Explanation

The successive development of different biotic communities at the same site till a climax community develops there, is called ecological succession (Hutt; 1885). The species that invade a bare area are celled pioneer species. In primary succession on rocks (xerarch succession) these are usually lichens which are able to secrete acids (lichenic acid) to dissolve rock, helping in weathering and soil formation. These later pave way to some very small plants like bryophytes (e.g., Mosses) which are able to take hold in the small amount of soil. Secondary succession or subsere is a biotic succession on a secondarily bare area, e.g., burned forests, area after deforestation. It takes 50-100 years (for grassland) and 100-200 years(for forest). Ferns are generally the first to grow after the forest fire because of their underground rhizomes.