Dynamic Response to Climate Change by Phragmites australis and Suaeda salsa in Liaohe Delta Wetland

Abstract

Because of its unique geographical location and its ecological function, the Liaohe Delta wetland is important in maintaining regional ecological balance and security. Monitoring and evaluating change in the wetland are therefore of great importance. We used medium- and high-resolution satellite data, meteorological station data and site measurement data to analyze changes in the area and spatial distribution of Phragmites australis and Suaeda salsa in the Liaohe Delta wetland from 1998 to 2017, as well as their growth response to climate change. The results showed that during the period 1998–2017, the area of both P. australis and S. salsa wetlands alternated through periods of decreasing, then increasing and then decreasing trends. The annual change in area and spatial distribution range of S. salsa fluctuated more than that of P. australis. The annual variation of normalized difference vegetation index (NDVI) in P. australis wetland showed an upward trend from 1998 to 2017. The area of P. australis cover that was improved, unchanged or decreased accounted for 81.8%, 12.3%, and 5.9%, respectively, of the total area. Evaporation and wind speed were the main meteorological factors affecting NDVI. The contribution rates of climate change and human activities to NDVI were 73.2% and 26.8%, respectively. The area where vegetation cover was mainly S. salsa and that was improved, unchanged or decreased accounted for 63.3%, 18.3%, and 18.4%, respectively, of the total area. No meteorological factors significantly affected NDVI in the region. The interaction between vegetation growth and meteorological factors may help to explain the increasing trend in vegetation cover. The improvement in wetland vegetation also led to carbon sequestration and an increase in sequestration capacity.