WATER LEVELS AND PHRAGMITES - DECLINE FROM LACK OF REGENERATION OR DIEBACK FROM SHOOT DEATH

This contribution combines field observation with the literature to ar gue that stabilised water levels are contributing to reed decline thro ugh a lack of vegetative and generative reproduction, and that eutroph ic conditions exacerbate this situation. The focus on what causes reed shoots to die has increased our knowledge of what limits the distribu tion of reed without necessarily increasing our understanding of reed decline. This raises the question as to whether reed beds are in fact dying, or whether reed decline is observable only in the absence of re generation. The distribution pattern and life-history of reed suggests that generative reproduction is lacking. It is proposed that the temp oral scale at which seedling establishment takes place is similar to t he time-frame of observed reed decline (10-50 years). As an ''encompas sing'' factor, water regime influences many of the specific factors un der investigation. Its role is therefore consistent with agreement in the literature that reed decline is caused by combinations of factors.