流域土地利用变化的水生态响应研究

Response of Freshwater Ecosystem to Land Use Change in Watersheds

流域土地利用变化造成水体物理、化学条件变化,并对诸多水生生物产生影响,进而破坏水系的生态系统结构和功能.研究显示:(1)流域土地利用变化将引起水文、底质、生境改变等物理响应,以及水体营养盐、细菌、有毒有害物含量、溶解氧变化等化学响应,分布式水文模型成为研究物理和化学响应的重要工具;(2)流域土地利用变化的生物响应表现为水生生物与自然用地类型呈正相关,而与农业用地、城镇用地呈负相关,并且存在明显的尺度效应,统计学分析是主要的研究方法;(3)大尺度的土地利用变化在水文过程下造成河段尺度上的外源物质输入、水文条件、底质结构等物理化学因子变化,是影响水生生物生境的直接原因.存在主要问题:(1)流域土地利用变化的生物响应关系机制尚不明晰;(2)流域土地利用变化的生物响应是通过物理响应、化学响应来间接作用的,但三者之间的非线性关系十分复杂;(3)水生生物对环境因子变化的敏感性和适用性存在较大差异.因此,未来研究应关注流域水文过程驱动下的物质迁移转化过程及由此带来的物理、化学和生物响应以及三者之间的关系,加强流域水文规律总结和参数率定,构建符合流域特征的参数数据库,并着力构建以保护水生态系统结构与功能为核心的流域山水林田湖系统综合管控模式.

The variation of physicochemical conditions in freshwater caused by land use change in watersheds influences aquatic organisms and damages the structure and function of the ecosystem. Previous studies have found that:( 1) Land use change in watersheds causes physical change responses,for example in hydrology,substrata and habitat,as well as chemical change responses in nutrient,bacteria,toxic and harmful substances and dissolved oxygen in freshwater ecosystems. Distributed hydrological model has become an important tool for simulating these changes.( 2) The results of biological response of land use change in watersheds indicates that aquatic organisms are positively correlated with natural land use types,but negatively correlated with agricultural and urban land use types,and a significant scale effect exists. Statistical analysis is one of the main study methods.( 3) The exogenous substance input,the hydrology,substrata and other physical and chemical alteration at reach-scale directly influence the aquatic organisms,which is caused by land use change at watershed-scale through the hydrological process. However,current studies are also facing some challenges: first,the mechanism of biological response of land use change is not clear yet.Second,the biological response of land use change is indirectly through physical and chemical responses,but the nonlinear relationship between the three is very complex. Third,there is also a great difference in the sensitivity and applicability of aquatic organisms to environmental factors. Therefore,future studies should pay more attention to the process of material migration and transformation under the background of hydrological processes,strengthen the exploration of hydrologyregularity and calibration of hydrological model at river basin scale,develop a parameter database matching the watershed characteristics,and focus on the construction of integrated management mode to mountains,rivers,forests,farmland and lakes system of watershed,to protect the structure and function of water ecosystems.