城市林业概述与发展趋势

随着社会经济的快速发展和城市化进程的加快,城市环境问题日益成为社会各界关注的焦点,城市林业在城市建设与发展中的地位和作用越来越受到重视。从自然属性与社会属性,地域范围与层次的角度介绍了城市林业的基本概念和内涵,并比较了城市林业与传统林业、现代园林在属性、经营管理和功能方面的差别。借助已有的研究数据和成果,阐述了城市林业在城市发展中的作用,提出了现代城市林业面临的机遇和挑战以及未来发展趋势。     

广东省珠江三角洲城市森林抗火树种筛选研究

在广东省珠江三角洲地区(火烧迹地和污染区、公园、风景区、村旁风景林等不同类型区林地)进行城市林业抗火树种的筛选研究,对所调查的52个树种进行含水率、粗脂肪含量、粗灰分含量以及对其中的6个树种的燃烧热值作了测定。结果表明：同时满足含水率≥40％、粗脂肪含量≤20‰以及粗灰分含量≥5％三个条件的有16个树种(铁冬青、假苹婆、细叶榕、腺叶野樱、红桂木、多花山竹子、半枫荷、牛矢果、朴树、秋枫、白颜、枫香、麻楝、阿丁枫、蝴蝶果、吊瓜木),可初步肯定这些树种具有较高的抗火性。其中白颜树、枫香、秋枫、麻楝、吊瓜木、蝴蝶果6个树种的燃烧热值比较低,均比木荷低,具有较高的抗火性,可作为城市林业生物防火推荐树种。     

农林类院校《细胞生物学》教学中植物类案例的应用

当前《细胞生物学》教材的主要内容来自于对酵母和动物的研究结果,而普通农林类院校生物学相关专业的教学内容以认识植物的生命活动规律为核心,讲授的具体内容与学生的专业联系并不密切。为弥补这种不足,我们在教学活动中特意将植物中细胞生物学相关研究的结论和最新研究进展融入到教学中,将细胞生物学的教学内容与专业特点紧密结合,激发学生的学习兴趣,提高教学效果。     

The European carbon balance. Part 4: integration of carbon and other trace‐gas fluxes

Overviewing the European carbon (C), greenhouse gas (GHG), and non‐GHG fluxes, gross primary productivity (GPP) is about 9.3 Pg yr^?1, and fossil fuel imports are 1.6 Pg yr^?1. GPP is about 1.25% of solar radiation, containing about 360 × 10¹⁸ J energy – five times the energy content of annual fossil fuel use. Net primary production (NPP) is 50%, terrestrial net biome productivity, NBP, 3%, and the net GHG balance, NGB, 0.3% of GPP. Human harvest uses 20% of NPP or 10% of GPP, or alternatively 1‰ of solar radiation after accounting for the inherent cost of agriculture and forestry, for production of pesticides and fertilizer, the return of organic fertilizer, and for the C equivalent cost of GHG emissions. C equivalents are defined on a global warming potential with a 100‐year time horizon. The equivalent of about 2.4% of the mineral fertilizer input is emitted as N₂O. Agricultural emissions to the atmosphere are about 40% of total methane, 60% of total NO‐N, 70% of total N₂O‐N, and 95% of total NH₃‐N emissions of Europe. European soils are a net C sink (114 Tg yr^?1), but considering the emissions of GHGs, soils are a source of about 26 Tg CO₂ C‐equivalent yr^?1. Forest, grassland and sediment C sinks are offset by GHG emissions from croplands, peatlands and inland waters. Non‐GHGs (NH₃, NOx) interact significantly with the GHG and the C cycle through ammonium nitrate aerosols and dry deposition. Wet deposition of nitrogen (N) supports about 50% of forest timber growth. Land use change is regionally important. The absolute flux values total about 50 Tg C yr^?1. Nevertheless, for the European trace‐gas balance, land‐use intensity is more important than land‐use change. This study shows that emissions of GHGs and non‐GHGs significantly distort the C cycle and eliminate apparent C sinks.     

基于干扰的汪清林区森林生态系统健康评价

以汪清林区60个林班为研究对象,提出基于干扰的森林生态系统健康评价模型H＝∑B2W2-∑B1W1,构建了基于干扰理论的汪清林区森林生态系统健康评价体系.其中,有害干扰指标层选取4个指标:森林病害、森林虫害、森林火险以及人为干扰,生态系统内部的增益指标层选取4个指标:树种多样性、群落层次结构、林分更新状况以及近自然度.利用层次分析法和变异系数结合的主客观赋权法计算得到各指标的权重,提出基于干扰的健康评价模型和等级划分标准.最终评价结果显示:汪清林区60个样地中,处于优质状态的样地有6块,占总样地数的10％,健康指数均大于0.2;处于健康状态的林分13块,占总样地数的21.67％,健康指数在0.1-0.2之间;处于亚健康状态的林分23块,占总样地数的38.33％,健康指数在0-0.1之间;处于不健康的林分18块,占总样地数的30％,健康指数小于0.结果表明,在天然林中,无论是针叶纯林还是针阔混交林、阔叶混交林,大多处于亚健康和健康的状况,这与他们近自然度高,物种多样性丰富、具有良好的自我调节能力有关.而在落叶松人工林分中,由于林分物种多样性低,群落结构简单,近自然度最小,林分的增益能力弱,因此不健康的占有绝大多数.该评价结果可为该林场展开相关的健康经营措施提供参考.     

