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The subject of this research are mixed forests of spruce and fir in the area of NP Kopaonik, which belong to the community of spruce and fir - Abieti-Piceetum abietis Mišić et Popović, 1978. The basis for the study of the structural development and production potential of these forests are data from 12 sample plots, with the average size of 0.18 ha. In terms of coenoecological affiliation all the sample plots belong to the group of ecological units - forests of spruce and fir (Abieti-Piceetum abietis, Mišić et Popović, 1978) on acid brown and brown podzolic soils, which are differentiated into 5 ecological units: Abieti-Piceetum abietis oxalidetosum on brown podzolic soil, Abieti-Piceetum abietis oxalidetosum on acid brown soil, Abieti-Piceetum abietis vaccinietosum on brown podzolic soil, Abieti-Piceetum abietis typicum on brown podzolic soil and Abieti-Piceetum abietis Dr.ymetosum on brown pozolic soil. In structural terms, these forests are characterized by very diverse structural forms, ranging from the structure of even-aged stands to typical multi-storey, unevenaged-aged stands. The form of cumulative curves of tree distribution is in most cases determined by spruce as the dominant species. At the same time, thin and medium-thick trees dominate, while the presence of stems with large dimensions is minimal. The average volume of these forestse is 777 m3•ha-1, with a mixture ratio of 0.7: 0.3 in favor of spruce. The average value of the current volume increment is 14 m3•ha-1, with a 68% share of spruce and 32% of fir. The percentage of increment ranges from 1.6% to 2.5% in all sample plots and is somewhat higher for fir. The site potential, stand characteristics and relations among the tree species have resulted in structural complexity, high productivity and ecological stability of these forests. Therefore, future forest management should avoid radical measures and procedures that would violate the established relationships and dynamic processes. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 37008: Sustainable management of the overall resources of forests in the Republic of Serbia]

The data of periodic complete measurements of permanent sample plots and compartments in which they were located in the period 1955/60-2005/2010 served as the basis for this research. Two sets of data from a 50-year time span enabled a comparative analysis of a number of structural and numerical elements of regularly managed selection forests of fir, spruce and beech that more or less spontaneously developed in the sample plots. The number of trees in low-diameter categories decreased in the regularly managed compartments, but it was partly compensated by regeneration and ingrowth, which amounted to 7.9 trees per year. In forests with spontaneous development, the ingrowth is either missing or minimal, and it amounts to 2.7 trees per year. From the aspect of preserving the natural composition of these forests and thus their biological stability, a significant decline in the number of beech trees is worrying, above all in the lowest-diameter categories. The accumulation of large-dimension trees is more pronounced in the sample plots in relation on the compartments with regular management. This trend resulted in high basal area values (max. was observed in compartment 131 and at the end of the analyzed period, it amounted to 37.8 m2•ha-1, and in SP-2 to 55.7 m2•ha-1) and volume (max. 605.4 m3•ha-1 was achieved in compartment 66, with a 79% share of fir, i.e. 898 m3•ha-1 in SP-2 in which the share of fir is 71%). Increase of volume in diameter catagories above 50 cm amounts to on average 120% in compartments, and in stands with spontaneous development to as much as 230%. Current volume increment is high and at the end of the period it amounted to on average 12.9 m3•ha-1 in the compartments, and 14.9 m3•ha-1 in the sample plots. In both these values the share of fir is 80%. However, increment percentage, as a more reliable indicator of vitality and good living and stand conditions decreased from 2.54% to 2.32% in the observed compartments and from 2.31% to 1.91% in the sample plots, under the conditions of spontaneous development. On the basis of the above, certain disturbances and negative trends can be identified, both in regularly managed forests and stands with spontaneous development, while they are significantly more pronounced in the latter case. This is reflected in the unfavorable spatial relationships and light regime, and consequently difficult regeneration and ingrowth (especially of beech) as well as the slowing dynamics of these forests, which finally disrupts their structure and functional value. In regularly managed forests, the reason for that is the rigid understanding of the felling ripeness diamater and lower intensity cutting of large-dimension inventory, which slowed down the dynamics and made regeneration and ingrowth difficult. More intensive operations in this part of the inventory would provide a better spatial distribution of trees (horizontal and vertical) and a a better light regime, while the development of these forests would be accelerated. This is confirmed by the fact that forests with self-regulation processes (spontaneous development) become gradually depleted in low and medium storey trees and turn into a one-layer structure with a horizontal canopy which was observed in the investigated sample plots. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 37008: Sustainable Management of Total Forest Potentials in the Republic of Serbia]

