Survival and early growth of Rhizophora species seedlings of selected provenances as affected by salinity
1993
Melana, D.M.
Water salinity is not a requirement for the survival of the three Rhizophora species; rather salinity is a stress they have to cope with. The species, however, differ in their level of tolerance. Suppression of height growth of seedlings of the three Rhizophora species due to salinity was more marked compared with other growth parameters studied, namely: diameter growth, leaf and biomass production. Leaf morphology and wood anatomy as affected by salinity were also looked into. Leaf length and pore frequency of wood were the parameters markedly affected by salinity. Regression and correlation analyses showed a general trend of inverse relationship of survival and growth with water salinity. Of the five nutrients, nitrogen, phosphorus, potassium, calcium and magnesium, calcium content in both soil and plant tissue of the three Rhizophora species showed a trend of significant inverse relationship with water salinity. Significantly high survival in 0-30 ppt water salinity for Bakauan-babae and Bakauan-lalaki, and 0-50 ppt for Bakauan-bangkau of the best provenance which was found to be Quezon and Surigao del Norte [Philippines] in this study. Optimum biomass production at salinity levels 0.20 ppt for Bakauan-babae; 0-30 ppt for Bakauan-lalaki and 0-10 ppt for Bakauan-bangkau. Variation of the level of tolerance or sensitivity of the three Rhizophora species to water salinity stress may adversely affect species diversity of mangrove ecosystems. This is in the light of environmental degradation causing drought and drying of rivers, cutting freshwater supply and probably inducing an increase in water salinity of mangrove areas
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