青檀耐荫性的初步研究

在连续３年测定比较几个不同树种的生理特性和树冠结构的基础上，本文对青檀的耐荫性进行了初步分析，结果表明，青檀的耐荫性随年龄的增大而降低，１２年生以前，青檀是耐荫的；１３至２５年生之间，青檀是喜光树种；２６年生以后青檀则逐渐变为阳性树种。比较的结果还表明，青檀的耐荫性较马尾松强，较杉木弱，从总体看属中偏阳树种。     

耐荫树种和不耐荫树种

耐荫树种与不耐荫树种相比,其光合作用在较低的温度和较少的光照条件下就开始。随着光照的增加,耐荫树种能以较低的光强达到最大的光合作用率,而不耐荫树种则不能。随着光照的持续增加,就出现相反情况。不耐荫树种能响应光照的持续增加,比耐荫树种达到更大的光合作用率,而耐荫树种则不能。一般说来,空旷地上的不耐荫树种比耐荫树种生长快。随着荫蔽的形成,两者的生长差异缩小。当荫蔽增加到一定程度时,耐荫树种的生长将超过不耐荫树种。选择人工更新方式时,应考虑树种的适光性及其随竞争和光照而形成的生     

间伐对辽东山区长白落叶松人工林生境和更新的影响

为弄清间伐对落叶松人工林内环境因子,进而对落叶松林内天然更新的影响,在辽东山区对40年生落叶松人工林进行了5种不同强度的间伐试验(分别为0%、10%、20%、30%和40%)。间伐后,对环境因子和更新状况进行了观测。结果表明,林冠开阔度随间伐强度增大而增加,间伐后其林冠下光量子数量、地表平均温度、不同层次土壤平均含水量与空隙度大小成线形关系;落叶松人工林间伐一年内,更新树种丰富度没有显著变化,而更新密度和更新频度都明显增加(p<0.05)。更新树种数量增加与树种特性有关,增长幅度为阳性树种>耐荫树种。所有的更新树种中,对林冠开阔度变化响应最大的是黄波罗(Phellodendronamurense)。实验结果证实了辽东地区落叶松人工林间伐后,更新数量变化与周围保留的树种分布、树种特性和立地条件有关。图9表2参43。     

淮北相山8个树种叶片的生态解剖特征

对淮北相山杂灌丛和混交林中8个树种叶片的生态解剖特征进行研究.结果表明,优势种叶片解剖可塑性显著大于亚优势种.叶片厚度、维管束厚度、海绵组织厚度、气孔密度、木质部韧皮部厚度比、栅栏组织厚度和栅栏组织海绵组织厚度比(S/P)等性状,在物种或生境之间的变异较大,称为关键解剖性状.与杂灌丛群落的阳生叶相比,混交林叶片表现出阴生特点:表皮及角质层薄,叶片较薄,栅栏组织不发达,S/P较大,输导组织相对不发达.8个树种叶片对其生境表现出多样化的适应方式,大致可分为3类:阳性旱生植物、耐荫性中生植物和阳性中生植物.演替早期植被中优势种多为阳性植物.     

迹地人工更新的树种选择与造林技术

迹地人工更新是消灭荒山、培育后备森林资源、实现林业可持续发展和改善生态环境的重要举措，也是培育地方财源、壮大林业产业和增加林农收益的主要途径之一。迹地人工更新主要是“三大迹地”，即采伐迹地、火烧迹地和森林病虫害迹地。浙江一带的采伐迹地和火烧迹地原树种以松木、杉木、柏木为主，森林病虫害迹地原树种以马尾松、黑松为主，还有部分受鞭角华扁叶蜂危害的柏木及柳杉。我们总结20多年来从事迹地人工更新的实践，认为较成功的迹地人工更新最主要的技术是：造林设计时坚持适地适树的原则，并注重更新树种的乡土化、阔叶化和多样化。只有这样培育的森林才具有较高的稳定性、较大的生长量、较高的蓄积量、经济效益好、森林功能多和物种资源较丰富的森林生态系统。     

