Effects Of Thinning In a Water-Limited Holm Oak Forest

ABSTRACT

A natural holm oak forest was selectively thinned to test thinning as a tool to reduce tree mortality, increase productivity, and reverse the recent regression of the dominant species (Quercus ilex) induced by climate change. Thinning increased aboveground productivity and reduced stem mortality in this Mediterranean forest during four years just after thinning, contributing to the maintenance of forest functioning under changing climatic conditions. Q. ilex was the only species positively affected by the thinning: stem growth increased for all stem sizes, and mortality was significantly lower in thinned plots. On the contrary, mortality rates of Phillyrea latifolia and Arbutus unedo were not significantly lower. Stem growth increased for P. latifolia only in the smallest stem-size class. Our results highlight the suitability of selective thinning for improving the forest productivity and ensuring the conservation of Mediterranean coppices. Other benefits of selective thinning, such as a decrease in the risk of fire dispersion and an increase in the water supply for human populations, are also discussed.     

干热河谷和干性森林水分特征的对比分析

本文研究了川西南山地安宁河流域干热河谷和干性森林的水分收支状况。结果表明:(1)干热河谷和干性森林的年降水量分别为1 067.95 mm和1 371.73 mm,年降水量的90%以上集中在6月～10月的雨季和夏秋季节;(2)干热河谷和干性森林年蒸发量为1 280 mm和1 089.75 mm,春夏蒸发占年蒸发量的65%和66%,旱季蒸发占年蒸发量的58%和61%,4月～6月是蒸发旺季,其次是7月～8月;(3)干热河谷和干性森林年水分盈余量分别为43.6 mm和481.95 mm,均存在季节性水分匮缺期,7月～10月、夏秋季节和雨季均是水分盈余期,其余为水分匮缺期;(4)干热河谷和干性森林年干燥度分别为1.205和0.8,表明该地区分别为半湿润和湿润性气候,还存在明显的季节差异,7月～10月、雨季和夏秋季节气候湿润,其余时期为半湿润或干旱气候;(5)干性森林在年降水量和水分盈余量上高于干热河谷,在年可能蒸发量和干燥度上明显低于干热河谷,这种差异还体现在水分参数的月分配、四季分配、旱雨季分配上;(6)干热河谷湿润程度差于干性森林,干热河谷植被和干性森林对各自水分收支状况具有良好的适应性;(7)封山育林需要注意旱季防火,人工促进还需要考虑土壤水分平衡规律和适地适树,进行"适度"造林。     

云南哀牢山自然保护区南华片区项目建设必要性分析

对哀牢山国家级自然保护区南华片区的生物多样性、经营现状和经营管理进行评价,对项目建设必要性分析结果:项目建设有利于该保护区的整体效应;有利于对珍稀植物物种和生态系统的保护;有利于对候鸟迁徙通道的保护;有利于社会经济的可持续发展;是加强科研和宣教工作的需要。最后阐述了项目建设的主要内容。     

森林生态系统中林分胸径和树高的Granger因果关系研究

滞后阶数为1时,胸径和树高互为Granger原因,这从理论上证明,建立胸径和树高模型是合理的.当滞后阶数为2时,胸径不再是树高的Granger原因,但树高仍是胸径的Granger原因,两者相比,树高的影响更深远.所以在森林培养时,应更加注重树高,以维持树高对胸径的影响.     

基于GIS技术的长汀县森林资源分类经营管理

依据国家林业局颁发的《全国森林资源经营管理分区施策导则》所提供的森林资源分类分区指标,利用GIS空间分析技术,综合长汀县林业基本图层、遥感影像数据、基础地理数据等,对福建省长汀县的森林资源进行了有效的分区分类,将其分为严格保护类型组、重点保护类型组、保护经营类型组和集约经营类型组4个类型,对分区的结果进行分析,并提出了相应的经营管理对策,为森林资源的有效经营管理提供了决策支持。     

速生人工林桉树木材材色处理初步研究

试验用漂白剂、酸性染料和其他化学药剂,采用单纯漂白、单纯染色、先漂白再染色和化学着色等4种不同的方案对人工林桉树木材进行材色改良处理研究.结果发现:单纯漂白可获得一定的材色改良效果;硫化物类、过硫酸铵类的药剂配方漂白效果不明显;硼氢化钠类的药剂配方可得到一定的漂白效果;双氧水类、次氯酸钠类的药剂配方可得到很好的漂白效果.单纯染色比较难获得好的材色处理效果.采用先漂白后染色的方法,获得的材色过于鲜艳.采用化学着色的方法,可获得较理想的材色改良效果;草酸类药剂配方着色效果明显,可消除材色缺陷,根据不同的配方和处理工艺可获得从浅粉红色到红棕色的色调;用双氧水做活性剂,引入带发色团的化学药剂,材色改良效果明显,通过调整配方药品的浓度和处理工艺可获得从浅黄色到橙黄色的不同色调和较佳的材质.     

