辽河三角洲湿地植被生态状况变化特征分析

归一化植被指数（NDVI）是反映植被状况的重要指标，对植被生长和区域生态状况的研究具有重要意义。为探究辽河三角洲植被生态状况变化特征和未来发展趋势，基于1995—2009年的NOAA/AVHRR NDVI和2009—2020年FY3/MERSI NDVI数据，通过修正拟合和S-G滤波法构建了1995—2020年长时间序列NDVI数据集。利用趋势分析法、变异系数和Hurst指数分析辽河三角洲（盘锦地区）NDVI时空分布特征，重点研究了水田和沼泽湿地的植被生态状况变化规律和未来发展趋势。结果表明：（1）从时间变化上看，26 a间辽河三角洲NDVI呈波动增加趋势，年平均增长率为0.32%;NDVI年内呈典型的单峰型分布，最大值出现在7月下旬或8月上旬。（2）从空间变化上看，区域内NDVI呈西南—东北方向递增，最高值主要分布在水田区，次高值分布在沼泽区。（3）绝大部分水田植被逐年变好，且植被生态状况比较稳定，低波动变化区域占96.72%，未来植被生态状况将持续改善的区域占61.05%。（4）沼泽植被逐年变好的区域占97.67%，变好最明显的区域主要分布在南部沿海地区和双台子河口附近，且该区域未...

Variable characteristics of vegetation ecological status in the Liaohe River Delta wetland

Background, aim, and scope The normalized difference vegetation index (NDVI) is an important indicator reflecting the status of vegetation, and is of great significance for the study of surface vegetation growth and regional ecological environment. Analysis the temporal and spatial variations in NDVI allowed exploration of the change characteristics and future development trend of the ecological status of vegetation in Panjin City, our research area in the center of the Liaohe River Delta. Exploring the change characteristics and future development trend of the ecological status of vegetation can effectively promote the protection of ecological environment. Materials and methods We used NOAA/AVHRR NDVI from 1995 to 2009 and FY3/MERSI NDVI from 2009 to 2020, to construct a long-term series of NDVI datasets from 1995 to 2020 by using a fitting equation and the Savitzky-Golay filtering method. Then, we used trend analysis, coefficient of variation, and the Hurst index to analyse the spatio-temporal characteristics of NDVI in our research area, as well as analysing the change rules and future trends of NDVI in paddy fields and marshes. Results The results showed that: (1) the NDVI indicated a fluctuating increase with an average annual rate of 0.32% over 26 a in the Liaohe River Delta. The NDVI showed a typical unimodal distribution in 1 a, and it reached its maximum value in late July or early August. (2) Spatially, the NDVI increased gradually from southwest to northeast. The highest and second highest values of NDVI were mainly distributed in paddy fields and marshes. (3) The NDVI in most areas of paddy fields improved yearly and was relatively stable, the areas of lowest fluctuation level accounting for 96.72%. The areas of continuous improvement of NDVI accounted for 61.05%. (4) The areas with an increasing trend of NDVI in marshes accounted for 97.67%. The best improvement in NDVI was distributed in the southern coastal area and the Shuangtaizi estuary, and improvements are likely to continue to be made into in the future. Discussion The NDVI showed a typical unimodal distribution in 1 a, consistent with the growth cycles of paddy and Phragmites australis. The growth and development of vegetation in the Panjin wetland is, therefore, the main factor affecting the temporal distribution of NDVI. The highest value of NDVI in Panjin was mainly distributed in the paddy field area of the Shuangtaizi River Basin and the Liaohe River Basin, and the second highest value was distributed in the marsh area of the Shuangtaizi River Basin. The results showed that paddy field and marsh vegetation were the main factors affecting the spatial distribution of NDVI in Panjin, and so research into NDVI in paddy fields and marshes can reflect the ecological status of vegetation in the Panjin wetland. Over the past 26 a, the wetland vegetation in most areas improving yearly, and its ecological status in most areas is stable, and improvements are likely to continue to be made into the future. Conclusions Over the years, as wetland protection policies and the enhancement of protection awareness have developed, the marsh wetland vegetation in the southern coastal and estuarine areas in Panjin has been effectively improved, and improvements are likely to continue to be made into the future. Recommendations and perspectives The study revealed the spatio-temporal characteristics and future trends of NDVI, and provides a scientific reference for ecological environmental protection and precise wetland restoration in the Liaohe River Delta.