米林亚高山森林采伐迹地类型及更新技术研究

本文在对西藏米林县亚高山采伐迹地植被和更新情况调查的基础上，对采伐迹地类型进行了划分。共区分出灌木迹地和草本迹地2大迹地类型，在此基础上，又划分出了4种迹地亚型；不同迹地类型的植物组成和生境特点以及更新状况均存在一定的差异。针对不同迹地类型的生态条件和更新状况，提出了具体的更新技术。     

漫话云南松古树

漫话云南松古树云南松又称飞松、青松。它耐干旱、瘠薄，天然更新良好，是云南首屈一指的用材树种。云南松林地面积占全省林地面积的５２％，活立木蓄积量占全省森林蓄积量总和的３２％，是分布区内荒山绿化和迹地更新的主要树种，是全省飞播造林面积最大的树种。松为“百...     

红松耐荫性研究综述

红松作为阔叶红松林的优势树种之一,一直受到人们的关注,文中阐述了红松耐荫性研究的意义及国内外研究现状,介绍了几种研究红松耐荫性的方法,结果均表明,红松在其幼苗时期具有一定的耐荫性.同时,指出了红松耐荫性研究中缺少耐荫性的评价指标体系和我国在红松耐荫性研究方面存在的问题.     

坝缘山地迹地更新及经营对策

坝缘山地迹地更新及经营对策李经天（塞罕坝机械林场）关键词迹地更新现状对策塞罕坝机械林场的山地迹地更新，是调整林种结构，提高林分质量，调整树种组成的重要措施，更主要的是培育速生丰产林，增加后备资源。现就大唤起林场近１０年来迹地更新情况，对更新技术和经营...     

云南玉龙山亚高山针叶林天然更新的研究

本文主要研究了玉龙山亚高山针叶林(3000—3800米)的天然更新。调查分析了坡向、坡度、乔木郁闭度、下木覆盖度、枯枝落叶层厚度与天然更新的关系。2.在不同树种的林冠下,天然更新有其一定的共同规律。同时,由于各树种特性的不同,显示出某些差异。总的来看,乔木郁闭度中等、下木稀疏、缓坡以及枯枝落叶层厚度在5厘米以下,最有利于高山针叶林天然更新。但不同树种要求不同的坡向,云杉宜于阳坡,冷杉宜于阴坡,混交林则宜于半阳坡。3.当高山针叶林被火烧后,原来林内耐荫的植物不见了,迹地上代之而起的是耐早喜光的种类,山杨、桦木和柳逐渐生长起来。在阳性树种的庇荫下,才又有耐荫针叶树种出现,开始漫长的演替过程。4.就玉龙山的调查研究,提出对滇西北高山针叶林的开发意见。该林区应在发挥森林效益的前提下,制订合理的经营方针。     

Influence of crown class and shade tolerance on individual tree development during deciduous forest succession in Connecticut, USA

Sixty years of individual tree crown class records were used to elucidate the influence of crown class (dominant, codominant, intermediate, or suppressed), shade tolerance (intolerant, midtolerant, or tolerant), and their interactions on the probability of individual tree movement among crown classes. Trees were measured at 10 year intervals between 1927 and 1987, excluding 1947, on 364 nominal 0.01 ha plots. A total of 14 154 individual tree records were used in this analysis. The transition rates among crown classes for 30 year intervals (1927–1957 and 1957–1987) were examined for all combinations of antecedent crown classes and tolerance rankings. The distribution of ingrowth among tolerance rankings was also examined.

Mortality rates increased with decreasing crown class for all tolerance rankings, and mortality rates increased with decreasing tolerance. Compared with tolerant trees, midtolerant and intolerant trees had higher rates of ascension into dominant and codominant crown classes and exhibited higher persistence rates in the dominant crown class. These factors suggest that midtolerant and intolerant trees have an advantage over tolerant trees in the higher crown classes, In contrast, tolerant trees had the advantage in suppressed and intermediate crown classes, with lower mortality rates, higher persistence, and higher rates of crown class ascension than for midtolerant or intolerant trees. Crown class stratification was driven by the change in relative advantage of each tolerance ranking among the crown class.

