Explain the Processes by Which Wasteland Can Be Colonised by Vegetation. (8 Marks)
Submitted By IMABEAST
Colonisation of a wasteland is the plant succession which occurs in an urban area which has been abandoned or untouched for 5 years. This form of colonisation is a form a secondary succession. Plant succession is the process in which one plant species replaces another over time which may be influenced by changes in the environment.
The first plants to develop are the pioneer plants. They are able to exist in areas where there is little water, obtaining nutrients by photosynthesis and grow in places with very little soil, like concrete. Some examples of pioneer plants are lichens and mosses. When these plants die they provide a mat of organic matter which, mixed with the weather mineral matter produces a protosoil that other plants can root into.
Stage two of the colonisation of the wasteland is when the Oxford ragwort starts to grow. It grows in the cracks in the surface because they provide sheltered places where seeds can germinate and retain moisture. During this stage, plant succession is rapid.
As these higher plants die off, they produce a thicker and more nutrient-rich soil. Taller plants can then become established. One of the most common is rosebay willow herb, which spreads initially by seeds and then by rhizomes which can extend up to 1m a year. A rhizome is an elongated horizontal underground plant stem producing shoots above and below the ground. These plants gradually shade out the lower plants stopping them from growing as they can’t photosynthesise.
The next stage of succession is the grassland species because as soil enrichment continues the amount of grass in the vegetation increases. The smaller meadow grasses and bents of earlier stages are replaced by taller species. At this stage the area takes on the appearance of grassland with weeds.
As the processes of soil enrichment and competition continue, the taller herbaceous plants are replaced by shrubs and, eventually, trees.