【作者】 张凯旋；

【导师】 达良俊；

【作者基本信息】 华东师范大学 ， 生态学， 2010， 博士

【摘要】 城市森林是由人类和自然过程相互作用所形成的复杂生态系统,其结构和功能是城市森林的首要特征,了解城市森林的结构及其与功能的关系、协调城市森林多种功能的发挥是更好地管理城市森林生态系统的关键。本研究以上海城市森林的重要组成部分环城林带为对象,在对环城林带进行全面群落调查和典型群落功能测定的基础上,从群落类型和结构特征,生态效益以及景观美学效益三个方面进行分析研究,以阐明环城林带的结构特征和健康状况,探究群落结构与生态效益和景观美学效益之间的关系,揭示影响生态效益和景观美学效益发挥的主要因子,既为上海环城林带结构优化和生态系统服务功能的提升提供理论依据,也为城市森林的建设和改造实践提供参考。主要结论如下：共记录维管植物87科184属226种,但少数树种主导整个林带,在树种构成上具有明显的集聚性。并且乡土树种应用比例低,乡土树种和外来树种的比例仅为1：3。群落类型丰富,分为7种植被类型,67个群落类型,以落叶阔叶林和常绿阔叶林为主,但缺乏地带性植被类型。群落物种多样性低,乔木层的平均物种数为1.68,灌木层平均物种数为0.92。群落结构过于简单,多呈中间稀疏两头多的“哑铃型”特征,以“乔木+自然草本”模式最多。主要建群种的种群结构以单峰型更新类型为主,只有少部分树种呈现间歇型,大多数群落难以实现自我更新,且生长势水平一般,从发展趋势上看是衰退的。林分密度过高,树木生长受限,呈现出随密度增加,树木胸径和冠幅减小的格局,并由此推断目前群落的最适密度为1000株/hm2左右,最适合树木的生长。群落多样性低下、生长不良主要是由于种植模式和管护方式造成的,由于大量引种外来种,忽视了乡土树种的应用,加之多采用纯林式的种植模式,造成群落的地带性差,结构不合理,而密植的种植模式增加了个体间的竞争,导致生长不良,同时高强度的管理和养护,清除了乔灌木幼苗和枯枝落叶层,造成了群落更新维持能力下降,养分归还能力差。此外上海地区土壤类型以高盐碱、高粘性为主,地势较低而地下水位较高,地形比较单一,促使上述问题更为突出。在群落类型划分的基础上,选取典型的植物群落对其调节温湿度、提供负离子、抑菌、降噪、净化大气和土壤改良6个方面的生态效益进行测定,并结合群落结构参数,探究影响生态效益的关键结构特征。在夏季,落叶针叶林池杉群落除抑菌功能以外,在其他功能上均具有较好的效果,而落叶阔叶林最差,其他类型的群落居中。在冬季,常绿阔叶林女贞群落在各方面均具有较高的生态效益,其次为常绿落叶阔叶混交林,而落叶阔叶林、针阔混交林和落叶针叶林表现较差。植物群落对土壤的改良作用主要表现在表层(0-20cm),其中落叶阔叶林悬铃木群落和落叶针叶林池杉群落的效果较好。在夏季,除土壤改良外,其他效益中的降温、增湿、空气负离子、降噪4种效益的大小受群落结构因子调控,这其中最显著的是叶面积指数、郁闭度和林分密度,叶面积指数与上述4种效益均呈显著正相关,而郁闭度和林分密度与其中的部分效益呈正相关。冬季,除土壤改良外,各种生态效益的大小均与群落结构因子相关,其中主要因子为叶面积指数、郁闭度和疏透度。整体上,叶面积指数、郁闭度越大,疏透度越小时,群落效益就越大。叶面积指数和郁闭度在一定程度上体现植物叶量,反映了光合、蒸腾等生理代谢活动的强度,同时,这两个因子在夏冬两季均与多项生态效益呈显著正相关,因此,叶面积指数和郁闭度是指示群落生态效益高低的重要结构参数。在群落类型划分的基础上,选取典型的植物群落评判各季相景观的美景度,并结合群落结构参数,探究影响景观美学效益的关键结构特征。不同植被类型中,落叶针叶林在不同季节均表现出最高的美景度,竹林的美景度最低。针叶林中,常绿针叶林的美景度四季均低于落叶针叶林；阔叶林中,落叶阔叶林的美景度在春季和夏季高于常绿落叶林,常绿阔叶林在秋季和冬季高于落叶阔叶林；混交林中,除秋季外,针阔混交林的美景度均高于常绿落叶阔叶混交林；林内景观平均和林外景观均表现为夏季最高,冬季最低。影响环城林带林内景观的结构因子主要为胸径因子(平均胸径和胸径变异系数)、郁闭度和疏透度。在春季,随着树木胸径的增长美景度增加；在夏季,郁闭度高会提升植物群落的美景度；在秋季,胸径变异较小的群落具有更好的观赏性；而在冬季,疏透度对林内景观美景度贡献最大。除结构特征外,群落的季相特征也是影响群落美景度的重要因子,在不同的季节,影响群落美景度的季相特征也会不同。黄色、紫色等明度较高的色相和开花量适中的群落在春季美景度最佳。在夏季生长势好、林冠层变化较小、树干清晰度的群落具有较高的美景度,观花相比于非观花可以显著提高夏季群落的美景度。彩叶色调变异性会影响群落秋季的美景度,色彩越纯,美景度越高。在冬季,具有深颜色树皮的群落美景度最高。群落外貌特征对林外景观美景度有显著的影响,其中林冠线对林外景观美景度贡献最大,其次为林缘线。林冠线起伏不大,竖向结构层次丰富会提高林外美景度,具有自然形林缘线的林外景观美景度最高。夏季,落叶针叶林池杉群落除抑菌效益外,其他生态效益和美景度均最大；常绿阔叶林、针阔混交林和常绿落叶阔叶混交林生态效益和景观美学效益的表现均低于落叶针叶林；落叶阔叶林虽然美景度较高,但生态效益却最低。冬季,常绿阔叶林女贞群落的各种生态效益和美景度均较高。落叶阔叶林、针阔混交林和常绿落叶阔叶混交林在生态效益和景观美学效益上表现均低于常绿阔叶林；落叶针叶林生态效益较差,但美景度最高。从群落结构特征对生态效益和景观美学效益的影响上看,夏季,郁闭度是影响群落生态效益和美学效益的主要因子,并且郁闭度越高,生态效益和美学效益越高,即通过提高群落的郁闭度,可以使生态效益和美景度得到同步增加。冬季,疏透度是影响两种效益发挥的主要因子,并呈现群落越紧密,生态效益越高,而群落越疏透,美景度越高,疏透度并没有对两种效益产生一致性的影响。在进行生态效益测定的群落中,郁闭度和疏透度呈显著负相关,即通过提高群落的郁闭度,也会使冬季生态效益增加。由于结构特征和季相特征均可以影响美景度,因此,可以通过增加群落中具有深颜色树皮的树种来提高冬季美景度,保证群落在冬季具有较好的生态效益同时也具有较高的美景度。更多还原

【Abstract】 Urban forests are complex ecosystems created by the interaction of anthropogenic and natural processes. Structure and function are the first features of an urban forest to be studied. One key to better management of urban forest ecosystem is to understand urban forest structure and its relationship to forest functions, and to coordinate the multiple functions of urban forest.As an important part of urban forests in Shanghai, "The Shanghai Green Belt" was selected as an object in this study. In this paper, the researches were mainly developed from the following three aspects, community types and structural characteristics, ecological benefits and aesthetic benefits, based on survey of plant communities and measurement of typical communities’ functions. The purpose of this research was to clarify the structural characteristics and health status of the Shanghai Green Belt, to explore the impacts of community structure on ecological benefits and aesthetic benefits, and to reveal the major structural factors. This study could provide theoretical basis for the Shanghai Green Belt structure optimization and ecosystem services improvement. Meanwhile, it also could provide models for the construction and improvement of urban forests. The main conclusions were as follows:The flora of vascular plant in the study area consisted of 226 species and varieties,184 genera and 87 families. But a few species dominated the whole belt, the ratio of native trees only 25%. There were 67 community types, which were divided into 7 vegetation types, most of them were deciduous broad-leaved forest and evergreen broad-leaved forest, however, few of them were zonal vegetation types. The species diversity of these communities was