酸雨对树木生长和木材材性的影响

根据大量的国内外文献资料就酸雨对树木生长和木材材性的影响进行了综述。主要包括酸雨对树木生长、木材构造、物理力学性质、化学性质和加工利用的影响,并对国内外研究现状、存在问题和发展趋势进行了分析,阐述了有待进一步研究的领域。     

温度对树木生长与木材形成影响的研究进展

对国内外有关温度影响树木生长与木材形成的研究现状进行了总结。影响树木生长及木材形成的诸多气候因子中，温度最重要，尤其是在干旱、半干旱地区或高纬度地区。近年来，有关树木生长与木材形成和温度变化关系的研究越来越引起人们的关注，并取得了较大的进展。最后对这一研究领域进行了展望。     

酸雨对杨树生长和木材化学性质的影响

对受酸雨危害和未受酸雨危害杨树的年轮宽度和木材化学性质的对比研究表明：酸雨对杨树生长和木材化学性质产生了明显的影响。酸雨会导致树木生长减缓,年轮宽度变窄,受害材的年轮宽度较健康材相对降低１２．６７％。受害材与健康材的ｐＨ值无明显差异,酸、碱缓冲容量有显著差异。与健康材相比,受害材的戊聚糖和木质素含量相对升高１．４３％和３．７２％,而综纤维素的含量相对减少３．４５％,灰分的含量相对减少８．３４％。受     

酸雨及大气污染对马尾松木材材性影响的研究──Ⅰ．木材化学性质与基本密度

对生长在酸雨及大气污染严重危害地区、轻度危害地区和未受危害地区三种条件下马尾松的木材化学性质和基本密度的对照研究表明，生长在受危害地区试材的心、边材生材含水率比在未受危害条件下生长的树木分别低３０％和２２％左右；基本密度与未受危害的树木无明显的差异。酸雨及大气污染危害对木材的化学性质有较为明显的影响，主要表现在：生长在受危害地区试木中的抽提物和木素含量高；而α－纤维素含量则比生长在未受危害地区的试材约低１％至３％；在严重危害条件下生长的试材中组成纤维素的葡萄糖比在受轻度危害和未受危害条件下生长的试材约低２％；在受酸雨和大气污染条件下生长的树木中的纤维素相对结晶度比在来受危害条件下生长的树木含量约低８％。在受危害严重地区生长的试材中的钾、钠、钙、镁、铝、铁、钛和锌的含量高于在轻度危害和未受危害地区生长的试材。其中铝和铁的含量比未受害地区的试材高一倍多，锌的含量高近三倍。生长在受酸雨和大气污染严重地区的试材各年轮中的淀粉和游离糖含量均低于生长在未受危害地区的试材。     

桉树无节材修枝技术研究进展与展望

本文综述了国内外桉树人工林无节材培育修枝技术的理论和研究。为了满足当今社会对高品质木材的大量需求,人们开始将桉树纸浆材人工林栽培向更高价值含量的锯材转化。众多研究表明,影响桉树木材外观等级的主要因素是节子。要从根本上解决木材质量的问题,合理而科学的修枝理论和实践显得尤为重要。修枝直接影响树冠动态发展,而树冠动态与树木的生长直接相关。尽管桉树自然整枝能力较强,但不能靠它获得大量无节材,修枝措施必不可少。修枝对树木生长和木材材质都会产生影响。合理的修枝强度会促进树木生长,而科学的修枝技术对高品质无节材的形成相当关键。为了使修枝达到最大效益,在非生长季节以及树冠郁闭前修去小枝活枝,并且保证修枝伤口平滑和注意伤口保护是最合适的修枝处理。伤口的愈合与诸多因素有关。     

酸雨对林木伤害研究综述

文章从酸雨的研究历史出发,阐述了酸雨的形成和分布,指出酸雨是一种全球性的环境问题;从酸雨污染对林木代谢功能、生长发育、木材特性这三大方面综述了国内外在酸雨给林木造成伤害方面的研究动态及其成果,并提出了在今后酸雨研究中应该重视的几大突破性问题。     

影响木材产品质量因素及控制方法的研究

木材产品质量是影响林业企业经济效益最关键的因素之一。本论文从树木生长特性、采伐技术、集材、造材等六种因子对木材产品质量影响进行了分析，并采取科学的方法加以控制，以减少木材损伤，提高木材产品质量。     

木材中SiO2 的含量及其作用

SiO2在木材中能提高木材机械、物理强度,克服各向异性、易燃、易腐、尺寸不稳定等缺陷.研究了有关木材中SiO2的含量及分布的情况;分析了影响木材中SiO2含量的主要因素,如土壤中无机元素的含量、树龄、树木的生长对矿质元素的需求和木材密度等;阐述了木材中SiO2含量对木材的物理力学性质的影响和作用;对今后的研究提出了方向.     

