黄河三角洲盐碱地主要造林树种的动态生长与生态效应

各树种的胸径随着林龄增加而增长,白蜡的树高随林龄延长也呈递增趋势,而其他树种的树高变化则没有明显规律性,在林龄13年内,杨树的胸径和树高生长要明显优于其他4个树种。刺槐、白蜡、白榆和臭椿的长期人工林可以显著降低土壤盐分,增加土壤的养分,从而培肥土壤,但对土壤pH稍有提升作用,碳汇量大小顺序为:白蜡刺槐白榆臭椿;刺槐人工林更新为杨树林后,林地土壤含盐量有所增加,但土壤肥力得到改善,明显提高了人工林的固碳性能。     

大叶白蜡等六树种在新疆造林的最佳时期探讨

<正> 我们在长期造林实践中发现,有许多树种,其幼树的成活和生长状况都因栽植季节和时间的不同而有所差异。因此,应根据树种的特性来选择较为适宜的造林季节和时期,以提高造林成活率和幼树生长量。本试验仅对大叶白蜡等六个平原造林树种进行了不同时期造林的效果探讨,试图为不同季节造林的树种选择,提供一些参考。一、试验方法(一)供试树种选用我院苗圃培育的大叶白蜡、沙枣、白柳、阿富汗杨和新疆白榆、河南白榆(以种源分) 等六个树种进行试验。苗木规格见表1。(二) 试验方法和技术要求选择春季和秋季两个造林季节。春季仅选一期(最适时间);秋季分三期:早秋期、中秋期和晚秋期。栽植时间和苗木状况见表2。     

控根对湿加松扦插苗生长与根系形态的动态影响

以湿加松扦插容器苗为材料,设置空气切根(30,50,70cm苗床)和不切根对照处理,分析处理后半年内株高、地径、地上部生物量、根系生物量、根长、根表面积、根直径、细根比例等指标的月变化。结果表明,控根影响了扦插苗的根系形态,但对扦插苗的生长与生物量无显著影响。处理4个月后,70cm苗床的切根处理显著促进了根系的伸长生长,但5个月时,切根苗木的根系转向粗生长的阶段,与对照相比,细根比例降低,而根直径增大。苗木生长量呈现与根直径的相关性逐渐增强、而与根长度相关性减弱的趋势,表明控根苗木根系形态的动态变化有利于促进苗木的生长。建议采用70cm苗床做湿加松扦插苗的空气切根。     

容器苗留袋、脱袋造林后水分动态及对苗木生长影响

采用ECH2O含水量监测系统,对侧柏容器苗留袋、脱袋造林后容器水分动态及苗木生长及生物量进行监测。林地土壤平均含水量>脱袋造林>留袋造林。根系数量、根系分布、苗木生长状况、标准株生物量脱袋造林均优于留袋造林。大规格移植容器苗造林时,在确保苗木根团完整的情况下,以采用脱袋造林栽植方式为好。     

盐碱区园林绿化的好树种——绒毛白蜡

绒毛白蜡(■),又名绒毛梣,木樨科,落叶乔木。该树原产美国,1907年首先引入山东省,现已在我国19个省、市、自治区广泛栽培,尤其在山东、天津等,已成为盐碱区城镇绿化和营造用材林、防护林的主要树种。据山东省和天津市栽培试验,在含盐量为0.8％的试验地上,绒毛白蜡造林成活率达91.7％,而臭椿成活率仅为11.1％;在土壤含盐量0.44％的盐碱地,绒毛白蜡三年保活率为95.2％,而白榆和刺槐分别为74％和59.9％;在含盐量0.53％街道上绿化,成活率达86.6％,而旱柳仅为43％。绒毛白蜡不但耐盐碱,而且冠形美、抗污染,树叶对二氧化硫、氯等有害气体的吸收能力比旱柳、五角枫、国槐、木槿都强。因此,是盐碱区城镇园林绿化和     

