engleski

Relationship of stand structure in Croatian pedunculate oak and common hornbeam forests with growth and yield tables as guidelines for forest management: Current state and challenges

Climate and other anthropogenic changes significantly alter the growing conditions of forest tree species in Croatia, especially so in the case of pedunculate oak. Dynamic changes in the site conditions demand a new approach for the management of forest stands. In Croatia, similar to many countries in the region and Central Europe, growth and yield tables are still used as major guidelines for forest planning and management. Foundations of these tables are usually made up of mathematical models which are static in nature and are developed on the data collected long before the onset of the climate change. Intention of our contribution is to relate the actual state of the structural elements of mixed pedunculate oak and hornbeam forests in Croatia with the values presented in the growth and yield tables of domestic authors currently in everyday use. Our goal was to expose the grade of (diss)agreement between the actual condition of these stands and the theoretical models used as the guidelines for their management. Comparison is based on stand basal area, since the values of stand basal area. For our research we have utilized database of "Croatian forests" Ltd., HS Fond, from which we extracted data on 5, 060 subcompartments with total area of 76, 000 ha through seven filtering steps. Methodology we applied allowed us to consider in our analyzes 77% of the total area of pedunculate oak and common hornbeam stands in Croatia. Results of our analyzes indicate significant variability of stand structural elements in investigated oak stands in all of their development stages. It is evident that the major part of the stands has the values of the relative growing stock between 0.8 and 1.0. However, there is still a significant part of stands outside of this, commonly accepted, range. Our results further indicate the apparent disproportion between the variability of the basic structural features of pedunculate oak stands and the static nature of the growth and yield tables. Reason for this lies in the simple mathematical construction of currently used growth and yield tables which aim to describe their development with stand age as the only independent variable. In reality, the development of these stands is a highly complex and dynamic process in which a significant role falls to the dimension and vitality of trees, inter- and intraspecies competition, productive capacity of the site and an array of anthropogenic induced site and climate changes. Our research results raise the question of the justifiability of further application of current growth and yield tables, based on their limited ability of integration of climatic an anthropogenic changes into predictions of future stand development. Therefore, within the scope of our contribution and based on the results of our research, we propose the construction of local mathematical models with integrated shift from stand based to tree based modeling efforts based on higher number of independent variables.

mixed pedunculate oak and common hornbeam forests; modeling; relative growing stock; growth and yield tables; stand structure

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