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. 15ty of forest soils in the territory of the CR. Generally, we can state that substrates of acid character predominate. It applies particularly to crystalline rocks such as granite, gneiss, mica schist, Cretaceous sandstones and also sandstones of Carpathian flysch. On these rocks under the interaction of climate and plant cover, soils developed being of acid reaction such as Podzols and acid Cambisols. Soils of slightly acid reaction such as Luvisols were formed on loess sediments and soils saturated with basic elements on igneous basic rocks of the České Středohoří Mts. Of special character are the soils that developed on alluvia of the Labe, Odra, Morava and Dyje rivers which can be primarily of neutral to slightly alkaline reaction. Soils developed on limestone karst rocks are of neutral acidity. MAŘAN (1944MAŘAN ( , 1948) also attributed the importance of natural soil-forming factors for the condition of soil acidity according to particular soil types but the character of surface humus was considered to be the principal factor. The fact was then generalized by MAŘAN (1948) as follows: (1) humus of closed conifer stands is much more acid than that of closed broadleaved stands of the same region, (2) forest floor layers are more acid than layers of mineral soil.Similarly ZLATNÍK et al. (1938) studying natural forests of Trans-Carpathian Ukraine described sites where soil acidity of upper horizons reached 4.5-4.8 pH and in some cases even 3.8, 3.6 and 3.4 pH.Therefore, in studying anthropogenic impacts it is necessary to take into consideration this natural condition affecting also the sensitivity of soil to acidification by spruce monocultures and particularly by acid depositions.In assessing the sensitivity of soils to acidification by air pollutants, it is possible to take into account the opinion of WIKLANDER (1978) that very acid soils are far less sensitive to further acidification. They are relatively stable, their pH being usually lower than pH of precipitation. Particularly podzol soils and acid brown forest soils rank among these soils. In coniferous forests, WIKLANDER (1978) considers decomposition processes of organic matter to be the main source of acidification.A special case can occur if E horizon is completely impoverished of soil colloidal fractions by podzolization processes and only an inert fraction of siliceous sand remains in it as shown by the profile of m...

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ABSTRACT: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. Matić (1996, 2003a,b), Oršanić and Drvodelić (2007) consider natural regeneration of oak to be a method which preserves the uninterrupted development of forest sites and biocoenoses being realized during 3 stages (preparatory felling, seed felling and final felling). In addition to this, Houšková et al. (2007) drew a conclusion: "Natural regeneration of pedunculate oak cannot be fully relied on in the Czech Republic due to the long-term absence of rich mast years and it is, therefore, necessary to continue the planning of artificial regeneration. "Farm forestry (alternate forest and farm crops) as one of the methods of clear-felling regeneration shows potential negative impacts on the soil environment (Libus et al. 2007), particularly decreasing porosity and water retention capacity at a depth of 25 to 35 cm. Soil/site preparation by ploughing shows also negative impacts due to decreased accumulation of carbon.From the aspect of the ecosystem approach in the floodplain forest management, attention is also paid (in addition to maintaining the high production level of the ecosystem tree layer) to other components, such as preserving and increasing biodiversity at the level of communities and species, nature and water resources protection and the function of forests in the landscape and socioeconomic consequences.Problems of these functions were also dealt with by the last ministerial conference held in Warsaw at the beginning of 2007. Resoluti...