Impacts of compound drought-heatwaves on the Ecohydrology of National Important Wetlands in Northeast China

The Northeast Region of China constitutes a main concentrated distribution area for wetland and a climatically sensitive zone. However, compound drought-heatwave (CDHW) events have intensified in Northeast China over the past four decades, posing a significant threat to wetland hydrological stability and ecological security. Accordingly, this study employed the Standardized Precipitation Index (SPI) and a relative threshold method to identify CDHW events in Northeast China during the period 1981–2020. The spatiotemporal variation characteristics of CDHW events and their impact mechanisms on the ecohydrology of National Important Wetlands were systematically analyzed. Results indicate that CDHW events in Northeast China have significantly increased in frequency, duration, cumulative intensity, and anomaly, with concentration in the northwest and southern parts of the region. Detrended NDVI anomalies indicate that vegetation in National Important Wetlands generally exhibited a negative response to CDHW events. The palustrine wetland exhibited anomaly values predominantly ranging from −0.2 to 0.1, indicating a substantially higher ecological sensitivity compared to other wetland types. In contrast, lacustrine and riverine wetlands exhibited negative anomalies, albeit with a relatively weaker response. National important wetland water levels exhibited a negative correlation with CDHW events. In particular, palustrine wetlands exhibited the strongest response ( R = −0.63, p < 0.05), whereas weaker correlations were observed in lacustrine and riverine wetlands. This suggests that CDHW events primarily disturb hydrological processes in palustrine wetlands. These insights can provide a scientific basis for optimizing ecohydrological regulation and management of National Important Wetlands in Northeast China under climate change scenarios • Compound drought-heatwave (CDHW) events intensified in Northeast China from 1981 to 2020. • Ecology and hydrology of National Important Wetlands respond negatively to CDHW. • Palustrine wetlands are the most ecologically and hydrologically sensitive to CDHW.