X射线水衬比法测定华山松种子生活力的研究

通过研究，运用Ｘ射线摄影技术，经浸种，培养，干燥，射线摄影，在４天内即可准确判断出华山松种子的潜在发芽能力－生活力，制作了射线科的标准图片，确定了最佳判图条件是：２５℃侵种４８ｈ，２５℃培养４８ｈ，４０℃干燥５ｈ；判图标准是：有生活力的种子的潜在发芽胚及胚乳之间界线模糊不清，胚隐红可见，胚乳亮度均匀。     

X射线水衬比法测定小桐子种子生活力研究

通过研究,运用X射线摄影技术,经浸种、培养、干燥、射线摄影,在3 d内即可准确判断出小桐子种子的潜在发芽能力——生活力.制作了射线判图的标准图片,确定了最佳判图条件是:25℃浸种24 h,25℃培养36 h,35℃干燥5 h;判图标准是:有生活力的种子,胚和胚乳之间界线模糊不清,胚隐约可见,胚乳较亮且亮度均匀.同时证明了小桐子生活力强弱与其本身干燥后失水量关系极大,发芽种子的平均失水量为13.6%,死亡种子的平均失水量是21.8%.     

湿地松种子衬比射线检验方法的研究

对温地松种子进行对比射线方法检验,结果表明,其最佳x射线摄影衬比过程为:将种子在25℃下浸种24h,擦干种子表面水分后,置入40%KI溶液中处理5h,在流水中冲洗5～6min,置于70℃下干燥24h。使用SOⅡ胶片和HY—35型射线机时,拍摄条件为:电压20kV,电流4mA,曝光时间100s,焦片距25cm。由此认为,未被浸渗而胚和胚乳发育良好的种子具生活力,可用来估算种子的发芽能力。用上述衬比方法测定35份湿地松种子,其发芽能力与实际发芽率相当一致。     

快速测定林木种子生活力的方法──四唑法

四唑法是快速测定种子生活力的一种有效方法。它是根据种子胚部是否染成红色及染色的部位、形状和大小，来判断种子生活力的。此法简单快速，准确可靠，不受种子休眠期的限制，可在林木种子收购、贮藏、调运及休眠种子的检验中推广应用。１ 测定方法１．１取样从纯净种子中随机抽取２５或５０粒为１组，共取４组，即４次重复。１．２种子预处理为了软化种皮，便于剥取种仁，要对种子进行预处理。一般种壳较薄，易吸水、剥胚的种子（如油松等），用始温４０℃水浸种２４ｈ即可。而种壳较厚且深休眠的种子（如核桃、山杏等），要浸种３～６ｄ…     

光肥对长白落叶松种子发芽的影响

利用１０％，２．５％，１％和０．５％浓度的光肥溶液及清水对照处理对长白落叶松种子进行发芽试验，浸种时间分别为４８小时和７２小时，结果表明：经１０％和２．５％的光肥溶液处理的种子萌发受到抑制，发芽率，发芽势均比对照显著降低，平均发芽天数较对照明显延迟；经１％光肥溶液处理的种子，其发芽率较对照提高４％（４８小时），１３％（７２小时），发芽势较对照提高４．５％（４８小时），１２．％（７２小时）经０．５％     

小叶锦鸡儿种子发芽试验条件的研究

对小叶锦鸡儿种子进行不同温度、浸种、基质、光照等条件的发芽试验结果表明：浸种处理对种子发芽有显著的抑制作用,发芽前不宜做任何浸种处理;发芽最适温度为２５℃或２８℃,蛭石、海棉、单层滤纸为良好发芽基质。自然光下发芽良好。发芽高峰期为第３天,发芽结束期为第７天。     

杨农间作对农田生态环境的改善

本文根据５ａ（１９９３～１９９７年）人工和自动气象仪器的观测资料,对不同模式杨农间作田中的温、湿、风和蒸发等小气候因子的时空分布及其效应进行了较为详尽的分析。结果表明：杨农间作的防风效能为４５％～８７％,平均５７％;可降低日最高气温０３℃～３４℃,平均降低１３℃;降低地面日最高温度６０℃,最高可达１９５℃;提高日平均绝对湿度０９ｈＰａ～２４ｈＰａ,平均１４ｈＰａ;提高日平均相对湿度１％～１３％,平均５％;减少水分蒸发１７％～３６％,平均２５％;在干热风日可使相对湿度＜３０％的持续时间减少４５ｈ。因此,杨农间作具有明显的防风、降温、增湿和减少蒸发的作用,这对改善田间小气候和农业生态环境,促进农业的高产、稳产具有重要意义。     

光肥对长白落叶松种子发芽的影响

利用１０％、２．５％、１％和０．５％浓度的光肥溶液及清水对照处理对长白落叶松种子进行发芽试验，浸种时间分别为４８小时和７２小时。结果表明：经１０％和２．５％的光肥溶液处理的种子萌发受到抑制，发芽率、发芽势均比对照显著降低，平均的发芽天数较对照明显延迟；经１％光肥溶液处理的种子，其发芽率较对照提高４％（４８小时）、１３％（７２小时），发芽势较对照提高４．５％＜４８小时）‘１２．５％＜７２小时）；经０．５％光肥溶液处理的种子，其发芽率较对照提高７％（４８小时）、１６．５％（７２小时），发芽势较对照提高３．５％（４８小时）、１３．５％（７２小时）。     

不同处理对黄花远志种子发芽的影响

对黄花远志种子采用砂擦、赤霉素浸种、温水浸种3因素、3水平正交试验设计进行沙藏催芽对比试验。结果表明:经过处理后的种子比未经处理种子平均发芽时间早14.4 d;平均发芽率提高27.4%;温水浸种对种子发芽影响显著,赤霉素浸种、砂擦对种子发芽有一定影响;以中度砂擦+赤霉素1200倍液浸种8 h+50℃温水浸种8 h组合处理后的种子发芽率最高,达93%。     

两种灌木种子萌发特性的研究

试验表明,白鹃梅种子有浅休眠特性,如在室温１５～１９℃混湿沙层积１５ｄ即可解除休眠,发芽率达９７％,活力指数达１１６１０;若用０２％ＫＮＯ３预处理,不仅能代替室温层积,而且优于室温层积,发芽率达９８％,活力指数达１４３０９２。火炬树种子具有深休眠特性,用浓Ｈ２ＳＯ４酸蚀４５ｈ,２ｄ初次计数,３ｄ发芽率达８３％,活力指数达２２０５１４;若不做预处理,即使是混湿沙冷层积在５℃或暖层积在１８～２５℃,２１８ｄ也不能解除其休眠。     

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.