油松建筑材林最适主伐龄研究

【目的】最适主伐年龄是依据不同的森林培育目标来确定合理采伐量、调整经营措施以及规划设计必不可缺的林业指标,对树种培育实现永续利用有重要的影响。探究基于建筑材目的油松Pinus tabulaeformis人工林的最适主伐龄,旨在为森林的可持续经营提供科学依据,并且对油松建筑材林高效培育和经济收益获得具有重要意义。【方法】以河北平泉阴坡厚土油松人工林为研究对象,先通过对比其他针叶建筑材树种材性指标,确定油松作为建筑材林培育的可行性。其次根据基本调查数据及当地造林资料,测定油松建筑材林材性指标,结合建筑材材种规格得出的不同径级木材出材量和出材率,考虑两者得到工艺成熟龄;测定经济指标,当投资收益最大化对应的年龄为经济成熟龄;测定材积生长量指标,连年生长量和平均生长量曲线相交对应的年龄为数量成熟龄,综合三者得出最适主伐年龄。【结果】1)培育油松建筑材林初植密度宜小,控制在2 500株/hm~2以下,在主伐前配合修枝措施、合理间伐以促进油松建筑材林的高效培育。2)培育中径级油松建筑材林的工艺成熟龄为47 a,培育大径级油松建筑材林的工艺成熟龄为50 a;经济成熟龄为47 a,数量成熟龄为35 a。【结论】油松作为建筑材林培育具有一定的可行性。阴坡厚土上培育油松中径级建筑材的最适主伐年龄为47 a;培育大径级建筑材的最适主伐年龄为50 a,可适当延迟3～5 a,以获得较高品质的大径级建筑材。     

豫南杉木人工林主伐年龄研究

通过对豫南杉木人工林不同立地指数级标准地和生产经营经济指标的调查,利用Richards等经典方程拟合豫南杉木生长的基本模型,编制生长过程表,确定数量成熟龄和工艺成熟龄,采用净现值和内部收益率分析杉木经济成熟龄。综合考虑数量成熟龄、工艺成熟龄和经济成熟龄结果表明:8立地指数不适合营造杉木用材林;10立地指数只能培育小径材,主伐年龄为22~24 a;12立地指数以培育小径材为主,主伐年龄为20 a,以培育中径材为辅,主伐年龄为22 a;14立地指数以培育中径材为主,主伐年龄可确定为20 a。     

人工实生林经济成熟龄的模拟初探

经济成熟龄是指使林木采伐后能产生最大净现值(PNW)的年龄。研究经济成熟,可以有效地驾驭林木的经济生长,为森林收获提供可靠的经济依据。本文以边际分析原理为基础,利用数学模型建立了相应的目标函数,利用 BASIC程序求解出经济成熟龄。     

长白落叶松人工林最佳经济成熟龄的确定

经济成熟龄是用经济分析手段，通过投入产出分析，把获得最大经济效益时的年龄确定为经济成熟龄。确定经济成熟龄的方法有多种。本研究采用净现值法和内部收益率法这两个应用比较广泛的方法来确定长白落叶松（ＬａｒｉｘｏｌｇｅｎｓｉｓｏｌｇｅｎｓｉｓＨｅｎｒｙ）人工...     

连江县人工湿地松林分经济成熟龄的研究

通过拟合湿地松林分生长因子数学模型,得到湿地松收获量表。根据连江县现行木材价格、营林成本、经营成本,以净现值法确定连江县人工湿地松林分的经济成熟龄为16年。经济成熟龄随贴现率的提高而提前。     

福建柏速生丰产用材林林分采伐年龄的探讨

依据收集于福建省福建柏主要分布区的标准地资料,采用理查德公式拟合福建柏林分生长模型,研究其数量、工艺成熟年龄;应用威布尔分布研究其林分胸径分布规律,并以平均净现值最大,确定其经济成熟年龄。     

