Monitoring the Dew Amount in Typical Ecosystems of Northeast China from 2005 to 2021

Dew is a part of the water cycle of ecosystems and is a source of water and humidity. The climate characteristics of the frost-free period in Northeast China are suitable for dew condensation, and dew is an important factor of water balance in this area. Northeast China is among the most significant warming areas in China, with an obvious “warm and dry” climate trend, which may affect dew condensation. To determine the dew amounts in different ecosystems in Northeast China and the influence of climate change on these amounts, dew condensation in farmland (corn), wetland (<i>Carex lasiocarpa</i>) and urban ecosystems (<i>Syringa oblata</i> Lindl.) was monitored during the growing period (May to October) from 2005 to 2021. The results showed that the annual average number of dew days was 132.8 in a wetland in Fujin, 122.9 in a farmland in Lishu and 118.1 in an urban area in Changchun. The daily dew intensity in the three ecosystems was lowest in May and highest in July and August. The average daily dew intensity was higher in the wetland (0.125 ± 0.069 mm) than the farmland (0.061 ± 0.026 mm) and urban area (0.028 ± 0.009 mm). The annual dew amount was also highest in the wetland (44.09 ± 7.51 mm) compared to the farmland (34.46 ± 3.54 mm) and much higher than that in the urban ecosystem (25.32 ± 3.29 mm). The annual dew in the farmland, wetland and urban ecosystems accounted for 7.92 ± 2.76%, 14.98 ± 5.93% and 6.71 ± 2.66% of the rainfall in the same period, respectively. The results indicated that dew was an important source of water and that wetlands had greater dew deposition than farmlands and urban areas. Considering the climate data during the dew condensation period from 1957 to 2021, the annual dew amount showed a decreasing trend of −0.40 mm/10a (<i>p</i> < 0.05) in Changchun. However, under the joint influence of relative humidity (RH) and wind speed (<i>V</i>), the impact of climate change on dew condensation was not obvious. This study further clarified the impact of climate change on the near-surface water cycle.