Describing vegetation succession after bracken control: Evaluation of the REBRA model

The initial response of ground flora within bracken control experimental pl ots at a study site in Breckland, East Anglia was monitored in order to pro vide test data fora model (REBRA), which predicts vegetation succession aft er bracken control. The accuracy of model predictions for vegetation respon se at the community level was considered using multivariate analysis. Diffe rences between vegetation assemblages were dominated by bracken litter and frond cover, with the hierarchy of treatment consistent between field obser vations and model predictions. Cutting once yearly exhibited the most limit ed vegetation response to management, whereas cutting twice yearly created the greatest change in the plant communities relative to untreated bracken. Spraying with asulam was an intermediate strategy with plant communities r everting to undesirable vegetation types after initial success in bracken c ontrol. Three factors responsible for discrepancies between recorded and pr edicted vegetation communities were identified: (1) bryophyte species which formed a consistent component of the recorded vegetation throughout the st udy were unable to be incorporated into model predictions; (2) model predic tions for reduction in bracken litter cover as a consequence of experimenta l treatment were under-estimated considerably; (3) following cutting treatm ents, competition arising from frond regrowth in the latter portion of the growing season and subsequent litter inputs were not considered within the model. Despite these confounding factors, the model appeared, within this l imited evaluation, to be a potentially valuable tool in formulating managem ent strategies to better direct succession after bracken control. (C) 2000 Academic Press.