Sheet Mulching as an Aid to Broadleaved Tree Establishment II. Comparison of Various Sizes of Black Polythene Mulch and Herbicide Treated Spot

Eight experiments, each having 15 treatments, were established.Sites with clayey, loamy and sandy soils were used. The treatmentsincluded herbicide spots of various sizes up to whole plotskept weed-free; polythene mats of various sizes up to wholeplots (10 x 8 m) covered in polythene; and polythene mats ofvarious sizes with the rest of the weeds within the plot treatedwith herbicide. In each experiment survival or growth or both increased thefurther weeds were kept from the trees. Growth was increasedmost on the sandy site. Survival was increased most in the experimentwhich used poor quality oak plants - from zero in the controltreatment to 63 per cent in the whole-plot polythene treatment.Herbicide spots were generally better than polythene mats whenthe area treated was less than one square metre per tree, butnot so good when larger areas were treated: this is attributedto weeds rooting under the mulches. Growth was increased whenthe weeds around the mulches were killed. Accidental herbicidedamage, voles gnawing the trees from beneath the mulches, andsoil anaerobism on poorly drained sites also influenced theresults.     

The Concept of Actual and Potential Production as an Aid to Forest Management

The environmental and biological factors which influence treegrowth are analysed to provide a concept for estimating thepotential production of a tree crop on any site. Some of thefactors which influence growth cannot be controlled by management,and therefore set an upper limit to the growth which shouldbe possible. This is termed the Management Potential Production.The idea of considering the actual tree growth on a site asbeing some fraction of the potential, rather than as a basison which to improve, is discussed in relation to the managementand research implications.     

An Economic Analysis to Aid the Marginal Decision on Rotation Length: I. Presentation of the Principle

This economic analysis of the rotation problem is based on theactual decision which the forest manager must make for everystand, i.e. whether to fell now or in five years or so. Thismarginal decision becomes important, and need only be carefullyconsidered, when the stand nears financial maturity. The marginalapproach is perhaps the most realistic approach to the problemof financial rotations. The financial decision is based uponthe recognized criterion of maximum net discounted revenue (N.D.R.)per unit total invested capital. Certain theories of productioneconomics are combined with the practical methods of forestvaluation. These principles are used to present the economicanalysis as a graphical choice of the rotation at which thecombined yield of pulpwood and sawtimber maximizes N.D.R. Finally,current product prices are introduced and the optimum rotationis found. These current prices may genuinely be assumed to beconstant for any particular five-year period. A subsequent paperwill develop the basic principle into a multi-product technique.The principle is presented essentially as a fundamental techniquefor the projects of forest economics: its application and useare considered here in general terms, and for a specific Sitkaspruce (Picea sitchensis) stand type. An instrument for therapid determination of financial rotation and N.D.R. has beendeveloped from this principle of rotation determination.     

湖南舜皇山常绿阔叶林种类组成数量综合特征I.乔木物种重要值

研究森林群落种类组成的数量综合特征,以期为揭示森林群落结构规律、营建以及保护或利用多功能的森林生态系统提供依据.用3个特征指标数值综合为重要值的定量方法,分层测定亚热带常绿阔叶林各物种在群落组成中的地位和作用.结果表明:经过顺向演替,中亚热带常绿阔叶林的种类组成比较丰富,在1000m2左右的3个样地内有乔木22～30种.乔木层的优势种主要由壳斗科、樟科、木兰科、槭树科等常绿树种所组成,大多为珍贵的用材树种和庭园绿化树种.乔木层中含有常绿、半常绿、落叶3个层片,攀援或附生多种层间植物,已形成多层的立体群落结构,表现出向更高阶段演替的外貌特征.     

