上海市湿地景观格局时空演变与驱动机制的量化研究

Abstract

基于1980-2018年上海市历史遥感数据，定量研究上海市湿地景观格局变化及其驱动机制。为此，采用Fragstats 4.2.1计算了景观格局指数，并在数据处理系统软件平台使用灰色关联系统分析了湿地景观格局与社会、经济以及自然环境之间的灰色关联度。结果表明：（1）自1980以来，上海市湿地面积持续缩减，尤其水田损失最多。截至到2018年，上海市共损失了21.06×10⁴hm²的湿地，现存湿地面积为38.22×10⁴hm²，其中人工湿地占85%，自然湿地占15%。人工湿地以水田为主，自然湿地以河流湿地为主。水田和河流斑块平均面积总体上呈波动缩小趋势。河流湿地的形状复杂性最高，其总面积在年际间缓慢缩减，平均分形维度指数年际间波动持平。水田平均分形维度指数年际间波动上升，景观形状向复杂化趋势发展。（2）1980-2010年间，湿地景观破碎化程度总体加剧，最大斑块指数呈波动下降趋势。2010年后，景观破碎化局势向好，最大斑块面积扩大。1980-2015年间，蔓延度指数呈波动下降趋势，香农多样性指数呈波动上升趋势。2015年是蔓延度指数和香农多样性指数变化的转折点。水库坑塘斑块形状较简单，年际间变化小，而且具有结构的自相似性。（3）湿地景观格局受自然、人为双重因素影响。城市扩张导致人工湿地面积减少。自然湿地的演变则主要受气温和降雨的影响。自然因素往往在较大的时空尺度上控制着湿地的景观格局变化。但随着经济的迅速发展，在较短的时间尺度上，国家政策等人为因素对景观格局的影响力逐渐增强。未来，国家对城市湿地保护政策的实施可以使湿地景观格局向好的方向演化。;Based on historical remotely sensed data covering the city of Shanghai between 1980 and 2018, we conducted quantitative studies on wetland landscape change and its driving mechanisms. In order to do so, we calculated landscape pattern indices by Fragstats 4.2.1 and analyzed the grey correlations between wetland landscape patterns and social, economic, and natural environments using grey relational analysis in data processing systems. The results showed that (1) the total area of wetlands, especially paddy fields, have been decreasing since the year 1980. By the year 2018, the wetland area has been reduced by 21.06×10⁴ hm². The total area of wetland in Shanghai was 38.22×10⁴ hm², and 85% of the area was the constructed wetland, the rest was the natural wetland. Constructed wetlands were mainly comprised by paddy fields, while natural wetlands were mainly river wetlands. The average areas of paddy fields and river patches showed fluctuated decreasing trends. The shape of river wetland patches was the most complex, and the total area of the river patches had been decreasing over the study period. The fractional dimensions index of the river patches fluctuated over the years but did not have a clear trend. The fractional dimension index of paddy fields fluctuated and had an increasing trend, and their landscape patterns had become more complex. (2) The degree of fragmentation of wetland landscapes intensified between 1980 and 2010, and the maximum patch index showed a fluctuated decreasing trend. Around the year 2010, the degree of fragmentation of wetland landscapes reversed, and the maximum patch index had become increasing. Between 1980 and 2015, the contagion index showed a fluctuated decreasing trend and the Shannon diversity index showed a fluctuated increasing trend. The year 2015 was the tipping point for the changes of the contagion index and the Shannon diversity index. The patch shape of reservoirs was relatively simple, and they had small inter-annual fluctuations and structural self-similarity. (3) The landscape patterns of wetlands were influenced by natural and human disturbances. Urbanization caused the decrease of constructed wetlands. The change of natural wetlands was mainly driven by the variations of temperature and precipitation. Natural factors usually had dominant influence on wetland landscape in large spatial and temporal scales. In the context of rapid economic development, human factors, such as national policy, had increasingly stronger influence on wetland landscape patterns in short temporal scale. In the future, the implementation of national policies on urban wetland conservation can help urban landscape patterns move toward better directions.