The impact of the container size and soil preparation on afforestation success of one year old holm oak (quercus ilex) seedlings in Croatian Mediterranean area

Background and Purpose: Morphological features of one year old holm oak (Quercus ilex) seedlings grown in different types of containers were analyzed in order to establish the effect of container type on seedlings’ development. The survival rates and the development of the seedlings were measured and monitored in the period of six years, on an experimental plot with the aim to assess the influence of container size and soil preparation on afforestation success in Mediterranean karst area. Materials and Methods: Four types of containers were used: MP53/12, MP33/18, T7/24 and T8/24. Morphological features of seedlings include: height, root collar diameter, biomass of the aboveground part, root biomass and total biomass. Two morphological indexes were calculated from the measured variables: S:R ratio and DQI. Morphological dimensions of root systems are, namely: total length, the number of tips, surface area and volume. Seedlings were arranged over the area of the experimental plot according to the randomized block method. Within each block (0,2 ha) two types of soil preparation prior to planting were performed: in pits with dimensions of 40 × 40 × 40 cm, and on the ripping ground. Each year during the experiment, seedlings were measured for height increment and survival rates (e.g. mortality), with respect to the container type and the planting method. Results: Almost all morphological features of seedlings have significantly higher values in larger containers (T7/24 and T8/24) compared to smaller containers (MP53/12 and MP33/18). Survival rates over six years in field experiment are influenced mainly by container size in interaction with soil preparation method (exp (β) = 6.5789; p < 0.0001). The container size exhibited influence on height increment of holm oak during first six years (F = 20.619, p = 0.000012). Conclusions: Soil preparation by ripping combined with high-quality seedlings played the most important role in the holm oak’s survival in the research area