湿地松造纸林主伐年龄的研究

四川省宜宾地区湿地松造纸林的主伐年龄，依据２９１个标准地，１７５８株材积测定样木，编制了该树种的二元立木材积表、材种材率表、现实林分平均生长过程表和模拟林分平均过程表。采用绝对值和相对值两种计算方法，求主伐木数量成熟龄；近材种标准确定材种工艺成熟龄；对不同年龄阶段的造纸工艺理化指标进行了测定分析，造纸工艺成熟龄；采贴现法进行分析，并净现值最大确定经济成熟龄。依据“以材种工艺成熟和造纸工艺成熟为基限     

马尾松人工林经济成熟龄的探讨

利用马尾松人工林标准地材料建立林分因子模型,预估各年龄时的产量,并结合技术经济指标采用净现值法对其经济成熟进行分析。结果表明:利率取5%时,马尾松人工林各种立地的经济成熟龄分别为:Ⅰ类地17年,Ⅱ类地18年,Ⅲ类地19年,Ⅳ类地21年。立地质量越好,经济成熟龄越小,立地质量等级每提高一级,经济成熟龄将提前1至2年。利率的变化对森林经济成熟龄有显著影响,利率提高,经济成熟龄下降。木材价格和森林经营成本对森林经济成熟有影响,但其作用不如利率影响显著。     

杉木人工林经济成熟年龄研究

本文以树干解析和择地调查资料为基础,选用Chapman—Ri—chards 函数,建立了8参数生长模型。用贴现法求净现值,以净现值和内部收益率最大确定经济成熟龄,进行经济效益分析。然后在此基础上确定主伐年龄。     

利用净现值法确定森林经济成熟龄

介绍了净现值的含义、计算方法及净现值方法的重要因子,并通过实例应用的分析,研究和探讨了利用净现值法确定森林经济成熟龄问题。     

Regeneration dynamics in aging black pine (<Emphasis Type="Italic">Pinus nigra</Emphasis> Arn.) plantations on the south slopes of the Middle Balkan Range in Bulgaria

To study the regeneration dynamics in mature black pine (Pinus nigra Arn.) plantations in the Middle Balkan Range, Bulgaria, a total of 48 research plots (sized 0.1 ha) were established; 26 plots were established in the foothills of the mountains (foothill zone) and 22 in the main massive (mountainous zone). Pine overstorey as well as advance regeneration in subplots were recorded. Analysis of variance and regression analysis showed that in general relative stand basal area (RSBA) was the most important predictor of deciduous advance regeneration density, top height as well as age span of the regeneration layer. In the mountainous zone soil depth (SD) and the presence of mature deciduous trees (MDT) explained a significant amount of the variation in regeneration features. Lower RSBA induced by earlier thinnings resulted in higher regeneration density, larger top heights and wider age span of deciduous species. Under the pine canopy oak regeneration can persist longer compared to natural broadleaved canopies. In the studied plantations pine regeneration was confined to few scattered seedlings and regeneration groups. Based on these findings silvicultural concepts for the further management of black pine plantations in the Middle Balkan Range are discussed.     

黄冕林场桉树人工林经营利用与经济效益分析

对广西黄冕林场3-5年生桉树人工林进行生长调查,探讨分析桉树经营利用经济效益。结果表明：桉树人工林中,不同林龄和同一林龄桉树人工林之间生长差异明显。不同的立地条件、初植林分密度对桉树人工林胸径、树高等生长影响很大。随着林分密度（标准地样木数）的增大,样木数与生长指标之间具有较强的负相关性。随着林龄的增大,这种林分密度负效应就越明显。从财务指标看,随着林龄的增大,总产值、纯利润和NPV均呈现增大的趋势,但IRR却并不如此,而是先增大后减少,在4a时,IRR达到最大值。从年份看,投资回收期为3a。结果表明桉树在广西黄冕林场这样的立地条件和气候条件下,表现适生、速生,且经济效益好,是营造短周期用材林的好树种。但为获得好的经济效益,必须注意树种、立地条件和栽培等措施的选择。     

