Fire has considerable impact on vegetation and organic soils properties. As we observed that the differences between vegetation of burnt and unburnt areas on the rich fen are visible 11 years after the fire, we assumed that the post-fire changes are long lasting, yet limited exclusively to the burnt areas. In order to check this hypothesis we studied spatial differentiation of physical and chemical properties of soils, and productivity capacities of burnt and unburnt areas in the fen in Biebrza National Park. We took soil samples from the neighboring burnt and unburnt areas, from the depth of 0–30 cm and 30–50 cm. We analyzed 21 parameters of the soils including: pH, ash content, moisture, bulk density, exchangeable K, Na, Ca, available P, N-NH4+, N-NO3−, total N, C, K, Na, Ca, Mg, Fe, P; and calculated C:N, C:P ratios. Surface layer of the burnt soils differed significantly from the unburnt soils in respect of 17 out of 21 parameters. The most pronounced difference was observed for available phosphorous (on average 6 times higher for the burnt soils). The differences in the deeper layer were mostly insignificant. The burnt areas were also characterized by twofold higher plant productivity than recorded for the unburnt areas. The influence of fire on peaty soils was long lasting but mostly limited to the surface layer of the soils. In the case of particular soil features, the post-fire differences were modified by advanced muck formation (moorshing) processes in the unburnt areas. Since the fire led to long lasting increase of fertility, the recovery of fen vegetation is unlikely.

Heavy metal (As, Mn, Ni, Sn, Ti) concentrations were determined in soil and plant samples collected in different areas of the railway junction Iława Główna, Poland. Soil and plant samples were collected in four functional parts of the junction, i.e. the loading ramp, main track within the platform area, rolling stock cleaning bay and the railway siding. Four plant species occurring in relatively higher abundance were selected for heavy metals analysis, although in the loading ramp and platform areas only one species could be collected in the amount which makes chemical analysis possible. The selected species included three perennials (Daucus carota, Pastinaca sativa and Taraxacum officinale) and one annual plant (Sonchus oleraceus).

The entire area of the railway junction showed elevated concentrations of heavy metals when compared to the control level. It was most pronounced for the platform area and railway siding. The concentration of arsenic, manganese and nickel in plants growing in these parts of the junction exceeded the toxic level. The highest contamination of soil and plants found in the platform area suggested advanced emission process of the analyzed metals from wheel and track abrasion. Literature review showed that the concentration of the investigated metals in soil was generally higher than that found in centers of cities and along traffic roads proving that the railway is an important linear source of soil contamination