Mortality and growth of cut pieces of viviparous mangrove ( Rhizophora apiculata and R. mucronata) seedlings in the field condition

Abstract

Viviparous seedlings of the mangrove species Rhizophora apiculata and R. mucronata were divided into even lengths of the top, middle, and bottom parts, and these cut pieces were planted in the field. The mortality and growth were monitored for 38 months after transplantation, and compared with intact seedlings planted in the same place. Both mean diameter and stem height of R. mucronata cut pieces were largest for the bottom parts, intermediate for the middle parts, and the smallest for the top parts. Among cut pieces of R. apiculata, the pattern for diameter was the same, but the mean stem height showed no differences among treatments. For both species, the mortality was associated with the initial volume of individual cut pieces. The bottom cut pieces with large volumes showed lowest mortality. Almost all cut pieces of R. apiculata formed prop roots above ground, but only 30% of R. mucronata cut pieces formed them. In the 38-month-old plantation, the mean diameters of the various cut-piece treatments of R. apiculata and R. mucronata were, respectively, 0.78–1.37 and 0.56–0.89 times as large as those for the intact seedlings; corresponding values for mean stem heights were 0.81–0.85 and 0.50–1.00. These results suggest a possibility that cut pieces can be a useful plantation material.