Growth of salt-secretor and non-salt secretor mangrove seedlings with varying salinity and their relations to habitat zonation

Abstract

The growth of six mangrove seedlings under varying salinity was studied concerning the habitat zonation. Healthy and mature propagules and seeds of selected mangroves, Rhizophora apiculata, R. stylosa, Ceriops tagal, Avicennia marina, A. alba, and Acanthus ilicifolius were collected from North Sumatran mangroves. Mangrove seedlings were grown for three months in 0.0%, 0.5%, 1.5%, 2.0% and 3.0% salinity concentration. The growth of mangrove seedlings emerged to show variation among the species. The growth of two salt secretor species of A. marina and A. alba were increased in the occurrence of salt with maximum activation at 2.0%. This escalation was reduced once salt concentration was increased above 2.0%. By contrast, two non-salt secretor species of R. apiculata and R. stylosa significantly expanded to 1.5% salinity, at that moment decreasing by accumulative salts. A salt secretor species of Ac showed the less salt tolerant of mangrove species. ilicifolius and a nonsalt-secretor of C. tagal, which their optimum growth was at 0.5% salinity. The tolerance of mangrove species to salt concentration tracked the sequence of Av. marina and Av. alba (most foreshore species) >R. stylosa and R. apiculata>C. tagal>Ac. ilicifolius (most landward species), which is following the natural species distribution and habitat zones.