By themeans of 3S techno logy, the landscape of B eijing was d iv ided into 6 primary landscape types and18 landscape patch types in the study, and a series of indexes w ere calcu lated by mode ls to analyze the spec ialstructure of Be ijing landscape. The results show: that the forest land is themax im al and basa l landscape patch type( area proportion is 42. 534% ), farm land ( 28. 888% ) and construction area ( 16. 639% ) are also the ma inlandscape types in B eijing. From landscape patch types and landscape patch catego ries levels, the landscape patchd istr ibuton is centralized, and patch shape is simple, the main landscape patch fractal d imension indexes are under1. 1, so urban landscape pattern is high ly influenced by human disturbance.

The research adopts open sampling method and TCT-GC/MS (Thermodesorption Cold Trap-Gas Chromatography/Mass Spectrometery) apparatus to collect and analyze the volatile organic compounds(VOCs) of Platycladus orientalis forest, with the intention of researching the compounds and diurnal variation of VOCs of P. orientalis forest in natural state in Beijing Western Hills in spring. The results are as follows: (1) There are 160 kinds (11 categories) of volatile organic compounds, containing Alkyl Hydrocarbon, Ketone, Alcohol, Acid, Aldehyde, Alkene, Ester, Aromatic hydrocarbon, Ether, Hydroxybenzene and Amide. The content of Alkyl Hydrocarbon, Ketone, Acid and Aldehyde occupy a greater percentage among all compounds. (2) The diurnal variation curve of total volatile organic compounds (TVOC) is characterized as "one peak at 11:00(36.44%) and one vale at 3:00(12.76%)". Generally, the concentration at daytime is higher than that of night, and higher in morning than in afternoon, with the maximum at noon. (3) The change of Alkyl Hydrocarbon concentration is greater in the morning and about midday, less in the afternoon and night. The diurnal variation curve of Ketone concentration appears as "three peaks and three vales". 1:00, 5:00—7:00 and 11:00 are peak time, 3:00, 9:00 and 17:00 are vale time. As to Acid, its concentration appears two obvious phases: the higher phase is from 9:00 to 17:00, with the maximum at 11:00, and the lower phase is from 19:00 to 7:00, with the minimum at 5:00. Concerning Aldehyde concentration, 17:00 and 19:00 are the higher phases and also has obvious difference with other time, while the lower phrase has no obvious difference with each other. (4) Alkene is the most important compound to human health. Its concentration appears as "one peak" at 15:00, which has obvious difference with other time. Totally, its content at daytime is higher than that at night, and higher in afternoon than in morning.

采用动态顶空吸附采集法对侧柏春季释放的挥发物(Volatile Organic Compounds ,VOCs)进行采集,同时利用Li-cor6400便携式光合系统测定仪测定其主要光合生理指标,分析了侧柏春季挥发物的主要成分、日变化规律及其影响因子。结果表明:(1)侧柏挥发物成分包括9类106种,主要挥发物成分是萜烯类化合物。对人体有益的有机挥发物包括萜烯类化合物、癸醛和乙酸乙酯,对人体有害的化合物包括三氯甲烷、笨和甲苯;(2)春季侧柏总挥发物(TVOCs)浓度日变化曲线呈"三峰两谷"型,5:00、13:00、19:00呈现高峰,凌晨23:00—1:00、下午17:00呈现低谷,对人体有益的成分出现在5:00、9:00、15:00、19:00,对人体不利的成分主要出现在中午15:00和夜间21:00—1:00且浓度较低;(3)温度较高、光照较强、湿度较低的时段总挥发物浓度总体较高,反之较低。蒸腾速率、净光合速率、气孔导度的日变化规律与总挥发物浓度日变化一致性较强。总挥发物浓度变化与蒸腾速率、净光合速率、气孔导度相关性极显著,与光照相关性显著,而与温度和湿度相关性不显著。

城市林业作为一个新兴行业正在我国城市化地区快速发展。城市林业建设有利于优化整个国土森林资源的宏观布局,从而更有效地改善城市生态环境,提高城市宜居品质,增强城市可持续发展能力。本文结合国家宏观战略需求,从城市林业的发展历程、建设思路和"六省六市"规划实践等方面系统阐述了城市林业的兴起与发展态势,同时,指出城市林业已经成为我国林业建设的一个新方向。

The planting site, size, and health condition of street tree Ginkgo biloba in Beijing urban area were investigated and the influence factors were analyzed based on filed survey. The results showed that G. biloba were mainly planted in tree pit within strip planting median. The average height, diameter at breast height and canopy diameter were 8.11 m, 13.22 cm and 4.07 m, respectively, 82.9% trees were less than 10 m in height, and most G. biloba trees were still in the initial stage of height and diameter increment. The tree health status was described with three classes: class I (healthy), class II (fair) and class III (unhealthy). The percentage of class I, II and III for G. biloba trees in Beijing urban area accounted for 16.0%, 37.2% and 42.9% respectively. The results of analysis showed that the health status of G. biloba was associated with the site condition, tree size and management practices. The trees planted in urban forest patch grew better than the trees planted in green belts and tree pits; meanwhile, the bigger trees were healthier than the smaller ones. In addition, the effects of urban heterogeneous environment and human activities on the health of Ginkgo biloba were analyzed and the suggestions on management were launched.