中文摘要：

长期监测是研究生态系统演变规律的基本方法。针对自然和半自然生态系统的长期监测工作已经比较完善，但以人类活动为主的城市生态系统的研究和监测工作国内外都还处于探索阶段。针对城市生态系统长期监测的需要，在介绍美国巴尔的摩和凤凰城城市生态系统长期研究监测工作的基础上，结合北京城市生态系统研究站的长期监测工作实践，分析了城市生态系统的基本特点，提出了城市生态系统长期监测的3个目的（为研究长期演变、为探索人与自然相互作用和为城市居民提供数据）、5个原则（综合与重点相结合原则、综合性和前瞻性原则、与城市相关部门监测融合原则、面向科学研究原则和长期一致性原则）、4项内容（生态要素、生态格局、生态过程和生态系统功能）和4种方法（遥感监测、长期调查样地监测、定位观测站监测和社会经济调查监测），将为我国开展长期城市生态系统监测和研究工作提供重要科学方法指导。

英文摘要：

Long-term monitoring is the essential method to investigate changes in ecological systems. The long-term monitoring of natural and semi-natural ecosystems has been practiced for several decades and its protocols have been accomplished. However, it is underdeveloped for the Long-Term Monitoring of Urban Ecosystem （LTMUE） that was dominated by human activities. For improving long-term monitoring of urban ecosystem, this paper will introduce the long-term monitoring practices carrying on in Baltimore and Phoenix long-term urban ecosystem studies in USA. Then, in terms of experiences of a decade monitoring practiced in Beijing Urban Ecosystem Research Station and the general characteristics of urban ecosystem, we analyzed the objectives, principles, contents and methods of LTMUE The objectives of LTMUE are to provide databases for scientists to investigate long-term changes in urban ecosystems, and study the interaction between human and nature, and for decision makers and residents to know and predict the changes that happened in urban ecosystems. In design of LTMUE, the five principles should be considered： Reasonably balancing comprehensive and key indicators monitored, focusing comprehensive and foresight indictors, infusing data government monitored, science-oriented monitoring and long-term consistence. The LTMUE includes ecological elements, pattern, processes and function monitoring. The mostly deployed methods are remote sensing, long-term plots, substation and social survey. This will be the important methodology to guide long-term urban ecosystem investigations in China.