Forests and forest management in Croatia

Coppice forest is a low growing form of forest. In these forests most of the trees were created by growth from cut stumps. The most common species used are: acacia, common and black hornbeam oak, beech, honey oak, holm oak, cera oak, black alder and chestnut.

Coppice forests are created intentionally, because of the need for firewood or because of the needs of hunting (they correspond to certain types of game). Some coppice forests can be caused by poor forest management. Stumps have a lower quality of growth of wood mass and and usually generate less ecosystem services compared to high forests. Therefore, it is advisable to gradually turn the stumps into high forests, so that they are of better quality.

There are 358 802,98 ha of this forest cultivation form in Croatia.

Degraded stands include scrubland, thickets, maquis and garrigues.

Scrubland - a degraded coppice forest where trees and bushes participate in the same floor or layer.

Thicket - a degraded form of scrubland, i.e. an area overgrown with bushes, mostly bushy in shape.

Maquis - the degradation stage of a holm oak forest formed from a stump.

Garig - degraded maquis of bushy evergreen species with an assemblage that covers about 50% of its surface, and the rest is a smaller clearing.

There are 665 794,35 ha of this forest cultivation form in Croatia.

Selective cut is felling in a selective stand, and its characteristic is that mature trees and thinnings are felled on the same area, as well as care and cleaning in the young generation of the stand.

Selective stands are stands of fir with other types of trees where we find distributed trees of different heights and chest diameters, and the management is tree-wise (each tree is a unit by itself) or group-wise (on some surface we have several smaller units, the size of 1-2 the height of the trees, which are managed separately). A selective stand is a stand in which, per unit area, there are fir trees and other natural tree species in that community, which are of different heights and thicknesses, arranged in a horizontal tree-like or clustered structure and in three layers of a vertical structure.

Selective stands are made up of trees of different ages, that is, selective management is such a way of dealing with the forest that achieves that trees of all ages grow in the forest, side by side. Selective forest is composed of a number of selective stands.

Selective stands in Croatia are related to the area of fir and are spread mainly in the area of the Dinarides, i.e. the area of Gorski Kotar and Lika, in the altitude zone, usually between 600 and 1300 m above sea level.

The selective stand has a permanently non-uniform appearance and the selective form of the assembly, while the canopies are arranged at different heights, so they completely fill the entire profile of the stand down to the ground, and the ground is repeatedly covered by canopies.

With regard to the vertical classification, the profile of the selected stands differ

• dominant,
• intermediate and
• suppressed trees.

In a superior position are those trees whose crowns develop freely or are slightly influenced by the crowns of neighboring trees and which have fought for space in the ground and above the ground. In an intermediate position are trees that compete with neighboring trees and fight for living space in the middle and upper layers, and in the case of favourable structural changes (felling), they fight for a dominant position in the stand. The trees in the understory layer are suppressed trees that are heavily shaded from above, with a small height increase and are also waiting to grow into the upper positions in the stand in a certain time and structural conditions.

Unlike single-age stands, where the stands are classified by age classes, age is not indicated in selective stands, so the structure of the wood stock is classified into three thickness classes (10-30 cm; 31-50 cm; and from 51 cm upwards).

The wood stock in a normal selection stand has slight oscillations over time and this amount should range from a minimum value at the beginning of the "patrol" to a maximum value at the end of the "patrol", therefore the structure of a normal selection stand should be constant over time. A patrol is the time that elapses between two regular felling operations in the same stand.

In an approximately normal selection forest, the amount of wood stock intended for felling is approximately equal to growth, i.e. in a normal selection forest we cut the growth that accumulates in one area of the stand on which felling is carried out in the same year. By selecting a tree for felling and felling in a selection stand, care and rejuvenation are carried out at the same time, a selection structure is formed, the forest is exploited and its hygiene is maintained.

In contrast to even-aged stands, in which the management goals are met with a given rotation (the time period from the formation of the stand to its rejuvenation), the management goals in selective stands are met by achieving the diameter of the cutting maturity of the main tree species, which are determined on the basis of the purpose of the forest, credit rating and goal management. According to the research on the diameter of the harvest maturity of the fir trees, the most favourable diameters of the harvest maturity of the fir trees were determined from 60 to 70 cm.

In normal uneven-aged stands, groups of trees of different ages and developmental stages are distributed, where the trees within each group are of the same age and developmental stage, and the management is group-based. The area of a single group of trees of the same age and development stage in uneven-aged stands should be from 0.2 ha to 2.0 ha. Groups of trees should be arranged in a mosaic and spatially separated within a single uneven-aged stand.

Due to its structure (smaller rejuvenation area, slight oscillations of the wood stock over time), the choice of uneven-aged management is applied in karst forests, private forest owners' forests, special purpose forests, protective forests and in forests that have an important protective function.

The normal wood stock of uneven-aged stands of high growth form is equal to half of the normal wood stock of a mature even-aged stand.

With regard to the goals of management in uneven-aged stands, the cutting maturity of each group is determined on the basis of the prescribed rotation of the main tree species, taking into account the purpose of the forest and the cultivation form.

In uneven-aged stands, age is not shown, so the structure of wood stock is shown in three thickness classes (10-30 cm; 31-50 cm and from 51 cm upwards). Likewise, the wood stock in a normal uneven-aged stand has slight oscillations over time, and this amount should range between the value at the beginning of the rotation (before felling) and the value at the end of the rotation (after felling). A rotation is the time that elapses between two regular felling operations in the same stand.

Group management on smaller areas is provided for in a uneven-aged way, where each group represents a separate part of the stand with specific silvicultural procedures. In this way, uneven-aged management has the features of regular (even-aged) management, but on smaller areas where all silvicultural procedures carried out are determined by the development stage of a certain group of trees within the stand.

Based on this, uneven-aged management has the characteristics of regular management, since cultivation operations of care and restoration are planned and carried out in the same way as in even-aged stands, only in spatially separated groups of 0.2 ha to 2.0 ha.

Uneven-aged management was made possible for the first time by the provisions of the Ordinance on forest management from 2006, but the current state of most stands that should be managed in a uneven-aged way, usually deviates from the theoretical assumptions of the normal structure of uneven-aged stands.