Results of this study suggest that the canopy stratum (upper canopy, lower canopy, or mixed) affected by disturbance is as important as disturbance scale, intensity, and frequency in influencing the composition of the suppressed crown class. Because the suppressed crown class is in a constant state of high flux, with fewer than 30% of the suppressed trees remaining in the suppressed crown class for any 30 year period, a small change in the relative persistence or ascension rates among tolerance rankings, whether by a different disturbance or climate regime, could alter the proportion of tolerance rankings in the suppressed crown class and ultimately result in an alternative succession.     

福建光泽南方铁杉群落植物组成与多样性分析

采用样地调查法研究了福建光泽香炉山南方铁杉天然林群落植物组成与多样性。结果表明:光泽南方铁杉天然林群落(2000 m2)共有维管束植物27科40属52种。南方铁杉群落乔木层常绿树种占据优势,而灌木层常绿树种占据压倒性优势,说明常绿树种幼苗幼树耐阴性比落叶树种强,从而在林下低光照环境下具有更强的竞争能力。南方铁杉群落的乔木和灌木层发达,而草本层发育差,物种数与群落多样性指数均为灌木层>乔木层>层外植物>草本层;而均匀度则多为层外植物>灌木层>乔木层>草本层。南方铁杉种群幼苗幼树数量较多(2151株.hm-2),但小树数量极少(24株.hm-2),有一定数量的中树和大树(405株.hm-2)。南方铁杉幼苗幼树耐阴性差,难以与耐阴性强的常绿乔灌木树种竞争,这可能是南方铁杉濒危的原因之一。     

Regeneration patterns of Eastern white pine (Pinus strobus L.) in hardwood-dominated forests in Virginia, USA

Eastern white pine (Pinus strobus L.) is a moderately shade-tolerant species that co-occurs with hardwood tree species in many forests of the eastern United States, as well as in pure stands. The species is valued for its timber, as well as for wildlife and recreation. Regeneration of this species is somewhat unpredictable and often occurs in patches of similarly-aged cohorts. We described the regeneration patterns of this species and examined their relation to environmental variables within hardwood forests of southwestern Virginia, USA. An average of 5.3 white pine patches per ha were observed in this study. The majority of patches consisted of saplings (85%), with 9% of patches in pole size classes, and 6% in seedling size classes. The average density of patches was 43.5 stems with an average age of 20 years. The size of patches averaged 80.6 m². The total density of seedlings and the number of regeneration patches of all sizes of regeneration (seedlings, saplings, and poles) in plots was related to the surrounding density of large white pine trees (potential seed trees). The density of seedlings or patches was not significantly related to current vegetation cover or soil surface cover variables, but more than half of regeneration patches were located in or adjacent to old canopy gaps, most of which were old logging gaps. While seedling regeneration may occur within the understory of these forests near seed trees, advancement to the sapling and pole stage appears to be associated with canopy gap formation.     

Growth of advance regeneration of Norway spruce after clear-cutting

We developed a basal area growth model for recovery of advance growth of Norway spruce trees after clear-cutting. Stem diameter growth at ground level and needle-mass characteristics were measured on permanent sample plots in Estonia. Both tree ring analysis (destructive sampling on one sample plot) and yearly repeated measurement data (two plots) were used to quantify advance growth. Basal area growth of small trees was estimated by multiple regression analysis. Previous-year basal area of the tree and basal area growth explained tree performance the next year. Tree needle-mass variables characterizing the acclimation status of the tree were included in the model as explanatory factors. Needle samples (one shoot from the upper third of each tree crown) were collected each year after the growth period from all sample trees. Needle masses of shoots from consecutive years were correlated and this variable was used as a predictor in the simulation model. Accelerating growth was observed in trees that exceeded the growth threshold in the year after release: the greater the needle mass per shoot, the greater the acceleration in growth. Competition among advance regeneration trees was included in the model: small trees under taller neighbors exhibited reduced growth. We found that trees released from a long period of heavy shade can survive, but the time needed for acclimation and resumption of competitive growth rates is considerably longer than for trees released from light shade. Such trees can be used for forest regeneration, but competition control (particularly reducing the proportion of fast-growing hardwoods) is required.     

