| Relationship between landscape pattern and ecological process has now been the focus in the field of land use and land cover change. It is of great importance to research how the landscape pattern affects the spatial varation of stream quality, which would give hint to the landscape optimization and local river protection. The most formidable challenge in the study on the relationship between regional landscape pattern and water quality (RLPW) in tidal plain is that there is no clear watershed boundary for most water quality monitoring gauge. This paper selects an integrated discipline of landscape ecology, ecological hydrology, and environmental management, takes Shanghai as our empirical study area, and discusses the above issue. Firstly the land use and landscape pattern change of Shanghai since 1947 is probed, and then the theory and method of RLPW is experimented in Shanghai, which is a typical tidal plain. Finally landscape optimization scenario is suggested for Pudong New Area, Shanghai which is an area in its great-speed urbanizing path. The main work and results is showed as below.(1) According to the basic data of land use, the land use change characteristic is quantified by the way of related models of regional land use change, it is showed that, i) The study area is completely urbanized during the past 60 years, which could be expressed by the sharp decline of agricultural land and the rapid growth of residential area and public constructions, ii) The disappeared agricultural land is accounted for the augment of residential, public, industrial area and road, 60% of the disappeared land is transited to residential area and public constructions, iii) the landscape change during the past 60 years of Shanghai denoted by landscape pattern indicators showed that, many indicators may be contradictory among one another, and some are confronted with the problem that they could not make a sensitive response for regional land use change, as to our findings, we suggest that the five indicators like Number of Patches (NP), Largest Patch Index (LPI), Mean Patch Area (AREA_MN), Edge Density (ED), Interspersion & Juxtaposition Index (IJI), could be treated as the most simple and all-sided landscape indicator system to quantify land use characteristic of a given area, especially an urbanizing area.(2) We re-established the topology of the river network GIS data from 1950s, and study on the curve and connectivity condition of the river network in center urban Shanghai, the study want to do this to show the land change effect on the tidal plain's most representative landscape, namely the high-density river network, and it showed that, i) quite many streams has disappeared during the past 60 years and transited to built-up area, the stream density has declined by 67 percent, and the stream number decreased from 465 to 63 with a sharp speed especially from the 1990s, when the disappearing speed may reach 11.28 km/a. the interesting is most of the disappeared streams are of lower order, whose length centralized from 200 to 1000 m. ii) negative effect occurred in the stream corridor denoted bye the decreased connectivity, before 1994 the connectivity index is more than unit, which reflect that the stream network belongs to reticulation in its structure, but when it goes to 2000s, the index become lower, which makes a sign that the stream network in center urban Shanghai never belongs to a reticulation but a tree in its platform.(3) Though there is great challenge in the RLPW research for tidal plain, as a pilot study, this paper introduces the GIS buffer method to set the boundary of hydrologic contributing area which is account for the non-point pollutants, and redundancy analysis (RDA) is referenced in this study for the landscape pattern indicator to explain the variation of water quality data. We find that, i) the landscape pattern controls the spatial variation of water quality, at all the five spatial scale, 100m, 200m, 400m, 800m, and 1500m radius buffer zone surround the water monitoring gauge, the landscape pattern variables can explain more than 50% of the data variation of water quality variables. However, the management of landscape, hydrologic linkage among all the water quality monitoring gauges (especially among the upstream and downstream), and point pollution in the study area also contribute for the environmental variation, ii) The RLPW in tidal plain also obey the rule of scale-dependent, there is only the substitution landscape variables account for the water quality variation, but at a larger scale like 800m or 1500m buffer zone, not only the substitution but the configuration figure, and hydrologic variable would all explain the RLPW. iii) percentage of total impervious area (TIA) is a key environmental indicator in tidal plain like Shanghai, the threshold of TIA is 60%, when TIA is lower than the value, the most water quality indices do not deteriorate as the TIA increase, but once TIA is greater than 60%, the river condition may immediately degraded, all water quality indices showed the phenomenon except DO. As found in this paper, the relationship between TIA and water quality variables is not scale dependent, and(4) The rapid growth of urban area may lead the area to a puzzle landscape pattern, we take Pudong New Area, Shanghai as our study area, firstly detect the land use change process sine the early 1990s, then the problems lies in the region spatial pattern nowadays is pointed out, and then, according the theory of ecological space and rule in landscape optimization like "Aggregate-with-outliers Pattern", we evaluated the ecological service of Pudong in a 500m×500m grid format, and the result is used as the resistance of ecological flow, base upon the MCR theory, we established an regional landscape pattern optimization scheme for Pudong which is composed of source patches, ecological corridors and ecological nodes. The result showed that the suggested ecological corridors are mostly arranged along the river corridors, which could become a theoretic sustain for the river protection in tidal plain during its rapid urbanization process.
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