南方桉树人工林雨雪冰冻经济损失评估与分析

针对雨雪冰冻灾害未满5年轮伐期的4类重灾林分开展经济损失评估。结果表明：在萌蘖经营前,不同重灾林分的经营成本与产量均有所差异,只有4年生的重灾林分木材利润为正值,其平均净收入和平均利润分别为16907.20元·hm^-2和2480.85元·hm^-2;其余类型的重灾林分因为经营期较短,木材产量较低不足以完全抵销经营期内的成本。在萌蘖经营中,亦只有4年生重灾林分的收益高于未受灾林分（CK）,其平均净现值（NPV）、内部收益率（IRR）和产出投入比（B/C）分别达18114.00元·hm^-2、57.95%和3.52,比最低分别高98.56%,39.21%和65.79%。不同类型萌蘖经营的NPV和IRR与木材价格和木材产量成正比,而与经营成本和贴现率成反比,IRR不随贴现率的变化而变动。本文还就如何提高灾后桉树人工林的经济效益进行了商讨。     

湿地松纸浆原料林密度控制与管理技术研究

为探索湿地松优质高产纸浆原料林密度控制与管理技术,进行了不同初植密度造林与间伐试验.试验结果表明:8a生、12a生密度试验林不同密度林分胸径、树高、蓄积量和总产量有极显著差异,8a生密度试验林不同密度林分木材性有极显著差异.林分在8a生时,平均树高生长效应是林分越密树高越高,林分平均胸径生长效应是林分密度越小胸径越大,蓄积量的生长效应是林分越密蓄积越大,木材材性是以中等林分密度质量最好.营造湿地松高产优质纸浆原料林适宜初植模式为2 m×2 m、2 m×2.5 m,即初植密度分别为2 505株/hm2和1 995株/hm2,此时2 505株/hm2林分按下层间伐方式间伐25%、1 995株/hm2林分按下层间伐方式间伐20%后4 a(林分年龄为12 a),这二种密度林分蓄积分别为224.08 m3·hm-2和206.64 m3·hm-2,蓄积加间伐材材积的总产量分别为244.56 m3·hm-2和218.72 m3·hm-2.为培育出质量和产量兼优的湿地松纸浆原料林,当林分生长到8 a生时,应及时地进行一次抚育间伐,间伐强度为20%～25%.     

采收方式对马尾松与黄藤间种林分经济效益的影响

收集黄藤试验地采收资料和马尾松标准地调查数据,评价13 a经营期内5种采收方式对马尾松与黄藤间种林分经济效益的影响.结果表明:不同的初采年龄和采收间隔期对13 a黄藤人工林经济效益具有重要的影响,其中7 a初采和6 a间隔期的采收方式获得最高的经济效益,净现值、内部收益率和收益成本比分别为18 144元·hm-2、13.45%、1.32;黄藤间种后对19年生马尾松林分平均胸径、树高及株数产生不利影响,进而导致马尾松林分的纯收益和净现值比未间种时分别减少7 500 元·hm-2、3 000 元·hm-2;马尾松林分经济效益的减少可从间种黄藤所获得货币收入得到补偿,在5种采收方式下黄藤间种对整个林地产生的林地增益水平和净现值增量分别为3.07%～12.74%、514～2 407 元·hm-2.     

日本落叶松大径材培育技术的研究

通过对26年生日本落叶松大径材的培育试验研究,结果表明:以保留密度600株·hm-2和750株·hm-2的效果最佳,伐后5年大径木可增加50%左右,是对照区的3倍,小径木下降70%左右。主伐时产量预测为:600株·hm-2的林分材积416.94 m3·hm-2,产值91.96万元·hm-2;750株·hm-2的林分材积453.28 m3·hm-2,产值93.62万元·hm-2。     

间伐的华山松＋云南松近成熟林密度及胸径断面积的变化研究

对宜良县禄丰村林场海拔高度1 850 m,于1954年起经营的华山松+云南松混交林在其形成成熟林的50年生长过程中,就其采取间伐措施后林分中两树种林木株数(密度)胸径及断面积的变化进行了定位研究.通过立地条件相同地段设置的2块0.1 hm2的固定样地(其中,一块样地为继1978年后于1984年、1990年、1997年和2004年进行4次间伐的林分,另一块样地为未进行任何间伐活动,作为对照的林分)的林木30年(1978～2007年)的定位连续观测,其间伐和对照样地林分的林木密度分别从3 070 株·hm-2和4 400 株·hm-2降为580 株·hm-2和850 株·hm-2,林分的林木株数组成从华山松分别占91.9 %和87.4 %降至69.0 %和49.4 %,云南松从8.1 %和12.6 %上升至31.0 %和50.6 %,表明该地区较适宜云南松生长.在定位观测的30年间,无论混交林中的华山松或云南松林木的平均胸径,间伐林分始终大于对照林分;1978和2007年,间伐林分的林木胸高总断面积呈现几近相等(2 403.9 m2·hm-2与2 384.9 m2·hm-2),而对照林分林木的胸高总断面积则呈现较大幅度地降低(3 260.0 m2·hm-2与2 988.6 m2·hm-2),揭示了在华山松+云南松混交林经营过程中间伐的必要性.     