优良乡土速生树种黎蒴的特性及其造林技术

黎蒴(Castanopsis fiss)为优良的乡土速生树种。介绍了该树种的生物学特性、主要用途、生态价值、速生丰产性能以及人工造林技术。     

Grizzly bears and forestry: I: Road vegetation and placement as an attractant to grizzly bears

Today's growing demand for timber is increasing road development in once roadless forest ecosystems. Roads create both local changes in plant communities and landscape-level changes in forest connectivity. Roads also increase human access, which can be detrimental to species such as grizzly bears. Because most grizzly bear mortalities occur near roads, we examined grizzly bear attractants near roads, which could increase bear use of roadsides and consequently increase human/grizzly bear interactions. We measured the prevalence of 16 grizzly bear foods near roads and examined patterns in road placement to better understand use of roaded habitats by grizzly bears in west-central Alberta. We found that roadsides had a higher frequency of ants, Equisetum spp., Taraxicum officinale, Trifolium spp., graminoids, and sedges; whereas, interior forest stands had a higher frequency of Shepherdia canadensis, Vaccinium myrtilloides, V. vitis-idaea, and ungulate pellets, an indicator of ungulate presence. In addition, roads near water had a greater occurrence of Arctostaphylos uva-ursi and Equisetum spp. than roads not near water, indicating that road placement influenced bear food diversity. Patterns in road placement varied between the upper and lower foothills, although models for the lower foothills predicted road placement in both regions. In the lower foothills, roads were constructed at low elevation, low soil moisture, high sun exposure, and intermediate terrain ruggedness, possibly similar to sites selected by bears. Reducing grizzly bear foods near roads should involve decreasing the width of roadside ditches, banning the planting of clover (Trifolium spp.), and reevaluating road placement in areas with high grizzly bear density.     

年龄无关的生长模型研究—以落叶松平均高为例

目的 构建年龄无关的理论生长模型,用于年龄未知或者年龄不是有效因子的情况下的林分生长模拟。 方法 基于理论模型理查德模型,利用隐含年龄的差分形式,构建年龄无关的生长模型来拟合落叶松林分的平均高,并将自由参数表达为林分相关因子和立地因子的函数。 结果 利用刀切法对模型进行验证,时间无关的模型的修正确定系数在0.92~0.94之间,而时间相关的模型修正确定系数为0.85,时间无关的模型修正确定系数提高了8%~10%;时间无关模型的均方根误差RMSE在1.30~1.59之间,远远小于时间相关模型的20.48。年龄无关的模型之间对比,引入气候因子的模型,修正确定系数均方根误差RMSE和TRE较没有引入的有明显的降低,说明气候因子的引入提高了模型的模拟效果。 结论 可以将年龄无关的理论模型应用于年龄不可用或者不相关的林分中。采用自由参数的方式将与年龄无关的立地因子和气候因子引入模型的拟合中,对比固定参数和自由参数的两类模型,可以发现自由参数的模型表现更好。在平均高生长模型中引入立地因子和气候因子,模型效果更好。     

湖南舜皇山常绿阔叶林种类组成数量综合特征Ⅲ群落结构图解

群落结构图解不仅能反映物种在群落中的地位,也能在一定程度上反映物种的动态及群落的演替趋势,所以它能较全面地比较天然混交林中各种树种在森林中的作用.用第V级大树结构图解和林木结构图解两种方法分别测定了中亚热带常绿阔叶林乔木层物种在森林组成中的优势度.结果表明:第V级大树结构图解能较客观地反映已进入稳定阶段群落的组成结构特征;林木结构图解能较好地反映处于顺向演替阶段群落的组成结构特征.     

Tree growth as indicator of tree vitality and of tree reaction to environmental stress: a review

