Dynamic change in time and space
Even the seemingly most stable types of ‘natural’ vegetation will be subject to change. Whilst most people will assume that most of the wild vegetation they see around them (for example roadside verges and woodlands) stays pretty much the same from year to year, there may in fact be dramatic changes in the composition of that vegetation or the relative abundance of the component species. For most of us, these changes take place on a sufficiently long timescale (even if it is just from year to year) for us not to register that change is taking place. We have already discussed short-term changes that occur through a growing season, as one species takes over from another in terms of visual display. But other changes take place over periods of more than one growing season. These are of direct relevance to the design and management of naturalistic vegetation, partly because they affect the way that the vegetation may be managed, and partly because they highlight again the point that ecologically-informed design and management of vegetation is about setting up a system that is inherently dynamic and to some extent unpredictable into the long term. We can recognise two types of longer-term dynamic change: fluctuations or cycles, whereby species composition may change but the overall character of the vegetation remains relatively constant, and successional change, whereby the actual character and type of vegetation may change over time.
