized plots.     

木麻黄苗期施肥和密度的田间试验

在田间按正交设计方案，进行木麻黄苗期氮、磷、钾施肥试验，并安排了木麻黄苗木五种不同密度试验，结果表明：合理配施氮、磷、钾肥能提高苗木生长量，最佳施肥组合为氮３００ｋｇ／ｈｍ２、磷９００ｋｇ／ｈｍ２、钾１５０ｋｇ／ｈｍ２；适当增大苗木株行距有利于苗高、地径的生长；在一定密度限度（１５００００株／ｈｍ２）下，苗木生物量随密度提高而增加。