The intensive monitoring plots (Level II) of ICP Forests serve to examine the effects of air pollution and other stress factors on forest condition, including tree vitality. However, tree vitality cannot be measured directly. Indicators, such as tree growth or crown transparency, may instead be used. Tree growth processes can be ranked by order of importance in foliage growth, root growth, bud growth, storage tissue growth, stem growth, growth of defence compounds and reproductive growth. Under stress photosynthesis is reduced and carbon allocation is altered. Stem growth may be reduced early on as it is not directly vital to the tree. Actual growth must be compared against a reference growth, such as the growth of trees without the presumed stress, the growth of presumed healthy trees, the growth in a presumed stress-free period or the expected growth derived from models. Several examples from intensive monitoring plots in Switzerland illustrate how tree-growth reactions to environmental stresses may serve as vitality indicator. Crown transparency and growth can complement each other. For example, defoliation by insects becomes first visible in crown transparency while stem growth reaction occurs with delay. On the other hand, extreme summer drought as observed in large parts of Europe in 2003 affects stem growth almost immediately, while foliage reduction becomes only visible months later. Residuals of tree growth models may also serve as indicators of changed environmental conditions. Certain stresses, such as drought or insect defoliation cause immediate reactions and are not detectable in five-year growth intervals. Therefore, annual or inter-annual stem growth should be assessed in long-term monitoring plots. An erratum to this article can be found at     

The effect of composition on the effectiveness and fixation of copper-chrome-arsenic and copper-chrome preservatives part I: Effectiveness

Summary A preliminary study of a wide range of copper-chrome-arsenic formulations indicates that the most offective are in the region, CuSO₄·5H₂O-35 to 45 per cent; K₂Cr₂O₇-40 per cent and above; As₂O₅·2H₂O-25 to 15 per cent or less. Effectiveness appears to depend more on the copper content than the copper-arsenic. Observations on selective absorption and leaching suggest that the chromium fixes the arsenic preferentially to the copper. Although there appears to be no major amount of fixation of copper by arsenic, at the start of addition of arsenic to copper-chrome formulations there is a small but significant decrease in the leaching of the copper suggesting either a small amount of fixation of copper by arsenic or the formation of an insoluble complex of all three components.Maximum fixation of arsenic was obtained when the Cr/As ratio (as salts) was 1.9 or greater. Maximum fixation of copper is not so simply defined but is round about a Cr/Cu ratio (as salts) of 1.7.The area of maximum effectiveness is not coincident with the area of maximum fixation of both copper and arsenic but slightly displaced towards a region of higher copper where there is still maximum fixation of arsenic but some loss of copper.     

基于模糊综合评判的森林群落稳定性评价体系模型构建——以黄龙山主要森林群落为例

基于模糊综合评判理论,以黄龙山分布的油松林、油松+辽东栎林、辽东栎林和白桦林4种森林群落类型为例,选择反映森林群落基本特征的种群更新潜力、林地土壤肥力、林地生产力、物种多样性和人为干扰这5项指标(共15个因子),构建森林群落稳定性评价模型,通过计算该评价模型的隶属函数值来评判森林群落稳定性.结果表明:黄龙山4种主要森林群落稳定性表现为辽东栎林>油松+辽东栎林>油松林>白桦林,评判结果符合当地森林群落发育状况;评价模型中评价因子的选择反映了森林群落稳定性的基本特征,突出了常用方法对群落调查获取的林业数据的应用;评价过程避免了繁琐的数学计算,可操作性强,具有较好的推广应用价值.基于5项指标的模糊综合评判的森林群落稳定性评价模型可以应用于森林群落稳定性评价.     

Some Effects of CO2, Daylength and Nutrition on the Growth of Young Forest Tree Plants I. In the Seedling Stage: I. In the Seedling Stage

An experiment was carried out to investigate the possibilitiesof accelerating seedling growth in three of the most importantforest tree species by increasing CO₂ concentration, daylengthand nutrition. Doubling the frequency of application of a standard liquid feedincreased plant height by 8–10 per cent but extendingthe daylength to 18 h had only a small initial effect whichwas not sustained. Increasing the CO₂ concentration significantly increased growthin both Sitka spruce and lodgepole pine but similar increaseswith Corsican pine were not statistically significant. The results indicated that under the conditions of the experimentthe tree height normally achieved after 16 weeks could be attainedin 14 to 15 weeks by increasing the CO₂ concentration fourfold.     

