Abstract:
Mangrove restoration has become a priority for the Sri Lankan government in its quest to
provide safeguard against ocean surges though restoration success is not retrospectively
monitored. The primer introduced by the Society of Ecological Restoration International (SER)
is barely used in success evaluation as it is time consuming and expensive at some point.
Therefore, this study aimed at testing the likelihood of using soil salinity and redox potential at
10 cm depth, as a simple proxy to measure success of Rhizophora mucronata mangrove
juveniles. Three mangrove restoration sites namely; Panama, Panakala and Halawa (belong to
dry zone) on the eastern coast of Sri Lanka were subjected to the study. Per each site, six R.
mucronata mangrove patches i.e. same aged, three successful (>25%) and three unsuccessful
patches (<10%), were selected. From each patch, 12 (twelve) soil samples were randomly
collected and soil salinity and redox potential of soils were measured with a multimeter. Soil
bulk density (SBD). Soil pH, soil porosity were studied additionally. Level of survival of R.
mucronata juveniles and cumulative height were recorded for each patch and considered as
response variables. Generalized Linear Model (GLM) was performed taking soil salinity and
redox potential as explanatory variables. According to the results, soil parameters showed
remarkable variations among the successful and unsuccessful patches. Mean soil salinity in the
successful sites (8.4±2.1 psu) was significantly lower than (p<0.05) the unsuccessful sites
(14.2±1.6 psu). On the contrary, the successful sites showed significantly higher (p<0.05) mean
redox potential (-38±14 mV) as compared to the unsuccessful sites (-192±47 mV). GLM results
indicated a significant interactive effect of soil salinity (low) and redox potential (high) on level
of survival and growth performances of planted R. mucronata juveniles. These conditions
collectively reflect soil maturity of mangrove restored sites. Therefore, we propose that
interactive effect; soil salinity × redox potential, can be used as a simple, worthy proxy in
evaluating success of R. mucronata mangrove juveniles.