湿地松改良种子园部分无性系的早期遗传评价

利用湿地松改良种子园的建园无性系生产的8个全同胞家系和20个自由授粉家系苗木共营建测定林3块。3－4年生的测定林数据分析结果表明，参试的自由授粉家系作全同胞家系的平均生长量显著地大于台山湿地松初级种子园的，20个自由授粉家系的树高、胸径、材积平均增益分别为5．54％，7．77％和23．41％，初步实现了建园目标；同一无性系的不同采种年份的自由授粉子代生长存在着差异，有随着种子园母树年龄的增大而表现渐佳的趋势；改良园中还存在着少量的误选无性系，需要继续作测定和淘汰。从无性系亲子的生长量相关分析中发现，生长较差的自由授粉家系，较大部分产自生长量缩小的母本无性系。     

山西太岳山油松人工林群落结构研究

油松是我国北方人工林重要的造林树种,是我国人工林种植中使用较早的一种树种。本文调查的油松人工林是山西沁源县马泉林场宋家沟。通过在太岳山马泉林场宋家沟设立标准样地,并进行调查、取样,旨在研究人工油松林的群落结构,包括油松林下的植物种类,及科、属、种的统计,同时计算油松林下植被的重要值及多样性指数,揭示油松林下植被多样性情况。同时,针对油松密度与林分平均胸径、平均树高的关系进行研究,找寻油松最佳的种植密度。寻求最佳的解决人工林生长、经营、管理问题的一些途径。     

Conversion of conifer plantations to native hardwoods: influences of overstory and fertilization on artificial regeneration

Forest tree species in the eastern US such as American chestnut (Castanea dentata (Marsh.) Borkh) and oaks (Quercus spp.) have been negatively impacted by forest changes over the past century. Many mature, introduced pine (Pinus spp.) plantations exist in the Midwest US following establishment 50–60 years ago yet have little economic and ecological value. As oak and chestnut have similar site preferences to pines, these stands may be ideal sites for hardwood restoration plantings. We sought to determine optimal management strategies for converting pine plantations by manipulating their canopies. We underplanted hybrid American chestnut and northern red oak (Quercus rubra L.) seedlings into three canopy treatments (control, shelterwood, clearcut) and included an open field treatment. For each of two growing seasons, 0, 30, or 60 g 19N–6P–12K of controlled-release fertilizer (CRF) were also applied to seedlings. Soil chemical parameters and leaf nutrients were analyzed throughout the study. Chestnut and oak seedlings had significantly greater height after two growing seasons in the clearcut and shelterwood than the control and open field, and chestnut had significantly greater diameter as well. Chestnut height and RCD growth were threefold that of oak after two growing seasons. In general, fertilization increased seedling growth more in the clearcut and open field than shelterwood and control for both species. Soils had significantly higher pH, K, and S in the open field than in pine stands. Results suggest that pine plantations may serve as target sites for restoration of these hardwood species. Shelterwoods and clearcuts are both favorable conversion options for oak and chestnut, and addition of CRF may augment further growth increase, especially in open environments.     

Natural regeneration characteristics of Pinus sylvestris var. mongolica forests on sandy land in Honghuaerji, China

Natural regeneration in Mongolian pine, Pinus sylvesttis var. mongolica, forest at Honghuaerji of China （the original of the natural Mongolian pine, forest on sandy land） was studied in 2004. The total mean values of regeneration indexes were higher in mature stands （more than 80% individual stems were older than 50 years）, the maximum of regeneration index reached 29 seedlings, m^ 2, with lowest values in the younger stand, e.g., in 32-year old and 43-year old stands. The stand age was an important factor determining the natural regeneration, which was the best in the older stands in this investigation （e.g. about 80-year old）. The regeneration index seemed not to be closely in relation to canopy openness although Mongolian pine is a photophilic tree species. In each type of gaps, natural regeneration was very well. Regeneration indexes were satisfactory at the south and east edges in the circle gaps; and at the east edge of the narrow-square gaps. Results indicated that Mongolian pine, seedlings could endure shading understory, but it would not enter the canopy layer without gap or large disturbance, e.g., fire, wind/snow damage or clear cutting etc. These results may provide potentially references to the management and afforestation of Mongolian pine, plantations on sandy land in arid and semi-arid areas. Researches such as the comprehensive comparisons on regeneration, structure and ecological conditions and so on between natural Mongolian pine, forests and plantations should be conducted in the future.     