呼伦贝尔沙地樟子松天然更新苗影响因素的研究

通过对呼伦贝尔沙地樟子松天然林天然更新苗特征及其影响因素的研究,结果表明:母树密度不同,天然更新苗数量和年龄结构存在明显差异;樟子松天然更新苗年龄结构在时间上具有明显的不连续性,樟子松天然更新苗密度因林分类型的差异明显不同。在疏林地(树龄30 a),平均更新苗密度每2 500 m2为13株,在火烧迹地平均更新苗密度每600 m2为28.5株,樟子松单株样地平均更新苗密度每600 m2为118.8株。不同年龄的天然更新苗保存密度和年平均降水量有显著或极显著关系,且随着林分郁闭度的增加,研究区天然更新苗密度呈现降低的趋势。     

The effects of belowground resources on aboveground allometric growth in Bornean tree species

Tree height and crown allometries reflect adaptations for resource acquisition and structural stability, as well as plastic responses to a heterogeneous environment. While both light and soil resources limit growth and influence competitive responses in tropical forests, the effects of belowground resources on allometries are less understood, especially within the understory. To characterize outcomes of tree competition along an edaphic resource gradient, we quantified variation in height and crown allometries of six Bornean tree species from contrasting regeneration niches (light-demanding vs. shade-tolerant) on two soil habitats (clay-fine loam and sandy loam) within a 52-ha forest dynamics plot. Using empirically-fit allometric parameters and diameter growth rates from plot census data, we modeled tree height and crown area growth over the projected life span of each species. Based on resource competition theory, we hypothesized that tree species specializing on and populations of generalist species growing on the relatively moister, more fertile clay-fine loam soil habitat would have faster height and crown growth rates, compared to those on the sandy loam habitat, regardless of regeneration niche. Among soil specialists and within generalists of both genera, trees growing on clay-fine loam had taller stems and larger crowns at a given age and faster height and crown area growth rates at most sizes than trees on sandy loam. Differences in height and crown growth were driven by the faster diameter growth rates of trees on clay-fine loam, not by differences in height- and crown-diameter allometries, as trees on sandy loam were significantly taller at a given diameter, and differences in crown allometry were not consistent across soil habitats. Characterizing the height and crown growth responses of trees along resource gradients provides insight into the mechanisms that maintain diversity in tropical forests. Our results point to the importance of adaptive and plastic responses to both above and belowground resource availability in determining the allometric growth of trees and suggest that this diversity of responses may contribute tree species coexistence through competition-based trade-off mechanisms and variation in growth among individuals. Additionally, as the importance estimating natural carbon sequestration increases with the escalating effects of anthropogenic climate change, differences in tree growth and architecture across soil habitats also have implications for the approximation of forest carbon storage on heterogeneous tropical soils.     

Beyond reduced-impact logging: Silvicultural treatments to increase growth rates of tropical trees

Use of reduced-impact logging (RIL) techniques has repeatedly been shown to reduce damage caused by logging. Unfortunately, these techniques do not necessarily ameliorate the low growth rates of many commercial species or otherwise assure recovery of the initial volume harvested during the next cutting cycle. In this study, we analyze the effect of logging and application of additional silvicultural treatments (liana cutting and girdling of competing trees) on the growth rates on trees in general and on of future crop trees (FCTs) of 24 commercial timber species. The study was carried out in a moist tropical forest in Bolivia, where we monitored twelve 27-ha plots for 4 years. Plots received one of four treatments in which logging intensity and silvicultural treatments were varied: control (no logging); normal (reduced-impact) logging; normal logging and low-intensity silviculture; and, increased logging intensity and high-intensity silviculture. Tree growth rates increased with intensity of logging and silvicultural treatments. The growth rates of FCTs of commercial species were 50–60% higher in plots that received silvicultural treatments than in the normal logging and control plots. Responses to silvicultural treatments varied among functional groups. The largest increase in growth rates was observed in FCTs belonging to the partially shade-tolerant and the shade-tolerant groups. These results indicate that silvicultural treatments, in addition to the use of RIL techniques, are more likely to result in a higher percentage of timber volume being recovered after the first cutting cycle than RIL alone.     

