Regeneration Dynamics and Development of Seedlings in Sessile Oak Forests in Relation to the Light Availability and Competing Vegetation

Natural regeneration of sessile oak forests is a complex process whose final outcome is influenced by numerous factors. The initial phase of development of sessile oak seedlings stands out as the most critical period in the process of natural regeneration of sessile oak forests. As the available light and competition from the accompanying woody species and ground vegetation are some of the main predictors of the success of sessile oak forest regeneration, this paper presents the results of studying the influence of these factors on the regeneration dynamics and development of sessile oak seedlings. The research was conducted in sessile oak forests in northeastern Serbia in the period from 2015 to 2020. At the end of the growing season each year, the following data were collected on 180 smaller sampling plots of 1 m(2) in different conditions of canopy openness: the number, height, and root collar diameter of sessile oak seedlings. Also, the percent cover of competing woody species and ground vegetation was estimated on these sample plots. The obtained results indicated that the success of sessile oak forest regeneration largely depends on the initial number of sessile oak seedlings and silvicultural treatments during the rejuvenation period, which determine the microclimatic conditions in the stand and control the competing vegetation. They also indicate that with an increase in the available light, the impact of the competing vegetation on the dynamics of regeneration and development of sessile oak seedlings is less pronounced. Accordingly, as young sessile oak seedlings need a large amount of light for survival and development, it is necessary to increase the available amount of light intensively in a short period of time (six-eight years) by reducing canopy openness and thus providing optimal conditions in which sessile oak seedlings can gain an advantage over the competing vegetation.