毛环竹笋用林丰产结构的研究

在影响因子的多因子相关分析和主成分分析的基础上,采用正交试验设计方法,通过立竹度、平均胸径、年龄结构等因素对竹笋产量、竹材产量、竹林收益等指标的影响来研究毛环竹笋用林的丰产结构,结果以立竹度为13 500株·hm-2、平均胸径为3～3.5 cm、年龄结构为2～4 a生各占1/3的林分竹笋产量最高;立竹度为13 500株·hm-2、平均胸径为3～5 cm、年龄结构为2～4 a生各占1/3的林分经济效益最高.     

兼顾碳汇和木材生产的长白落叶松人工林最优轮伐期

【目的】针对当前人工林经营重木材收益、轻碳汇效益的问题,探究兼顾碳汇和木材生产的人工林最优轮伐期,为人工林多目标经营提供理论依据。【方法】以黑龙江省东北林业大学帽儿山实验林场35块长白落叶松人工林样地为研究对象,以Faustmann-Hartman模型为基础,综合考虑乔木层生物量碳库、生物质能源碳库、采伐剩余物碳库和木材产品碳库,构建长白落叶松人工林碳汇木材复合经营的最优轮伐期确定模型;设计4种模拟情景,情景1考虑木材收益、生物质能源收益和经营成本,情景2—4分别在情景1的基础上依次加入乔木层生物量碳库、采伐剩余物碳库和木材产品碳库,对各模拟情景分别量化不同碳价格、贴现率、枝叶生物质能源比例等因素对长白落叶松人工林最优轮伐期、木材产量、碳汇量以及林地期望值的影响。【结果】基准情景下(碳价格100元·t^-1,贴现率5%,枝叶生物质能源比例20%),林地期望值整体随林分年龄增加呈先增加后减小的趋势,可采用二次多项式进行模拟(R■> 0.60)。情景1—4的最优轮伐期均为35年,其所对应的林地期望值分别为50 288、53 638、53 263和53 071元·h...     

楠木人工林生态系统生物量、碳含量、碳贮量及其分布

对32年生楠木人工林生物量、碳含量、碳贮量及其空间分布进行测定.结果表明;楠木林分平均生物量为174.33 t·hm-2,其中乔木层为166.73 t·hm-2,占林分生物量的95.6%;楠木林分生态系统各组分碳含量为树干0.576 9 gC·8-1,树皮0.465 4 gC·g-1,树枝0.523 2 gC·g-1,树叶0.495 8 gC·g-1,树根0.493 1 gC·g-1,灌木层0.498 9gC·g-1,草本层0.473 3 gC·g-1,苔藓层0.414 3 gC·g-1,枯落物层0.388 2 gC·g-1;土壤碳含量平均值为0.013 9gC·g-1,随土层深度增加各层次土壤碳含量逐渐减少;楠木林分生态系统总碳贮量为227.59 t·hm-2,其中乔木层91.33 t·hm-1,占楠木林分生态系统总碳贮量的40.13%,灌木层0.38 t·hm-2,只占0.17%,草本层1.71 t·hm-2,占0.76%,苔藓层0.63 t·hm-2,占0.28%,枯落物层0.66 t·hm-2,占0.29%,林地土壤(0～80 cm)碳贮量为 132.88t·hm-2,占58.40%;其碳库空间分布序列为土壤(0～80 cm)＞乔木层＞草本层＞枯落物层＞苔藓层＞灌木层;楠木林分净生产量为8.570 6 t·hm-2a-1,其中乔木层净生产量为6.669 1 t·hm-2a-1,占林分总量的77.82%.楠木林分碳素年固定量4.253 6 t·hm-2a-1,其中乔木层碳素年固定量3.573 6 t·hm-2a-1,占林分总量的84.01%.     

顶果木人工林经济效益与成熟年龄研究

通过树干解析造材获得木材产量,采用动态和静态相结合的经济评价方法对桂中地区36年生顶果木人工林经济效益与成熟年龄进行研究。结果显示:顶果木36 a主伐时可获得木材845.7 m3·hm-2,木材销售收入889409.8元·hm-2。静态指标中,总利润达683642.2元·hm-2,投资利润率为9.23%,投资利税率为10.25%,投资回收期为35.02 a;动态经济指标的财务净现值为3972.0元·hm-2,财务内部收益率为13.22%。静态和动态经济指标均表明36 a的顶果木人工林造林项目盈利能力较强。造林项目敏感性分析表明,木材价格变化对经济效益的影响最明显,规格材盈亏临界价格为223.8元·m-3,财务净现值最大时作为经济成熟龄为18 a。     

新疆天山林区森林潜在生产力的计算(英文)

本文利用Miami模型和Thornthwaite Memorial模型分析计算了新疆天山林区范围内8个 县的森林潜在生产力,并利用Thornthwaite Memorial模型分析计算了其潜在木材产量。研 究表明,天山林区林分当前平均产量为3.7 m3"hm-2"a-1,只有平均潜在生产力的49%。     

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.