BIOLOGY Volume 1 - A Guide to General Biology - 2004

10. ORGANISMS AND THE ENVIRONMENT

10.6. Community Ecology (Synecology)

10.6.3. Application of Succession Principles to Land Restoration

The rate of succession can be of great practical, i.e., economic, significance. Mining spoil heaps, railway embankments, and road verges are just three Examples of sites where rapid plant colonization is desirable for soil stabilization. In the case of mining operations, land restoration—enhancing the aesthetic value of the landscape and, where possible, restoring fertile topsoil—is also crucial. Some spoil heaps are colonized by plants very rapidly. For instance, trees establish themselves in abandoned china clay pits within 10—20 years, while simultaneously developing The Nitrogen Cycle necessary to sustain forest cover. This latter point is extremely important. It means that the restoration of such sites can take place virtually without human intervention. As a rule, all that is required is an initial sowing of a grass-legume mixture to act as nitrogen fixers, after which the vegetation regenerates on its own.

Other spoil heaps, such as coal mine colliery spoil tips, are much more difficult to restore. Their soil is frequently highly acidic and sometimes contaminated with heavy metals. Natural succession will proceed very slowly here, as very few organisms are capable of surviving under such conditions. Various Methods must therefore be employed to accelerate the process. The tip is leveled, and acidity is reduced by liming, by adding organic matter which is practically absent from the raw spoil, or by covering it with a layer of topsoil (the latter being very costly). Organic matter improves the Water-holding capacity of the soil, binds toxic heavy metals, acts as a buffer to mitigate pH fluctuations, and provides food for earthworms. Earthworms mix the developing soil and improve its aeration. Inexpensive organic soil conditioners often include domestic wastes, such as sewage sludge from wastewater Treatment plants, shredded municipal waste, manure, sawdust, etc.