1 Prof. dr. sc. Nikola Pernar, doc. dr. sc. Darko Baksic, Ivan Perkovic dipl. ing., Sveuciliste u Zagrebu, Sumarski fakultet, Zavod za ekologiju i uzgajanje suma, Svetosimunska 25, Zagreb, Hrvatska 2 Prof. dr. sc. Emil Klimo, Ing. PhD. Michal Rybnicek, Ing. PhD. Hanus Vavrcik, Doc. ing. PhD. Vladimir H. Gryc, Mendelovo Sveuciliste u Brnu, Fakultet sumarstva i drvne tehnologije, Brno, Ceska Republika AKUMULACIJA UGLJIKA I DUSIKA U SASTOJINI CRNE JOHE (Alnus glutinosa Gaertn.) U PODRAVINI

This research was conducted in a 95-year-old, highly productive stand of black alder growing in the Drava plain in Croatia. The goal was to investigate the main features of carbon-nitrogen accumulation and dynamics in the stand of black alder (Alnus glutinosa (L.) Gaertn.), as an indicator of ecosystem stability and sustainability of managing such stands. Soil physiography was investigated in a permanent sample plot sized 1 ha with growing stock of 751 m(3) ha(-1). In the course of one season of leaf litter decomposition, the forest floor and soil from the A horizon were sampled on three occasions; the first sampling took place after leaf drop in 2009, the second at the beginning of vegetation (April 2010), and the third before leaf drop (beginning of November 2010). The forest floor mass was determined and so was the carbon and nitrogen content in the forest floor, in the bark, in the physiologically mature leaf and in the soil, as well as the soil pH value. Dendrochronological analysis was performed on black alder wood specimens to determine wood density and carbon and nitrogen content. Data from piezometers set up within the plot for the period 1997-2000 were used to interpret the water regime. According to the research, the soil is Haplic Gleysol (Endoarenic), with a relatively shallow A horizon, of sandy-clayey to loamy-sandy texture, of weakly acidic and in the deeper part weakly alkaline reaction. The water regime is characterized by a shallow and stable groundwater level which occasionally causes shallow (up to 2030 cm) flooding in the out-of-vegetation period, and does not drop below 130 cm in the vegetation period. The forest floor mass ranges from 4.71 Mg ha(-1) after leaf drop, over 3.36 Mg ha(-1) in the spring, to 0.51 Mg ha(-1) in the autumn before renewed leaf drop, which indicates complete decomposition of black alder leaf litter in a yearly cycle. During this period the C:N ratio decreases from 19 to 14.8. Carbon and nitrogen content in the A horizon increases from autumn to spring, but drops again afterwards. Simultaneously, the pH value significantly drops from autumn to spring, but rises again by autumn. In mid-summer, carbon accumulation in the above-ground biomass of the stand is 214.6 Mg ha(-1) while in the soil it is 143.5 Mg ha(-1) on average. On the other hand, nitrogen accumulation is higher in the soil: while it is 2 Mg ha(-1) in the above-ground biomass, it reaches over 14 Mg ha(-1) (13.8 on average) in the soil. Overall accumulation of organic carbon in the ecosystem is 359.5 Mg ha(-1), and of nitrogen it is 15.8 Mg ha(-1). The research has confirmed that this is an exceptionally vital stand, evidently with excellent ecological conditions for the growth of black alder. The vitality and long-term stability of this stand is best reflected in the stable ring width index in the past 80 years, as confirmed by the very large growing stock amounting to 751 m(3) ha(-1) for a stand aged 93-98 (above the taxation limit of 7 cm).

In Europe an abundance of humus taxonomies exists starting with early approaches in the late 19th century. Frequently used in an international context, they do not cover all site conditions in the European area. Although having basic concepts and general lines, the European (and North American, Canadian) classification systems differ in important parameters used for the description and classification of humus forms. These discrepancies result in incongruities, so require adjustments when exchanging partially compatible soil data, even between nearby countries. In 2003, 26 European specialists in humus forms met in Trento (Italy) and decided to formulate rules of classification based on morphogenetic descriptions and diagnostic horizons, adapted to European ecological conditions. Taking into account old and new European and North American systems of humus forms classification, six main references (Anmoor, Mull, Moder, Mor, Amphi and Tangel) were defined, each of them further dividing into detailed categories. This inventory assigned a strong discriminatory power to the action of the pedofauna. Both semiterrestrial (anoxic) and terrestrial (aerated) topsoils were classified. The descriptors of the diagnostic horizons were conceived in accordance with the spirit of recent international soil classifications. Assigning an “ecological value” to each main humus form along a gradient dividing those characterized by accumulation of poorly transformed organic matter, from very biologically active forms degrading and incorporating all organic remains, this European system of classification avoids a hierarchical structure and allows an elastic approach open to additional ecological contributions and renditions.