low. The result showed that the average number of species in the tree layer was 1.68, and in the shrub layer was 0.92. The community structure was excessively simple, featured as the dumbbell that was sparse in the middle and dense on both sides, most of which was the model of "tree with natural herb". The population structure of edificators was mainly the unimodal regeneration type, only a few species were sporadic type. Most populations could not recruit well, and lots of trees are in poor growth, causing declining in structure developing. The high stand density had limited the growth. The results indicated that, diameter at breast height (DBH) and crown diameter would decrease with the increased density, and it was inferred that the optimum density for the growth of the current community was about 1,000 individuals/hm2.Because of the inappropriate planting pattern and management regime, the species diversity in various communities was low. As the introduced exotic species received more attention than native species, and more application of the monoculture pattern, the community structure was unreasonable. Dense planting pattern intensified competition and further resulted in poor growth. At the same time, high intensity of management removed seedlings and litter, causing the decreased viability of community regeneration and poor ability of nutrient return. In addition, the problems were deteriorated due to the saline and cohesive soil, low terrain, high groundwater level and homogeneous landform in Shanghai.On the basis of community type classification, typical communities were selected for ecological benefits measurement, which was evaluated from the aspects of temperature and humidity amelioration, negative-ion supply, antibacterial function, noise reduction, air pollution reduction and soil improvement. Combined with community structural parameters, the key structural characteristics that influenced the ecological benefits were explored.In summer, deciduous coniferous forest Taxodium distichum var. imbricarium Comm. performed well on these ecological functions except for antibacterial function, while deciduous broad-leaved forest provide the fewest ecological benefits. In winter, evergreen broad-leaved forest Ligustrum lucidum Comm. provided the most ecological benefits in every aspect. The next one was evergreen and deciduous broad-leaved forest, and the performances of deciduous broad-leaved forest, broad-leaved and coniferous mixed forest and deciduous coniferous forest were not that good. The soil improvement effect of plant communities mainly arised in the surface of soil (0-20cm), where deciduous broad-leaved forest Platanus x hispanica Comm. and deciduous coniferous forest Taxodium distichum var. imbricarium Comm. deserved better assessment.In summer, except for soil improvement, other benefits, such as temperature and humidity amelioration, negative-ion supply and noise reduction, were mainly controlled by leaf area index (LAI), canopy closure and stand density. LAI and the above four benefits were significantly positively correlated. While the canopy closure and stand density just showed positive correlation with some of the benefits. In winter, except for soil improvement, other ecological benefits were mainly associated with LAI, canopy closure and canopy porosity. Hence, the plant community with higher LAI, greater canopy closure and lower canopy porosity will perform greater ecological benefits.To some extent, LAI and canopy closure indicated the amount of leaves, which indirectly associated with the intensity of photosynthesis and transpiration. These two factors showed significant positive correlation with ecological benefits. Therefore, LAI and canopy closure were the important structural parameters that indicated the ecological benefits of plant community.On the basis of community type classification, typical communities were selected for aesthetic assessment of each seasonal landscape. Combined with community structural parameters, the key structural characteristics that impact the aesthetic benefits were explored.The scenic beauty estimation (SBE) values of deciduous coniferous forest were the highest in all four seasons among different vegetation types, and SBE values of bamboo forest were the lowest. Among the coniferous forests, the SBE values