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A quantitative analysis of pedo-physiological indicators aimed at determining changes in the soil attributable to the effects of spruce plantations was done. The study was conducted at eight sites in central and north-western Croatia where spruce plantations were planted in the late 20th century. At each site, a pedological profile was opened within the spruce plantation and the endo-morphological parameters of the soil were determined. Composite soil samples from two depths (0-10 cm and 10-20 cm) and from the forest floor were taken in the spruce plantation and compared with samples taken at plots covered by natural vegetation (natural stands) located in the surroundings. The following pedo-physiographic indicators were measured on the collected soil samples: quantity of forest floor, particle size distribution of soil, pH values in H2O and in CaCl2 aqueous solution (concentration 0.01 mol dm-3), content of Corg, content of Ntot and content of bioavailable nutrients (using the Mehlich III method). The results showed that the forest floor had a higher mass in the spruce plantations than in natural stands. The mineral soil showed clear trends of influence of the spruce plantations on soil in terms of reduced pH values. Most plots in the spruce plantations showed a lower nitrogen content in the soil, a higher C/N ratio and lower content of bioavailable phosphorus. This study provides an insight into the amelioration effects of spruce plantations on soil, and represent a reliable basis for decision-making in planning specific interventions in terrestrial ecosystems, such as the establishment of new forest plantations.

Ice and snow caves are distributed throughout Croatia in the Dinaric karst mountain belt. Most of them are located on Velebit Mt., 1200 m a.s.l. in the zone with snow (boreal) climate. In the past, some of them were used for ice excavation for water and conservation purposes. First mentions occurred in the 17th century and the first researches in 19th century. During the second half of 20th century in some ice cave microclimates, geomorphological and glaciochemical researches started. According to data from deep shafts in Velebit Mt., there is the deepest recorded cave ice in the World. The depth of the ice recorded there is up to 550 m. In the frame of chemical researches, tritium and element concentration, stable isotope and age of the ice were studied.

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 Spacva (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.

Research on oil residuals in lowland forest soil was carried out in 6 sample plots in the lowland forest ecosystem located in an oil field. Four plots were differently affected in terms of discharged oil and the time lapsed after the accident, as well as in terms of micro-relief terrain features. One plot was established in a reclaimed mud ditch site, while the control plot was set up in a micro-relief elevation outside the influence of oil pollution.

We have performed measurements of the cave microclimate, water quality parameters and radon concentration to a depth of -1000 m in Velebita Cave system (Northern Velebit, Croa­tia). The results were analyzed as a function of the cave depth and geomorphological characteristics. Two different air tem­perature gradients were obtained, which can be attributed to a cave morphology and air circulation in the upper part of the pit. The water quality parameters show that the studied waters are poorly mineralized and are of weakly alkaline type. Water chemistry is probably predominantly controlled by the petrog­raphy of the bedrock (limestone) and the cave morphology. Water in the cave is not affected by pollution. The average value of radon concentration is rather low, much lower than in some other Croatian caves.