The subject of the Rájec project (the Drahanská vysočina Upland) consists in the analysis of eco­lo­gi­cal impacts of intensive management in spruce monocultures growing on original sites of beech. Long-term studies were aimed at particular stand and environment stages after clear-felling regeneration and at the origin of a spruce monoculture of the 2nd generation. The establishment of the spruce monoculture can be considered to be most important. The highest attention was paid to the monoculture both from the aspect of carbon and nitrogen in particular components of the forest stand and their transport processes as well as from the aspect of water regime and biodiversity. The study was also aimed at the first stage of the clear-felled area development after felling a mature stand and also at functions of the herb vegetation, which reached its maximum production 4 to 7 years after felling. The paper objective was to assess spruce monocultures even outside their natural range from the aspect of changes in the forest environment as well as from the aspect of possible global changes of climate.

Like in other types of forests the greatest changes in the soil of floodplain forest stands occur during their regeneration. These changes are manifested as changes in the content and dynamics of organic matter in the soil. Research was conducted in oak and ash floodplain forests in the eastern part of Croatia and in southern Moravia in the Czech Republic. The results showed that the type and extent of these changes depended, in addition to environmental factors, also on the technology of forest regeneration. The natural regeneration of oak in floodplain forests of Spačva (eastern Croatia) protects soil from dramatic changes in soil by successive regeneration felling and that it retains the plant cover permanently. The weight of organic matter on the soil surface is increased after regeneration till the period when the effect of thinning becomes evident (about 70 years). In the surface mineral layer of soil the pH value increases after shelterwood felling. Stand regeneration with clear-cutting results in a rapid change in the conditions of surface humus accumulation and decomposition. The process of organic residue accumulation is interrupted in the clearings. In the preparation of soil/site by ploughing, the concentrations of nitrogen and carbon slightly decrease. The management impact depends on the method of site preparation for the establishment of a new stand. The selection of a method of the floodplain forest regeneration (particularly of oak) is markedly dependent on actual ecological conditions and on ecological and historical experience of the given region.

The accumulation of organic matter in the surface, organic horizon (forest floor) has been investigated in two plant communities, Blechno-Abietetum (B-A) and Omphalodo-Fagetum (O-F) in the same climate. The dominant soil type in the community B-A is podzol. Dystric cambisol occurs in the inclusions, whereas the dominant soil type in the community O-F is calcocambisol with melanosol (mollic leptosol) in the inclusions. The results showed significant differences in the organic matter accumulation between these two communities. In the community B-A the accumulation of organic matter varies from 46, 614 to 90, 299 kg ha-1 on average, and in the community O-F it is from 7, 536 to 16, 651 kg ha-1. The structure of the forest floor in the community B-A is dominated by over 80% of humified organic matter in the form of the Oh subhorizon. According to the analysis of the forest floor quality, the forest floor in the community O-F contained a higher concentration of Ca and Mg compared to the community B-A. No differences were found in terms of other nutrient concentrations ; however, due to high organic matter accumulations in the forest floor of the community B-A, it accumulated significantly more analysed nutrient elements, with the exception of Ca. High accumulations of organic carbon and total nitrogen are particularly distinct. High total nitrogen accumulation in the Oh subhorizon indicates its relative immobilisation in the community B-A.

Damage to forest stands and their decline in the Czech Republic evoked a necessity to elucidate the function of soil in these processes. Main factors affecting acidification of forest soils are assessed in the paper. On the one hand, it refers to natural factors such as properties of soil-forming substrates and species composition of forest stands, on the other hand, to the effects of anthropogenic character such as influences of man-made spruce monocultures and effects of acid depositions. Special attention is paid to the development of forest soils in the Krušné hory Mts., where the effects of acid depositions are highest.

