城市景观格局演变的水环境效应研究综述

人类活动导致的城市土地利用覆被变化在景观生态学上表现为城市景观类型的更替和城市景观格局的演变。我国城市景观格局中自然植被景观基质大幅被人工硬化地面所取代,自然景观斑块破碎化,城市道路和排水管网等人工廊道大量增加,造成"源""汇"景观的比例失衡和格局失调,从而产生城市景观格局演变的水环境负效应,如非点源污染、水生生态系统失衡和城市内涝等,且水环境负效应存在时间尺度差异和空间尺度响应多样性。对城市景观类型及其格局演变产生的城市水环境效应相关研究进行总结,针对现有研究中存在的城市景观格局演变带来的生态过程变化研究较少、影响城市水环境的景观格局变化阈值不明确、研究结果推广难和重复性较差、人工廊道与城市水环境效应关系关注度较低和水环境负效应综合度研究欠缺等不足之处,提出未来研究的着力点,对实现可持续城市具有一定意义。

Research review on effects of urban landscape pattern changes on water environment

Urban water environment is an important part of urban ecosystem including natural and man-made water, and the natural elements and urban landscape which are closely related to water at catchment scale. Healthy urban water environment could product positive ecological effects such as water retention and impoundment, environmental decontamination, material transportation, making energy flow smoothly and conserving biodiversity. However, the change of urban land cover induces the deterioration of urban water environment and leads to negative water environment effects, such as non-point pollution, imbalance of aquatic ecosystem and urban flooding. The replacement of urban landscape types and evolution of urban landscape pattern caused by human activities display at following aspects: widespread vegetation matrix is largely replaced by artificial hardened ground while natural landscape patches are fragmentized and manual corridors including urban roads and drainage network increase sharply, resulting in the disproportion of water pollution "source" and "sink" landscape types and landscape pattern. Through statistical analysis and model simulation, researchers at home and abroad find that: the cultivated land and urban construction land are the main sources of non-point pollution while natural vegetation landscape types contribute to the reduction of non-point source pollution. Urban surface hardening reduces the environmental capacity of urban water environment by influencing urban hydrological cycle, for instance, surface runoff, evaporation and infiltration and so on. Together with environmental capacity reduction, the eutrophication of urban water environment makes negative effects on the balance of aquatic ecosystem. Negative water environment effects responding to urban landscape pattern will change with spatial and temporal scales. This paper summarizes current researches about the effects of urban landscape types and pattern evolution on water environment and points out the deficiencies of recent researches, such as the lack of specific research coupling landscape pattern change and ecological process, the indeterminacy of the landscape pattern threshold influencing urban water environment, the difficulty in popularizing and repeating research results, neglecting the relationship between urban artificial corridor and water environment effects, and the lack of comprehensive research about negative water environment effects. At last, we put forward five key points of future researches: the lagging response of urban water environment to the change of urban landscape pattern; the differences of water environment effects with different types and distributions; the combined influences from the urban landscape pattern, including matrix, corridor and patch; development of new model which concentrates on urban water environmental effects; a set of related index for urban planning and urban water environmental effects. Our study will contribute to better understanding of urban sustainability.