辽西半干旱地区矸石废弃地造林树种筛选

对辽西半干旱地区矸石废弃地以排矸年龄为界限,划分为4个类型,在不同类型上进行人工造林试验,通过对比试验筛选适生造林树种。结果表明:Ⅰ类矸石废弃地适宜的造林树种排序为紫穗槐>锦鸡儿>白榆>沙棘>沙枣;在Ⅱ类矸石废弃地上适宜造林树种排序为紫穗槐>锦鸡儿>火炬树>臭椿>白榆>刺槐;Ⅲ类矸石废弃地适宜的造林树种排序为火炬树>臭椿>刺槐>白榆>杨树>侧柏>樟子松;Ⅳ类地区矸石废弃地适宜的造林树种排序为火炬树>臭椿>刺槐>杨树>旱柳>白榆>侧柏>樟子松。     

6年生互叶白千层根系形态与缩根技术

研究6年生互叶白千层自然生长的根系组成与分布,并对3年生互叶白千层采取切根与滴灌的缩根处理。自然生长根系水平根系较长且粗壮发达,根基部细根分布较少,影响互叶白千层移栽恢复。切根和滴灌处理可以缩短主侧根长度,诱导细根生长,细根生物量明显增加,且大部分集中在植株根系20 cm水平范围内。综合考量以3年生苗木根茎外10 cm处切根,并在种植株根系20 cm范围内采用导向性滴灌处理苗木根系生长较好,有利于互叶白千层大苗的移栽恢复。     

3个树种幼苗细根不同根序形态特征及其与生物量分配关系比较

刨花楠、山樱花、福建柏3个树种1年生幼苗为材料,对根、茎、叶生物量及不同根序细根的平均直径(D)、比根长(SRL)、根表面积(SSA)和根组织密度(RTD)等形态指标进行测定、比较、分析其不同根系细根形态特征差异,并对其根序形态特征与生物量分配关系进行分析。结果显示:(1)同一等级细根的SRL、SSA和RTD等形态指标在同一树种间变动较大;同一根序细根在不同树种之间及同一树种在不同根级之间的细根D、SRL、SSA及RTD等形态指标也存在差异。(2)不同树种幼苗的不同根序细根的D、SRL、SSA和RTD等形态指标与幼苗生物量分配关系表现不同。刨花楠与福建柏幼苗生物量分配与其2、3级细根关系密切,而福建山樱花幼苗生物量分配则主要与其1、3级细根关系紧密。研究结果表明,不同树种幼苗不同根系细根的D、SRL、SSA及RTD等形态指标存在差异,其对生物量分配的影响也各有不同。     

渭北主要造林树种细根生长及分布与土壤密度关系

采用野外样地调查和盆栽试验的方法 ,研究了土壤密度对渭北主要造林树种细根生长及分布特征的影响。结果表明 ,在 0～ 10 0cm的深度内 ,不论是阴坡还是阳坡 ,油松林地的土壤密度均表现出随土层的加深逐渐增大的趋势 ;刺槐林地的土壤密度大于油松林地 ,且各土层间的差异不大。油松林地各土层土壤密度与不同径级根系长度存在显著的负相关关系。盆栽基质密度对不同树种苗木根系的生长和发育的影响虽各异 ,但在基质密度和孔隙度适中的条件下均生长良好 ,生物量达到最大。盆栽基质的密度对刺槐和油松根系的生长和发育的影响最显著 ;侧柏和山杏的细根生长发育受土壤密度的影响较小 ,其根系生物量在不同密度的基质中没有明显变化。     

栎类薪材树种的选择研究

在四川盆地,通过对麻栎、栓皮栎、辽东栎、檞树、高山栎和板栗等,6个栎类树种苗期生长、林木生长量、生物量、萌生力、抗病虫危害能力等的对比试验,6个树种的前期根系生长均较上部分快,3年生林木根系的生物量占总生物量的32—73％;萌生林的生物量较同年生实生林大2～3倍。实生林和萌生林的生物量均是:麻栎>板栗>栓皮栎>辽东栎>檞树。选择出麻栎和栓皮栎是该区最适宜的栎类薪材树种;板栗是具有一定薪材价值的经济树种。     

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.