辽西地区水土保持林主要林分类型及结构特征分析

对辽西地区现有几种主要的水土保持林分类型进行了结构特征分析，结果表明，混交类型的水土保持林，其林分层次结构、生长情况均好于油松纯林，物种我样性指数高于纯林；林分生物量以油松－刺槐形成的乔木混交林最高，达96．550t/hm^2，比油松纯林提高57．658t/hm^2；各类型混交林林地土壤理化性质有了很大的改善，混交类型林地土壤容重比纯林减小0．05－0．2g/cm^3、孔隙度提高0．76％－3．45％、有机质提高0．03％－0．73％、全氮含量提高0．004％－0．036％，说明油松阔叶混交林在改善土壤理化性质方面起了重要作用；林分枯枝落叶量及持水量也明显高于油松纯林，油松－刺槐形成的乔木混交林是辽西地区林分结构较为理想的混交类型。     

日本落叶松、色赤杨混交林土壤特征及林分生物量研究初报

日本落叶松与色赤杨带状混交林15年生时，乔木层生物量高于纯林20．4％，灌木层和草本分别比纯林提高96％和66％，根系生物量提高20％。有机质、全N分别比纯林提高27％和36％，速效P、速效K分别提高135％和5％。pH值提高0．65。     

马尾松、红锥混交林林冠结构的研究

本研究通过对马尾松、红锥混交林及马尾松纯林的林冠结构及叶面积指数进行了对比分析。结果表明,混交林分两树种的林冠是镶嵌分布,林分总叶量平均比松纯林的高40.2％,林冠长比松纯林长69.13％,透光率只占松纯林的26.35％—66.62％,提高了叶面积指数,比松纯林的高64.59％。说明混交林比纯林更充分地利用太阳光能,提高林分生物生产力。     

桉树与厚荚相思混交林生物量及对土壤影响研究

对雷州林业局营造桉树与厚荚相思混交林进行生物量测定及对土壤影响分析结果表明:6年生尾叶桉无性系MLA与厚荚相思行间混交林地上部分群体生物量比纯林提高36.6％以上,行间混交的MLA单株叶量、细根分别比纯林MLA提高38.4％、82.8％;带状混交林分叶量比纯林提高4.9倍,带状混交的MLA单株叶量、细根分别比纯林提高19.5％、4.7％。4年生时混交林凋落物干重比纯林提高31％以上,0——30cm土层有机质、全氮、全钾分别比纯林提高17.2％、26.9％、19.3％。     

人工混交林不同混交方式的生长动态

对辽东山区人工混交林的生长动态进行了调查分析，结果表明，红松块状混交林型的材积生长量是红松纯林的109％-124％，落叶松块状混交林型的材积生长量是落叶松纯林的108％-151％，各混交林型中的红松、落叶松乔木层生物量比红松、落叶松纯林高3．1％-28．6％和2．8％-16％。在块状、带状混交林中的红松、落叶松，其干、枝、叶、根的生物量绝大部分都高于各自的纯林，混交林的根系分布面积比纯林提高23％。     

杉木拟赤杨混交林土壤肥力研究

杉木是我国南方重要的速生用材树种，但长期的连栽会引起地力衰退。通过对杉木拟赤杨混交林土壤的物理性质和化学性质等进行研究，认为混交林土壤结构状况，水分物理性质均比杉木纯林得到较大程度的改善，同时０－２０ｃｍ土层有机质，全Ｎ，全Ｐ比杉木纯林增加１２．４３％，１４．２９％和７．３２％；水解Ｎ，速产Ｐ，速效Ｋ分别增加１５．４９％，７．８９％和６．７８％，混交林土壤肥力状况明显优于杉木纯林。     

杉木福建柏混交林效益研究

通过对杉木福建柏混交林中单株生物量组成、土壤团粒组成、土壤孔隙和水分状况的研究分析， 结果表明： 混交林中杉木每ｈｍ ２ 蓄积量是杉木纯林的１６９ 倍， 细根量是杉木纯林的１５ 倍； 与纯林相比， 混交林中０～２０ｃｍ 土层＞ ０２５ｍ ｍ 水稳性团聚体高出９０１％ ； 结构体破坏率低１５８２％ ； 有机质和水解性 Ｎ 含量分别高０２４５％ 和１３１×１０－ ６； 毛管孔隙、非毛管孔隙、总孔隙高００９％ 、０９１％ 、１００％ ， 土壤容重低００５７ｇｃｍ － ３； 最大持水量、最小持水量、毛管持水量分别高３００％ 、３５０％ 、２０４％ ； 混交林４０ｃｍ 土层含水量也比纯林大１５５ｔ·ｈｍ － ２。由于混交林的结构较为合理，能一定程度改善土壤理化性质、提高林分生产力，是一种值得推广的造林模式。     

杉木、黄山松人工混交林的生长特性

对杉木分布区北缘的安徽省大别山高海拔山地的杉木、黄山松人工混交林生长特点进行了系统研究。结果表明：在立地条件、林分密度和经营措施一致的条件下，混交林比杉木纯林具有更高的生产力，中龄期的混交林立木蓄积量和总胸高断面积分别为１８８．７８～２８９．６７ｍ３／ｈｍ２和３６．３１～４２．１５ｍ３／ｈｍ２，比纯林提高６０．２７％和１９．８５％；混交林生物量高达１２８．２７～１７９．１８ｔ／ｈｍ２，高于纯林２１．９９％～７０．４０％；混交林地上部生物量密度为１２．００～１５．８７ｔ／ｈｍ２·ｍ，而杉纯林为１０．２４～１１．６４ｔ／ｈｍ２·ｍ。树高与胸径的关系分析揭示混交林在幼龄期，杉木个体树干在垂直方向的生长有显著促进，到中龄期则在径向的生长有明显提高。不同林分杉木胸径生长过程有较大差异，混交林中杉木胸径生长在高峰期后随年龄增长保持一定水平，而纯林杉木则呈明显的下降趋势；黄山松个体不论是混交林或纯林，其胸径生长在１０～１２年生后均随年龄增长而下降。     

桦树柠条混交林生长效应的试验

通过对桦树柠条混交林及桦树纯林、柠条纯林的林木生长量、林分生物量、根系分布规律等的调查研究,结果表明,混交林的桦树高生长量比纯林桦树提高47．6％～119．5％,胸径提高44．1％～143．1％;混交林的林木生长量及单株生物量均高于纯林;混交林中桦树根系分布比纯林均匀,使林木充分利用土壤养分、水分、空间,利于林木的生长。     

桉树与厚荚相思混交林的生物量及对土壤影响研究

对雷州林业局营造桉树与厚荚相思混交林进行生物量测定及对土壤影响的分析结果表明：尾叶桉与厚荚相思混交林６年生地上部分群体生物量比尾叶桉纯林多３６．６％以上,单株叶量,细根行间混交的尾叶桉分别比纯林的尾叶桉多３８．４％,８２．８％,带状混交的尾叶桉比纯林的尾叶桉分别多１９．５％,４．７％,林分叶量带状混交林比纯林大４．９倍。４年生时混交林凋落物干重比纯林多３１％以上。混交林０－３９ｃｍ土层有机质,全氮     

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.