西藏森林植被乔木层碳储量与碳密度估算

利用第八次森林资源连续清查数据和不同树种的树干密度、含碳率等参数,运用生物量清单法,估算了西藏自治区森林乔木层植被碳储量和碳密度.结果表明: 西藏森林生态系统乔木层植被总碳储量为1.067×10⁹ t,平均碳密度为72.49 t·hm^-2.不同林分乔木层碳储量依次为:乔木林>散生木>疏林>四旁树.不同林种乔木层碳储量大小依次为:防护林>特殊用途林>用材林>薪炭林,其中前两者所占比例为88.5%;不同林种乔木层平均碳密度为88.09 t·hm^-2.不同林组乔木层碳储量与其分布面积排序一致,依次为:成熟林>过熟林>近熟林>中龄林>幼龄林.其中,成熟林乔木层碳储量占不同林组乔木层总碳储量的50%,并且不同林组乔木层碳储量随着林龄的增加呈先上升后下降的趋势.     

Expansion of bamboo forests caused by reduced bamboo-shoot harvest under different natural and artificial conditions

To elucidate the expansion of bamboo (Phyllostachys pubescens Mazel ex Houzeau de Lehaie) forests, we used multiple linear regression analysis and determined whether there were site differences for data obtained in Hirasawa, Otaki-machi, Chiba Prefecture, and Kofuki, Takehara City, Hiroshima Prefecture, Japan. Vegetation maps from 1984 and 2001 for Hirasawa, and from 1986, 1996, 2000, and 2006 for Kofuki, were compared, and the annual expansion rate of each P. pubescens forest was calculated. We evaluated nine indices, including original bamboo forest area, neighbouring vegetation, slope inclination and aspect, distance from roads, and shipment of bamboo shoots. Shipment of bamboo shoots was a positive factor for P. pubescens forest expansion, whereas the proportion of adjacent short vegetation, northness (the cosine of slope aspect), and area negatively affected the expansion in Hirasawa (R ² = 0.683). On the other hand, distance from roads and eastness (the sine of slope aspect) positively affected expansion, while slope inclination was a negative factor in Kofuki (R ² = 0.942). We calculated that P. pubescens forests expanded at about 2% per year in regions of reduced shipments of bamboo-shoot harvest. We showed that not only natural conditions but also management factors affect P. pubescens forest expansion. Regional differences in natural and anthropogenic effects on expansion were also found.     

我国热带地区胶-茶-鸡农林复合系统能流分析

以海南省文昌市典型的胶茶鸡农林复合系统模式为研究对象,分析了我国热带地区单作胶园、胶茶间作园及养鸡胶园的能流路径、能量输入、输出结构及能流转化效率。结果表明,单作、间作及养鸡胶园的光能利用率逐渐提高,其能量产投比为1.50、1.88、0.20;有机能投入比为0.138、0.119、0.977,养鸡胶园最高;无机能投入比分别为0.862、0.881、0.023;养鸡胶园中人工辅助能投入比相对减少,其产出能最大.     

Clearcutting Maine: Implications for the Theory of Common Property Resources

One of the basic tenets of the theory of common property resources is that private property rights work to conserve natural resources. There is growing evidence, however, that some large forest owners in Maine are cutting their forests heavily, using poor-quality silviculture techniques. This overexploitation is being done by paper companies, forest contractors, and some private land owners, who are being motivated by very different sets of factors. This article explores the reasons that private owners of forest resources are overexploiting their own lands and the implications of this for the theory of common property resources. Secure private property rights alone will not be enough to conserve resources and do away with externalities when the owners are operating in a system demanding constant short-term profits, where they are producing undifferentiated commodities in a highly competitive market, where the future value of slow-growing resources is very low, and where harvesting has so many ramifying biological and social effects.     

集体林区实施天保工程的对策和建议

 由于集体林区经济结构单一,长期以来在木材生产方面的高税费政策,造成地方财政和林业发展对木材生产的依赖,实施天保工程使集体林区的经济发展面临挑战。为了既达到降低森林资源消耗,扩大造林规模的目的,又减轻林区财政增收、农民脱贫、林业自身建设乃至社会文化发展方面的压力,必须调整林业税费政策、落实中央补助资金。同时,在地方政府的组织领导下,改变农村能源结构、建设现代林业体系。