ABSTRACT:The aim of this study was to determine the effect of agricultural land afforestation on soil characteristics. Two sites in two regions of the Czech Republic were evaluated, at lower as well as higher submountain elevations: in the regions of the Orlické hory Mts. and Kostelec nad Černými lesy, afforested, arable and pasture lands were compared for basic chemical and physical characteristics. It was determined: pH, CEC, exchangeable nutrients, SOC, bulk density, volume density, porosity (differentiated by pore size), water conductivity and soil aggregate stability. This study demonstrated the important influence of previous land use upon soil characteristics. The characteristics of the arable horizon can persist for many years; in forests, the mineral horizons (15-30 cm) can persist within 15-30 years after afforestation. Afforestation, which caused an increase in soil porosity by decreasing reduced bulk density and increasing capillary and gravitational pores (increasing the water-holding capacity and soil air capacity), is important for maintaining the soil stability. The positive effect on infiltration and retention capacity resulted not only from the presence of a forest overstorey, but also from the presence of permanent grass cover of pasture land.

ABSTRACT:The objective of this work is to evaluate the effect of alginite on the growth parameters of seedlings of Douglas-fir, Scots pine and line mixture of pedunculate oak, red oak and Norway maple (broadleaves) on former agricultural land with an unfavourable hydrophysical regime. The research plot consists of 36 sub-plots, each subplot has a size of 400 m 2 . The following doses of alginite were applied: control (variant A without alginite), 0.5 kg of alginite (B) and 1.5 kg of alginite (C) when planting both conifers and mixtures of broadleaves. Number of seedlings on the sub-plots was 400 individuals, only in the case of Douglas-fir the number was 200 individuals. Therefore every combination of tree species and the amount of alginite had 4 replications. The parameters of growth and development of individual trees (height, increment and mortality) show that after 2 years, both doses of alginite had statistically positive effects on height increments.

ABSTRACT:The paper documents the mid-term changes of the soil characteristics and upper soil dynamics in the stands of introduced tree species, grand fir and Douglas-fir, on the former agricultural lands. These species were compared with Norway spruce stand and original grassland in the same site conditions at the Hrubá Skála locality (Eastern Bohemia). The plot was established in 1980 on Luvisol type of soil, sandy clay. Altitude ranges between 350 and 360 m a.s.l., mean annual temperature was 7.8°C, mean annual precipitation 703 mm. Results confirmed the starting process of the development of humus forms typical for forest ecosystems, despite the initial stage was dominant. The amount of surface humus (holorganic horizons) did not differ between the tree species stands and the agricultural land, but the grassland humus layer contained much more mineral particles. The grand fir was confirmed as a species favourably affecting the site, Douglas-fir affecting it less favourably in the given conditions compared with Norway spruce. Different dynamics was documented for soil reaction, characteristics of soil adsorption complex, soil acidity and nutrient dynamics.

Service tree (Sorbus domestica L.) is a significant species with regard to the biodiversity of specific habitats. Its reproduction in natural conditions appears to be problematic and in the interest of preserving the countryside, forests and their biodiversity, it is necessary to apply controlled reproduction procedures. Therefore, when applying such procedures it is of crucial importance to optimize the storage and use of seed material. The objective of the present article is to evaluate the germination rates of seeds which were stored in the long term. 95% of the seeds preserved at low temperatures above zero in a normal refrigerator for 8 years germinated after stratification in wet sand. The germination rate of the same seeds when moistened without stratification was 0%. However, after removal of the seed coat, 76% of these seeds germinated without stratification. Storage of air-dried seeds in the cold (at temperatures above zero) is ideal and is better than freezing them to -20°C, as reported in the literature. Wet peat is completely unsuitable for stratification.

Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) is the most common utilized introduced tree species in the tem-is the most common utilized introduced tree species in the temperate zone, planted in many European countries. Also, in the Czech Republic it represents the most planted exotic species as well. Its planted area exceeds 6,000 ha and represents 0.25% of the forest area of the country. In the last years, this species is supposed as convenient substitution for declining Norway spruce (Picea abies [L.] Karst.) stands under current climatic change (extreme drought, bark beetle outbreak). The changed species composition affects also soil dynamic processes, including litter decomposition and transformation. In the presented study, the respiration rate and nitrification intensity were compared in the stand parts dominated by Norway spruce and Douglas-fir in comparable site conditions (410 m a.s.l., 650 mm, 8 ºC, gleyic Luvisol, fresh oak-fir site with Oxalis acetosella, age 97 years). Analyses were performed in laboratory conditions by standard methods determining actual (basal) and potential respiration activity and intensity of ammonia and nitrate ion production. Admixture of Douglas-fir considerably intensified decomposition activities (soil respiration) and profoundly increased the nitrification rate in the surface humus and uppermost mineral soil layer – Ah horizon. Increased interest in the Douglas-fir silviculture needs increased care for forest soil dynamics with respect of nitrogen balance.