苦竹林分结构对鲜笋产量的影响分析

苦竹是川南地区优良的笋用竹种。本研究比较了不同年龄结构、胸径结构,以及林分密度3个因子下苦竹的产笋能力差异。结果表明:年龄结构、林分平均胸径、立竹度对苦竹鲜笋产量均有显著的影响,而胸径整齐度对苦竹鲜笋产量影响不显著。其中1年生+2年生+3年生竹龄主导型的竹林产笋能力最好,鲜笋产量达4 770 kg·hm~(-2),发笋数达13 900个·hm~(-2);平均胸径6 cm的竹林鲜笋产量最高,达到4 580 hm~2;立竹度10 000～12 000株·hm~(-2)的竹林产笋能力最好,鲜笋产量达4 700 hm~2,发笋数达1 550 hm~2。结合各因子来看,以1、2、3年生竹竹龄主导型+中大的林分平均胸径(4～6 cm)+中等立竹度(10 000～12 000株·hm~(-2))的苦竹林鲜笋产量最高,是比较理想的苦竹林分结构。     

毛环竹高产笋用林结构的研究

采用正交试验设计方法 ,通过立竹密度、平均胸径、年龄结构等指标研究毛环竹笋用林的高产地上结构 ,结果以立竹密度 10 0 0 0株·hm-2 ,平均胸径 3～ 3 5cm ,年龄结构为 1～ 3年生各 30 %、4年生 10 %的毛环竹林分产量最高 ,1hm2 可产笋4 0 0 0 0个、10 0 0 0kg。     

合江方竹笋产量与林分结构的相关性

通过对合江方竹笋产量与每hm2总株数、林分平均胸径、年龄等23个因子的相关性研究可知:合江方竹笋产量与林分平均胸径,每hm2内胸径为4~5 cm5、~6 cm株数,竹株年龄2 a3、a4、a生株数计6个因子呈显著或极显著正相关关系;每hm2内与1 a5、a生株数计2个因子呈显著或极显著的负相关关系;与海拔、每hm2内总株数、平均年龄等15个因子的相关关系不显著。在影响林分竹笋产量的23个因子中,林分平均胸径和每hm2内2~4 a生株数是衡量竹笋产量高低的重要指标。通过提高林分平均胸径和增加林分中2~4 a生株数比例是对目前合江方竹笋用林进行技改的主要手段。同时,采用欧氏距离类平均法可将13个样地划分为高产型、中产型、低产型3个类型。     

毛竹材用林高产优化施肥与结构模型的建立

采用四因素二次回归最优设计建立氮、磷、钾施肥及留竹密度与毛竹林竹材产量间的回归模型 ,同时根据投入、产出价格建立施肥和留养立竹的经济效益方程。经F值检验 ,方程均拟合较好。进一步统计分析表明 :留养立竹密度和施用氮肥是影响竹林产量的主导因子 ,参试各因素对产量贡献率的排序为留竹密度 >氮肥 >钾肥 >磷肥。采用产量和效益两目标函数的双频分析 ,得到 95 %置信域的毛竹林优化施肥方案 :施尿素 4 88～ 6 0 7 6kg·hm- 2 ,平均 5 4 7 8kg·hm- 2 ;过磷酸钙 2 5 2 7～ 2 6 1 2kg·hm- 2 ,平均 2 5 7kg·hm- 2 ;氯化钾 4 3 3～ 12 3 2kg·hm- 2 ,平均83 3kg·hm- 2 ;对平均胸径 10cm左右的毛竹林 ,优化的立竹留养密度 2 36 3～ 2 5 82株·hm- 2 ,平均 2 4 72株·hm- 2 。     

不同林分结构对绵竹产量的影响研究

绵竹是四川优良的乡土竹种。本研究在绵竹主要分布区沐川、叙永设置了125个经营水平大体一致的样地开展不同林分结构(年龄结构、均匀度、整齐度和立竹度)对绵竹产量的影响研究。结果表明:绵竹林的年龄结构、整齐度和立竹度对竹材产量有显著影响,而均匀度对产量影响不显著。当绵竹林以1 a~2 a年生竹为主,整齐度为10,立竹度在10 000株·hm~(-2)时,绵竹竹材产量最高,是绵竹林最优林分结构。     

