Effects of Temperature Variations and Urban Heat Island on the Seasonal Development of Woody Plants in the South of Primorsky Krai

This study demonstrates the influence of temperature variations, precipitation, and the urban heat island (UHI) effect on the seasonal development of woody plants. Shifts in phenodates of woody plants caused by temperature changes and associated with the UHI effect are determined. Synchronous phenological observations were carried out in 2019–2021 in the Ussuriysk forest district and the city of Ussuriysk (Primorsky krai). According to the Timiryazevsky weather station, a significant trend of increasing average annual temperature was noted from 2011 to 2023 at a rate of 0.15°С year^–1. The comparison of the temperature regime in the city and in the forest confirms the presence of the UHI effect. The difference in the average monthly temperatures between the city and the forest fluctuated in the range of 0.2–2.5°С in 2019 and 0.1–1.9°С in 2020. The temperature in each month was higher in the city than in the forest. Differences in meteorological parameters of the forest and the city lead to a corresponding shift in the timing of the advancement of phenophases of plants. Based on the results of a comparison of phenological development of eight species in urban and forest conditions, it was found that on average the date of the phenological phase advancement in the city comes 5.2 days earlier and, for thermophilic southern species, 7.7 days earlier. Differences in the sums of temperatures required for the onset of a certain phase are within 1–80°С. Bird cherry is the best bioindicator of climate change in the conditions of Southern Primorye, as this is the species demonstrating the closest relationship between the sum of effective temperatures and spring phenological phases. Using published data of phenological observations in the study area, the average shift in phenodates in plants over 85 years was determined, which averaged 7 days. The duration of the growing season in southern Primorsky krai is determined by the average annual air temperature. A linear dependence was obtained, showing that, with an increase in temperature by 1°C, the growing season is extended 4.4 days, and this is primarily due to the shift in the beginning of the growing season to an earlier date.