国内板栗空篷研究综述

近几十年来,国内研究板栗空篷取得了显著成果,阐明了板栗空篷的成因及其防治方法。板栗空发生机理是：生殖器官发育不良,授粉受精不良,总苞和子房中有机养分及矿质营养（尤其是硼,磷元素）水平低下等。板栗空篷防治方法有：（１）选用优良品种;（２）培养最佳的树体结构;（３）合理配置授粉树;（４）适当疏雄,疏篷,减少树体养分消耗,（５）加强肥水管理,保持树体健壮生长;（６）适时喷布营养液和植物生长调节剂。     

板栗花粉管生长特性

为确定最佳授粉时期,解决板栗空苞率高的问题,对‘早板栗’和‘早大栗’2个板栗品种进行套袋隔离和人工辅助授粉试验。结果表明:早板栗,早大栗2个品种从花粉萌发至花粉管生长到达胚珠均需要1个月左右;早大栗胚珠5月初开始发育,经过1个月的发育在5月底可形成成熟的八核胚囊,早板栗整个雌配子体发育过程比早大栗晚4~7 d;早大栗5月4日~5月14日之间柱头接受花粉的能力均较强,早板栗5月9日~5月14日前后有接受花粉的能力。结合花粉管生长速度、有效授粉时期和雌配子体发育情况确定品种早大栗的最佳授粉时期应在5月4日~5月14日,品种早板栗的最佳授粉时期应在5月9日~5月14日。     

如何减少板栗空苞

栽培板栗，往往由于栽树时没有重视栽植授粉树、授粉品种树配置不合理、授粉树栽植株树少，导致主栽品种栗树授粉受精不良，造成板栗空苞(俗称“空蓬”、“哑苞”)，有的栗产区，空苞率平均达到40％左右，空苞率高的，达到90％以上。     

板栗空苞的防治

<正>板栗空苞就是栗棚中没有栗子,群众叫"哑巴栗子"、"哑栗树"。这种空苞或叫空棚现象,严重影响板栗的产量。据调查,板栗正常生长的地区平均有15%的空苞率。不少地区的空苞率占50%,北京、河北、山东及南方各省都有严重发生。板栗空苞发生有一定的地区性,发生严重的地区年年都很严重,特别是嫁接树有时成片形成空包,已成为板栗     

板栗“空苞”防治措施

板栗所谓“空苞”,是指总苞中没有栗子,亦称之为“空篷”。板栗雌花数量一般较多,且落花落果现象也不太严重,但总苞如在发育和受精过程中生长停滞,胚胎早期败育,即导致形成“空苞”。其防治措施如下。一、科学合理栽植园地应选择 pH值4．6-7．5的微酸性土壤。土层深厚、湿润而排水良好、含有机质的砂质或沙岩、花岗岩风化的砂质壤土,对栗树生长发育最有利。板栗为异花授粉植物,自花结实率低,雌雄花期不一致,所以,建园时应科学配置适宜的授粉树, 或少数品种混栽,以利相互授粉,提高结实率,减少“空苞”。     

板栗空苞的形成原因及防治措施的研究

板栗空苞就是栗棚中没有栗子,群众叫“哑巴栗子”。这种空苞现象严重影响板栗的产量,并消耗大量营养。据调查,板栗正常生长的地区平均有15％的空苞率,不少地区空苞率占50％,易县赵家沟村有些山坡地空苞率占87％,严重影响板栗的产量,造成严重经济损失。因此,对板栗空苞的形成原因及防治措施进行研究是十分必要的。     

怎样使板栗多开雌花

板栗雌雄同株异花,雌花的多与产量密切相关。现介绍如下方法,可使板栗多开雌花,增加产量。 1、萌芽期进行适度抹芽,可促进结果枝的生长和增开雌花。抹芽量依枝条而定,健壮枝留5—6个大芽,一般留2—3条大芽,其它全部抹掉。     

怎样改造生长不良的柑桔树

在柑桔生产中,时常产生“小老树”、“衰弱树”、“旺长树”、“实生树”和“烂脚树”等五种不良柑桔树,严重影响柑桔产量和质量的提高。四川仪陇县截止1989年底,总定植的650万株柑桔中,约有205万株的柑桔树属于五种不良柑桔树之列,尤以“小老树”、“衰弱树”和“烂脚树”为最多,阻碍着柑桔经济的健康发展。近两年来,该县广大果树科技干部与果农在总结经验的基础上,找出了五种不良柑桔树的成因和改造途径,现总结如下。 1 原因及症状 (1) 小老树:主要是由于柑桔苗木定植在未经改造的紫色石骨子土上,或定植在极其浅薄、十分粘重的土壤上,以致虽定植多年而结果极少。其症状为:树体生长迟缓,枝叶生长     

板栗空蓬的原因及防治

板栗系壳斗科栗属,是原产我国的经济林树种。适应性广,抗干旱、耐瘠薄、寿命长,被群众称为“铁杆庄稼”。由于种种原因,造成一部分果树形成有蓬不实的现象,群众叫“哑巴栗子”、“哑巴树”。空蓬现象严重影响产量,根据造成空蓬的原因,分类介绍防治措施。1　改接换优由于板栗长期沿用实生繁殖,植株个体性状表现多种多样,有些果树天生空蓬现象严重。对于这类果树,建园时应选择当地主栽品种中的优良品种作主栽品种。对实生栗园中空蓬率高的植株进行高接,改劣换优。同时配置与主栽品种花粉亲和力好,花期一致,花粉量大的品种作授粉树。对配置授粉…     

板栗空棚产生原因及降低空棚率技术措施的研究

北京的板栗多集中分布在怀柔、昌平、密云等区县,属燕山板栗。因品质极佳,在国际市场享有声誉,是换汇率较高的出口物资。历史上多为实生繁殖,种间、单株之间差异大,加上管理粗放,产量低而不稳,空棚树的存在又严重影响产量的提高,即使嫁接优种,在有些板栗产区仍表现出空棚,有的甚至成片是空棚树。经调查,品种不同亦程度不同地存在空棚率,一般为7-15％,高在40％以上。单株之间差异更大,空棚率低的为2-4％,高的     

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.