A comparative analysis of National Forest Inventories (NFI) of many countries, including Serbia was made in the manuscript, in terms of methodology and in terms of the definition of different information collected about forest ecosystems. Further development of the NFI Serbia was also analyzed. It was determined that there are differences in national methodologies, but that they are not substantial and do not constitute an obstacle to the creation of uniform databases of forests at the regional and global levels as a prerequisite for political and professional action aimed at protecting and ensuring sustainability of all forest functions. Contrary to that, differences between national definitions for information that are collected by inventory are numerous, distinct and as such represent a major obstacle to the mentioned aspirations. The solution of the problem is standardization, i.e. in the far more acceptable harmonization process (adaptation) NFI, whereby such frameworks of that activity are imposed by the FAO (globally) and COST Action E43 (mainly in the European region). NFI Serbia, on the threshold of second realization, is burdened with a numerous institutional, organizational and methodological problems and dilemmas, inherited from the first measurement of Serbian forests. Therefore, an urgent recruitment of relevant experts is necessary to resolve and overcome problems, in order to ensure all the prerequisites for a successful implementation and obtaining reliable data of the second NFI, so that the future NFI can be alleviated of the conditions in which it is currently located. [Projekat Ministartsva nauke Republike Srbije, br. 37008: Održivo gazdovanje ukupnim potencijalima šuma u Republici Srbiji]

In situations where it is necessary to consider a variety of options when making decisions in forestry (and in general), with the choice influenced by hardly comparable criteria and a number of conflicting interests, a possible solution is to use multiple criteria methods. One of these methods, which can be applied in forestry, is mathematical programming (in particular, linear programming). Linear programming has a long tradition of being used in the U.S. and European forestry, whereas in the forestry of Serbia it still represents a theoretically and practically unknown tool. Therefore, in this paper we analyze the possibility of applying the methods of linear programming in developing a plan of regeneration cutting in the poplar plantations of FMU "Topolik" managed by PE "Vojvodinasume." Using the aimed function (linear programming) and the corresponding software package the maximum yield that can be achieved by cutting the plantation was obtained. The planned management period was from 2012 to 2021 and its volume was 155 852 m3. The preset condition that the yield in half-periods remains equal was fulfilled (half-period I 77,925 m3, half-period II 77,927 m3). The maximum yield obtained with this methodology was by 4,040 m3 lower than the theoretically possible yield that would be obtained if all stands were cut down at the end of the second half-period, i.e. higher by 8,430 m3 than the yield that would be obtained if cutting of the stands were performed at the start of the management period. The results obtained and foreign experience in this area clearly indicate that linear programming can successfully be used to solve this problem and even more complex problems (than the one presented in this paper) in our local forest practice (multidimensional planning with a series of constraints). [Projekat Ministarstva nauke Republike Srbije, br. 37008: Održivo gazdovanje ukupnim potencijalima suma u Republici Srbiji]

