一类有十一个赤道环的七次多项式系统

研究了一类七次系统无穷远点的中心条件与赤道极限环分支问题.通过将实系统转化为复系统研究,给出了计算无穷远点奇点量的递推公式,并在计算机上用Mathematica推导出该系统无穷远点前13个奇点量,进一步导出了无穷远点成为中心的条件和十三阶细焦点的条件,在此基础上首次得到了七次系统无穷远点分支出11个极限环的一个实例.     

人心果AFLP反应体系的建立与优化

为给人心果分子生物学研究奠定基础,以人心果嫩叶为材料,采用改良CTAB法提取到高质量的总DNA,可用于AFLP实验分析。通过优化酶切—连接反应、预扩增和扩增反应过程中的关键因素,建立了适合人心果的AFLP实验体系和反应条件,得到了带型清晰、多态性丰富的AFLP指纹图谱。研究结果对人心果遗传多样性分析及其分子标记辅助育种具有重要意义。     

基于COMGIS的古树名木管理信息系统设计

阐述了如何利用组件式GIS开发平台SuperMap Objects 5.0,VB.NET编程语言,SQL Server开发古树名木管理系统的方法;探讨了系统的总体结构设计,包括技术路线、系统功能设计及数据库设计;重点分析了系统实现过程中采用的若干关键技术.     

云南省集体林权制度改革存在的问题及建议

介绍集体林林权制度改革的背景,经过调查,认为当前云南省各县(市)集体林权制度改革工作存在的问题主要有:督促、指导和检查不到位,宣传发动、技术培训工作不到位,存在不按工作程序开展工作情况,村民参与率低,对"三榜"公示制不按要求进行、林改工作急于求成等,提出加强林改队伍建设,加大宣传力度、扎实做好技术培训,严格按要求规范操作,不能将林改工作政治任务化等建议.     

城市森林生态系统服务价值指标体系与评价方法

"城市森林"这一概念出现在美国和加拿大,是一门在形成和发展的新兴学科,关于它的范围、层次划分及定义,目前尚无统一、公认的标准(Cene,1996;高清,1984;Rowantree,1984;彭镇华,2003).     

在ISO9001标准模式下建立林业调查规划设计质量管理体系的探讨

基于质量管理的基本原则、方法和实践,对在ISO9001标准模式下建立林业调查规划设计质量管理体系进行探讨,从质量管理体系建立的必要性、基本要求、体系文件、实施要点等方面。阐述了林业调查规划设计质量管理体系建立的思路与方法。旨在提高林业调查规划设计管理水平和成果质量,满足开放式的市场竞争需要,更好地服务于现代林业建设事业。     

基于网页的SBE法研究广州城市公园木本花卉景观

通过对广州市公园木本花卉景观的调查和拍摄相关植物景观照片,采用研究自然风景质量评价的心理物理学方法中的评分法——SBE法(Scenic Beauty Estimation Procedures),让公众通过网络的方式,以网页为媒介对木本花卉景观进行评价;通过对评价数据的标准化处理和SAS系统的数据分析,寻找木本花卉景观的最佳配置方式,为该类植物景观的营建提供科学的依据,并探索一条快速、简便而有效的景观评价模式。     

Modelling the long-term impacts of selective logging on genetic diversity and demographic structure of four tropical tree species in the Amazon forest

In the last three decades, Amazon tropical forests have experienced high rates of deforestation, both by clearing for agriculture and by logging. In this study, we use computer simulations to examine the potential effects of forest logging on genetic diversity and demographic recovery (basal area development) of four neotropical tree species over a time frame reflecting multiple logging events. The study species, Bagassa guianensis Aubl., Hymenaea courbaril L., Manilkara huberi (Ducke) Chevalier, and Symphonia globulifera L.f., are all taxa which are commonly exploited for timber in the Brazilian Amazon. The simulations were parameterized using empirical data from field studies in the Tapajós National Forest, Pará State, Brazil, including genotypes at microsatellite loci, demography, ecology and growth for each species. Eight scenarios, combining two different cutting cycles and two minimum cutting diameters, were examined for each of the four species. The scenarios represent the actual forest practices used in Brazil and French Guiana (cutting diameter 45 and 60 cm, and cutting cycle of 30 and 65 years, respectively). Logging scenarios were applied for six cutting cycles, and final genetic and demographic data were compared to baseline data from corresponding control scenarios. At the end of the simulated period the basal area was strongly reduced under all conditions in B. guianensis, H. courbaril, and M. huberi. In only two scenarios was a species able to recover its basal area following logging (S. globulifera with both 45- and 60-cm cutting diameters under a 65-year cutting cycle). In the logging scenarios, all species showed a loss of alleles and genotypes and an increased genetic distance (calculated between each population at the start and the end of the simulations). These effects were higher under the most intensive logging cycles (30 years, 45 cm). However, effective number of alleles, expected and observed heterozygosities, and the fixation index were little affected by the logging simulations. Over all, we conclude that, even under very optimistic conditions for growth and recruitment, current logging practices are not sustainable in terms of basal area. Our simulations show that different species respond differently to logging, both demographically and genetically. No single set of logging parameters can be applied to the forest as a whole. Rather, forest management practices must be species-specific, taking into account not only growth parameters but also ecological and reproductive variables, in order to move toward long-term forest sustainability.     

The lateral spread of tree root systems in boreal forests: Estimates based on N uptake and distribution of sporocarps of ectomycorrhizal fungi

In nutrient poor environments, such as boreal forests, many of the most important interactions between plants take place belowground. Here, we report the results of two approaches to obtain estimates of the lateral spread of tree roots.     

抚仙湖流域旅游规划用地生态环境评价研究

运用遥感监测技术和样地调查的方法,选取水土流失、生物多样性、生物丰富度、生物量、植被覆盖率5个评价分指标,利用层次分析法建立评价指标体系,分指标对云南省抚仙湖流域的旅游规划用地进行了生态环境现状评价,并运用综合指数评价法建立了生态环境综合评价模型,对研究区域整体生态环境质量做出了综合评价。