| The wetland of Jiuduan Shaol may be the only basic one keeps the original state of estuarine wetland in the Yangtze River Estuary, and is an important part of Chinese natural ecological protection network. Its good natural conditions provides superior life, growth environment for a variety of biological. Wetland of Jiuduan Shaol between the Yangtze River and the confluence of the East China sea, not only can deposit retention of river water and sea water flood, effective adsorption nutrients in the east China sea water to reduce the occurrence of red tides in the East China sea, but also to protect against salt water erosion, purifying water quality, play an important role in protecting shoreline, it is an important ecological barrier of the Yangtze River delta region. Tidal channel is one of the main landscape types in Jiuduan Shaol. It is the entry and exit channel for tidal currents in Jiuduan Shaol, and the main aisle of mass and energy exchanges between tidal flat of wetland and sea.This study is based on high spatial resolution remote sensing data, using softwares such as Arc GIS to get the tidal channels information and forming different time stage tidal channels distribution. Using seven kinds of ecological landscape indicators to analyze and describe the evolution of the tidal channel system time sequence and spatial distribution differences, then do the fractal dimension research and dynamic change trend prediction of tidal channels. In the course of the study, we got the following results:(1) Taking tidal channels in the Jiuduan Shaol in Yangtze River estuary as a research object, information of which is extracted from 1997 to 2013 remote sensing data, then analyze the influence on ecological landscape of Jiuduan Shaol tidal channels by Deep-Water Channel Project in the Yangtze River estuary by using the landscape indexes such as Total Class Area(CA), Number of Patches(NP), Patch Density(PD), Percentage of Landscape(PLAND), Landscape Shape Index(LSI), Fractal Dimension Index(FRAC), Largest Patch Index(LPI). We find that, in the 1st and the 2nd phase of project, tidal channels area proportion is increased than the previous period, but with the end of the 2nd phase project to 2013, tidal channels account for the proportion of the total landscape area is reduced in successive years; NP, PD, LSI and LPI present some ups and downs change in the first phase of Deep-Water Channel Project, after this tidal channels of Jiuduan Shaol are kept the same change trend, namely that the tidal channels aggregation degree is on the decrease year by year, distribution of tidal channels are more separate which shows the tidal channels fragmentation increase year by year. With the end of the third phase construction, the shape of the tidal channels become not similar gradually and tend to be more discrete, the shape complexity is increased, tidal channels development also more and more mature and complicated.(2) Taking tidal channels at the Jiuduan Shaol in Yangtze River estuary as a research case, information of which was extracted from Landsat-8 remote sensing image of panchromatic band on August 13, 2013, then tidal channels were graded by using the principle of Horton – Strahler. Fractal dimensions research was conducted by using the grid method for various grades of tidal channels, calculated the each grades of Jiuduan Shaol tidal channels’ fractal dimension values at both left and right sides. Taking the width of the tidal channels into consideration, fractal dimension values were compared and analyzed. We find that the same grade of Jiuduan Shaol tidal channels, which on the left side of the dimension change range are greater than that on the right, namely that the tidal channels on the left side are more complex than those on the right. In different grade of tidal channels, the change range of minimum width is little, but that of the maximum is much. There is little relevance between the changes in the width of the different grade of tidal channels and its fractal dimension difference values between left and right sides. In different grade of tidal channels, whether left or right, fractal dimension values increase with the average width and the grade number of tidal channels.(3) With the aid of Arc GIS10 software, through the 1997-2013, a total of 7 extracted by remote sensing image data of tidal channels and the non-tidal channels landscape classification result attribute statistics, Tidal channels its areal retention rate is far more than the non-tidal channels. And at the end of the first phase of the Deep-Water Channel Project and third phase construction finished, these two periods had two similar maximum numbers. Using the Markov model to predict the change trend of tidal channels after project completion, from 2008 to 2013, under the situation that no mutations in the landscape and the forces of nature and human disturbance intensity is constant, Research area, wetland at Jiuduan Shaol tidal channels area ratio shows the tendency of small amplitude increase when after the Yangtze estuary Deep-Water Channel Project construction completion the and longer period of time, the corresponding non tidal channels area proportion of total wetlands area ratio is decreasing year by year. Under steady state, the ratio between those two finally keep in 8.030% and 91.970%. |
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