木质部内负压传递方式的研究

利用杨树、法桐1年生枝条作试验材料,通过施加不同的负压进行传递实验,结果证明木质部内的负压是靠压力平衡方式传递的。水分的移动方式是从上到下分段依次进行的,负压的大小与移动速度呈显著的正相关关系。     

天然次生白桦木质部及韧皮部营养元素含量的分布及动态特性

对东北东部山区天然次生白桦林内白桦树干木质部、韧皮部中营养元素含量空间分布及动态特性的研究结果表明：（１）随树高增加，木质部、韧皮部中Ｎ、Ｐ、Ｋ、Ｍｇ含量呈增加趋势，而Ｃａ则相反；（２）木质部、韧皮部中Ｍｎ、Ｆｅ变幅较大，Ｚｎ、Ｎ变幅较小，而Ｃａ在木质部中变幅较大，在韧皮部中变幅较小；（３）木质部中各营养元素含量动态变化与叶、１年生枝中相应营养元素含量变化有相近的规律性。     

杨树菌根研究进展

杨树菌根真菌资源丰富，有３０种外生菌根真菌和５种ＶＡ菌根真菌可与其共生形成外生菌根和ＶＡ菌根，菌根的形态和解剖特征与菌根真菌的种类有关。菌根可以促进杨树苗木养分和水分的吸收，提高苗木的生长量，增强其抗旱性，并且可以诱导杨树体内酚类物质代谢中酶类（ＰＯ、ＰＰＯ、ＰＡＬ等）活性的提高，加速抗病性物质（酚类等）的合成，增强杨树抗溃疡病的能力     

榆树和柠条的水分生理生态特性研究

采用Ｐ－Ｖ技术对榆树，柠条Ｐ－Ｖ水分参数进行了测定，分析结果表明，在维持充分膨压时，榆树，柠条的渗透吸水能力的相似；在土壤水分出现严重持续胁迫后，柠条比榆树有更强的维持细胞的生命能力。     

水溶性纤维

水溶性纤维国外早有研究和生产，有的采用天然可溶性高分子物（如海藻酸），有的采用半合成可溶性高分子物（如羧乙基纤维素、羟甲基纤维素），有的采用合成可溶性高分子物（如聚氧乙烯）等，这些方法因存在着成本高，成品质量不稳定等问题，没有能够实现或坚持工业化生产。随着聚乙烯醇（以下简称ＰＶＡ）的出现及其用途的发展，用ＰＶＡ为基本原料已作为研制生产水溶性纤维的主要方法。日本于６０年代初首次以ＰＶＡ为主要原料进行工业化生产水溶性纤维，ＰＶＡ水溶性纤维的出现，对世界服装形式的多样化，工业、农业和医疗卫生方面的某些…     

红皮柳人工栽培丰产技术及利用

红皮柳（Salix purpurea）别名：柳条、绵柳、簸箕柳、笆斗柳。生于河沟溪边。分布于我国大部地区，东北地区有广泛分布。是重要的护岸树、风景林。茎可作编筐材料。     

P－V曲线的制作及其在树木抗旱性研究中运用的讨论

对我国北方地区优良抗旱造林树种Ｐ－Ｖ曲线的不同测定、绘制方法及如何更好地运用Ｐ－Ｖ曲线研究植物体内部水分关系进行了初步探讨，并证实Ｐ－Ｖ曲线所得部分水分参数与植物的抗旱性之间存在着密切关系，可以作为鉴别植物抗旱性强弱的重要指标。     

P—V曲线的制作及其在树木抗旱性研究中运用的讨论

对我国北方地区优良抗旱造林树种Ｐ－Ｖ曲线的不同测定，绘制方法及如何更好地运用Ｐ－Ｖ曲线研究植物体内部水分关系进行了初步探讨，并证实Ｐ－Ｖ曲线所得部分水分参数与植物的抗旱性之间存在着密切关系，可以作为鉴别植物抗旱性强弱的重要指标。     

青海共和盆地不同林龄乌柳林的水分利用策略

利用稳定同位素技术,测定共和盆地不同林龄(5、9、25 a)乌柳枝条木质部和土壤各层水分的δD值、δ18O值,分析它们是否随林龄变化而选择性地利用不同深度的土壤水分,并通过测定不同林龄乌柳叶片的δ13C值,分析比较它们的长期水分利用效率。结果表明:5 a乌柳主要利用源自降雨的10～50 cm深处的浅层土壤水分,9 a乌柳主要利用降雨补充的20 cm和地下水补充的30～50、150 cm深处的土壤水分,25 a乌柳主要利用降雨补充的10～20cm和地下水补充的50 cm深处的土壤水分。3个林龄乌柳的水分利用效率差异显著,5 a乌柳的水分利用效率明显高于9 a和25 a乌柳,9 a和25 a乌柳水分利用效率类似。水分利用策略的分析结果表明:9～25 a乌柳处于稳定时期。     

细胞分裂素:杨树气孔运动的调节剂

通过在三种杨树无性系，Ｉ－２１４（Ｐｏｐｕｌｕｓ×ｅｕｒａｎｅｒｉｃａｎａｃｖ．Ｉ－２１４）（ｌｔａｌｉｃａ）、中东杨（Ｐ．ｂｅｒｏｌｉｎｅｎｓｉｓ）（Ｂｅｒｏｌｉｎｅｎｓｉｓ）和群众杨（Ｐ．ｐｏｐｕｌａｒｉｓ３５－４４）（Ｐｏｐｕｌａｒｉｓ）一年生盆栽插条苗的木质部导入ＡＢＡ和细胞分裂素，研究了这两类激素在气孔调控中的作用。尽管不同无性系的气孔在对ＡＢＡ的敏感性上存在显著差异，但ＡＢＡ仍可导致气孔的关闭，然而在蒸腾流中的细胞分裂素（与ＡＢＡ共导入或分别导入）可以明显地抑制ＡＢＡ的作用。并且玉米素还能推迟土壤干旱所诱导的气孔关闭，在水分胁迫条件下，内源细胞分裂素浓度下降而同时ＡＢＡ上升．据此提出了复合胁迫信号的概念，即在根冠通讯中，是ＡＢＡ和细胞分裂素共同调控气孔的运动。另外还研究了玉米素、激动素、６－ＢＡ等不同细胞分裂素与ＡＢＡ的相互作用，结果发现６－ＢＡ与玉米素和激动素的作用相反，它不能抑制ＡＢＡ的作用，反而促进其对气孔的关闭     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。     

Natural Regeneration in Clear-cuts: Effects of Scarification,Slash Removal and Clear-cut Age

The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided.     

Risk Perception Among Non-industrial Private Forest Owners

Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken.     

Interactions in decomposition and N mineralization between tropical legume residue components

In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts (stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea (Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea, largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols. Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its components are mixed.     

Pasture production and tree growth in a young pine plantation fertilized with inorganic fertilizers and milk sewage in northwestern Spain

The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization, (2) milk sewage sludge at 40 kg N ha⁻¹ target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha⁻¹. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹); (2) Lolium perenne L. var. Tove (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea (Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m², with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral systems. This revised version was published online in June 2006 with corrections to the Cover Date.