Railroad ecology is a term used to refer to the study of the ecological community growing along railroad tracks. Such ecosystems have been studied primarily in Europe. Similar conditions appear also by roads used by vehicles.

Conditions

Railroad beds, like road beds, are designed to drain water away from the tracks, so there is usually a bed of rock and gravel resulting in fast drainage away from the tracks. At the same time, this drainage often accumulates in areas fairly near the tracks where drainage is poor, forming small artificial wetlands. These unnatural conditions combine to form different zones, some in which water is scarce, others in which water is abundant.

Maintenance

Railroad companies routinely clear-cut and/or spray with herbicide any vegetation that grows too close to the tracks. This favors vegetation that is able to respond favorably to clearcutting, and/or resist herbicides.

On overhead electrified railroad

Railway electrification system

A railway electrification system supplies electrical energy to railway locomotives and multiple units as well as trams so that they can operate without having an on-board prime mover. There are several different electrification systems in use throughout the world...

 lines, clear-cutting must be more extensive, vertically as well as horizontally, in order to prevent vegetation (especially tree limbs) from interfering with the pantographs

Pantograph (rail)

A pantograph for rail lines is a hinged electric-rod device that collects electric current from overhead lines for electric trains or trams. The pantograph typically connects to a one-wire line, with the track acting as the ground wire...

 on a moving train, breaking off and falling on the wires, or simply from arcing

Electric arc

An electric arc is an electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive media such as air. A synonym is arc discharge. An arc discharge is characterized by a lower voltage than a glow discharge, and relies on...

 in proximity to high voltage transmission cables. The same vegetative selection processes described in the previous paragraph apply, but may additionally favor climbing vines due to the presence of catenary and transmission poles in addition to the wooden communications and signal pole lines

Utility pole

A utility pole is a pole used to support overhead power lines and various other public utilities, such as cable, fibre optic cable, and related equipment such as transformers and street lights. It can be referred to as a telephone pole, power pole, hydro pole, telegraph pole, or telegraph post,...

 which often exist(ed) along nonelectrified lines.

History

Historically, conditions along railroad beds were much different than they are today; coal engines used to blanket the area with soot, favoring species adapted to these conditions (some of which only occurred naturally in volcanic areas). Newer engines produced a less remarkable environment, but many of the same plants have remained and adapted to this new environment.

Invasive Species

Railway tracks (like roads and highways) are often colonized by non-native invasive species. In North America, such species include trees such as Ailanthus altissima, Paulownia tomentosa

Paulownia tomentosa

Paulownia tomentosa is a deciduous tree in the genus Paulownia, native to central and western China, but invasive in the US...

, Siberian Elm

Siberian Elm

Ulmus pumila, the Siberian Elm, is native to Central Asia, eastern Siberia, Mongolia, Xizang , northern China, India and Korea . It is also known as the Asiatic Elm, Dwarf Elm and Chinese Elm. Two varieties are recognized: var pumila and var. arborea, the latter known as Turkestan elm...

, and Norway Maple

Norway Maple

Acer platanoides is a species of maple native to eastern and central Europe and southwest Asia, from France east to Russia, north to southern Scandinavia and southeast to northern Iran....

, and invasive non-woody plants such as Japanese Knotweed

Japanese knotweed

Japanese Knotweed is a large, herbaceous perennial plant, native to eastern Asia in Japan, China and Korea...

 and Phragmites

Phragmites

Phragmites, the Common reed, is a large perennial grass found in wetlands throughout temperate and tropical regions of the world. Phragmites australis is sometimes regarded as the sole species of the genus Phragmites, though some botanists divide Phragmites australis into three or four species...

. The railway tracks provide corridors along which these species can spread and thrive, even when the surrounding areas might be less hospitable to them.