The occurrence, frequency, and severity of drought are accelerating due to global warming. Understanding the vulnerability of plantation forests to climate change, particularly to drought events, is critical to revealing the underlying mechanisms of tree resilience, recovery, and acclimation, which are important for plantation management. How the stand age affects the climate sensitivity of tree growth, as well as the direction, magnitude, and duration of the drought legacy, in plantation forests in northeast China is still unclear. In this study, we used MODIS-derived NDVI time series with gridded climate data from 2000 to 2020 to fill this knowledge gap. The selected plantation forests were dominated by four coniferous species: Korean pine (Pinus koraiensis), Scots pine (Pinus sylvestris), Japanese larch (Larix kaempferi), and Dahurian larch (Larix gmelinii). The results show that the climate sensitivity of tree growth differed among species and age groups. The growth of Korean pine and Scots pine was mostly dependent upon precipitation, while the growth of Japanese larch and Dahurian larch was determined primarily by temperature. Old Japanese larch (21–40 years) and Dahurian larch trees (31–60 years) were more sensitive to temperature and precipitation than young conspecifics, whereas old Korean pine (41–60 years) and Scots pine (31–60 years) were less sensitive to precipitation and temperature than young conspecifics. Furthermore, the legacy of drought lasted one year for Korean pine, Japanese larch, and Dahurian larch and over three years for Scots pine. Old trees were more severely affected by drought, particularly Scots pine and Dahurian larch. The findings of the study can help improve plantation forest management for better adaptation to future climate change.

This paper focuses on the Harbin section of the Songhua River in the cold region of northern China. The occurrence characteristics and pollution level of microplastics (MPs) are explored in both the ice and water of urban inland rivers and estuaries during the ice-covered periods. The abundance of MPs in Majiagou ice averaged 324.4 ± 261.5 particles/L, and the abundance of MPs in Songhua ice averaged 65.0 ± 68.2 particles/L. In the water with different depths of Songhua, the MP abundance ranged from 1.0 ± 0.7 particles/L to 12.9 ± 9.4 particles/L, with an average of 5.6 ± 7.6 particles/L. The amount of MPs in ice is about 11 times that in water, where ice formation is mainly responsible for the decline in the MP abundance in aquatic environments. The abundance of MPs in urban inland rivers gradually increased from south to north, while that in the mainstream of the Songhua River showed an increasing trend from east to west. Detected MPs were mainly fiber and white in shape and color, respectively, with a particle size < 0.5 mm. The extent of microplastics in ice is greater than that in water, and melting in the following spring will exacerbate the environmental impact. The results identified the discharge of domestic sewage as the main source of MPs in urban inland rivers. Polyethylene, polypropylene, and polyacrylonitrile were the main types of polymers. The results of the ecological risk assessment showed that the MP pollution in the Harbin section of the Songhua River reached moderate and severe pollution levels during the ice-covered periods. Its potential risk should receive more attention, and control should be strengthened.

The ice-covered periods is a natural phenomenon where ice forms on the water surface of rivers in areas with high latitude and cold climate. Ice blocks the diffusion of pollutants, thus causing changes in water quality characteristics. This paper focuses on the Harbin section of the Songhua River in the cold region of northern China. The occurrence characteristics and pollution level of microplastics (MPs) are explored in both ice and water of urban inland rivers and estuaries during the ice-covered periods. The results identified the discharge of domestic sewage as the main source of MPs in urban inland rivers. The abundance of MPs in MaJiaGou average of 324.36 ± 261.45 item/L, the abundance of MPs in SongHua ice raverage of 65.02 ± 68.15 item/L, while in the water with different depths of SongHua, the MPs it ranged from 1.03 ± 0.66 item/L to 12.86 ± 9.35 item/L,average is 5.59 ± 7.57 item/L.The amount of MPs in ice is about 11 times that in water.Ice formation caused a decline in MPs prevalence within the aquatic environment primarily due to the inclusion of a relatively large proportion of MPs within the ice mass during freezing. Additionally, it restricted atmospheric MPs from entering the river waters, contributing to the decrease.The abundance of MPs in urban inland rivers gradually increased from south to north, while that in the mainstream of the Songhua River showed an increasing trend from east to west. Detected MPs were mainly fibrous and white in shape and color, respectively, with a particle size < 0.5 mm. The fragmentation of micro plastics in ice is greater than that in water. Polyethylene, polypropylene, and polyacrylonitrile,etc were the main types of polymers. The results of ecological risk assessment showed that the MPs pollution in the Harbin section of the Songhua River reached moderate and severe pollution levels during the ice-covered periods Its potential risk should receive more attention and control should be strengthened. The research results have important reference significance for providing basic information for river pollution control and ecological protection in cold regions, providing a new direction for future research. In the future, more attention should be directed to the transfer and toxic effects of environmental MPs.