闽南山地秃杉混交造林效果初步研究

通过秃杉与光皮桦2∶1和4∶1比例及秃杉与杉木1∶1比例行状混交,与营造秃杉纯林进行造林效果对比,结果表明：不同类型林分中秃杉生长量顺序为秃杉+光皮桦2∶1混交林>秃杉+光皮桦4∶1混交林>秃杉+杉木1∶1混交林>秃杉纯林;混交林土壤>0.25 mm的团聚体含量、有机质含量、速效磷含量和速效钾含量等高于纯林,而混交林土壤结构体破坏率低于纯林。秃杉与光皮桦2∶1的比例行状混交的效果最佳。     

闽南山地杉木光皮桦混交造林初步研究

通过对12年生的杉木光皮桦1∶1和3∶3行状混交林以及杉木纯林的试验研究,结果表明,杉木与光皮桦按照1∶1和3∶3行状混交后,杉木的平均树高、胸径、单株材积以及林分总蓄积量均超过杉木纯林,而且差异达到显著水平。杉木光皮桦混交林土壤的结构疏松、持水性强,土壤的肥力高于杉木纯林。     

杉木光皮桦混交林效益的调查研究

对桂西北杉木光皮桦混交林和杉木纯林的对比研究表明,３５年生杉桦混交林的立木蓄积量为４４１．０８７ｍ＾３／ｈｍ＾２,比杉木纯林高３．６％。混交林枯枝地层现存量及其Ｎ、Ｐ、Ｋ、Ｃａ、Ｍｇ五种元素的积累量分别为１３．１８ｔ／ｈｍ＾２和２９９．５ｋｇ／ｈｍ＾２,分别比杉木纯林高９．７％和６９．９％。８混交林地（０～１００ｃｍ）土壤容重为０．８１～１．２２ｇ／ｃｍ＾３,比杉木纯林低１．０％～８．０％,而土壤孔隙度,通气度和持水量分别比杉木纯林高２．０％～３．９％。土壤有机质、全氮、水解氮、有效磷和速效钾分别比杉木纯高５．５％～４９．８％。     

杉木光皮桦混交林生长及其改土效果

从林木生长及其与生态环境之间相互关系入手,对杉木光皮桦混交林与杉木、光皮桦纯林进行调查研究。结果表明:二者混交改善了林内的小气候条件和土壤的理化性状,对林木生长的促进作用明显,有利于地力的维持和形成稳定的人工林群落。营造杉木光皮桦混交林是杉木纯林皆伐迹地更新,防治地力衰退的有效途径之一。     

杉木混交林营造试验初报

通过将杉木分别与檫树等10个树种混交试验,结论明显。檫树、木荷、香樟、光皮桦、马褂木、拟赤杨及马昆松适合与杉木混交;深山含笑混交后生长不良,桤木和银鹊树则全部死亡。从林分生长量看,杉木木荷混交林大于杉木纯林;杉木檫树、杉木香樟及杉木光皮桦混交林大于或相当于杉木纯林;杉木马褂木及杉木拟赤杨混交林生长量略小于杉木纯林。试验证明,混交林对改良土壤、恢复地力及改善林分生态环境有良好的效果,并有明显的抗性效益和社会效益。混交方式以梅花状和网格状为好,混交比例以1:5～1:6为宜。     

杉木与光皮桦混交造林效果初报

在安溪竹园国有林场开展了杉木-光皮桦混交林(3杉2桦)、光皮桦纯林和杉木纯林对比试验,结果表明:杉木-光皮桦混交林中杉木、光皮桦的生长量均分别大于杉木纯林、光皮桦纯林;5年生时混交林中光皮桦生长量大于杉木,10年生、15年生时杉木的胸径、单株材积均超过光皮桦;杉木-光皮桦混交林土壤与杉木纯林、光皮桦纯林相比更加疏松透气、肥力高。由此提出了生产上杉木、光皮桦造林应提倡营造混交林的建议。     

杉木光皮桦混交造林生长效果调查分析

对杉木光皮桦混交林、纯林生长效果进行了调查,杉木光皮桦混林木经过10年的经营管理,现林木生长效果良好。结果显示：其林木生长不同,杉木光皮桦混交林的林分生长量比杉木、光皮桦纯林的林分生长量生长较好,混交林的平均树高,比纯林的平均树高分别大14．32％、6．5％,平均胸径分别粗19．42％、11．85％,单株材积平均分别大57．14％、29．47％,蓄积量平均分别多55．34％、27．61％。土壤肥力均有提高,N、P、K分别增大2．73％、1_80％,8．OO％、3．85％,5．07％、3．57％。     

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。     

不同造林密度和混交树种对光皮桦幼林生长的影响

通过对光皮桦不同造林密度、不同混交树种的试验研究,结果表明:光皮桦不同造林密度林分的生长有较大差异,其胸径、冠幅由大到小依次为:1 100株.hm-2、800株.hm-2、1 600株.hm-2、2 500株.hm-2,树高以1 100株.hm-2的林分最大,其余比较相近。光皮桦与不同树种混交生长有较大差异,各生长指标以杉木×光皮桦混交林最好,其余依次为:福建柏×光皮桦、木荷×光皮桦、马尾松×光皮桦;光皮桦纯林生长指标与福建柏光皮桦混交林比较接近。杉木×光皮桦和福建柏×光皮桦是较好的混交组合。     

杉木乳源木莲混交对地力影响的初步研究

对１０年生乳源木莲与杉木的混交林及杉木纯林的林地枯枝落叶量及分解速率、土壤理化性质等进行调查分析。结果表明：混交林结构林地物理性质优于杉木纯林，土壤水稳性团聚体组成多，土壤疏松多孔；土壤有机质、全Ｎ、全Ｐ分别比杉木纯林提高１２．２％、１１．８％和４．５％，土壤速效养分（Ｎ、Ｐ、Ｋ）亦分别提高２９．６％、１０．５％、１０．１％，该混交对地力改良有积极作用。     

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.