单位叶面积的主干生长量——对树木生长势的一种测定

对树木碳素收入的分析指出,主干木材的产量比起根系的枝梢来并不占优势。因此,分配给主干木材产量的碳的比率,可以作为评定树木生长势的一个尺度。与其直接分析碳素循环,倒不如用分析每平方米叶子所生产的主干木材量来说明树木生长势。这个总的前提可以使我们对叶面积的估测与正在进行的一项研究结各起来,该     

树木生长应力与木材利用

在采伐树木时常常听到由锯口处传出的噼噼啪啪的爆裂声,若观察伐倒原木的端面可发现木材裂隙,严重者木材沿纵向产生辟裂。在制材或木材加工中也常见板、方材出现开裂、翅曲现现。究其原因主要是由于树木自身的生长应力(内含应力)在采伐、加工过程中失去应力平衡而突然释放所致。树木的生长应力大(对木材而言可称为术材的残余应力),影响木材的使用价值和降低木材的利用率。这是因为:发生端裂的     

低丘生态脆弱区植被恢复与经济开发研究

在丽水、兰溪、永康营造了果园、经济林、菇木林和用材表防护林，对5年生试验材进行了生长调查、产量统计、经济效益分析、水土流失观测及土壤微生物分析。研究结果表明，在低山丘陵生态脆弱区营造和恢复人工植被，能改善已破坏的生态环境和获得较高的经济效益。     

竹林生态经营类型探讨

传统竹林经营多以获取最大经济效益为出发点,较少关注竹林的生态效益,竹林分类经营可充分发挥竹林的多种效益。文章根据林地权属、区域分布、立地类型,林分起源、竹种、林分组成、生产力水平和经营目标等影响竹林经营的8大因子,将竹林划分为森林竹林、农作竹林、园林竹林、种质资源竹林4大类,并分析了每种类型的经营目标和主要经营措施。     

二十世纪的世界林业

20世纪的世界林业,为解决森林资源继续减少,木材供需矛盾,生态环境恶化和能源危机等问题,在发挥森林的多种效益,实行森林的永继利用和林业的综合集约经营的指导思想下向前发展。其主要特点是:保护和发展森林资源,科学管理和集约经营森林资源,合理节约利用森林资源。预测,到21世纪,世界林业必将向社会化、综合化与集约化方向有较大的发展。     

Comparison of socio-economic and ecological benefits of bamboo and trees: the perspectives of local communities in south-western Ghana

Natural forests are disappearing in many tropical countries, resulting in loss of biodiversity and erosion of forest-dependent livelihoods. The maintenance and restoration of forests as well as a search for alternative natural resources that can concurrently improve the environment and enhance incomes of local communities has become crucial. Bamboo is suggested as a resource, which could substitute trees for socio-economic and ecological purposes in developing countries in the (sub)tropics. However, the relative importance of bamboos and trees for socio-economic and ecological purposes in bamboo-growing communities is not yet studied. Here, we present a study conducted to compare the socio-economic and ecological benefits of bamboo and trees from the perspectives of three bamboo-growing communities in the Wassa East District of Ghana. The compared benefits were ranked on a five-point Likert scale and significance of differences was tested at the 95% confidence level. For socio-economic benefits, trees were ranked significantly higher than bamboo for domestic energy, medicinal use and commercial harvesting; however, furniture, building and construction were not significantly different. For ecological benefits, bamboo was ranked significantly higher than trees for erosion control and riverbank protection. Trees, on the other hand, were ranked significantly higher than bamboo for biodiversity conservation, carbon sequestration and oxygen generation. The results imply that transforming bamboo into suitable products to meet communities’ energy needs could alleviate pressure on trees in natural forests.     

