木兰林区落叶松人工林可持续发展探讨

该文指出按可持续发展理论衡量,木兰林区大面积高密度落叶松人工纯林存在着严重的生态弊端:病虫害防治困难;森林防火困难;土壤理化性质恶化;林内太阳辐射严重受影响;林间地被植物减少。最后根据可持续发展理论,提出了对木兰林区落叶松人工纯林的改造对策。     

危害落叶松的两种线小卷蛾发生规律及监测策略

落叶松线小卷蛾和松线小卷蛾在塞罕坝林场混杂发生,主要危害华北落叶松嫩芽及枝梢。海拔1600m以上林区是其主要危害区,在沟顶阳坡最先成灾。成虫期降水量少利于其增殖。监测的重点是海拔1600m以上的华北落叶松纯林。     

塞罕坝人工落叶松用材林营养面积初探

<正>塞罕坝是个大型人工林林场,是我省落叶松人工林生产基地。目前大面积人工用材林均已郁闭,林场的任务由造林为主转入了全面经营为主。近年来,林业科技人员对林场各种经营措施做了很多调查研究,提出了不少新的见解。笔者试图通过对落叶松人工林营养面积的研究,探讨林分保留密度的问题,以便为其合理经营提供理论依据,更好地指导生产。 林木营养面积是人工林尤其是人工用材林经营中的一个关键问题,直接关系到木材生产的数量和质量。在用材林经营中,若能根据林     

长白落叶松人工用材林培育经济效益分析

长白落叶松 (Larixolgensis)是东北林区的乡土树种 ,其适应性强、生长快、用途广 ,在造林树种中占有重要位置。现根据经营水平 ,把长白落叶松人工用材林划分为现实林、丰产林和模式林 ,并从各年龄段的人工用材林培育投入和产出数据入手 ,采用国际上通行的 3种经济分析评价方法 ,对 3种人工用材林进行比较分析 ,以便为长白落叶松人工用材林栽培技术的推广及建立工业用材林基地提供决策依据。1　资料的收集与整理研究数据取自黑龙江省林业科学研究所的研究成果。在整理数据的过程中 ,对原始数据进行了认真的审查 ,各林龄的收获数据分布于Ⅱ产…     

不同整地方式对落叶松人工林更新效果的影响

落叶松是华北北部塞罕坝地区的主要用材林树种,近几年来,随着用材林经营性采伐面积的逐渐增加,伐后更新的任务也随之加大。为探索不同整地方式对落叶松人工林生长的影响,对不同整地方式的人工更新进行了试验。试验结果表明,机械整地造林成活率、当年生长量都明显优于人工穴状整地方式。因此,建议在平坦、开阔的人工林皆伐作业地块上进行落叶松人工更新,最好在造林的前一年雨季之前采用机械整地,在坡度陡峭、狭窄地段结合人工整地,可以有效提高造林成活率、年生长量,节约投资,确保一次成林。     

塞罕坝林区森林可燃物含水率及火险预报

通过对塞罕坝林区9月至翌年6月中旬整个森林防火期枯草、落叶松枯落物、樟子松枯落物、落叶松嫩枝、樟子松嫩枝含水率的观测,研究了含水率随时间变化的动态规律;以当日气象因子中的温度、湿度与连续无降水日为自变量,利用多元统计的方法建立了3种可燃物类型的含水率回归方程,并编制了适合塞罕坝林区的森林火险预报系统.     

坝上落叶松人工林主要害虫的发生与防治

塞罕坝机械林场大面积的落叶松人工纯林，自８０年代中以来虫害加剧，主要为落叶松尺蠖与落叶松腮扁叶蜂。经两年的调查研究，已摸索出它们在该林区的发生发展规律，并采取了有效的防治措施。     

五台山林区天然林经营模式探讨

五台山林区拥有丰富的天然林资源,林相整齐,林木生长速度快,材质优良.介绍了华北落叶松、云杉、油松、白桦等天然纯林或混交林的经营模式,以期为该林区可持续发展提供技术参考.     

施尿素二胺肥对华北落叶松生长的影响探讨

指出了华北落叶松是塞罕坝地区三大针叶用材林树种之一,也是塞罕坝地区栽植面积最大的树种,在维护塞罕坝地区生态环境方面起着重要作用。对6年生华北落叶松苗木施1∶1比例的尿素和二胺肥料,分析施肥对其生长发育的影响。结果表明:施尿素二胺后华北落叶松苗木的树高、基径、冠幅以及枝条的长度和基径都显著好于未施肥的苗木。提出了在华北落叶松幼林阶段可以适当施尿素二胺肥料来促进苗木的快速生长。     

落叶松锉叶蜂发生与环境因子的关系

落叶松锉叶蜂Pristiphora laricis(Hartig)是危害塞罕坝人工落叶松林的主要害虫,为控制其危害,掌握其发生规律,对影响落叶松锉叶蜂发生的环境因子进行了调查研究.结果表明,该虫的发生与林分、地形及气候因子关系密切,发生程度一般表现为纯林重于混交林,林缘重于林内,成熟林重于中幼龄林,树冠下层重于中上层,高海拔区重于低海拔区,阳坡重于阴坡,山脊重于山谷;温度越高越有利于幼虫的生长发育,幼虫孵化越早.     

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.