Article

The woody species Securinega tinctoria (L.) Rothm., Nerium Oleander,. L. and Dianthus lusitanus Brol. are being monitored in order to evaluate the effects of the Alqueva reservoir (Guadiana River, Alentejo, Portugal). Securinega tinctoria is a threatened narrow endemic speces. Nerium oleander belongs to the riparian galleries and Dinathus lusitanus grows on rocky habitats. The three species are considered important for the maintenance of their habitat structure. Thc Alqueva dam is under construction and the effects of its reservoir on the plant species are being evaluated and quantified by demographic, phenologic and reproductive biology sludies. In these sludies, it is neeessary to define classes of individuals (cohorts) grouped by a common functional characteristic. Beeause the age delermination in these individuals (i.e. the sludy of growth rings) may require destructive. biometric parameters related to floral production capacity or phenophase were studied using regression models. The most significant models and the parameters that better declined the groups or cohorts are presented. The modelling orthese relationshi ps givc the size strutture oflhe populations in lime zero. This allows lor unalysis or their evolulion and tlle irnpact asscssmcnt 01' Ihc u<lm's conslruction on the studied spccics in Ihe nexl years.