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Application of digitalisation in studying the structure of uneven-aged stands in non-economic forests of Croatia

Uneven-aged forests in Croatia are exclusively characterised by European fir (Abies alba Mill.), which alongside with autochthonous oak species (Quercus) and common beech (Fagus sylvatica L.) is a basic tree species in Croatia. Approximately 10% of its share in the growing stock (30, 374mil.m3))and about 150, 000ha of uneven-aged forests, which are composed of fir, beech, spruce and other species, justify our attributing considerable significance to this species.Uneven-aged beech-fir forests are a dominant characteristics of mountainous region of Croatia.These forests are considered to be selection forests due to their specific structure, management patterns, biological properties and ecological requirements of European fir, primarily.Natural composition of forests has been changed in the majority of the world countries through the intervention of man. In Croatia, however, almost unlike any other country in Europe, the majority of forests has kept its natural properties.more than fifty years ago and for the purpose of protection of ecosystems and natural phenomena, the following national parks were acknowledged:"Plitvička jezera" and "Paklenica"(1949, followed in 1953 by "Risnjak", in 1960 "Mljet", in 1980 "Kornati", in 1985 "Brijuni" and "Krka" and in 2000 "Sjeverni Velebit"(North Velebit).Total area of nationals parks in Croatia is 99, 800ha.A certain number of experimental plots has been established on the territory of national parks, i.e. in the region of non-economic forests, for the purpose of monitoring growth and development of forests in natural conditions.The aim of research was gaining further insight into the condition and relationship among certain structural elements of non-economic uneven-aged stands, potentials for regeneration and application of new monitoring practices for stand structures on the example crown digitalistaion. Research was carried out in the National park "Risnjak", one of 8 national parks in Croatia, whose area is 6, 400ha.The greatest portion of the park is covered in forests and the rest are meadows, RUDINE and rock.The biggest height above sea-level is 1528m, and the lowest 676m.Lime and dolomite are dominant.Prevailing community is beech and fir forest(Abieti-Fagetum dinaricum Treg.1957), while the dominant soil type is brown soil on lime and dolomite(calcocambisol).Research was cerried out on experimental plot which is located on 680m above sea-level, on dolomite parent rock and the soil type is rendzina.The following conclusions can be drawn from research on non-economic forests of uneven-aged stands of beech and fir by the elaboration of digital model crown projections: 1.Uneven-aged stand structure is dturbed becuse of excessive number overmature trees of European fir, with the distribution of number of trees indicates complete absence of fir in lowest diameter degrees.Aggressive andlow-quality beech in underwood layer has filled this space, particularly in the shrubbery layer, which is one of the reasons for absence of natural regeneration. 2.Crown canopy of 88, 46% and excessive volume of wood are very important factors of occurrence and development of young generation from seed. 3.Quantity, quality and vitality of young plants on monitored experimental plot do not ensure future development of expected regular process of natural regeneration. 4.Passive control measures are not suitable for forest ecosystems of National parks, which means that silvicultural measures and interventions of man are necessary only to an extent of directing and assisting positive natural processes. 5.Digital models of crown projections facilitae computing-digital monitoring of changes in the stand structure and their simulation opens new potentials in studying stand structure by the application of new technologies in forest management. 6.Obtained three-dimensional models of crown projections facilitate the establishment of the fourth dimension with reference to a function of time, which can be a significant factor in studying the structure of uneven-aged stands and research of future developments.

uneven-aged stand; Europen fir; beech; non-economic forest; national park; computor-digital monitoring; digital models of crown

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