Outline on Factors for Vegetation Evolution Over Time
Uploaded by ihatesuchin on Jul 05, 2004
Outline the factors that are responsible for vegetation change over time
Vegetation develops in many different and varied environments with each environment having different effects on the vegetation change over time. This essay will examine these different factors, in different environments. It will examine different sereal stages in different environment, the lithosere or rock environment, the psammosere or sand environment, the halosere or saltwater environment and hydrosere or fresh water environment.
A sere is a stage of events by which the vegetation of an area develops over time. This begins with the pioneer community and end with the climatic climax vegetation. The first plants to colonise an area are called the pioneer community. The climatic climax vegetation is when the ultimate vegetation development has taken place and the environment has reached equilibrium e.g. when the natural vegetation has reached a stable balance with the climate and soil of an area. As an environment goes through more sereal stages the number of species of plants will increase as will their height. The island of Krakatoa in the Sundra strait between Java and Sumatra is a volcanic island, which erupted in 1883. Its development was rapid only taking twenty-five years to develop from the pioneer community to climatic climax vegetation because of the high humidity and temperatures and the rapid weathering of the volcanic rock. The diagram below shows the way an environment such as Krakatoa develops.
There are two types of sereal succession primary and secondary. Primary sereal succession occurs on a new or previously sterile land. It occurs in four different types of environment lithosere, psammosere, halosere and hydrosere. A lithosere is a rock environment. These are initially colonised by blue-green bacteria, which are completely self-sufficient. Therefore the pioneer community is the mosses and lichens which are capable of living in areas which lack soil. The lichens and mosses help to weather the rock along with other types of weathering. This along with the decayed matter of mosses and lichens helps to form a veneer of soil, which can support more advanced plant life. Seeds usually of grass then colonise this soil as time passes the grasses will give way to fast growing shrubs which in turn will be replaced by fast growing trees. Finally these will face competition from slow growing trees such as ash and oak. Although each stage of the succession has been superseded the vegetation from each previous sereal...