The power of knowledge: information transfer and açaí intensification in the peri-urban interface of Belém,Brazil

Academic scholarship and development paradigms promote non-timber forest products (NTFPs) as potential options to link environmental conservation with sustainable economic development objectives for rural communities worldwide. The açaí berry (Euterpe oleracea) is a native palm found in forest ecosystems of northern Brazil and historically extracted and sold in regional markets. Recent increases in national and international açaí demand have resulted in dramatic price increases. Management decisions on a local producer level reflect trends not typically associated with traditional NTFPs as future production and income expectations increase. This case study draws on research conducted in peri-urban communities in close proximity to Belém, Brazil. The work draws links between recent açaí intensification trends in upland areas and information pathways that are contributing to this pattern. This paper argues that external information sources regarding land use choices are prioritized over local knowledge and market indicators which previously have been described as drivers for intensification processes of NTFPs. This qualitative analysis highlights the power structures that influence information sharing and in turn, land use choices on a community level. The results of this analysis are important for NTFP intervention initiatives focused on risk management for smallholders. Finally, this study is a useful complement for ecological studies currently being conducted on intensification processes of non-timber forest products.     

Refugee impact on collective management of forest resources: a case study of Bhutanese refugees in Nepal's Eastern Terai region

This article analyzes the relationship between forest resources, refugees, and the host population. The findings of the research suggest that the host population are heavily dependent on the local forest for their daily needs such as fuelwood, timber, grazing area, fodder for domestic animals, foods, and medicine in addition to cultural and esthetic needs. The forest has also been relied upon for agricultural needs such as manufacture of agricultural tools, maintenance of irrigation water systems, erosion control, and fertilizer needs. The forest was under a sustained demand as any other Terai forest of Nepal. After the arrival of refugees in 1992, the demand for forest resources increased substantially. Initially, the construction of the refugee camps decreased the total forest area and also required some felling of trees. More significantly, the refugees themselves became active users of the forest resource, which generated extra pressure on the forest and created scarcity of forest resources. Before the arrival of the refugees, forest management and monitoring of illegal use of the forest resources were carried out by the government through its local forester office. The local residents were active users of the forest resources, but were passive in managing and maintaining the forest resource. However, competition from the refugees instilled a desire in the local population to safeguard and protect the dwindling resource against the external threat by creating the Humse Dumse Community Forest.     

Chemical changes of kenaf core binderless boards during hot pressing (I): influence of the pressing temperature condition

Self-bonding is the main factor of the performance expression of binderless boards, and therefore its clarification is considered to be an important issue. For this purpose, a series of chemical analyses were conducted on kenaf core binderless boards and their chemical changes during the hot-pressing process are discussed in this article. First of all, binderless boards were prepared from kenaf core powder at different pressing temperatures (without steam-explosion process) and were used for chemical analyses after they were reduced into powders and extracted with methanol. To investigate their chemical changes, lignin, holocellulose, and neutral sugar contents were determined, Fourier transform infrared (FTIR) spectra were recorded, and the nitrobenzene oxidation procedure was applied. As a result, it was found that parts of lignin and hemicelullose were decomposed during the hot-pressing process; however, the contribution of the resulting fractions to selfbonding was not observed. In addition, progress of condensation reactions in lignin and the formation of chemical bonds by low molecular weight conjugated carbonyl compounds in methanol extractives were observed. Thermal softening of lignin is also suggested to play an important role in the expression of board performance.     

Initial shapes of stress-strain curve of wood specimen subjected to repeated combined compression and vibration stresses and the piezoelectric behavior

This study investigated the relationship between the initial shape of the stress (σ)-strain (ε) curve of a Chamaecyparis obtusa wood specimen subjected to repeated combined compression and vibration stresses at various angles between the fiber direction and load direction and the piezoelectric behavior. The main findings of the study are: (1) the σ-ε curve became convex initially, and then the stress was proportional to the strain. The σ-ε curve had almost the same shape during both loading and unloading. (2) The σ-piezoelectric voltage (P) curve was nonlinear, with a maximal point or cusp on the curve, which had almost the same shape during both loading and unloading, as was also observed for the σ-ε curve. (3) The plot of the first derivative of the stress [dσ/dε (= σ′)] against ε was nonlinear. The σ′-ε and P-ε curves at various angles were fairly similar. (4) The stress at the maximal point (or cusp) of the σ-P curve decreased with an increase in the angle between the fiber direction and load direction. The tendency of the stresses was very similar to that of Young’s modulus and compression strength calculated from Hook’s law and Hankinson’s law, respectively.