Effects of mineral soil and forest floor on the regeneration of pedunculate oak, beech and red oak

Abstract

Early regeneration is a critical life stage that affects the future species composition of forests. Knowledge about regeneration success under different environmental conditions allows better understanding of forest dynamics. We studied the effects of seedbed conditions on the establishment and performance of seedlings of pedunculate oak, beech and red oak. In 50 plots of a tree-diversity oriented research platform in mature forests in northern Belgium (TREEWEB), we installed a field experiment with three treatments (potting soil, mineral soil, mineral soil + forest floor), in which we sowed seeds of each species. We monitored early establishment and survival, height, root and shoot biomass of the seedlings after two growing seasons. Mineral soil negatively affected seedling establishment and performance relative to the potting soil. The negative soil effects did not vary with measured abiotic soil properties. In general, the forest floor did not deteriorate or mitigate the soil effects, and only for root biomass did the forest floor partly compensate the negative soil effects. Forest floor effects did not vary with the measured forest floor properties. In the studied forests, creating bare soil was not enough to promote regeneration; improving soil properties might be important for the success of natural regeneration.