engleski

Structural Elements of the Pedunculate Oaks Crown as an Important Factor in Forestry Management in Croatia

The tree crowns and forest soils are the main factors for all life activities in the stand. The effect that the tree crown has in the stand is manifold. Of all the structural elements, the tree crown, as one of the most susceptible and most obvious indicators of the physiological state of the stand, presents an interesting medium for observation and research. In the broad sense of the word, the structure of the crown means the size and shape of the crown, its growth and development, its arrangement in space and time and its proportions in relation to the remainder of the tree’s parts. During the past thirty years, as part of ecological-management research of forest types in Croatia, studying the crown’s structure has held an important place. Issues include researching the intensity of growth and development of the crown both horizontally and vertically in relation to dbh and the age of the stand, the period of maximum growth of the crown and the laws that govern them. Subsequently, the crown’s shape, its area and volume, the site index, the amount of crown and horizontal projections on the ground and the crown complex are researched as important conditional factors for natural regeneration. Searching for laws between the variables, i.e. expressing empirical equations, is an important area of research for foresters. This aim can be attained if the following questions are answered: what type and how strong is the relationship (correlation) between certain elements of the crown’s structure and the tree’s diameter? Further, the interdependence of the researched variables with other parts of the tree has to be established and the most acceptable equation function has to be found, i.e. a regression model. Finally, a mean morphological shape of the pedunculate oak’s and common hornbeam’s crown structure has to be expressed. Researching the laws governing changes in the width, length and area of the crown with an increase in the trunk’s diameter is of a linear character and its dependence can be expressed by a linear equation. The volume of the crown according to diameter classes changes its size whose laws change can be expressed by a non-linear regression in the form of an exponential function. The form quotient of the crown is 0.56. The relative development of the crown’s length is 45% of the tree’s height and the relative development of the crown’s diameter (the relationship between the tree’s diameter and the crown’s diameter) is on average 17 fold. Growth in the crown’s diameter in an average stand’s tree has a maximum value of 15.69 cm, where the tree’s diameter is 8 cm, its age 17 years and the soil’s ground covering of the crown is 70 %, and is a good prerequisite to natural regeneration. Interception is highest in middle-aged (21.9 %) and lowest in young stands (2.3 %). Precipitation flow down the tree per 1 m˛ in the crowns of young trees is 23.9 times greater than in mature trees. The obtained laws can be utilised to advise about correct and timely management, increase the amount of information available about the state of stands, solve current problems in the forestry profession and increase awareness about the role and significance of the crown in the forest’s development.

pedunculate oak (Quercus robur; L.); structural elements of the crown; growth and development of the crown.

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