DIGITALNA ARHIVA ŠUMARSKOG LISTA
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S. Malić. I. Aiiic, M. Oršanic: SILVICULTURAL TREATMENTS AIMliD AT IMPROVING THE ANTI-EROSION ... Šumarski list - SUPLEMF.NT {2005), 17-30 The second case involves regeneration of a transitional forest, when the elements of a climatogenic forest community are successfully regenerated under the canopy of the pioneer pine stand. In this case, regeneration must be performed using the methods under the crown cover of the old trees, usually with shelterwood cuts in small areas (Anić 2003). The small areas may be in the form of circles, or less frequently in the form of strips. Their density, area and form should be listed in a carefully executed silvicultural plan, which should also contain a cartographic scheme of the initial regeneration areas, logging directions and methods of area enlargement, in dependence of the tree species being regenerated and the geomorphology of the whole regeneration area. Regeneration begins in the initial regeneration area, which is gradually expanded and joined with another using one of the cutting methods: shelter- wood cutting or marginal cutting. When young natural generation is insufficiently dense, regeneration may be a combination of natural and artificial regeneration. Artificial regeneration requires the use of seedlings and seeds in the quantities prescribed for a given tree species (Matić 1949). The third case relates to regenerating a stand with pioneer tree species, which is usually Aleppo pine or black pine. On steep, erodible slopes, regeneration is accomplished in small circular areas. The canopy can be severely broken since these arc pioneer, heliophilic tree species. On mildly sloping terrains the size of initial regeneration areas may be larger. Indirect conversion of degraded forms is actually a natural process of their progressive development. This process is enhanced and supported with active protection, which will be discussed later. Direct conversion of a silvicultural form usually denotes the conversion of a forest stand of a low silvicultural form into a stand of a high silvicultural form by regeneration. It is performed with the shelterwood method and commonly involves the combination of natural and artificial regeneration. This procedure is applied in many old pubescent oak coppices in Croatia (Matić etal. 1996). Active protection comprises procedures aimed at protecting forests and degraded forest forms in the Mediterranean area from those factors which have been the agents of degradation processes. These procedures are primarily preventive measures against fires, illegal and uncontrolled felling, browsing and grazing. In higher degradation forms (a transitional form between maquis towards a low forest and in a thicket-like low forest), it is possible to apply tending treatments with cleaning, which accelerates and regulates the process of direct conversion of a degraded form. This is particularly important in the sites in which the forest stands are intended to perform anti-erosive and water-protective functions. All the above silvicultural operations should be planned and carefully performed to achieve the highest quality. The quality of silvicultural procedures must be the only control measure (Matić 1989). The speed of execution or the number of the procedures without regard for quality may save money in the short run, but will lead to forest degradation and increased cost of forest improvement in the long run. Damage that may be incurred usually has long-term consequences. CONCLUSION The two principal groups of silvicultural treatments are tending and regeneration. The goal of forest tending is to regulate and sustain an optimally structured forest stand in natural and undisturbed site conditions. These conditions must be maintained in all stages of a stand´s development. Tending affects both the stand structure and the site. A well-tended forest ecosystem is capable of optimal fulfilment of its commercial and non-commercial functions (ecological and social). The anti-erosion and water-protective functions are among the most important ecological functions that a well- tended forest ecosystem provides. The vital task of regenerating a forest is to preserve the forest soil from adverse impacts which may cause degradation processes. The forest soil is protected with a permanent cover of the stand´ crown canopy. This is why forests should be regenerated under the crown cover using the shelterwood system or the selection sys tern. Regeneration over small areas should be recommended. Since its beginning, the Croatian forestry has advocated the natural approach to forests. This approach involves natural forest regeneration with the shelter- wood method and the maintenance of the optimal structure of the forest stand with tending. This has resulted in exceptionally natural forests capable of fulfilling their commercial and non-commercial functions. Their naturalness is one of the prime reasons for which the Croatian forestry has earned recognition for ecological production of mercantile timber from all its forests. Even more importantly, Croatia is one of the richest European countries in potable water. Forests grown and tended according to the principles of the Zagreb School of Silviculture are one of the main reasons for such a favourable condition. |