粗放经营苦竹笋用林立竹年龄结构优化研究

对粗放经营的苦竹林林分结构与竹笋产出的关系进行了调查,利用SPSS软件构建了竹笋产量与立竹年龄结构的关系模型：Y=9192．375＋0．02027N＋0．12607D-0．11412X1＋0．24912X2＋0．33746X3-0．09919X4（R=0．94）,提出了在粗放经营初期的优化年龄结构,立竹度7200～8100株／hm^2时竹笋产出高,1—4年生立竹比例为3：3：3：1。     

天目山国家级自然保护区毛竹扩散过程的林分结构变化研究

为了弄清毛竹在自然条件下的扩散过程,通过样带法在天目山国家级自然保护区对毛竹扩散过程的立竹度、胸径、竹高及年龄结构进行了调查研究。结果表明,毛竹在扩散过程中其立竹度无论在垂直方向还是在水平方向上都随着扩散距离增加逐渐减少,立竹度由最大5 600株.hm-2减少到200株.hm-2;在毛竹纯林中由各种年龄的竹子组成(1～11年),年龄结构呈现不均匀性;随着距周边林分越近,主要由年龄较小的竹子组成,一般为1～3年;扩散到周边林分地带的毛竹胸径、株高均比纯林里的生长好。因此,在自然条件下毛竹林正向周边林分扩散,逐渐形成以毛竹为优势种的林分。研究结果为合理科学地经营自然保护区毛竹提供理论依据。     

撩壕施肥对毛竹林分结构的影响

历时10年对撩壕施肥的毛竹林生长特性和林分结构变化进行调查研究,结果表明:(1)不同径级毛竹均分布在林分密度3 750~10 305株/hm~2的中密度到高密度的范围之内,当林分密度为8 250株/hm~2的中密度时,林分平均胸径和新竹平均胸径达到生长高峰;当林分密度为10 305株/hm~2的高密度时,平均枝下高、秆全高和枝下高占全高的比例也达到最大值。(2)撩壕施肥竹林立竹株数为8 625株/hm~2,其中胸径12~17 cm的大径竹占该竹林总株数61.2%,比对照竹林增加4.02倍;胸径9~11 cm的中径竹占该竹林总株数33.2%,比对照竹林增加38.4%;胸径8 cm以下的小径竹占该竹林总株数5.6%,为对照竹林的87.4%。(3)撩壕施肥竹林Ⅰ~Ⅳ度竹为幼、壮、中龄竹,立竹株数和蓄积量占林分比例均在70%以上,处于绝对优势,繁殖功能旺盛;Ⅴ~Ⅶ度竹为次老龄竹和老龄竹,立竹株数和蓄积量占林分比例均在30%以下,繁殖能力有所下降,但因能增加立竹密度,有利于为新竹提供营养。     

垦复与砍灌措施对毛竹林生长和竹林结构的影响

在安徽霍山县开展了林地垦复和砍灌措施对毛竹林生长和竹林结构影响的试验研究。连续3年监测结果表明：垦复处理的林分平均胸径、1~2年生竹胸径、1~2年生竹比例、立竹度等指标分别为9.88 cm、9.96 cm、44.30%、2 918株/hm²,分别比对照提高3.67%、5.29%、8.45%、450株/hm²;砍灌处理的林分平均胸径、1~2年生竹胸径、1~2年生竹比例、立竹度等指标分别为9.82 cm、10.67 cm、27.26%、3 293株/hm²,分别比对照提高3.81%、6.17%、23.29%、475株/hm²。研究表明,抚育措施可促进毛竹林生长,优化竹林结构。     

临安市雷竹林经营状况调查与分析

根据1991—2013年临安市雷竹笋产业数据,选取临安市雷竹分布重点乡镇的99个农户,采用问卷调查和实地测量相结合的方式对劳动力、覆盖技术、经营成本、施肥次数及竹林结构状况等进行调查与分析。结果表明:临安市雷竹林覆盖笋和自然笋的投产面积、产量、产值大致呈现出增长趋势,产量和产值整体表现为波动并显稍增长趋势;临安市雷竹林经营过程中劳动力不足现象明显;采用覆盖技术的农户占调查农户总数的66.7%;雷竹林覆盖过程中,经营成本最高的是覆盖物,为83715元·hm~(-2),占总成本的80%左右;雷竹林年施肥次数以3次最多;平均胸径、立竹度、竹龄,覆盖雷竹林分别为4.14 cm、19710株·hm~(-2)、2.56 a,而未覆盖雷竹林分别为3.93 cm、19170株·hm~(-2)、2.13 a,雷竹胸径、立竹度与覆盖与否相关性不大,而平均竹龄覆盖竹林基本上高于未覆盖竹林。     

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.