of evergreen coniferous forest were lower than deciduous coniferous forest in all four seasons. Among the broad-leaved forests, the SBE values of deciduous broad-leaved forest were higher than evergreen deciduous forest in spring and summer, but reversely in autumn and winter. Among mixed forests, except for autumn, the SBE values of broad-leaved and coniferous mixed forest were higher than evergreen and deciduous broad-leaved mixed forest. The average SBE values of in-forest and outer-forest landscape were both the highest in summer, and the lowest in winter.The structural factors that impacted in-forest landscape of the Shanghai Green Belt were mainly average DBH and variation coefficient of diameter, canopy closure and canopy porosity. In spring, the communities with greater DBH had higher SBE values. In summer, the high level of canopy closure could improve the SBE values of plant community. In autumn, the communities with lower variation coefficient of diameter had higher SBE values. In winter, canopy porosity had greatest effect on SBE values of in-forest landscape.In addition to structural characteristics, the seasonal characteristics of plant community were also important factors that impacted the community SBE values. The seasonal characteristics influencing the community SBE values were diverse in different seasons. The communities marked with high brightness color such as yellow or purple and moderate amount of bloom, had the higher SBE values in spring. In summer, the communities, which shown better growth vigor, smaller changes in forest canopy and clearer trunk, had higher SBE values. Flowering trees could significantly improve the SBE values of community in summer. Color variation of the colorful leaves could impact the SBE values of community in autumn, and the purer the color was, the higher SBE values would be. In winter, the community with dark bark had the highest SBE values.Physical characteristics of the community had a significant impact on the outer-forest landscape. Forest canopy line provided the bigger contribution to the SBE values, followed by the forest edge line. Undulating canopy line and complex structural layers would increase the outer-forest SBE values, and community with natural forest edge shape had the highest outer-forest SBE values. In summer, except for antibacterial function, deciduous coniferous forest Taxodium distichum var. imbricarium Comm. provided the best ecological benefits and aesthetic benefits. The ecological benefits and aesthetic benefits of evergreen broad-leaved forest, broad-leaved and coniferous mixed forest, and evergreen and deciduous broad-leaved mixed forest were lower than deciduous coniferous forest. The SBE values of deciduous broad-leaved forest was higher, but ecological benefits were lowest.In winter, evergreen broad-leaved forest Ligustrum lucidum Comm. performed well in ecological benefits and aesthetic benefits. The ecological benefits and aesthetic benefits of deciduous broad-leaved forest, broad-leaved and coniferous mixed forest, and evergreen and deciduous broad-leaved mixed forest were lower than evergreen broad-leaved forest. The ecological benefits of deciduous coniferous forest were lower, but the SBE value was the highest.The relationship between the community structure and the ecological benefits and aesthetic benefits, shown us that canopy closure was positively related with both two benefits in summer, which means that by increasing the canopy closure of community, the ecological benefits and aesthetic benefits can both be optimized.In winter, the main structural parameter related with these two benefits was canopy porosity. The compacter the community was, the greater the ecological benefits would be provided. The sparser the community was, the higher the aesthetic benefits were. Canopy porosity did not made accordant effect on these two benefits. Canopy closure showed a significant negative correlation with canopy porosity. In consequence, by increasing the canopy closure of plant community, the ecological benefits can also be raised in winter. As structural characteristics and seasonal characteristics could impact aesthetic benefits, the trees with dark bark could be applied to increase SBE values in winter and to guarantee the aesthetic benefits as well as ecological benefits.更多还原