Silvicultural systems for southern bottomland hardwood forests

Silvicultural systems integrate both regeneration and intermediate operations in an orderly process for managing forest stands. The clearcutting method of regeneration favors the development of species that are moderately intolerant to intolerant of shade. In fact, clearcutting is the most proven and widely used method of successfully regenerating bottomland oak species in the South. The seed-tree method of regeneration favors the establishment of light-seeded species. Mechanical soil scarification may be necessary if the desired species requires bare mineral soil for establishment. The shelterwood method of regeneration can provide for the development of heavy-seeded species, but has produced highly variable results with southern bottomland oaks. The single-tree selection method of regeneration favors the development of shade-tolerant species. When single-tree selection is applied repeatedly to stands containing commercially valuable shade-intolerant species, composition will gradually shift to less-valuable, more-tolerant species. Consequently, the single-tree selection method of regeneration is not recommended for any commercially valuable bottomland hardwood tree species. Group selection, in its strictest application, creates only small openings that usually fail to allow sufficient light to the forest floor for satisfactory establishment and development of shade-intolerant bottomland species. Patch cutting, a combination of uneven-aged (group selection) and even-aged (clearcutting) silviculture, designed to create larger openings, has been successfully used to produce an uneven-aged stand that consists of many small, irregularly shaped, even-aged groups. Silvicultural systems should include a planned program of intermediate operations designed to enhance the growth and development of those species favored during the regeneration process. Improvement cutting and commercial thinning are increasingly common in southern bottomland hardwood forests. Other partial cuttings employed today in bottomland hardwood forests typically involve some form of crop-tree release. Specific recommendations for the selection of silvicultural systems are presented for the eight most important species groups found in southern bottomland hardwood forests.     

Improved management of fruit trees in West African parklands

West African agroforestry systems are changing because agricultural intensification and a changing climate put the tree component at risk. Since local fruit trees play an important role in human nutrition and income generation, this is critical for rural livelihoods. This special issue presents a range of papers devoted to local fruit trees and their potential to improve local livelihoods. The topics cover studies of regeneration, use of mycorrhiza, tree/crop interactions, pollination, variation in fruit quality and genetic variation in adaptability. It is shown that there are many possibilities to improve benefits from trees. Some are likely to have immediate effect on livelihoods, such as cultivation of shade-tolerant crops under trees or improved management of pollinators. Others will require long term efforts, such as using natural variability of trees in breeding programmes to improve adaptation, quality and yield. In any case, to maintain the benefit from trees in the long run it will be necessary to identify appropriate strategies for regeneration of species that are currently in decline.     

Canopy effects on vegetation caused by harvesting and regeneration treatments

This paper reviews the primary effects of canopy on understorey vegetation to provide insight into the management of the canopy space to benefit tree regeneration. Site conditions, like nutrient and water availability, overstorey conditions, e.g. tree species, and canopy density, are important determinants of ground vegetation. An investigation of canopy effects is concerned about how the canopy trees modify site conditions. As canopy density may be deliberately modified during regeneration treatments, the effect of canopy density on individual species in the herbaceous layer and tree regeneration is important. This autecological perspective focuses on the successional traits of species to help understand species differences in fecundity, survival, density and growth. From a synecological perspective, the importance of successional traits for the outcome of competition between species arising from differences in canopy densities is highlighted. This review shows that moderately dense canopies may favour tree regeneration over aggressive shade-intolerant graminoids or forbs. This is particularly true for shade-tolerant and intermediate shade-tolerant tree species. To better understand and utilise this phenomenon, research should try to identify and isolate different canopy effects.