Forest future s by Swedish students – developing a mind mapping method for data collection

Forests are an important natural resource in Sweden. They are used for multiple purposes, for example, providing economic returns from timber harvest, conservation of biodiversity, provision of wild berries and mushrooms and recreational benefits. People’s perceptions of forests and forest use are currently under transformation due to drivers like globalization and urbanization. The aim of this study was to analyse in particular Swedish university student’s visions of future forests using a newly developed survey method based on mind mapping. An online survey with mind map technique was used to collect data from university students in Umeå, northern Sweden. The study focused on features of forests, products derived from forests and activities in forests. The results indicate that students regard ecological, social and economic aspects of forests as important for future forests and the use of them. In particular, the role of non-wood forest products, like berries and mushrooms, as well as recreational features of forests were central to many of the students. The multitude of different visions suggests that forest management decisions of today, directing the future of forests, need to consider the multiple use of forests to be able to satisfy forest preferences also of younger generations.     

Production efficiency of community forest management in Nepal

Nepal's forests have been transferred to community management with the twin objectives of supplying forest products and addressing local environmental problems. Community forests provide a range of benefits, from direct forest products such as timber and non-provisioning ecosystem services such as soil protection. There is a need to understand the extent to which environmental and community benefits are joint products or substitutes. Stochastic frontier production analysis (SFPA) was used to study the production relationship between environmental and community benefits and production efficiency analysis to study the extent to which communities were able to achieve maximum benefits. SFPA indicated that the magnitude of direct forest product benefits was influenced by various socioeconomic and forest related factors such as distance to the government office, community forest size, and group heterogeneity negatively affect community forest products benefits. On the other hand, links to the market, forest products dependency, and the number of households in the community augment benefits from community forests. In addition, forest product benefits and environmental benefits were complementary to each other. Production efficiency analysis showed that communities were not producing forest products efficiently. Factors such as social capital contributed positively to production efficiency, whereas caste heterogeneity in the executive committees of community forest user groups was negatively associated with efficiency. These findings can contribute to better implementation of community forestry programmes in Nepal, improving the welfare of communities by increasing direct forest product benefits without environmental harm.     

城市特色森林建设思考与实践

城市森林的概念以及内涵表明了城市特色森林建设是当前提高城市园林绿地的生态质量重要途径,本着城市园林绿地的各种效益平衡点出发,依据城市5大类园林绿地的不同功能侧重作为8大类城市特色森林模式建立的切入点,明确了不同类城市特色森林建设的内容、适用范围以及主要措施,最后通过案例的阐释进一步表明了特色森林模式运用的可行性和有效性。       

Forests as carbon sinks--benefits and consequences

With their ratification of the Kyoto Protocol, many countries have established forests on previously non-forested land with the view of offsetting greenhouse gas emissions. While these forests indisputably result in increased carbon storage in above-ground biomass, consideration of other major implications is often neglected. Forest establishment results in changes in albedo and soil carbon storage, reduced runoff and downstream water supply, and effects on biodiversity. Such effects of forest establishment may be less desirable from environmental, economic and social perspectives. While there have been many studies of the impacts of forest establishment on individual aspects, policy makers need to be able to integrate the benefits and consequences to assist in making decisions on land management. Further, the relative magnitude of the effects of forestry needs to be considered in the context of elevated atmospheric carbon dioxide partial pressure and climate change resulting in increasing temperature and changes in the amount and distribution of rainfall. This introductory review highlights the major benefits and consequences of forest establishment and demonstrates progress in integrating across the services provided by forests. New modelling approaches are being developed that allow analysis of benefits, consequences and trade-offs to assist policy makers in decisions to manage the provision of multiple resources.     

China’s Forests and Their Impact on Global Carbon Cycle

Forests have multiple benefits and functions, including mitigation of climate change. The impacts of forests on the global carbon cycle include forests as carbon sinks, wood-based products as carbon sinks, bio-energy, and production and use of non-timber products. In the past decades, forest cover of China has increased from 8.6% to 18.21% by large-scale afforestation and conversion of cropland into forests. Forest biomass carbon (C) stock increased from 4.3 Pg C (1 Pg C = 1 015 g C) in the early 1980s to 5...     

我国沿海防护林体系建设的构想

我国沿海地区是个多灾地区,主要自然灾害有台风、干旱、水土流失等,且缺少木材和烧柴。作者分析了我国沿海防护林的现状,进而提出建设生态经济型沿海防护林的构想,即不仅发挥其生态防护功能,还应充分发挥其社会经济功能。沿海防护林体系应作为生态经济产业来进行开发和建设。而因地制宜,科学合理地确定沿海防护林体系的组成,优化其结构,则是实现稳定高效多功能的关键。