Pregledni rad

Silvicultural Treatments as a Method of Increasing the Value of Private Forests in Gorski Kotar

Slavko Matić ; Zagreb
Damir Delač ; Hrvatsko šumarsko društvo

Sažetak

Privately owned forests in Croatia cover an area of 581,770 ha, which is 22 % of the total area of forests and forestland in the Republic of Croatia. The total growing stock in private forests in Croatia amounts to 78 301 000 m3, or 20 % of the overall growing stock of the entire forest management area. The average growing stock is 163 m3/ha and the increment is 4.4 m3/ha or 2.7 %.
Privately owned forests in the area managed by Delnice Forest Administration extend over 22,380 ha. These forests are presently classified into uneven-aged forests, which is not conducive to their future management. Bearing in mind their condition regarding the silvicultural form, biological properties and ecological requirements of the tree species participating in their formation, the management of these forests should follow the methods applied to forests of high silvicultural form or seed forests, which are regular and selection forests, and to coppices. Forests of high silvicultural form are regular or even-aged seed forests covering an area of 13,264 ha, while selection seed forests cover an area of 6,085 ha. Regular coppice forests are found over an area of 3,031 ha.
Placing these different forest forms into a uniform uneven-aged class prevents, among other things, the application of those necessary silvicultural operations which are aimed at attaining better stability, productivity and sustainability, or sustainable development.
Based on the above structural indicators, especially the growing stock and increment of these forests, we may conclude that the current condition of private forests in this area is equally bad and worrying as that of other private forests in Croatia.
Such a situation may be attributed to a number of factors, such as, for example, the inexpert application of silvicultural treatments, the disintegration of rural environments, property fragmentation, the owners’ social status, the insecurity of private ownership, the length of the production cycle, insufficient control and sanctioning, and finally, the disobeyance of legal regulations.
Some objective reasons for which these forests are difficult to manage are:
– Fragmentation of property (the average size of a plot is preceded by two zeros). Unsolved ownership-legal relationships, as well as an unstimulating, slow and expensive system of solving ownership problems,
– Disproportion between the cadastre of cultures and the real condition in the field, and the disproportion between the cadastre and the land registry,
– Management at the level of cadastre units prevents the application of more complex management with forest resources,
– Prejudices of forest owners towards pooling resources (Cooperatives) due to negative experiences from the recent past,
– Movement of the younger, more vital part of the population from rural into urban areas.
Forest owners and forest owners’ associations should direct their activities concerned with increasing forest quality toward the following fields, treatments and activities:
– Tending and regeneration treatments in selection forests with selection cuts.
– Tending and regeneration treatments in regular high forests and coppices.
– Tending and restocking those areas subject to natural succession of pioneer species with valuable broadleaved and coniferous species.
– Establishing cultures of valuable, fast-growing and marketable broadleaved and coniferous species over abandoned grasslands and other areas.
– Organizing timber harvesting and marketing, as well as utilization of timber for bioenergy after the forests have been tended, established and regenerated.
Selection management is the most suitable method for fir forests or for those forests in which the fir is the dominant species, such as, for example, mixed forests of fir and beech, fir, beech and spruce, and fir and spruce.
The management goals in a selection forest are accomplished by selecting and marking the trees to be cut. These management goals are: raise mixed selection stands which will ensure good quality increment, stand stability and plentiful natural new growth; use the productive site capacity to the maximum; and achieve the highest production values.
Felling operations in a selection forest achieve multiple goals of tending and regeneration, forming the selection structure, utilizing forests and maintaining their hygiene. There are two groups of silvicultural procedures; tending of the young generation – young growth and young forest, and selection, which includes thinning and harvesting mature trees. All the procedures in a selection forest are temporally and spatially concentrated, thus creating an indelible whole. If any of the above activities is omitted, the structure of the selection forest will be disrupted and its increment, regeneration and stability will be affected.
Tree marking in a selection forest should always take account of the goals for which this activity is undertaken. These goals are permanent regeneration, stand tending, continuous maintenance of the selection structure, stand utilization and maintenance of the sanitary-hygienic function.
In a normal selection forest with normal growing stock, a 10-year annual increment is cut. Under normal circumstances, this is 25 % of the total growing stock in the stand. If the growing stock is higher than normal, cutting intensity should not exceed 30 %. If it is lower, cutting intensity may be reduced to 15 %. This is borderline intensity which should not be exceeded. This means that cutting should be postponed until another cutting cycle is over, in this case another 10 years. Higher or lower intensities could endanger the selection structure, i.e. the increment, regeneration and stability of the selection stand. Inappropriately applied intensities cannot maintain a selection stand in the optimal structural conditions which will ensure maximal production and optimal regeneration. Regrettably, this is one of the most serious current problems in selection management and selection forests.
