Encroachment of forest species into operating and abandoned railway areas in north-eastern Poland

Abstract

Floristic investigations concerning vascular plants, supplemented by a determination of the basic soil parameters and concentration of four heavy metals (Cu, Zn, Mn, Fe), were carried out in 12 railway areas located in north-eastern Poland (eight located on tracks withdrawn from use, four located on operating tracks). The vegetation types of the areas in the immediate vicinity of the selected sites differed (forest, grassland or meadow, ruderal). The soil samples exhibited considerable uniformity with respect to their pH values, and, although the nutrient levels varied, the concentration of the latter did not seem to be a factor limiting plant growth. The concentration of heavy metals did not hinder plant growth. Although the chemical features of the soil were within limits that did not make plant growth difficult, the process of plant regeneration proceeded differently, depending on the accessibility of diaspores from the surrounding areas. The decreasing rate of therophytes, especially aliens, manifested a stage of succession on abandoned tracks. In the case of ground flora, gradual “preparation” of the habitat (shadow factor on the track) was very important. The degree of advancement of forest regeneration on abandoned tracks was more strongly evidenced by the constant return of ground flora species, and not by trees as was commonly thought.

Keywords:

• Forest plants
• forest regeneration
• railway
• soil features

Acknowledgements

The authors acknowledge the Ministry of Science and Higher Education for grant No N305 076 32/2694 which made this work possible. We are also very grateful to the Polish Rail Regional Head Office in Białystok, and especially to Jerzy Wojtkowiak and Roman Bołbot, for key information about the exploitation of railway lines.