Seasonality and Long-Term Trends of NDVI Values in Different Land Use Types in the Eastern Part of the Baltic Sea Basin

• The growing season starts earlier and ends later in the eastern parts of the Baltic Sea region. All changes during investigation period (1982–2015) are statistically significant. • February to March air temperature is the most important factor determining the start of the growing season, while the temperature in September and October determines the end date. • The correlation between precipitation and NDVI values is weak throughout the growing seasons, since vegetation can be negatively affected by both excess and deficit of precipitation. This study analyses changes in Normalized Difference Vegetation Index (NDVI) values in the eastern Baltic region. The main aim of the work is to evaluate changes in growing season indicators (onset, end time, time of maximum greenness and duration) and their relationship with meteorological conditions (air temperature and precipitation) in 1982–2015. NDVI seasonality and long-term trends were analysed for different types of land use: arable land, pastures, wetlands, mixed and coniferous forests. In the southwestern part of the study area, the growing season lasts longest, while in the northeast, the growing season is shorter on average by 10 weeks than in the other parts of the analysed territory. The air temperature in February and March is the most important factor determining the start of the growing season and the air temperature in September and October determines the end date of the growing season. Precipitation has a much smaller effect, especially at the beginning of the growing season. The effect of meteorological conditions on peak greenness is weak and, in most cases, statistically insignificant. At the end of the analysed period (1982–2015), the growing season started earlier and ended later (in both cases the changes were 3–4 weeks) than at the beginning of the study period. All these changes are statistically significant. The duration of the growing season increased by 6–7 weeks.