Silvicultural and economic aspects of pure and mixed native tree species plantations on degraded pasturelands in humid Costa Rica

Reforestation of degraded land in tropical regions provides one means of restoring ecosystems and improving rural livelihoods. Most plantations in humid tropical regions are established in pure plots, including few species of high commercial value, generally exotics. The present study compares growth and economic viability of 15–16 year-old trees of native species in pure and mixed plantations on degraded pasturelands at La Selva Biological Station, Costa Rica. The species with the best growth were Vochysia guatemalensis, Virola koschnyi, Jacaranda copaia, Terminalia amazonia, and Hieronyma alchorneoides. The mixed plantations performed better than pure plantations for all growth variables considered, including height, diameter at breast height, volume, and aboveground biomass. Mixed plantations outperformed pure plantations economically, with Net Present Value (NPV) of 1,124 to1,124 to 8,155/ha and Internal Rate of Return (IRR) of 7.7–15.6% depending on the species mixture. The most profitable pure plantations were those of Vochysia guatemalensis, with NPV and IRR of $6,035/ha and 14.3%, respectively; Hieronyma alchorneoides ($6,035/ha and 14.3%, respectively; Hieronyma alchorneoides (2,654 and 10.8%); and Virola koschnyi ($1,906/ha and 9.22%). These are the estimated benefits that would be accrued at harvest. These projections are realistic since the decision to harvest is generally mandated not just by profit maximization but by economic necessity, thus many small- to medium-scale farmers in Costa Rica harvest plantations prior to the completion of the rotation length. Mixed plantation may be the preferred system for reforestation with native species designed for timber production or carbon sequestration because this system is more economically viable and productive than pure plantations.     

Biomass production,nutrient cycling and distribution in age-sequence Chinese fir(Cunninghamia lanceolate) plantations in subtropical China

Biomass production and nutrient(N, P, K, Ca and Mg) accumulation, distribution and cycling were quantified in young, mature and over-mature(10-, 22-, and34-year old) Chinese fir [Cunninghamia lanceolate(Lamb.) Hook] plantations in southern China. Total stand biomass of young, mature and over-mature stands was 38,104 and 138 t ha-1respectively. Biomass production increased significantly with age. Stem wood represented the highest percentage of stand biomass, accounting for 41,55 and 63 % in the young, mature and over-mature plantations respectively. Nutrients concentration was highest in live needles and branches, and lowest in stem wood. The plantations accumulated more N, followed by K, Ca, Mg,and P. Nutrient return amount, nutrient utilization efficiency, nutrient turnover time, the ratio of nutrient returnand uptake increased with stand age, which implies that young Chinese fir deplete soil nutrients to maintain growth,and efficiently utilize nutrients to decrease dependence on soil nutrients as they age. Harvesting young Chinese fir plantations would therefore lead to high nutrient loss, but prolonging the rotation length could improve soil recovery,and help sustain productivity in the long-term. Improved nutrient return through litterfall as stands get older may also be beneficial to nutrient pool recovery.     

晋中东部山区油松人工林地位指数表的编制

为了评价立地质量,用１５５块油松人工林标准地,用三个数学模型进行拟合,最后选定用模型１gＨ＝０．１４２９＋０．５１５３１gＡ编制地位指数表,基准年龄为２５a,用变 异系数法导出６,７,８,９四条地位指数曲线。经用相关指数检验和优势木解析木进行Ｘ＾２检验,结果表明：该地位指数表适用于晋中东部册区的油松人工林。     

动态马尔科夫直径生长模型的研究

建立了模拟山桉人工林直径生长的动态马尔科夫随机模型。估计模型参数用到了山桉密度试验的直径观测数据。采用多项分对数描述直径转移，模型的建立应用了两阶段的广义最小二乘法：第一阶段模拟每一个直径级的直径转移与密度和年龄之间的关系，第二阶段处理第一阶段模型参数随直径级的变动，得到以密度，得到以密度，年龄和径级为自变量预测直径转移概率的紧凑表达式。统计检验表明，应用该模型预测山桉林分直径分布的有效性优于采用