Models of field layer vegetation interactions in an experimental secondary woodland

Catastrophe theory, developed to model discontinuous situations, is used here to examine vegetation and environment relationships which do not fit conventional ordination models. t creation and introduction experiments can lead to a mix of plant communities competing for the same space. This study describes the development of ground vegetation in a young plantation woodland, used for field layer enhancement experiments 10 years ago. The field layer flora is now observed to be a patchy mix of either spontaneous vegetation of mainly coarse grasses and competitive forbs or an introduced community of shade tolerant woodland herbs. The composition of any area is partly dependent on the original experimental treatments and partly on the current environmental variables. fication of the vegetation shows the clear division between these communities but standard ordination methods appear to provide poor models of the vegetation structure. The nature of these data suggests that a catastrophe model may be a useful way of representing some of the key relationships in this woodland. This model implies a non-linear relationship between vegetation and light levels and an important, previously unsuspected role for potassium.