Budburst dynamics of Norway spruce seedlings (Picea abies Karst.) – selection for late spring frosts resistence

Norway spruce is one of the most commonly used species for new forest planting in Europe. It is planted in a large number of habitats, often without following the previous results in the success of afforestation. In order to improve Norway spruce afforestation, open field tests were established in which developmental phenophases are monitored. The use of planting material of different provenances, which had not previously been tested for habitat conditions, was often the cause of the decline of newly planted forests. Early budburst of Norway spruce causes losses due to the freezing of terminal buds. Norway spruce testing for different habitat conditions in Bosnia and Herzegovina (B&H) was conducted at two ecologically different localities: Srebrenica (eastern part of B&H) and Drinic (western part of B&H). During 3 years, the budburst on the seedlings originating from 6 populations (Han Pijesak 1, Han Pijesak 2, Foca, Olovo, Kneževo and Potoci) was monitored. The budburst dynamics was monitored in 2013, 2015 and 2016 and it was recorded for each seedling in two progeny tests. Seedlings from the Kneževo population budbursted the earliest. The seedlings would start budburst on different days of the year, depending partly on the temperature sums and their origin. The earliest budburst was recorded in 2013 (119th day of the year in Srebrenica and 121st day of the year in Drinic). During 2015 and 2016, the budburst started later (125th day in Srebrenica and 129th day in Drinic). Temperature cumulants indicate that a smaller sum of temperatures was required for the buburst in the Srebrenica test than in the Drinic test. However, the temperature sums did not clearly indicate the budburst pattern because they were different for each observed year, but the populations ranking was almost the same. This indicates the influence of some other variables on the budburst. The knowing of the data on the budburst dynamics are a prerequisite for a successful selection of starting populations from which planting material is produced and new forests are later planted. Population Kneževo had the earliest budburst but population Han Pijesak 2 had the latest budburst.