Beech and spruce stands which have officially been classified as uneven-aged stands and which have not been managed selectively but with selection cuts show a negative developmental trend. This kind of management results in decreased growing stock, absence of natural regeneration, reduced tree quality and lower increment.
In such stands management based on regular principles should be organized over small areas (each structural unit – special silvicultural treatment). Silvicultural treatments are spatially divided over small areas. In other words, each structural unit represents a special part of the stand which requires a special silvicultural treatment. They are spatially separated but temporally concentrated.
Management with shelterwood cuts in small areas with a longer regeneration period achieves biological diversity of beech and spruce forests. This type of regeneration enables, over a longer time period, a good yield of seeds of the principal and other tree species and the survival of their young generation.
Regeneration in regular forests is generally done in 3 cuts (preparatory, seed and final) and less frequently in 4 or 5 cuts, where subsequent cuts are introduced. The preparatory cut is undertaken with 20 % intensity and the seed cut with 50 % intensity in a good seed year. The remaining wood volume is cut as needed, either with one or two subsequent cuts or, more frequently, with one final cut.
Regular forests are tended throughout the life cycle of the stand, that is, until the shelterwood cuts are applied. Tending consists of the following stages: tending of the young growth after the final cut, cleaning in the developmental stage of the young growth and saplings, and tending with thinning.
Tending of the young growth after the final cut is usually done once only, while cleaning or negative selection is done once or twice until the moment the stand reaches its maximal height increment. At this stage future trees are identified, which in beech and spruce forests takes place around the age of 30. At this age stands may be tended with thinning.
Coppices of beech, pubescent oak and other hard broadleaves are regenerated with shelterwood cuts. The goal is to convert a coppice into the forest of high silvicultural form or seed forest.
Regenerating a coppice with clearcutting and planting conifer species is a serious mistake. Conifers may be planted in degraded forest soils which have lost the properties that provide the parent climatogenic stand with optimal conditions for growth and development.
Coppices should be tended throughout the rotation period.
The tending stages in a coppice include reducing the number of poor quality and superfluous shoots on the stump, tending coppices with cleaning or negative selection, and tending coppices with thinning or positive selection.
In the current economic and social conditions in Croatia arable areas are systematically being reduced and the size of abandoned agricultural land is increasing. These areas are subjected to the spontaneous expansion of less valuable tree species and shrubs, classified as pioneer species. Being the first to occur, they are spontaneously followed by transitional species. The 100-year-long process ends with the occurrence of principal or climatogenic species (fir, beech, oaks).
Pioneer and transitional tree species gradually convert degraded forest soil into forest soil suitable for climatogenic or principal species. The basic tree species that bear the characteristics of pioneer species are those from the genera of alders, willows, poplars, birches and others. Domestic, autochthonous tree species from other genera, with the exception of the genera of oaks, beech and fir, belong to transitional tree species. Together with pioneer species, they gradually colonize abandoned agricultural and other lands.
Forest cultures should be established on abandoned agricultural areas in order to increase their market and non-market values. These cultures are established by planting broadleaved species from the genera of wild cherry, pear, apple, as well as maple, ash, lime, whitebeam, rowan, service tree, wild service tree, bird cherry, walnut, and others. Coniferous species to be planted include species from the genera of spruces, larches and pines.
The choice of the tree species depends on the site conditions that prevail in the treated area, where the soil and the climate have a decisive role.
The pioneer, transitional or secondary tree species have an important role in the structure of all Croatian natural forests. They are particularly suitable for the establishment of cultures which supply good quality and valuable timber. Timber of all these species is applied in mechanical and chemical processing industries, and in energy production. The establishment of energy forests with short rotations and small planting distances will gain increasing importance in Croatian forestry.
Due to the present energy crisis, the share of timber in the energy balance of the most developed European countries is constantly growing. Timber from forests has been accepted everywhere in Europe as an important and renewable source of bioenergy.
Although the Croatian forestry is making initial, modest steps in this field, there is no reason that forest owners in Gorski Kotar should not be included in this European trend. They have at their disposal about 3,000,000 m3 of growing stock, the annual increment of 80,000 m3, and the prescribed annual yield of about 40,000 m3, of which 40 % or 16,000 m3 is wood of thinner dimensions suitable for energy. At present, the major portion of this wood remains in the forest and perishes. This alone provides sufficient motive for the owners to pool forces, fight for their place on the market and join the chain of bioenergy producers for both the domestic and foreign markets.

Ključne riječi

bioenergy; forest cultures; pioneer species; regeneration; regular forests; selection forests; tending; uneven-aged forests

Hrčak ID:

24155

URI

https://hrcak.srce.hr/24155

Datum izdavanja:

30.4.2008.

Podaci na drugim jezicima: hrvatski

Posjeta: 2.732 *