Response of artificially defoliated Betula pendula seedlings to additional soil nutrient supply

The impact of leaf damage on the growth of young silver birch seedlings with and without additional nutrient supply was investigated by simulating leaf-insect damage and applying different levels (25%, 50% and 75%) of artificial defoliation. Based on field-practical and cost-effective methods, we determined how fertilization practices compensate for foliage loss, and the combined effect on silver birch seedling growth. The mineral fertilizers applied to the 25-75%-defoliated silver birch seedlings reduced the growth in aboveground biomass compared to the fertilized but undamaged seedlings. Our results showed that when the birch seedlings received more nutrients they did not compensate for the loss of foliar mass. However, the seedlings loosing part of their foliar mass and receiving no additional fertilizers did compensate for the foliage loss and their root growth was not weakened, using soil nutrients more effectively. Mineral fertilization up to optimal nutritional balance could be a beneficial tool for increasing growth rate and biomass accumulation in the short-term period. However, our study demonstrated that additional fertilization does not necessarily lead to growth compensation of partly defoliated young birch trees