Discuss the relative importance of physical and human factors in accounting for changes to vegetation over time within ecosystems in the British Isles

There are many factors that account for the changes to the vegetation over time within ecosystems in the British Isles, such as human activity, climate, soil, light availability and intensity and natural disasters. The characteristics of the vegetation that are influenced by these factors are height, distribution, variety of species, adaptations and density of the vegetation. Some of these factors have relatively little influence on the succession development, whereas others have a dramatic influence over a long period of time, such as human activity. These factors, over time, result in the progression of a succession until the climatic climax vegetation is reached. However, sometimes these factors can mean that a plagioclimax is reached, as they prevent the succession from progressing any further and the climatic climax vegetation is never achieved, which in the UK are Oak, Hawthorne and Birch trees. This succession results in the development of an ecosystem. An ecosystem is a dynamic, stable environment which is composed of interacting and functioning biotic and abiotic components and can be of any size. There can be composed of variety of successions, such as lithoseres in grassland and woodland areas for example the Isle of Aaron, psamoseres along the coastline or small scale urban successions in urbanised areas.
In an ecosystem, all the component are characterised as biotic, for example animals and plants, or abiotic for example climate, pH, soil characteristics or drainage. These biotic and abiotic factors determine the changes to the vegetation in the ecosystem overtime as they have a great effect on it, such as flooding and animal grazing. Within the ecosystem, there are inputs, outputs, stores and flows which transfer minerals, nutrients, water and light energy. The most important input is light energy from the sun, which is the source of any food chain. Producers start a food chain, but they would not be able to do so without the 2% of energy provided