Valuable broadleaves, including also wych elms, belong to the category of rare tree species in the growing stock of Serbia. The conservation of Serbian forest diversity and the genetic potential of these tree species require a multidisciplinary study. In this respect, we undertook a dendrometric and health analysis of a wych elm tree on Goc, as it is a rarity by its dimensions, not only from the local, but also from the regional aspects. The tree is 266 years old, its diameter at breast height is 2.09 m, height 42.1 m, and volume (d>3 cm) 56.35 m3. Current height increment culminated early, at the age of 20-30 years, attaining 0.5 m, and current diameter increment at the age of 40-50 years when its value was 14.4 mm. The above data point to a high productivity of this elm tree and to favourable site and stand conditions of its development. On the other hand, its current diameter increment and height over the last period (1.7 mm, and 0.03 m respectively) indicate that the tree was in the phase of physiological dying. 10 species of fungi were identified on the tree (facultative parasites or saprophytes), the most significant being Armillaria mellea and Aurantioporus fissilis, which caused central heartwood decay. Other fungi developed saprophytically in the dead part of the stem or in dead branches. Eight insect species (secondary and tertiary pests) were identified, including the two most dangerous elm beetles (Scolytus scolytus and S. multistriatus). Together with the species Saperda punctata and Cerambyx scopolii, they accelerated the dying process of twigs and branches, as well as of the whole tree. Ambrosia beetle Xyleborus monographus infested the stem and the large dead branches and caused minor technical damage in wood. The species Dorcus paralelopipedus, Oryctes nasicornis and Valgus hemipterus supported the faster progress of wood-rotting fungi and thus contributed to physiological weakening and shortened the life cycle of the study elm tree.

Mixed forests of broadleaves and conifers, thanks to their high productivity and high biodiversity, are the most valuable part of the growing stock in Serbia. The aim of this research was to analyze the mixed old-growth forests of fir, spruce and beech in the reserve ?Racanska Sljivovica? so as to define the laws which could be applied in the future forest management on Mt. Tara. The research was based on the data of six periodic complete inventories followed by standard dendrometric and statistical processing. Forest structure was similar to the typical selection structure. The recruitment dynamics (except beech) was relatively favourable, with the ratio to dead trees amounting to 1.72. The number of trees and the volume increased constantly, attaining 422.2 trees?ha-1, i.e. 800.3 m3?ha-1, and the volume increment was above 12 m3?ha-1, despite a slight drop. Silver fir was the protagonist of the selection structure and productivity. It is necessary to stimulate the survival and development of beech at the concrete site, to examine the balanced number of trees and volume, and to investigate the relationship between the number of recruited trees and the stand volume.

Based on the data of the National Forest Inventory, this paper presents the basic characteristics of forest ecosystems in Serbia by different qualitative and quantitative parameters. The following parameters were dealt with: land use, forest ownership, origin, naturalness, preservation status, mixture and structural form of forests, percentage of tree species, stand category, volume distribution by diameter degrees, as well as the quantity of dead wood and carbon stock in the forests of Ser?bia. The analysis of the presented state enables the definition of some of strategic problems which individually and acting together burden our forest ecosystems, and whose detailed elaboration, measures and methods of enhancement will be fully expressed in the highest planning document - National Forest Programme. A special section, but without being sufficiently analytical, presents the main data on the growing stock of the Autonomous Province Kosovo and Metohija taken from the Report of the Norwegian Forestry Group.

The study of tree stem form-form factors and form quotients, and their dependence, and the relation with other volume elements is a necessary precondition for the construction of volume tables by indirect methods, which are increasingly applied. After determining the magnitudes of the above indicators of tree stem form, this paper studies the correlation between normal form quotients and normal form factor, then the correlation between normal form factor and tree diameter and height, as well as the correlation of normal and artificial form factor.

This paper presents the comparative analysis of stand state, productivity and silvicultural demands in beech stands of mixed origin, with a predominating percentage of trees of coppice origin, in different site and stand conditions, in the area of Cestobrodica and Straza. The main cruising elements were analyzed in three ecological units: Number of trees, basal area, volume, volume increment, mean stand diameters and height and the development of individual trees. The differences of the study ecological units, presented through the values of cruising elements and the phases of diameter, height and volume development of individual trees, are computed by the analysis of variance and LSD test. The analysis and the concluded significant differences enabled the real and comprehensive understanding of the state of these stands, based on which the long-term objectives of forest management were decided (conversion into a high silvicultural form) and actual silvicultural demands and measures - high selection thinning.