Growing spruce monocultures in Central Europe out of their natural range and clear-felling regeneration of these stands provoke interest of ecologists and foresters. The study was conducted in the region of the Drahanska vrchovina upland (the Rajec project), altitude 620 m, mean annual precipitation 638 mm, mean annual temperature 6.3degreesC. Soils are classified as acid Cambisols developed on granodiorite with the admixture of loess loam in the upper part of the soil profile. The original beech stand was converted to a spruce monoculture about 1900. The clearcut area resulted due to whole-tree logging carried out in winter months of 1977-1978. The clearcut was reforested in spring 1978. Since 1978, the development is monitored of important ecological parameters. Changes in species composition (beech replaced by Norway spruce) resulted in the change of the surface humus form and deceleration of nitrogen cycle. The whole-tree logging resulted in the loss of considerable amounts of nutrients. Due to means of mechanization used in skidding operations soil compaction occurred. Logging operations resulted in the surface humus heterogeneity. In the clearcut area, herb communities gradually predominated markedly affecting the nitrogen cycle. After canopy closure of the newly established spruce stand the following aspects were monitored: its nutrition particularly by nitrogen and the development of the condition of surface humus especially in relation to a stand where a cleaning was carried out and to a stand where no cleaning was performed.

With the increasing limitation of personal and financial resources in forest management, the role of preventive forest protection becomes more and more important. Aiming at the improvement or the warranty of special forest functions and the reduction of production risks, a wide range of tools reaching from mechanistic to statistical models can be used. Referring to the goal of the present study, a system with widest possible applicability (primarily for spruce-abundant forests in Austria) has been established, which belongs to the category of mechanistic models. This model is to derive the predisposition of a given stand or a larger forest unit for various biotic and abiotic destructive agents. It contains a set of indicators - found by an intensive literature analysis - which are presumed to be essential for the prediction of predisposing site and stand situations. The final system will combine singular predisposition-models of special damaging agents such as storm, snow, hoarfrost and air pollutants as well as phytophagous insects or important fungi. The prediction-system for each impairing factor consists of an award-penalty-point system with facultative knock-out-criteria, where a list of relevant impacts is made up. These lists contain indicators such as altitude, slope or soil type for the site-related assessment as well as tree species, stand density or developmental phase, for example, for stand-related assessment. The indicators have been split into classes in order to establish a scale, where a specific score is assigned to every scale level corresponding to its contribution to the overall-predisposition. In consideration of the predisposition-increasing or -decreasing effect of those very scale levels, positive or negative signs have been put to each score. Applying the system to a given site or stand, the specific scores of each correct scale level of the indicator list are summed up to an actual total amount. The result is related to a pessimal total amount and this percentage can be interpreted as a relative predisposition.

Silvicultural decision making in damaged off-site Norway spruce stands is a multiple-objective and multiple-attribute decision making problem. To support the decision maker in analysing such complex decision problems DSSs (decision support system) can provide valuable help. In this contribution a comprehensive outline of a DSS for silvicultural decision making with Norway spruce stands is presented. Selected components of a DSS are described and demonstrated for the evaluation of silvicultural treatment options and growth stock objectives. In this contribution, we apply (a) a static model for site requirements of tree species to assess species suitability under different climatic conditions, (b) the analytic hierarchy process (AHP sensu Saaty 1977) to determine preferences for different silvicultural treatment options as well as for growth stock objectives. The trade-off between contrasting preferences is modelled with a multiple-attribute utility function.

Floodplain forests in the alluvium of the Morava and Dyje rivers are particularly stressed by important changes in the water regime conditioned by regulation measures as well as episodic climate fluctuations in last 10 to 20 years. Floodplain forest ecosystems are able to fix large amounts of particularly nitrogen and phosphorus in relation to the high level of plant biomass production and high soil adsorption capacity. The ecosystems form also a barrier against wind erosion From heavily fertilized surrounding agricultural soils. With respect to the fact it is possible to recommend the protection and extension of the ecosystems in order their function in the landscape to be Fully restored. Water courses flowing into the Nove Mlyny reservoirs are polluted and the cleaning function of the reservoirs is evident. The use of water from the reservoir No. 3 for artificial flooding cannot Fully replace the process of natural floods occurring in the past. In addition to the production function, floodplain forests fulfil also other functions, e.g. recreational, educational, aesthetic and groundwater quality protection. Revitalization projects condition increasing the heterogeneity of forest sites, maintaining the production level and increasing biodiversity on the level of plant species and communities.