银杏品种经济性状分析及其与土壤相关性研究. Ⅰ不同银杏品种经济性状的比较

用单因素多重比较DDCBJ模型对大梅核与大马铃在石灰岩母质上，大梅核与细梅核在花岗岩母质上，大佛指银杏、中椭圆子及中长子银杏在板页岩上的经济性状作了差异显著性检验，检验结果是：①各品种（类型）间其含水率、Vc含量、蛋白质含量、还原糖含量、总糖含量、淀粉含量、单果重等经济性状差异未达到显著水平．②中椭圆子和中长子银杏在板页岩上出核率达到了差异显著性水平．③同一品种群的不同品种（类型）间或不同品种群不同水平下的各品种（类型）间其单核重非常接近或已达到差异显著性水平。     

Establishment of full-sib families in Shorea platyclados using paternity analysis: an alternative to controlled pollination

Full-sib families are produced from artificially controlled pollination in tree breeding. This mating design is, however, very costly and logistically difficult as most tree species are large in size. With the development of molecular markers, known relationships among the offspring could be established from the maximum likelihood in paternity analysis. In this study, we successfully established full-sib families on the basis of paternity analysis of offspring derived from two Shorea platyclados seed parents from the natural forest. A total of 2,049 and 970 offspring were collected from two mother trees M01 and M06, respectively. Potential pollen donors surrounding the mother trees were sampled, specifically a total of 77 adult trees within the 10-ha plot for M01 and 28 adult trees within the 4-ha plot for M06. For mother tree M01, parentage was assigned to 45.4% of the offspring at the 95% confidence level with 59 full-sib families established. For mother tree M06, parentage was assigned to 19.9% of the offspring at the 95% confidence level with 19 full-sib families established. The establishment of full-sib families in S. platyclados enables breeding in dipterocarp tree species, once a decade-long proposition, to become more efficient in a cost-saving manner.     

马尾松人工林养分循环研究Ⅰ．不同坡位马尾松林生物量与养分现存量

对相同经营措施、同一坡面、不同坡位３０年生马尾松人工林进行林分生长情况、林地概况、生物量及养分现存量等的调查结果表明：坡位对林分的平均树高、胸径、材积、生物量积累和养分现存量的影响显著。材积、地上部分生物量和养分现存量，下坡林分分别是上坡林分的３．０倍、３．３倍和４．０倍，中坡林分分别是上坡林分的２．４倍、２．６倍和３．０倍。     

An empirical analysis of bill co-sponsorship in the U.S. Senate: The Tree Act of 2007

Public choice economists view the legislative process as a political market, in which interest groups attempt to influence the production of legislation that has pecuniary and non-pecuniary consequences for them; politicians provide these groups with relevant legislation. In this context, bill co-sponsorship acts as a signal to interest groups that a legislator is working to promote their interests and thereby maximize the payoffs received from such groups. In this paper we seek to identify factors associated with bill co-sponsorship, to determine whether interest group politics significantly explain bill co-sponsorship behavior in the U.S. Senate. Specifically, we examine Senate Bill 402, a bill seeking to amend the Internal Revenue Code of 1986 to allow a deduction for qualified timber gains. Senate co-sponsorship decisions concerning S.B. 402 are assessed using a model that identifies various political and industry (forestry) interests/characteristics. We demonstrate that a Senator's co-sponsorship of this bill is correlated with his/her seniority, tax-cutting ideology, strength of electoral victory in his/her most recent election, campaign contributions received from forestry interests, the relative contribution of forestry to Gross State Product, and the percent of total land in his/her state that is privately owned.     

Agroforestry as an approach to minimizing nutrient loss from heavily fertilized soils: The Florida experience

Agroforestry Systems - Nutrient buildup in the soil caused by increased animal manure and fertilizer use in agricultural and forestry practices may increase the potential for their loss from the...     

构建我国自然保护区区域共管体系的思考——以太白山自然保护区为例

基于新保护区管理理念和太白山国家级自然保护区所面对威胁因素和利益相关方的分析,探析自然保护区区域共管体系的内涵.提出通过建立以区域生物多样性保护委员会为首,宗教共管委员会、社区共管委员会、生态旅游共管委员会为支撑的"区域共管体系"组织结构.为确保区域共管体系得以建立和有效运行,应建立引导、回馈、监督、互动、激励等保障机制.