The study of tree form - form factors and form quotients and their interrelationship and the relation with other elements of volume is a necessary precondition for the construction of volume tables by the increasingly applied indirect methods. After the magnitudes of these parameters of tree form were defined, we studied the correlation between normal form quotients and normal form factor, between normal form factor and tree diameter and height, and between normal form factor and artificial form factor.

Assortment structure in beech coppice stands was studied in the area of Boljevac. Assortment structure was evaluated according to the articles of the valid standard (JUS). The assortments represented in the assortment structure, based on the stemwood quality are: Logs for matches, sawlogs I II and III classes, mine timber, technical roundwood, pulpwood, wood for excelsior and fuelwood, I and II classes. The results of the analyses show that the value assortment structure (sum of the values of assortments produced from one tree) grows significantly with the increase of tree diameter and this dependence is presented by a degree function. The value percentage of logs for matches, sawlogs of the I and II classes, technical roundwood, mine timber, fuelwood and pulpwood, grows with the increase of the tree diameter. The occurrence of better quality logs (sawlogs) in these stands, in contrast to the beech coppice stand in the area of Crni Vrh results from the more favourable diameter structure. There are no statistically significant differences between the value assortment structure on the established sample plot series within the same locality, consequently the data ere united. Because of the differences in stand age, the data are not unified for the localities, although there are no statistically significant differences between value assortment structure for diameter degrees represented in them. False heart (red heart) is one of very significant defects of beech wood, and its incidence, inter alia, depends on tree age. The low effect of this defect of wood resulted in a significant percentage of logs for matches. Along with the value assortment structure this paper also presents the percentage of assortments depending on tree diameter.

Assortment structure in beech coppice stands was studied for the region of Crni vrh. Assortment structure was determined according to the standard (JUS) in two ecological units. The study results show that the assortment value structure significantly increases with the increase of tree diameter and that there are no statistically significant differences in assortment structure between the selected ecological units. The dependence of the assortment value structure on tree diameter can be represented by an exponential function. The value percentage of assortments made of stem wood in theoretical crosscutting depending on tree diameter has an increasing tendency, except for the wood for excelsior.

Considering the great significance of volume increment in forestry, it is understandable that there are numerous methods of its assessment. However, all these methods have some disadvantages, either the accuracy of the obtained results, too large scope of works of forest inventory (economicity), or the restriction only to stands of certain silvicultural type. To make the method of stand volume increment more economic and simplified, we defined regression models for volume increment percentage assessment in fir, spruce, Austrian pine and Scots pine stands in Serbia. Empirical data were fitted by four regression models for each tree species. The criteria for the final selection of models for the determination of volume increment percentage were the relevant statistic parameters of regression and correlation analysis, and the degree of concordance of "real" and fitted ("table") values of volume increment percentage. The selected models for the above tree species are Fir Spruce Austrian pine Scots pine In the practical work of the assessment of current volume increment in the stand, in regular forest inventories, the method of volume increment percentage should be implemented with correction factors for the fitting of "table" (obtained by this method) values of volume increment and "real" values (obtained by the method of diameter increment), on at least 10 % of the stands of the same or similar stand class (same or similar tree species and stand form). In this way, the costs of forest inventory would be reduced, and the obtained results would range within the limits of the required accuracy .

The reliability of information on the growing stock state is the basic prerequisite of real forest management plans. In this sense, practical works on forest management, including data processing, which creates the information base in forestry, should be carried out in the most correct way, disregarding the numerous problems (subjective and objective) which result from the conditions in which the works are performed. Improvisations in any phase of the works, as illustrated by the example presented in this paper, create a wrong idea on the forest state, which further results in unreal and inadequate forest management plans. In all situations in which the data in plan documents do not agree with the real forest state, disregarding the increased financial expenditures, the works on forest management should be revised and plan documents should be made. In this way, we eliminate the potential consequences which would result from the realisation of the planed works based on unreal forest state, which would be reflected both in the economic and in the ecological senses, without the possibility to remove the consequences in a short time period.