Analysis of vegetation cover changes and their influencing factors in area surrounding Dongting Lake

Abstract

[Objective] As a typical wetland ecosystem in the middle and lower reaches of the Yangtze River, the area surrounding Dongting Lake plays a vital role in regional ecological security and flood mitigation. The spatiotemporal variation characteristics of vegetation cover in the area surrounding Dongting Lake are investigated, and the influencing factors are further analyzed, aiming to provide a scientific basis for the dynamic monitoring and integrated management of ecosystems in lake areas. [Methods] The normalized difference vegetation index(NDVI) was used as the primary indicator of vegetation cover changes. Combined with terrestrial water storage anomaly(TWSA) data derived from spherical harmonic products from the Gravity Recovery and Climate Experiment(GRACE) satellites and multi-source meteorological data, the spatiotemporal characteristics of vegetation change in the area surrounding Dongting Lake from 2003 to 2022 were systematically analyzed. The driving mechanisms behind the influencing factors of NDVI were investigated. [Results] (1) From 2003 to 2022, the annual average NDVI in the area surrounding Dongting Lake ranged between 0.49 and 0.56, with an interannual increase rate of approximately 0.002 4/yr.(2) Spatially, NDVI showed significant increases in the northwest and southeast, with NDVI change rates gradually decreasing from these regions toward the central region of the lake area.(3) During the study period, five moderate or more severe hydrological drought events were identified based on water storage deficit index(WSDI), with a total duration of 26 months and a cumulative terrestrial water storage deficit of 3551 mm. During the five hydrological drought events, NDVI anomalies were all negative, indicating that water storage deficits suppressed vegetation growth. NDVI responded rapidly to precipitation variations. NDVI responded to temperature variations with a lag of about one month, yet it occurred one month earlier than its response to TWSA. El Ni1o-Southern Oscillation(ENSO) indirectly affected vegetation by modulating atmospheric circulation, and vegetation showed a significant long-term lagged response to ENSO. [Conclusion] The annual average NDVI in the area surrounding Dongting Lake exhibited an overall fluctuating upward trend from 2003 to 2022, indicating improved regional vegetation cover under ecological conservation policies. Precipitation and temperature are identified as the primary climatic factors of vegetation growth. Notably, TWSA, as a comprehensive indicator reflecting surface water, groundwater, and soil moisture, plays a significant regulatory role in vegetation dynamics.

Keywords

vegetation cover change / area surrounding Dongting Lake / NDVI / terrestrial water storage anomaly / hydrological drought / ENSO / time-lagged response / influencing factors